All posts by Wyss Institute

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A gentle grip on gelatinous creatures

Jellyfish are about 95% water, making them some of the most diaphanous, delicate animals on the planet. But the remaining 5% of them have yielded important scientific discoveries, like green fluorescent protein (GFP) that is now used extensively by scientists to study gene expression, and life-cycle reversal that could hold the keys to combating aging. Jellyfish may very well harbor other, potentially life-changing secrets, but the difficulty of collecting them has severely limited the study of such “forgotten fauna.” The sampling tools available to marine biologists on remotely operated vehicles (ROVs) were largely developed for the marine oil and gas industries, and are much better-suited to grasping and manipulating rocks and heavy equipment than jellies, often shredding them to pieces in attempts to capture them.

A new ultra-soft gripper developed at the Wyss Institute and Baruch College uses fettuccini-like silicone “fingers” inflated with water to gently but firmly grasp jellyfish and release them without harm, allowing scientists to safely interact with these delicate creatures in their own habitats. Credit: Anand Varma

Now, a new technology developed by researchers at Harvard’s Wyss Institute for Biologically Inspired Engineering, John A. Paulson School of Engineering and Applied Sciences (SEAS), and Baruch College at CUNY offers a novel solution to that problem in the form of an ultra-soft, underwater gripper that uses hydraulic pressure to gently but firmly wrap its fettuccini-like fingers around a single jellyfish, then release it without causing harm. The gripper is described in a new paper published in Science Robotics.

“Our ultra-gentle gripper is a clear improvement over existing deep-sea sampling devices for jellies and other soft-bodied creatures that are otherwise nearly impossible to collect intact,” said first author Nina Sinatra, Ph.D., a former graduate student in the lab of Robert Wood at the Wyss Institute. “This technology can also be extended to improve underwater analysis techniques and allow extensive study of the ecological and genetic features of marine organisms without taking them out of the water.”

The gripper’s six “fingers” are composed of thin, flat strips of silicone with a hollow channel inside bonded to a layer of flexible but stiffer polymer nanofibers. The fingers are attached to a rectangular, 3D-printed plastic “palm” and, when their channels are filled with water, curl in the direction of the nanofiber-coated side. The fingers each exert an extremely low amount of pressure – about 0.0455 kPA, or less than one-tenth of the pressure of a human’s eyelid on their eye. By contrast, current state-of-the-art soft marine grippers, which are used to capture delicate but more robust animals than jellyfish, exert about 1 kPA.

First author Nina Sinatra, Ph.D. tests the ultra-soft gripper on a jellyfish at the New England Aquarium. Credit: Anand Varma

The researchers fitted their ultra-gentle gripper to a specially created hand-held device and tested its ability to grasp an artificial silicone jellyfish in a tank of water to determine the positioning and precision required to collect a sample successfully, as well as the optimum angle and speed at which to capture a jellyfish. They then moved on to the real thing at the New England Aquarium, where they used the grippers to grab swimming moon jellies, jelly blubbers, and spotted jellies, all about the size of a golf ball.

The gripper was successfully able to trap each jellyfish against the palm of the device, and the jellyfish were unable to break free from the fingers’ grasp until the gripper was depressurized. The jellyfish showed no signs of stress or other adverse effects after being released, and the fingers were able to open and close roughly 100 times before showing signs of wear and tear.

“Marine biologists have been waiting a long time for a tool that replicates the gentleness of human hands in interacting with delicate animals like jellyfish from inaccessible environments,” said co-author David Gruber, Ph.D., who is a Professor of Biology and Environmental Science at Baruch College, CUNY and a National Geographic Explorer. “This gripper is part of an ever-growing soft robotic toolbox that promises to make underwater species collection easier and safer, which would greatly improve the pace and quality of research on animals that have been under-studied for hundreds of years, giving us a more complete picture of the complex ecosystems that make up our oceans.”

The ultra-soft gripper is the latest innovation in the use of soft robotics for underwater sampling, an ongoing collaboration between Gruber and Wyss Founding Core Faculty member Robert Wood, Ph.D. that has produced the origami-inspired RAD sampler and multi-functional “squishy fingers” to collect a diverse array of hard-to-capture organisms, including squids, octopuses, sponges, sea whips, corals, and more.

“Soft robotics is an ideal solution to long-standing problems like this one across a wide variety of fields, because it combines the programmability and robustness of traditional robots with unprecedented gentleness thanks to the flexible materials used,” said Wood, who is the co-lead of the Wyss Institute’s Bioinspired Soft Robotics Platform, the Charles River Professor of Engineering and Applied Sciences at SEAS, and a National Geographic Explorer.

“At the Wyss Institute we are always asking, ‘How can we make this better?’ I am extremely impressed by the ingenuity and out-of-the-box thinking that Rob Wood and his team have applied to solve a real-world problem that exists in the open ocean, rather than in the laboratory. This could help to greatly advance ocean science,” said Wyss Institute Founding Director Donald Ingber, M.D., Ph.D., who is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School, the Vascular Biology Program at Boston Children’s Hospital, and Professor of Bioengineering at SEAS.

A new ultra-soft gripper developed at the Wyss Institute uses fettuccini-like silicone “fingers” inflated with water to gently but firmly grasp jellyfish and release them without harm, allowing scientists to safely interact with these delicate creatures in their own habitats. Credit: Wyss Institute at Harvard

The team is continuing to refine the ultra-soft gripper’s design, and aims to conduct studies that evaluate the jellyfishes’ physiological response to being held by the gripper, to more definitively prove that they do not cause the animals stress. Wood and Gruber are also co-Principal Investigators of the Schmidt Ocean Institute’s “Designing the Future” project, and will be further testing their various underwater robots on an upcoming expedition aboard the research ship Falkor in 2020.

Additional authors of the paper are Clark Teeple, Daniel Vogt, M.S., and Kevin Kit Parker, Ph.D. from the Wyss Institute and Harvard SEAS. Parker is a Founding Core Faculty member of the Wyss Institute and the Tarr Family Professor of Bioengineering and Applied Physics at SEAS. The research was supported by the National Science Foundation, The Harvard University Materials Research Science and Engineering Center, The National Academies Keck Futures Initiative, and the National Geographic Society.

Suit up with a robot to walk AND run more easily

The light-weight versatile exosuit assists hip extension during uphill walking and at different running speeds in natural terrain. Credit: Wyss Institute at Harvard University

By Benjamin Boettner

Between walking at a leisurely pace and running for your life, human gaits can cover a wide range of speeds. Typically, we choose the gait that allows us to consume the least amount of energy at a given speed. For example, at low speeds, the metabolic rate of walking is lower than that of running in a slow jog; vice versa at high speeds, the metabolic cost of running is lower than that of speed walking.

Researchers in academic and industry labs have previously developed robotic devices for rehabilitation and other areas of life that can either assist walking or running, but no untethered portable device could efficiently do both. Assisting walking and running with a single device is challenging because of the fundamentally different biomechanics of the two gaits. However, both gaits have in common an extension of the hip joint, which starts around the time when the foot comes in contact with the ground and requires considerable energy for propelling the body forward.

As reported today in Science, a team of researchers at Harvard’s Wyss Institute for Biologically Inspired Engineering and John A. Paulson School of Engineering and Applied Sciences (SEAS), and the University of Nebraska Omaha now has developed a portable exosuit that assists with gait-specific hip extension during both walking and running. Their lightweight exosuit is made of textile components worn at the waist and thighs, and a mobile actuation system attached to the lower back which is controlled by an algorithm that can robustly detect the transition from walking to running and vice versa.

The team first showed that the exosuit worn by users in treadmill-based indoor tests, on average, reduced their metabolic costs of walking by 9.3% and of running by 4% compared to when they were walking and running without the device. “We were excited to see that the device also performed well during uphill walking, at different running speeds and during overground testing outside, which showed the versatility of the system,” said Conor Walsh, Ph.D., who led the study. Walsh is a Core Faculty member of the Wyss Institute, the Gordon McKay Professor of Engineering and Applied Sciences at SEAS, and Founder of the Harvard Biodesign Lab. “While the metabolic reductions we found are modest, our study demonstrates that it is possible to have a portable wearable robot assist more than just a single activity, helping to pave the way for these systems to become ubiquitous in our lives,” said Walsh.

The hip exosuit was developed as part of the Defense Advanced Research Projects Agency (DARPA)’s former Warrior Web program and is the culmination of years of research and optimization of the soft exosuit technology by the team. A previous multi-joint exosuit developed by the team could assist both the hip and ankle during walking, and a medical version of the exosuit aimed at improving gait rehabilitation for stroke survivors is now commercially available in the US and Europe, via a collaboration with ReWalk Robotics.

The team’s most recent hip-assisting exosuit is designed to be simpler and lighter weight compared to their past multi-joint exosuit. It assists the wearer via a cable actuation system. The actuation cables apply a tensile force between the waist belt and thigh wraps to generate an external extension torque at the hip joint that works in concert with the gluteal muscles. The device weighs 5kg in total with more than 90% of its weight located close to the body’s center of mass. “This approach to concentrating the weight, combined with the flexible apparel interface, minimizes the energetic burden and movement restriction to the wearer,” said co-first-author Jinsoo Kim, a SEAS graduate student in Walsh’s group. “This is important for walking, but even more so for running as the limbs move back and forth much faster.” Kim shared the first-authorship with Giuk Lee, Ph.D., a former postdoctoral fellow on Walsh’s team and now Assistant Professor at Chung-Ang University in Seoul, South Korea.

