The Seinfeld idiom, “worlds are colliding,” is probably the best description of work in the age of Corona. Pre-pandemic, it was easy to departmentalize one’s professional life from one’s home existence. Clearly, my dishpan hands have hindered my writing schedule. Thank goodness for the robots in my life, scrubbing and vacuuming my floors; if only they could power themselves with the crumbs they suck up.
The World Bank estimates that 3.5 million tons of solid waste is produced by humans everyday, with America accounting for more than 250 million tons a year or over 4 pounds of trash per citizen. This figure does not include the 34 billion gallons of human organic materials that is processed in water treatment centers across the country each year. To the fictional Dr. Emmett Brown, this garbage is akin to “black gold” – ecologically powering cities, cars, and machines. In reality, the movie, “Back to The Future II” was inspired by the biomass gasification movement of 20th century in powering cars with wood during World War II when petroleum was scarce. The technology has advanced so much that a few years ago the GENeco water treatment plant in the United Kingdom built a biomethane gas bus that relied solely on sewage. In reflecting on the importance of the technology, Collin Field of Bath Bus Company declared, “We will never, ever, ever, while we are on this planet, run out of human waste.”
Less than twenty miles away from the GENco plant, Professor Loannis Leropoulos of the University of Bristol’s Robotics Laboratory is working on the next generation of bio-engineered fuel cells. Last week, Dr. Leropoulos demonstrated his revolutionary Microbial Fuel Cells (MFCs) for me. As witnessed, he is not just inspired by nature, but harnessing its beauty to power the next generation of robots. The MFCs mimic an animal’s stomach with microbes breaking down food to create adenosine triphosphate (ATP). The Bristol lab began building MFCs to power its suite of EcoBots. “I started this journey about twenty years ago with the main purpose of building sustainable autonomous robots for remote area access,” reflects Leropoulos. He was inspired by Dr. Stuart Wilkinson’s Gastrobot in the early 2000s that first promoted the idea of “an intelligent machine that digests real food for energy.” At the time the media hyped Wilkinson’s invention as a flesh-eating robot, when in reality it digested sugar cubes, turning the carbohydrates into electrical energy. Unfortunately, the Gastrobot’s clumsy oversized form factor suffered from long charging times with an 18-hour “carbo-loading” process for every 15 minutes of power.
Springboarding off of Wilkinson’s concept, Leropoulos’ team started with the idea of using MFC to power machines by putting the microbes directly inside the unit to more efficiently produce energy from any sugar-based substance, even waste (e.g., urine, feces, and trash). The Professor described the elegance of his technology that creates a “uniform colonization” of microbes multiplying every 8 minutes with parent lifecycles succeeded by daughter cells in a continuous pattern of ‘feed-growth-energy’. He compares it to the human microflora process of breaking down fresh food in the digestive system that results in healthy bathroom visits, “the same is with Microbial Fuel Cells as long as we continue feeding them, the MFCs will continue to generate electricity.” The Bristol professor boasts that batteries are better performing than anything on the market as biological lifeforms have no denigration since “the progeny keep refreshing the community or electrodes so we have stable levels of power.” By contrast, the most popular non-fossil fuel available, lithium, degrades over time and leads to destructive mining practices in scarring the Earth in search of declining ore resources with the explosion of mobile phones, portable devices, and electric vehicles.
While MFCs are still in their infancy, Leropoulos shared with me his plan for commercializing the invention. His lab recently announced the success of its MFCs prototypes in powering mobile phones, smart watches, and other devices (including the EcoBots). In addition, Leropoulos has pushed his team to miniaturize the size of his batteries from its 6″ prototype to smaller than a AA, while at the same time rivaling the performance of alkaline. Backed by the Gates foundation, he has also reduced the production costs from $18 to $1 a unit, this is before achieving the economies of scale with mass production. Today, his business plan has expanded beyond just autonomous robots to power smart homes, by connecting multiple MFCs to a house’s sanitation and waste systems. “Our research is all about optimizing miniaturization and stacking them with minimum losses so we can end up with a car battery-like shape and size that gives us the amount of power we require,” explains the professor. When I questioned Leropoulos about using MFCs in the future of autonomous fleets, and even to offset the high energy demands of something like bitcoin mining, he remarked, “