A major challenge the team had to solve was that the exosuit needed to be able to distinguish between walking and running gaits and change its actuation profiles accordingly with the right amount of assistance provided at the right time of the gait cycle.

To explain the different kinetics during the gait cycles, biomechanists often compare walking to the motions of an inverted pendulum and running to the motions of a spring-mass system. During walking, the body’s center of mass moves upward after heel-strike, then reaches maximum height at the middle of the stance phase to descend towards the end of the stance phase. In running, the movement of the center of mass is opposite. It descends towards a minimum height at the middle of the stance phase and then moves upward towards push-off.

“We took advantage of these biomechanical insights to develop our biologically inspired gait classification algorithm that can robustly and reliably detect a transition from one gait to the other by monitoring the acceleration of an individual’s center of mass with sensors that are attached to the body,” said co-corresponding author Philippe Malcolm, Ph.D., Assistant Professor at University of Nebraska Omaha. “Once a gait transition is detected, the exosuit automatically adjusts the timing of its actuation profile to assist the other gait, as we demonstrated by its ability to reduce metabolic oxygen consumption in wearers.”

In ongoing work, the team is focused on optimizing all aspects of the technology, including further reducing weight, individualizing assistance and improving ease of use. “It is very satisfying to see how far our approach has come,” said Walsh, “and we are excited to continue to apply it to a range of applications, including assisting those with gait impairments, industry workers at risk of injury performing physically strenuous tasks, or recreational weekend warriors.”

The team’s portable exosuit is made of textile components worn at the waist and thighs, and a mobile actuation system attached to the lower back which uses an algorithm that robustly predicts transitions between walking and running gaits. Credit: Wyss Institute at Harvard University

“This breakthrough study coming out of the Wyss Institute’s Bioinspired Soft Robotics platform gives us a glimpse into a future where wearable robotic devices can improve the lives of the healthy, as well as serve those with injuries or in need of rehabilitation,” said Wyss Institute Founding Director Donald Ingber, M.D., Ph.D., who is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School, the Vascular Biology Program at Boston Children’s Hospital, and Professor of Bioengineering at SEAS.

Other authors on the study are past and present members of Walsh’s team, including data analyst Roman Heimgartner; Research Fellow Dheepak Arumukhom Revi; Control Engineer Nikos Karavas, Ph.D.; Functional Apparel Designer Danielle Nathanson; Robotics Engineer Ignacio Galiana, Ph.D.; Robotics Engineer Asa Eckert-Erdheim; Electromechanical Engineer Patrick Murphy; Engineer David Perry; Software Engineer Nicolas Menard, and graduate student Dabin Kim Choe. The study was funded by the Defense Advanced Research Projects Agency’s Warrior Web Program, the National Science Foundation and Harvard’s Wyss Institute for Biologically Inspired Engineering.

The RoboBee flies solo

Changes to the Robobee — including an additional pair of wings and improvements to the actuators and transmission ratio — made the vehicle more efficient and allowed the addition of solar cells and an electronics panel. This Robobee is the first to fly without a power cord and is the lightest, untethered vehicle to achieve sustained flight. Credit: Harvard Microrobotics Lab/Harvard SEAS

By Leah Burrows

In the Harvard Microrobotics Lab, on a late afternoon in August, decades of research culminated in a moment of stress as the tiny, groundbreaking Robobee made its first solo flight.

Graduate student Elizabeth Farrell Helbling, Ph.D.’19, and postdoctoral fellow Noah T. Jafferis, Ph.D. from Harvard’s Wyss Institute for Biologically Inspired Engineering, the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), and the Graduate School of Arts and Sciences caught the moment on camera.

Helbling, who has worked on the project for six years, counted down: “Three, two, one, go.”

The bright halogens switched on and the solar-powered Robobee launched into the air. For a terrifying second, the tiny robot, still without on-board steering and control, careened towards the lights.

Off camera, Helbling exclaimed and cut the power. The Robobee fell dead out of the air, caught by its Kevlar safety harness.

“That went really close to me,” Helbling said, with a nervous laugh.

“It went up,” Jafferis, who has also worked on the project for about six years, responded excitedly from the high-speed camera monitor where he was recording the test.

And with that, Harvard University’s Robobee reached its latest major milestone — becoming the lightest vehicle ever to achieve sustained untethered flight.

“This is a result several decades in the making,” said Robert Wood, Ph.D., Core Faculty member of the Wyss Institute, the Charles River Professor of Engineering and Applied Sciences at SEAS, and principle investigator of the Robobee project. “Powering flight is something of a Catch-22 as the tradeoff between mass and power becomes extremely problematic at small scales where flight is inherently inefficient.  It doesn’t help that even the smallest commercially available batteries weigh much more than the robot. We have developed strategies to address this challenge by increasing vehicle efficiency, creating extremely lightweight power circuits, and integrating high efficiency solar cells.”

The milestone is described in Nature.

To achieve untethered flight, this latest iteration of the Robobee underwent several important changes, including the addition of a second pair of wings. “The change from two to four wings, along with less visible changes to the actuator and transmission ratio, made the vehicle more efficient, gave it more lift, and allowed us to put everything we need on board without using more power,” said Jafferis. (The addition of the wings also earned this Robobee the nickname X-Wing, after the four-winged starfighters from Star Wars.)

That extra lift, with no additional power requirements, allowed the researchers to cut the power cord — which has kept the Robobee tethered for nearly a decade — and attach solar cells and an electronics panel to the vehicle.

The solar cells, the smallest commercially available, weigh 10 milligrams each and get 0.76 milliwatts per milligram of power when the sun is at full intensity. The Robobee X-Wing needs the power of about three Earth suns to fly, making outdoor flight out of reach for now. Instead, the researchers simulate that level of sunlight in the lab with halogen lights. The solar cells are connected to an electronics panel under the bee, which converts the low voltage signals of the solar array into high voltage drive signals needed to control the actuators. The solar cells sit about three centimeters above the wings, to avoid interference.

In all, the final vehicle, with the solar cells and electronics, weights 259 milligrams (about a quarter of a paper clip) and uses about 120 milliwatts of power, which is less power than it would take to light a single bulb on a string of LED Christmas lights.

“When you see engineering in movies, if something doesn’t work, people hack at it once or twice and suddenly it works. Real science isn’t like that,” said Helbling. “We hacked at this problem in every which way to finally achieve what we did. In the end, it’s pretty thrilling.” The researchers will continue to hack away, aiming to bring down the power and add on-board control to enable the Robobee to fly outside.

To achieve untethered flight, the latest iteration of the Robobee underwent several important changes, including the addition of a second pair of wings. (Video courtesy of the Harvard Microrobotics Lab/Harvard SEAS)

“Over the life of this project we have sequentially developed solutions to challenging problems, like how to build complex devices at millimeter scales, how to create high-performance millimeter-scale artificial muscles, bioinspired designs, and novel sensors, and flight control strategies,” said Wood. “Now that power solutions are emerging, the next step is onboard control. Beyond these robots, we are excited that these underlying technologies are finding applications in other areas such as minimally-invasive surgical devices, wearable sensors, assistive robots, and haptic communication devices – to name just a few.”

Harvard has developed a portfolio of intellectual property (IP) related to the fabrication process for millimeter-scale devices. This IP, as well as related technologies, can be applied to microrobotics, medical devices, consumer electronics and a wide range of complex electromechanical systems. Harvard’s Office of Technology Development is exploring opportunities for commercial impact in these fields.

This research was co-authored by Michael Karpelson, Ph.D., Staff Electrical Engineer on the Institute’s Advanced Technology Team. It was supported by the National Science Foundation and the Office of Naval Research.

The little robot that could

Root is controlled using an iPad app that has three different levels of coding, allowing students as young as four years old to learn the fundamentals of programming. Credit: Wyss Institute at Harvard University

iRobot Corp. announced its acquisition of Root Robotics, Inc., whose educational Root coding robot got its start as a summer research project at the Wyss Institute for Biologically Inspired Engineering in 2011 and subsequently developed into a robust learning tool that is being used in over 500 schools to teach children between the ages of four and twelve how to code in an engaging, intuitive way. iRobot plans to incorporate the Root robot into its growing portfolio of educational robot products, and continue the work of scaling up production and expanding Root’s programming content that began when Root Robotics was founded by former Wyss Institute members in 2017.

The Root robot can be programmed to perform a variety of actions based on what students draw on a whiteboard, including avoid obstacles, play music, and flash its lights. Credit: Wyss Institute at Harvard University

“We’re honored that we got to see a Wyss Institute technology go from its earliest stages to where we are today, with the opportunity to make a gigantic impact on the world,” said Zivthan Dubrovsky, former Bioinspired Robotics Platform Lead at the Wyss Institute and co-founder of Root Robotics who is now the General Manager of Educational Robots at iRobot. “We’re excited to see how this new chapter in Root’s story can further amplify our mission of making STEM education accessible to students of any age in any classroom around the world.”

Root began in the lab of Wyss Core Faculty Member and Bioinspired Robotics Platform co-lead Radhika Nagpal, Ph.D., who was investigating the idea of robots that could climb metal structures using magnetic wheels. “Most whiteboards in classrooms are backed with metal, so I thought it would be wonderful if a robot could automatically erase the whiteboard as I was teaching – ironically, we referred to it as a ‘Roomba® for whiteboards,’ because many aspects were directly inspired by iRobot’s Roomba at the time,” said Nagpal, who is also the Fred Kavli Professor of Computer Science at Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS). “Once we had a working prototype, the educational potential of this robot was immediately obvious. If it could be programmed to detect ink, navigate to it, and erase it, then it could be used to teach students about coding algorithms of increasing complexity.”

That prototype was largely built by Raphael Cherney, first as a Research Engineer in Nagpal’s group at Harvard in 2011, and then beginning in 2013 when he was hired to work on developing Root full-time along with Dubrovsky and other members of the Wyss Institute. “When Raphael and Radhika pitched me the idea of Root, I fell in love with it immediately,” said Dubrovsky. “My three daughters were all very young at the time and I wanted them to have exposure to STEM concepts like coding and engineering, but I was frustrated by the lack of educational systems that were designed for children their age. The idea of being able to create that for them was really what motivated me to throw all my weight behind the project.”

Under Cherney and Dubrovsky’s leadership, Root’s repertoire expanded to include drawing shapes on the whiteboard as it wheeled around, navigating through obstacles drawn on the whiteboard, playing music, and more. The team also developed Root’s coding interface, which has three levels of increasing complexity that are designed to help students from preschool to high school easily grasp the concepts of programming and use them to create their own projects. “The tangible nature of a robot really brings the code to life, because the robot is ‘real’ in a way that code isn’t – you can watch it physically carrying out the instructions that you’ve programmed into it,” said Cherney, who co-founded Root Robotics and is now a Principal Systems Engineer at iRobot. “It helps turn coding into a social activity, especially for kids, as they learn to work in teams and see coding as a fun and natural thing to do.”

Over the next three years the team iterated on Root’s prototype and began testing it in classrooms in and around Boston, getting feedback from students and teachers to get the robot closer to its production-ready form. “Robots are very hard to build, and the support we had from the Wyss Institute let us do it right, instead of just fast,” said Cherney. “We were able to develop Root from a prototype to a product that worked in schools and was doing what we envisioned, and the whole process was much smoother than it would have been if we had just been a team working in a garage.”

By 2016, they felt ready for commercialization. They ran a Kickstarter® campaign as a market test to see if they had a viable consumer business, and raised nearly $400,000 from almost 2,000 backers, far exceeding their target of $250,000. Buoyed by this vote of confidence from potential customers, Dubrovsky and Cherney left the Wyss Institute in the summer of 2017 to co-found Root Robotics with Nagpal serving as Scientific Advisor and $2.5 million in seed funds, and a license from Harvard’s Office of Technology Development. While most of their time at the Wyss Institute was spent getting the robot right, the company focused on getting the content of Root’s programming app up to par, setting up a classroom in their office and inviting students to come try out the robot, then updating their content with insights learned from those experiences.

Once they achieved their vision for three different levels of programming targeting students of different ages, they shipped Root robots to their Kickstarter backers and made it available for purchase on their website in September 2018. Since then, over a million coding projects have been run on the Root app. “What’s been most rewarding for me personally is seeing my kids take Root to their classrooms and show their teachers and their peers what they’ve been able to make a robot do. Getting to see them problem-solve and iterate and then achieve something they’re proud of is priceless,” said Dubrovsky. “I’ve been pleasantly surprised by seeing people come up with new things to do with the robot that we never thought of,” added Cherney. “The way it seems to immediately unlock creativity is beautiful and inspiring.”

The Root robot has tremendous value as a tool for teaching students not only coding, but also concepts of AI, engineering and autonomous robots, all of which are very important for our future.

Colin Angle, iRobot
Root Robotics co-founders Raphael Cherney (left) and Zee Dubrovsky (center) are joining iRobot’s Educational Robotics division. Root started as a project in the lab of Wyss Faculty member Radhika Nagpal (right). Credit: Wyss Institute at Harvard University

“One of the things that really attracted us to Root was that it was designed as an education product from the ground up, which fits perfectly with our own deep passion for using robots as a way of turbo charging STEM education,” said Colin Angle, chairman and CEO of iRobot. “The Root robot has tremendous value as a tool for teaching students not only coding, but also concepts of AI, engineering and autonomous robots, all of which are very important for our future.”

Nagpal is still sometimes floored by the fact that what started as an idea for a simple whiteboard-erasing robot ended up developing into such a robust teaching tool. “Without the Wyss Institute, I would not have even thought to try and commercialize this idea,” she said. “It supported an amazing team of engineers in creating and testing Root over several years, which allowed us to be able to raise the funds to launch the company with a product that was so well-developed that it now has the potential to really scale up and make a big difference in the world.”

“Root Robotics is one of the great success stories to come out of the Wyss Institute, partially because of how quickly the team recognized its potential impact and focused on de-risking it both technically and commercially,” said Wyss Founding Director Donald Ingber, M.D., Ph.D. “It was fantastic to see Root take root at the Institute, and we are immensely proud of them and their ability to develop a technology that can truly bring about positive change in our world by targeting children who are the creators and visionaries of tomorrow.” Ingber is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and the Vascular Biology Program at Boston Children’s Hospital, as well as Professor of Bioengineering at SEAS.

Laying the ground for robotic strategies in environmental protection

By Benjamin Boettner
Along developed riverbanks, physical barriers can help contain flooding and combat erosion. In arid regions, check dams can help retain soil after rainfall and restore damaged landscapes. In construction projects, metal plates can provide support for excavations, retaining walls on slopes, or permanent foundations. All of these applications can be addressed with the use of sheet piles, elements folded from flat material and driven vertically into the ground to form walls and stabilize soil. Proper soil stabilization is key to sustainable land management in industries such as construction, mining, and agriculture; and land degradation, the loss of ecosystem services from a given terrain, is a driver of climate change and is estimated to cost up to $10 trillion annually.

With this motivation, a team of roboticists at Harvard’s Wyss Institute for Biologically Inspired Engineering has developed a robot that can autonomously drive interlocking steel sheet piles into soil. The structures that it builds could function as retaining walls or check dams for erosion control. The study will be presented at the upcoming 2019 IEEE International Conference on Robotics and Automation.

Researchers at the Wyss Institute have developed a robot designed to drive interlocking sheet piles into the ground to help stabilize soil. Teams of such robots could help combat erosion, restore damaged landscapes, and facilitate sustainable land management in a variety of settings. Credit: Wyss Institute at Harvard University
Romu, the Wyss Institute’s sheet pile driving robot has been extensively tested in a sandbox in the laboratory. Credit: Wyss Institute at Harvard University

Conventional sheet pile driving processes are extremely energy intensive. Only a fraction of the weight of typical heavy machinery is used for applying downward force. The Wyss team’s “Romu” robot, on the other hand, is able to leverage its own weight to drive sheet piles into the ground. This is made possible by each of its four wheels being coupled to a separate linear actuator, which also allows it to adapt to uneven terrain and ensure that piles are driven vertically. From a raised position, Romu grips a sheet pile and then lowers its chassis, pressing the pile into the soil with the help of an on-board vibratory hammer. By gripping the pile again at a higher position and repeating this process, the robot can drive a pile much taller than its own range of vertical motion. After driving a pile to sufficient depth, Romu advances and installs the next pile such that it interlocks with the previous one, thereby forming a continuous wall. Once it has used all of the piles it carries, it may return to a supply cache to restock.

The study grew out of previous work at the Wyss Institute on teams or swarms of robots for construction applications. In work inspired by mound-building termites, Core Faculty member Radhika Nagpal and Senior Research Scientist Justin Werfel designed an autonomous robotic construction crew called TERMES, whose members worked together to build complex structures from specialized bricks. Further work by Werfel and researcher Nathan Melenbrink explored strut-climbing robots capable of building cantilevering truss structures, addressing applications like bridges. However, neither of these studies addressed the challenge of anchoring structures to the ground. The Romu project began as an exploration of methods for automated site preparation and installation of foundations for the earlier systems to build on; as it developed, the team determined that such interventions could also be directly applicable to land restoration tasks in remote environments.

The robot is designed to drive interlocking sheet piles into granular soils like sand on a beach. Credit: Wyss Institute at Harvard University

“In addition to tests in the lab, we demonstrated Romu operating on a nearby beach,” said Melenbrink. “This kind of demonstration can be an icebreaker for a broader conversation around opportunities for automation in construction and land management. We’re interested in engaging with experts in related fields who might see potential benefit for the kind of automated interventions we’re developing.”

The researchers envision large numbers of Romu robots working together as a collective or swarm. They demonstrated in computer simulations that teams of Romu robots could make use of environmental cues like slope steepness in order to build walls in effective locations, making efficient use of limited resources. “The swarm approach gives advantages like speedup through parallelism, robustness to the loss of individual robots, and scalability for large teams,” said Werfel. “By responding in real-time to the conditions they actually encounter as they work, the robots can adapt to unexpected or changing situations, without needing to rely on a lot of supporting infrastructure for abilities like site surveying, communication, or localization.”

“The name Terramanus ferromurus (Romu) is a nod to the concept of ‘machine ecology’ in which autonomous systems can be introduced into natural environments as new participants, taking specific actions to complement and promote human environmental stewardship,” said Melenbrink. In the future, the Terramanus “genus” could be extended by additional robots carrying out different tasks to protect or restore ecosystem services. Based on their findings, the team now is interested in investigating interventions ranging from groundwater retention structures for supporting agriculture in arid regions, to responsive flood barrier construction for hurricane preparedness. Future versions of the robot could perform other interventions such as spraying soil-binding agents or installing silt fencing, such that a family of these robots could act to stabilize soil in a wide range of situations.

In many scenarios for environmental protection or restoration, the opportunity for action is limited by the availability of human labor and by site access for heavy machinery. Smaller, more versatile construction machines could provide a solution. “Clearly, the needs of many degraded landscapes are not being met with the currently available tools and techniques,” said Melenbrink. “Now, 100 years after the dawn of the heavy equipment age, we’re asking whether there might be more resilient and responsive ways to approach land management and restoration.”

“This sheet pile driving robot with its demonstrated ability to perform in a natural setting signals a path on which the Wyss Institute’s robotics and swarm robotics capabilities can be brought to bear on both natural and man-made environments where conventional machinery, man power limitations, or cost is inadequate to prevent often disastrous consequences. This robot also could address disaster situations where walling off dangerous chemical spills or released radioactive fluids makes it difficult or impossible for humans to intervene,” said Wyss Institute Founding Director Donald Ingber, M.D., Ph.D., who is also the Judah Folkman Professor of Vascular Biology at HMS and the Vascular Biology Program at Boston Children’s Hospital, as well as Professor of Bioengineering at SEAS.

A rubber computer eliminates the last hard components from soft robots

The toggle gripper holding a screwdriver. Credit: Daniel Preston / Harvard University
By Caitlin McDermott-Murphy, Harvard University Department of Chemistry and Chemical Biology

A soft robot, attached to a balloon and submerged in a transparent column of water, dives and surfaces, then dives and surfaces again, like a fish chasing flies. Soft robots have performed this kind of trick before. But unlike most soft robots, this one is made and operated with no hard or electronic parts. Inside, a soft, rubber computer tells the balloon when to ascend or descend. For the first time, this robot relies exclusively on soft digital logic.

In the last decade, soft robots have surged into the metal-dominant world of robotics. Grippers made from rubbery silicone materials are already used in assembly lines: Cushioned claws handle delicate fruit and vegetables like tomatoes, celery, and sausage links or extract bottles and sweaters from crates. In laboratories, the grippers can pick up slippery fish, live mice, and even insects, eliminating the need for more human interaction.

Soft robots already require simpler control systems than their hard counterparts. The grippers are so compliant, they simply cannot exert enough pressure to damage an object and without the need to calibrate pressure, a simple on-off switch suffices. But until now, most soft robots still rely on some hardware: Metal valves open and close channels of air that operate the rubbery grippers and arms, and a computer tells those valves when to move.

Now, researchers have built a soft computer using just rubber and air. “We’re emulating the thought process of an electronic computer, using only soft materials and pneumatic signals, replacing electronics with pressurized air,” says Daniel J. Preston, first author on a paper published in PNAS and a postdoctoral researcher working with George Whitesides, a Founding Core Faculty member of Harvard’s Wyss Institute for Biologically Inspired Engineering, and the Woodford L. and Ann A. Flowers University Professor at Harvard University’s Department of Chemistry and Chemical Biology.

To make decisions, computers use digital logic gates, electronic circuits that receive messages (inputs) and determine reactions (outputs) based on their programming. Our circuitry isn’t so different: When a doctor strikes a tendon below our kneecap (input), the nervous system is programmed to jerk (output).

Preston’s soft computer mimics this system using silicone tubing and pressurized air. To achieve the minimum types of logic gates required for complex operations—in this case, NOT, AND, and OR—he programmed the soft valves to react to different air pressures. For the NOT logic gate, for example, if the input is high pressure, the output will be low pressure. With these three logic gates, Preston says, “you could replicate any behavior found on any electronic computer.”

The bobbing fish-like robot in the water tank, for example, uses an environmental pressure sensor (a modified NOT gate) to determine what action to take. The robot dives when the circuit senses low pressure at the top of the tank and surfaces when it senses high pressure at depth. The robot can also surface on command if someone pushes an external soft button.

Robots built with only soft parts have several benefits. In industrial settings, like automobile factories, massive metal machines operate with blind speed and power. If a human gets in the way, a hard robot could cause irreparable damage. But if a soft robot bumps into a human, Preston says, “you wouldn’t have to worry about injury or a catastrophic failure.” They can only exert so much force.

But soft robots are more than just safer: They are generally cheaper and simpler to make, light weight, resistant to damage and corrosive materials, and durable. Add intelligence and soft robots could be used for much more than just handling tomatoes. For example, a robot could sense a user’s temperature and deliver a soft squeeze to indicate a fever, alert a diver when the water pressure rises too high, or push through debris after a natural disaster to help find victims and offer aid.

Soft robots can also venture where electronics struggle: High radiative fields, like those produced after a nuclear malfunction or in outer-space, and inside Magnetic Resonance Imaging (MRI) machines. In the wake of a hurricane or flooding, a hardy soft robot could manage hazardous terrain and noxious air. “If it gets run over by a car, it just keeps going, which is something we don’t have with hard robots,” Preston says.

Preston and colleagues are not the first to control robots without electronics. Other research teams have designed microfluidic circuits, which can use liquid and air to create nonelectronic logic gates. One microfluidic oscillator helped a soft octopus-shaped robot flail all eight arms.

Yet, microfluidic logic circuits often rely on hard materials like glass or hard plastics, and they use such thin channels that only small amounts of air can move through at a time, slowing the robot’s motion. In comparison, Preston’s channels are larger—close to one millimeter in diameter—which enables much faster air flow rates. His air-based grippers can grasp an object in a matter of seconds.

Microfluidic circuits are also less energy efficient. Even at rest, the devices use a pneumatic resistor, which flows air from the atmosphere to either a vacuum or pressure source to maintain stasis. Preston’s circuits require no energy input when dormant. Such energy conservation could be crucial in emergency or disaster situations where the robots travel far from a reliable energy source.

The soft, pneumatic robots also offer an enticing possibility: Invisibility. Depending on which material Preston selects, he could design a robot that is index-matched to a specific substance. So, if he chooses a material that camouflages in water, the robot would appear transparent when submerged. In the future, he and his colleagues hope to create autonomous robots that are invisible to the naked eye or even sonar detection. “It’s just a matter of choosing the right materials,” he says.

For Preston, the right materials are elastomers or rubbers. While other fields chase higher power with machine learning and artificial intelligence, the Whitesides team turns away from the mounting complexity. “There’s a lot of capability there,” Preston says, “but it’s also good to take a step back and think about whether or not there’s a simpler way to do things that gives you the same result, especially if it’s not only simpler, it’s also cheaper.”

A safe, wearable soft sensor

This biocompatible sensor is made from a non-toxic, highly conductive liquid solution that could be used in diagnostics, therapeutics, human-computer interfaces, and virtual reality. Credit: Harvard SEAS

By Leah Burrows
Children born prematurely often develop neuromotor and cognitive developmental disabilities. The best way to reduce the impacts of those disabilities is to catch them early through a series of cognitive and motor tests. But accurately measuring and recording the motor functions of small children is tricky. As any parent will tell you, toddlers tend to dislike wearing bulky devices on their hands and have a predilection for ingesting things they shouldn’t.

Harvard University researchers have developed a soft, non-toxic wearable sensor that unobtrusively attaches to the hand and measures the force of a grasp and the motion of the hand and fingers.

The research was published in Advanced Functional Materials and is a collaboration between the Wyss Institute for Biologically Inspired Engineering, The Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), Beth Israel Deaconess Medical Center, and Boston Children’s Hospital.

One novel element of the sensor is a non-toxic, highly conductive liquid solution.

“We have developed a new type of conductive liquid that is no more dangerous than a small drop of salt water,” said Siyi Xu, a graduate student at SEAS and first author of the paper. “It is four times more conductive than previous biocompatible solutions, leading to cleaner, less noisy data.”

The sensing solution is made from potassium iodide, which is a common dietary supplement, and glycerol, which is a common food additive. After a short mixing period, the glycerol breaks the crystal structure of potassium iodide and forms potassium cations (K+) and iodide ions (I-), making the liquid conductive. Because glycerol has a lower evaporation rate than water, and the potassium iodide is highly soluble, the liquid is both stable across a range of temperatures and humidity levels, and highly conductive.

“Previous biocompatible soft sensors have been made using sodium chloride-glycerol solutions but these solutions have low conductivities, which makes the sensor data very noisy, and it also takes about 10 hours to prepare,” said Xu. “We’ve shortened that down to about 20 minutes and get very clean data.”


Safe, soft sensors on the top and tip of the index finger detect the movements, strain and force of the finger while performing different activities, such as flexing and extending the finger and picking up weights and boxes. Credit: Harvard SEAS

The design of the sensors also takes the need of children into account. Rather than a bulky glove, the silicon-rubber sensor sits on top of the finger and on the finger pad.

“We often see that children who are born early or who have been diagnosed with early developmental disorders have highly sensitive skin,” said Eugene Goldfield, Ph.D., coauthor of the study, and Associate Faculty Member of the Wyss Institute at Harvard University and an Associate Professor in the Program in Behavioral Sciences at Boston Children’s Hospital and Harvard Medical School. “By sticking to the top of the finger, this device gives accurate information while getting around the sensitively of the child’s hand.”

Goldfield is the Principal investigator of the Flexible Electronics for Toddlers project at the Wyss Institute, which designs modular robotic systems for toddlers born prematurely and at risk for cerebral palsy.

Goldfield and his colleagues currently study motor function using the Motion Capture Lab at SEAS and Wyss. While motion capture can tell a lot about movement, it cannot measure force, which it critical to diagnosing neuromotor and cognitive developmental disabilities.

“Early diagnosis is the name of the game when it comes to treating these developmental disabilities and this wearable sensor can give us a lot of advantages not currently available,” said Goldfield.

This paper only tested the device on adult hands. Next, the researchers plan to scale down the device and test it on the hands of children.

“The ability to quantify complex human motions gives us an unprecedented diagnostic tool,” says senior author Robert Wood, Ph.D., Founding Core Faculty Member of the Wyss Institute and the Charles River Professor of Engineering and Applied Sciences at SEAS. “The focus on the development of motor skills in toddlers presents unique challenges for how to integrate many sensors into a small, lightweight, and unobtrusive wearable device. These new sensors solve these challenges – and if we can create wearable sensors for such a demanding task, we believe that this will also open up applications in diagnostics, therapeutics, human-computer interfaces, and virtual reality.”

This research was also authored by SEAS researcher Daniel M. Vogt; Wyss Institute researchers Wen-Hao Hsu, John Osborne, Timothy Walsh, Jonathan R. Foster, Sarah K. Sullivan, and Andreas Rousing; and Beth Israel Deaconess Medical Center researcher Vincent C. Smith. It was supported by the National Institutes of Health.

PUBLICATION – Advanced Functional Materials : Biocompatible Soft Fluidic Strain and Force Sensors for Wearable Devices
WYSS TECHNOLOGY – “Flexi-mitts”for tracking neurodevelopment in very low birth weight premature infants

Robots with sticky feet can climb up, down, and all around

By Lindsay Brownell

Jet engines can have up to 25,000 individual parts, making regular maintenance a tedious task that can take over a month per engine. Many components are located deep inside the engine and cannot be inspected without taking the machine apart, adding time and costs to maintenance. This problem is not only confined to jet engines, either; many complicated, expensive machines like construction equipment, generators, and scientific instruments require large investments of time and money to inspect and maintain.

HAMR-E uses electroadhesive pads on its feet and a special gait pattern to climb on vertical, inverted, and curved surfaces, like the inside of this jet engine. Credit: Wyss Institute at Harvard University

Researchers at Harvard University’s Wyss Institute for Biologically Inspired Engineering and John A. Paulson School of Engineering and Applied Sciences (SEAS) have created a micro-robot whose electroadhesive foot pads, origami ankle joints, and specially engineered walking gait allow it to climb on vertical and upside-down conductive surfaces, like the inside walls of a commercial jet engine. The work is reported in Science Robotics.

“Now that these robots can explore in three dimensions instead of just moving back and forth on a flat surface, there’s a whole new world that they can move around in and engage with,” said first author Sébastien de Rivaz, a former Research Fellow at the Wyss Institute and SEAS who now works at Apple. “They could one day enable non-invasive inspection of hard-to-reach areas of large machines, saving companies time and money and making those machines safer.”

The new robot, called HAMR-E (Harvard Ambulatory Micro-Robot with Electroadhesion), was developed in response to a challenge issued to the Harvard Microrobotics Lab by Rolls-Royce, which asked if it would be possible to design and build an army of micro-robots capable of climbing inside parts of its jet engines that are inaccessible to human workers. Existing climbing robots can tackle vertical surfaces, but experience problems when trying to climb upside-down, as they require a large amount of adhesive force to prevent them from falling.

The team based HAMR-E on one of its existing micro-robots, HAMR, whose four legs enable it to walk on flat surfaces and swim through water. While the basic design of HAMR-E is similar to HAMR, the scientists had to solve a series of challenges to get HAMR-E to successfully stick to and traverse the vertical, inverted, and curved surfaces that it would encounter in a jet engine.

First, they needed to create adhesive foot pads that would keep the robot attached to the surface even when upside-down, but also release to allow the robot to “walk” by lifting and placing its feet. The pads consist of a polyimide-insulated copper electrode, which enables the generation of electrostatic forces between the pads and the underlying conductive surface. The foot pads can be easily released and re-engaged by switching the electric field on and off, which operates at a voltage similar to that required to move the robot’s legs, thus requiring very little additional power. The electroadhesive foot pads can generate shear forces of 5.56 grams and normal forces of 6.20 grams – more than enough to keep the 1.48-gram robot from sliding down or falling off its climbing surface. In addition to providing high adhesive forces, the pads were designed to be able to flex, thus allowing the robot to climb on curved or uneven surfaces.

HAMR-E is small but mighty, and could one day carry instruments and cameras to inspect small spaces. Credit: Wyss Institute at Harvard University

The scientists also created new ankle joints for HAMR-E that can rotate in three dimensions to compensate for rotations of its legs as it walks, allowing it to maintain its orientation on its climbing surface. The joints were manufactured out of layered fiberglass and polyimide, and folded into an origami-like structure that allows the ankles of all the legs to rotate freely, and to passively align with the terrain as HAMR-E climbs.

Finally, the researchers created a special walking pattern for HAMR-E, as it needs to have three foot pads touching a vertical or inverted surface at all times to prevent it from falling or sliding off. One foot releases from the surface, swings forward, and reattaches while the remaining three feet stay attached to the surface. At the same time, a small amount of torque is applied by the foot diagonally across from the lifted foot to keep the robot from moving away from the climbing surface during the leg-swinging phase. This process is repeated for the three other legs to create a full walking cycle, and is synchronized with the pattern of electric field switching on each foot.

When HAMR-E was tested on vertical and inverted surfaces, it was able to achieve more than one hundred steps in a row without detaching. It walked at speeds comparable to other small climbing robots on inverted surfaces and slightly slower than other climbing robots on vertical surfaces, but was significantly faster than other robots on horizontal surfaces, making it a good candidate for exploring environments that have a variety of surfaces in different arrangements in space. It is also able to perform 180-degree turns on horizontal surfaces.

HAMR-E also successfully maneuvered around a curved, inverted section of a jet engine while staying attached, and its passive ankle joints and adhesive foot pads were able to accommodate the rough and uneven features of the engine surface simply by increasing the electroadhesion voltage.

This iteration of HAMR-E is the first and most convincing step towards showing that this approach to a centimeter-scale climbing robot is possible, and that such robots could in the future be used to explore any sort of infrastructure, including buildings, pipes, engines, generators, and more

ROBERT WOOD

The team is continuing to refine HAMR-E, and plans to incorporate sensors into its legs that can detect and compensate for detached foot pads, which will help prevent it from falling off of vertical or inverted surfaces. HAMR-E’s payload capacity is also greater than its own weight, opening the possibility of carrying a power supply and other electronics and sensors to inspect various environments. The team is also exploring options for using HAMR-E on non-conductive surfaces.

“This iteration of HAMR-E is the first and most convincing step towards showing that this approach to a centimeter-scale climbing robot is possible, and that such robots could in the future be used to explore any sort of infrastructure, including buildings, pipes, engines, generators, and more,” said corresponding author Robert Wood, Ph.D., who is a Founding Core Faculty member of the Wyss Institute as well as the Charles River Professor of Engineering and Applied Sciences at SEAS.

“While academic scientists are very good at coming up with fundamental questions to explore in the lab, sometimes collaborations with industrial scientists who understand real-world problems are required to develop innovative technologies that can be translated into useful products. We are excited to help catalyze these collaborations here at the Wyss Institute, and to see the breakthrough advances that emerge,” said Wyss Founding Director Donald Ingber, M.D., Ph.D., who is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and the Vascular Biology Program at Boston Children’s Hospital, and Professor of Bioengineering at SEAS.

This study is co-authored by Benjamin Goldberg, Ph.D., Neel Doshi, Kaushik Jayaram, Ph.D., and Jack Zhou from the Wyss Institute and Harvard SEAS.

Support for this research was contributed by the Wyss Institute for Biologically Inspired Engineering at Harvard University, Rolls-Royce, and the US Army Research Office.

Multi-joint, personalized soft exosuit breaks new ground

The multi-joint soft exosuit consists of textile apparel components worn at the waist, thighs and calves that guide mechanical forces from an optimized mobile actuation system attached to a rucksack via cables to the ankle and hip joints. In addition, a new tuning method helps personalize the exosuit’s effects to wearers’ specific gaits. Credit: Harvard Biodesign Lab

By Benjamin Boettner

In the future, smart textile-based soft robotic exosuits could be worn by soldiers, fire fighters and rescue workers to help them traverse difficult terrain and arrive fresh at their destinations so that they can perform their respective tasks more effectively. They could also become a powerful means to enhance mobility and quality of living for people suffering from neurodegenerative disorders and for the elderly.

Conor Walsh’s team at the Wyss Institute for Biologically Inspired Engineering at Harvard University and the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) has been at the forefront of developing different soft wearable robotic devices that support mobility by applying mechanical forces to critical joints of the body, including at the ankle or hip joints, or in the case of a multi-joint soft exosuit both. Because of its potential for relieving overburdened solders in the field, the Defense Advanced Research Projects Agency (DARPA) funded the team’s efforts as part of its former Warrior Web program.

While the researchers have demonstrated that lab-based versions of soft exosuits can provide clear benefits to wearers, allowing them to spend less energy while walking and running, there remains a need for fully wearable exosuits that are suitable for use in the real world.

Now, in a study reported in the proceedings of the 2018 IEEE International Conference on Robotics and Automation (ICRA), the team presented their latest generation of a mobile multi-joint exosuit, which has been improved on all fronts and tested in the field through long marches over uneven terrain. Using the same exosuit in a second study published in the Journal of NeuroEngineering and Rehabilitation (JNER), the researchers developed an automatic tuning method to customize its assistance based on how an individual’s body is responding to it, and demonstrated significant energy savings.

The multi-joint soft exosuit consists of textile apparel components worn at the waist, thighs, and calves. Through an optimized mobile actuation system worn near the waist and integrated into a military rucksack, mechanical forces are transmitted via cables that are guided through the exosuit’s soft components to ankle and hip joints. This way, the exosuit adds power to the ankles and hips to assist with leg movements during the walking cycle.

“We have updated all components in this new version of the multi-joint soft exosuit: the apparel is more user-friendly, easy to put on and accommodating to different body shapes; the actuation is more robust, lighter, quieter and smaller; and the control system allows us to apply forces to hips and ankles more robustly and consistently,” said David Perry, a co-author of the ICRA study and a Staff Engineer on Walsh’s team. As part of the DARPA program, the exosuit was field-tested in Aberdeen, MD, in collaboration with the Army Research Labs, where soldiers walked through a 12-mile cross-country course.

“We previously demonstrated that it is possible to use online optimization methods that by quantifying energy savings in the lab automatically individualize control parameters across different wearers. However, we needed a means to tune control parameters quickly and efficiently to the different gaits of soldiers at the Army outside a laboratory,” said Walsh, Ph.D., Core Faculty member of the Wyss Institute, the John L. Loeb Associate Professor of Engineering and Applied Sciences at SEAS, and Founder of the Harvard Biodesign Lab.

In the JNER study, the team presented a suitable new tuning method that uses exosuit sensors to optimize the positive power delivered at the ankle joints. When a wearer begins walking, the system measures the power and gradually adjusts controller parameters until it finds those that maximize the exosuit’s effects based on the wearer’s individual gait mechanics. The method can be used as a proxy measure for elaborate energy measurements.

“We evaluated the metabolic parameters in the seven study participants wearing exosuits that underwent the tuning process and found that the method reduced the metabolic cost of walking by about 14.8% compared to walking without the device and by about 22% compared to walking with the device unpowered,” said Sangjun Lee, the first author of both studies and a Graduate Student with Walsh at SEAS.

“These studies represent the exciting culmination of our DARPA-funded efforts. We are now continuing to optimize the technology for specific uses in the Army where dynamic movements are important; and we are exploring it for assisting workers in factories performing strenuous physical tasks,” said Walsh. “In addition, the field has recognized there is still a lot to understand on the basic science of co-adaptation of humans and wearable robots. Future co-optimization strategies and new training approaches could help further enhance individualization effects and enable wearers that initially respond poorly to exosuits to adapt to them as well and benefit from their assistance”.

“This research marks an important point in the Wyss Institute’s Bioinspired Soft Robotics Initiative and its development of soft exosuits in that it opens a path on which robotic devices could be adopted and personalized in real world scenarios by healthy and disabled wearers,” said Wyss Institute Founding Director Donald Ingber, M.D., Ph.D., who is also the Judah Folkman Professor of Vascular Biology at HMS and the Vascular Biology Program at Boston Children’s Hospital, and Professor of Bioengineering at SEAS.

Additional members of Walsh’s team were authors on either or both studies. Nikos Karavas, Ph.D., Brendan T. Quinlivan, Danielle Louise Ryan, Asa Eckert-Erdheim, Patrick Murphy, Taylor Greenberg Goldy, Nicolas Menard, Maria Athanassiu, Jinsoo Kim, Giuk Lee, Ph.D., and Ignacio Galiana, Ph.D., were authors on the ICRA study; and Jinsoo Kim, Lauren Baker, Andrew Long, Ph.D., Nikos Karavas, Ph.D., Nicolas Menard, and Ignacio Galiana, Ph.D., on the JNER study. The studies, in addition to DARPA’s Warrior Web program, were funded by Harvard’s Wyss Institute and SEAS.

A new spin for soft micro-actuators

Credit: Wyss Institute Harvard

By Benjamin Boettner

Manipulating delicate tissues such as blood vessels during difficult surgeries, or gripping fragile organisms in the deep sea presents a challenge to surgeons and researchers alike. Roboticists have made inroads into this problem by developing soft actuators on the microscale that are made of elastic materials and, through the expansion or contraction of embedded active components, can change their shapes to gently handle objects without damaging them. However, the specific designs and materials used for their fabrication so far still limit their range of motion and the strength they can exert at scales on which surgeons and researchers would like to use them.

“The fabrication of soft micro-actuators is currently facing two main limitations: the reinforcement layers that direct bending often increase the overall size of the device,” explained Nina Sinatra, a Graduate Student working with Wyss Institute Core Faculty members Robert Wood, Ph.D., and Kevin Kit Parker, Ph.D., at Harvard’s Wyss Institute for Biologically Inspired Engineering and the Harvard Paulson School of Engineering and Applied Sciences (SEAS). “Also, bending micro-actuators in different ways, such as with twisting motions, thus far required that the geometry of the actuator had to be re-designed.”

Now, researchers led by Wood and Parker at the Wyss Institute and SEAS, including Sinatra, have joined their forces to create a new type of soft micro-actuator that can be fabricated using simple shapes and geometries, to exhibit greater toughness and different bend or bend-twist motions. As reported in the Journal of Micromechanics and Microengineering, the team for the first time achieved this feat by combining two very different fabrication approaches and materials with complementary functions.

This video explains how two fabrication techniques, soft lithography and rotary jet spinning of nanofibers, are combined to create a new type of micro-actuator for the manipulation of small fragile objects in challenging environments. Credit: Wyss Institute at Harvard University

“At the start of the project, we hypothesized that we could extend the toughness and bending capabilities of soft micro-actuators simply by reinforcing them with a thin layer of a nanofiber network,” said Sinatra, the study’s first author.

To test this idea, the team first used soft lithography to fabricate the micro-actuator’s elastic component as a thin, elongated shape with a rectangular cross-section. The flexible polymer polydimethylsiloxane (PDMS) was used for this component because of its elastic and chemical properties and compatibility with many biomedical and industrial applications. Soft lithography is a layered fabrication technique that is widely deployed to create diverse micro-scale structures from soft elastomeric materials with the help of stamps, molds, or masks. Choosing to manufacture the micro-actuator layer-by-layer also allowed them to embed a hollow channel along one side, which, in the finished design, can be pressurized with air or liquid to trigger the micro-actuator’s motions.

For the micro-actuator’s nanofiber component, the team took advantage of a rotary jet spinning (RJS) technique previously developed by Parker’s group to create nanofibers from biological materials in an ongoing effort to manufacture regenerating heart valves for patients in need. In RJS, a rotating nozzle extrudes a solution of proteins or polymers that solidify as thin nanofibers; to fabricate nanofabrics for soft micro-actuators, the team used solutions of strong and stretchable synthetic polymers such as nylon and polyurethane. They collected the extruded nanofibers in aligned sheets and bonded laser-cut sections of the sheets to the side opposite of the channel in the soft PDMS component. As the channel is pressurized, the nanofabric will reinforce one side of the actuator and preferentially induce bending toward this direction. This step completed the final composite micro-actuator.

With one end of the actuator free and the other end fixed to a pressure source, the team found their original hypothesis confirmed: the composite soft micro-actuators were 2.3 times tougher than control micro-actuators made of PDMS alone and capable of withstanding pressures almost 26% higher. “By varying the nanofiber orientation and incising angled patterns into nanofiber sheets, we could program bend-twist motions into the soft micro-actuators, which widens our design space and the usability of these micro-devices significantly,” said Sinatra. The resulting micro-actuators are the slimmest soft pneumatic devices to achieve a more complex bending-twisting motion, which point to the potential for unprecedented delicate manipulation on the microscale.

“This new prototype of nanofiber-enforced soft micro-actuators is a compelling starting point for real-world applications that, interfacing this new actuator design with other tools, can facilitate micromanipulation of various fragile objects in challenging environments,” said Wood, who also is the Charles River Professor of Engineering and Applied Sciences at SEAS.

Robot transitions from soft to rigid

As the vacuum is applied to the flexible material, it becomes stiff and able to support the weight of the drone. Credit: Yashraj Narang

By Leah Burrows

Even octopuses understand the importance of elbows. When these squishy, loose-limbed cephalopods need to make a precise movement — such as guiding food into their mouth — the muscles in their tentacles contract to create a temporary revolute joint. These joints limit the wobbliness of the arm, enabling more controlled movements.

Now, researchers from the Wyss Institute for Biologically Inspired Engineering at Harvard University and the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have shown how a multi-layered structure can allow robots to mimic the octopus’ kinematics, creating and eliminating joints on command. The structure can also allow robots to rapidly change their stiffness, damping, and dynamics.

The research is published in two papers in Advanced Functional Materials and IEEE Robotics and Automation Letters.

“This research helps bridge the gap between soft robotics and traditional rigid robotics,” said Yashraj Narang, first author of both studies and graduate student at SEAS. “We believe that this class of technology may foster a new generation of machines and structures that cannot simply be classified as soft or rigid.”

When a vacuum is applied, the layers of flexible material becomes stiff and can hold arbitrary shapes, and be molded into additional forms. Credit: Yashraj Narang/Harvard SEAS

The structure is surprisingly simple, consisting of multiple layers of flexible material wrapped in a plastic envelope and connected to a vacuum source. When the vacuum is off, the structure behaves exactly as you would expect, bending, twisting and flopping without holding shape. But when a vacuum is applied, it becomes stiff and can hold arbitrary shapes, and it can be molded into additional forms.

This transition is the result of a phenomenon called laminar jamming, in which the application of pressure creates friction that strongly couples a group of flexible materials.

“The frictional forces generated by the pressure act like glue,” said Narang. “We can control the stiffness, damping, kinematics, and dynamics of the structure by changing the number of layers, tuning the pressure applied to it, and adjusting the spacing between multiple stacks of layers.”

The research team, which included Wyss Associate Faculty member Robert Howe, Ph.D., the Abbott and James Lawrence Professor of Engineering at SEAS; Joost Vlassak, Ph.D., the Abbott and James Lawrence Professor of Materials Engineering at SEAS; and Alperen Degirmenci, a SEAS graduate student, extensively modeled the mechanical behavior of laminar jamming to better control its capabilities.

Next, they built real-world devices using the structures, including a two-fingered gripper that, without a vacuum, could wrap around and hold onto large objects and, with a vacuum, could pinch and hold onto small objects about the size of a marble.

The researchers also demonstrated the structure’s capabilities as shock absorbers by attaching them to a drone as a landing gear. The team tuned the stiffness and damping of the structures to absorb the impact of landing.

The structure is a proof-of-concept that could have many applications in the future, from surgical robots to wearable devices and flexible speakers.

“Our work has explained the phenomenon of laminar jamming and shown how it can provide robots with highly versatile mechanical behavior,” said Howe, who is the senior author of the paper. “We believe that this technology will eventually lead to robots that can change state between soft, continuous devices that can safely interact with humans, and rigid, discrete devices that can meet the demands of industrial automation.”

 This research was supported in part by the National Science Foundation.

Personalizing wearable devices

A Bayesian optimization method that integrates the metabolic costs in wearers of this hip-assisting exosuit enabled the individualized fine-tuning of assistive forces. Credit: Ye Ding/Harvard University
By Leah Burrows

When it comes to soft, assistive devices — like the exosuit being designed by the Harvard Biodesign Lab — the wearer and the robot need to be in sync. But every human moves a bit differently and tailoring the robot’s parameters for an individual user is a time-consuming and inefficient process.

Now, researchers from the Wyss Institute for Biologically Inspired Engineering and the Harvard John A. Paulson School of Engineering and Applied and Sciences (SEAS) have developed an efficient machine learning algorithm that can quickly tailor personalized control strategies for soft, wearable exosuits.

The research is described in Science Robotics.

“This new method is an effective and fast way to optimize control parameter settings for assistive wearable devices,” said Ye Ding, a Postdoctoral Fellow at SEAS and co-first author of the research. “Using this method, we achieved a huge improvement in metabolic performance for the wearers of a hip extension assistive device.”

When humans walk, we constantly tweak how we move to save energy (also known as metabolic cost).

“Before, if you had three different users walking with assistive devices, you would need three different assistance strategies,” said Myunghee Kim, Ph.D., postdoctoral research fellow at SEAS and co-first author of the paper. “Finding the right control parameters for each wearer used to be a difficult, step-by-step process because not only do all humans walk a little differently but the experiments required to manually tune parameters are complicated and time consuming.”

The researchers, led by Conor Walsh, Ph.D., Core Faculty member at the Wyss Institute and the John L. Loeb Associate Professor of Engineering and Applied Sciences, and Scott Kuindersma, Ph.D., Assistant Professor of Engineering and Computer Science at SEAS, developed an algorithm that can cut through that variability and rapidly identify the best control parameters that work best  for minimizing the energy used for walking.

The researchers used so-called human-in-the-loop optimization, which uses real-time measurements of human physiological signals, such as breathing rate, to adjust the control parameters of the device. As the algorithm honed in on the best parameters, it directed the exosuit on when and where to deliver its assistive force to improve hip extension. The Bayesian Optimization approach used by the team was first report in a paper last year in PLOS ONE.

The combination of the algorithm and suit reduced metabolic cost by 17.4 percent compared to walking without the device. This was a more than 60 percent improvement compared to the team’s previous work.

“Optimization and learning algorithms will have a big impact on future wearable robotic devices designed to assist a range of behaviors,” said Kuindersma. “These results show that optimizing even very simple controllers can provide a significant, individualized benefit to users while walking. Extending these ideas to consider more expressive control strategies and people with diverse needs and abilities will be an exciting next step.” 

“With wearable robots like soft exosuits, it is critical that the right assistance is delivered at the right time so that they can work synergistically with the wearer,” said Walsh. “With these online optimization algorithms, systems can learn how do achieve this automatically in about twenty minutes, thus maximizing benefit to the wearer.”

Next, the team aims to apply the optimization to a more complex device that assists multiple joints, such as hip and ankle, at the same time.

“In this paper, we demonstrated a high reduction in metabolic cost by just optimizing hip extension,” said Ding. “This goes to show what you can do with a great brain and great hardware.”

This research was supported by the Defense Advanced Research Projects Agency, Warrior Web Program, Harvard’s Wyss Institute for Biologically Inspired Engineering, and the Harvard John A. Paulson School of Engineering and Applied Science.

Soft robots that can sense touch, pressure, movement and temperature

This soft robotic gripper is the result of a platform technology developed by Harvard researchers to create soft robots with embedded sensors that can sense inputs as diverse as movement, pressure, touch, and temperature. Credit: Ryan L. Truby/Harvard University

By Leah Burrows

Researchers at Harvard University have built soft robots inspired by nature that can crawl, swim, grasp delicate objects and even assist a beating heart, but none of these devices has been able to sense and respond to the world around them.

That’s about to change.

Inspired by our bodies’ sensory capabilities, researchers at the Wyss Institute for Biologically Inspired Engineering and the Harvard John A. Paulson School of Engineering and Applied Sciences have developed a platform for creating soft robots with embedded sensors that can sense movement, pressure, touch, and even temperature.

The research is published in Advanced Materials.

“Our research represents a foundational advance in soft robotics,” said Ryan Truby, first author of the paper and recent Ph.D. graduate at SEAS. “Our manufacturing platform enables complex sensing motifs to be easily integrated into soft robotic systems.”

Integrating sensors within soft robots has been difficult in part because most sensors, such as those used in traditional electronics, are rigid.  To address this challenge, the researchers developed an organic ionic liquid-based conductive ink that can be 3D printed within the soft elastomer matrices that comprise most soft robots.

“To date, most integrated sensor/actuator systems used in soft robotics have been quite rudimentary,” said Michael Wehner, former Postdoctoral Fellow at SEAS and co-author of the paper. “By directly printing ionic liquid sensors within these soft systems, we open new avenues to device design and fabrication that will ultimately allow true closed loop control of soft robots.”

Wehner is now an Assistant Professor at the University of California, Santa Cruz.

To fabricate the device, the researchers relied on an established 3D printing technique developed in the lab of Jennifer Lewis, Sc.D., Core Faculty Member of the Wyss Institute and the Hansjörg Wyss Professor of Biologically Inspired Engineering at SEAS. The technique — known as embedded 3D printing — seamlessly and quickly integrates multiple features and materials within a single soft body.

“This work represents the latest example of the enabling capabilities afforded by embedded 3D printing – a technique pioneered by our lab,” said Lewis.

“The function and design flexibility of this method is unparalleled,” said Truby. “This new ink combined with our embedded 3D printing process allows us to combine both soft sensing and actuation in one integrated soft robotic system.”

To test the sensors, the team printed a soft robotic gripper comprised of three soft fingers or actuators. The researchers tested the gripper’s ability to sense inflation pressure, curvature, contact, and temperature. They embedded multiple contact sensors, so the gripper could sense light and deep touches.

“Soft robotics are typically limited by conventional molding techniques that constrain geometry choices, or, in the case of commercial 3D printing, material selection that hampers design choices,” said Robert Wood, Ph.D., Core Faculty Member of the Wyss Institute and the Charles River Professor of Engineering and Applied Sciences at SEAS, and co-author of the paper.  “The techniques developed in the Lewis Lab have the opportunity to revolutionize how robots are created — moving away from sequential processes and creating complex and monolithic robots with embedded sensors and actuators.”

Next, the researchers hope to harness the power of machine learning to train these devices to grasp objects of varying size, shape, surface texture, and temperature.

The research was coauthored by Abigail Grosskopf, Daniel Vogt and Sebastien Uzel. It was supported it part by through Harvard MRSEC and Harvard’s Wyss Institute for Biologically Inspired Engineering.

Snake-inspired robot uses kirigami to move

This soft robot is made using kirigami — an ancient Japanese paper craft that relies on cuts, rather than origami folds, to change the properties of a material. As the robot stretches, the kirigami is transformed into a 3D-textured surface. Credit: Ahmad Rafsanjani/Harvard SEAS

By Leah Burrows

Who needs legs? With their sleek bodies, snakes can slither up to 14 miles-per-hour, squeeze into tight spaces, scale trees, and swim. How do they do it? It’s all in the scales. As a snake moves, its scales grip the ground and propel the body forward — similar to how crampons help hikers establish footholds in slippery ice. This so-called “friction-assisted locomotion” is possible because of the shape and positioning of snake’s scales.

Now, a team of researchers from the Wyss Institute at Harvard University and the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) has developed a soft robot that uses those same principles of locomotion to crawl without any rigid components. The soft robotic scales are made using kirigami — an ancient Japanese paper craft that relies on cuts, rather than origami folds, to change the properties of a material.  As the robot stretches, the flat kirigami surface is transformed into a 3D-textured surface, which grips the ground just like snake skin.

The research is published in Science Robotics.

“There has been a lot of research in recent years into how to fabricate these kinds of morphable, stretchable structures,” said Ahmad Rafsanjani, Ph.D., a postdoctoral fellow at SEAS and first author of the paper. “We have shown that kirigami principles can be integrated into soft robots to achieve locomotion in a way that is simpler, faster, and cheaper than most previous techniques.”

The researchers started with a simple, flat plastic sheet. Using a laser cutter, they embedded an array of centimeter-scale cuts, experimenting with different shapes and sizes. Once the sheet was cut, the researchers wrapped it around a tube-like elastomer actuator, which expands and contracts with air like a balloon.

When the actuator expands, the kirigami cuts pop out, forming a rough surface that grips the ground. When the actuator deflates, the cuts fold flat, propelling the crawler forward.

Wyss and Harvard researchers have built a fully untethered, soft robot, with integrated on-board control, sensing, actuation and power supply packed into a tiny tail. Credit: Ahmad Rafsanjani/Harvard SEAS

The researchers built a fully untethered robot, with its integrated on-board control, sensing, actuation, and power supply all packed into a tiny tail. They tested it crawling throughout Harvard’s campus.

The team experimented with various-shaped cuts, including triangular, circular, and trapezoidal. They found that trapezoidal cuts — which most closely resemble the shape of snake scales —gave the robot a longer stride.

“We show that the locomotive properties of these kirigami-skins can be harnessed by properly balancing the cut geometry and the actuation protocol,” said Rafsanjani. “Moving forward, these components can be further optimized to improve the response of the system.”

“We believe that our kirigami-based strategy opens avenues for the design of a new class of soft crawlers,” said the paper’s senior author Katia Bertoldi, Ph.D., an Associate Faculty member of the Wyss Institute and the William and Ami Kuan Danoff Professor of Applied Mechanics at SEAS. “These all-terrain soft robots could one day travel across difficult environments for exploration, inspection, monitoring, and search and rescue missions, or perform complex, laparoscopic medical procedures.”

This research was co-authored by Yuerou Zhang; Bangyuan Liu, a visiting student in the Bertoldi lab; and Shmuel M. Rubinstein, Ph.D., Associate Professor of Applied Physics at SEAS. It was supported by the National Science Foundation.

The millimeter-scale robot opens new avenues for microsurgery, microassembly and micromanipulation

Completely unfolded, the milliDelta with 15 mm-by-15 mm-20 mm roughly compares to a cent piece, and uses piezoelectric actuators, and flexural joints in its three arms to control high-frequency movements of a stage on top. Credit: Wyss Institute at Harvard University

By Benjamin Boettner

Because of their high precision and speed, Delta robots are deployed in many industrial processes, including pick-and-place assemblies, machining, welding and food packaging. Starting with the first version developed by Reymond Clavel for a chocolate factory to quickly place chocolate pralines in their packages, Delta robots use three individually controlled and lightweight arms that guide a platform to move fast and accurately in three directions. The platform is either used as a stage, similar to the ones being used in flight simulators, or coupled to a manipulating device that can, for example, grasp, move, and release objects in prescribed patterns. Over time, roboticists have designed smaller and smaller Delta robots for tasks in limited workspaces, yet shrinking them further to the millimeter scale with conventional manufacturing techniques and components has proven fruitless.

Reported in Science Robotics, a new design, the milliDelta robot, developed by Robert Wood’s team at Harvard’s Wyss Institute for Biologically Inspired Engineering and John A. Paulson School of Engineering and Applied Sciences (SEAS) overcomes this miniaturization challenge. By integrating their microfabrication technique with high-performance composite materials that can incorporate flexural joints and bending actuators, the milliDelta can operate with high speed, force, and micrometer precision, which make it compatible with a range of micromanipulation tasks in manufacturing and medicine.

In 2011, inspired by pop-up books and origami, Wood’s team developed a micro-fabrication approach that enables the assembly of robots from flat sheets of composite materials. Pop-up MEMS (short for “microelectromechanical systems”) manufacturing has since been used for the construction of dynamic centimeter-scale machines that can simply walk away, or, as in the case of the RoboBee, can fly. In their new study, the researchers applied their approach to develop a Delta robot measuring a mere 15 mm-by-15 mm-by-20 mm.

“The physics of scaling told us that bringing down the size of Delta robots would increase their speed and acceleration, and pop-up MEMS manufacturing with its ability to use any material or combination of materials seemed an ideal way to attack this problem,” said Wood, who is a Core Faculty member at the Wyss Institute and co-leader of its Bioinspired Robotics platform. Wood is also the Charles River Professor of Engineering and Applied Sciences at SEAS. “This approach also allowed us to rapidly go through a number of iterations that led us to the final milliDelta.”

The milliDelta design incorporates a composite laminate structure with embedded flexural joints that approximate the more complicated joints found in large scale Delta robots. “With the help of an assembly jig, this laminate can be precisely folded into a millimeter-scale Delta robot. The milliDelta also utilizes piezoelectric actuators, which allow it to perform movements at frequencies 15 to 20 times higher than those of other currently available Delta robots,” said first-author Hayley McClintock, a Wyss Institute Staff Researcher on Wood’s team.

In addition, the team demonstrated that the milliDelta can operate in a workspace of about seven cubic millimeters and that it can apply forces and exhibit trajectories that, together with its high frequencies, could make it ideal for micromanipulations in industrial pick-and-place processes and microscopic surgeries such as retinal microsurgeries performed on the human eye.

The work by Wood’s team demonstrating the enhanced speed and control of their milliDelta robot at the millimeter scale opens entirely new avenues of development for industrial and medical robots, which are currently beyond the reach of existing technologies. Donald Ingber

Putting the milliDelta’s potential for microsurgeries and other micromanipulations to a first test, the researchers explored their robot as a hand tremor-cancelling device. “We first mapped the paths that the tip of a toothpick circumscribed when held by an individual, computed those, and fed them into the milliDelta robot, which was able to match and cancel them out,” said co-first author Fatma Zeynep Temel, Ph.D., a SEAS Postdoctoral Fellow in Wood’s team. The researchers think that specialized milliDelta robots could either be added on to existing robotic devices, or be developed as standalone devices like, for example, platforms for the manipulation of cells in research and clinical laboratories.

“The work by Wood’s team demonstrating the enhanced speed and control of their milliDelta robot at the millimeter scale opens entirely new avenues of development for industrial and medical robots, which are currently beyond the reach of existing technologies. It’s yet another example of how our Bioinspired Robotics platform is leading the way into the future,” said Wyss Institute Founding Director Donald Ingber, M.D., Ph.D., who is also the Judah Folkman Professor of Vascular Biology at HMS and the Vascular Biology Program at Boston Children’s Hospital, as well as Professor of Bioengineering at SEAS.

Other authors on the study are Neel Doshi, a SEAS Graduate Student, and Je-sung Koh, Ph.D., a former Postdoctoral Fellow on Wood’s Wyss Institute/SEAS team and now Assistant Professor at Ajou University in Korea. The work was funded by Harvard’s Wyss Institute for Biologically Inspired Engineering and a National Defense Science and Engineering Graduate Fellowship.

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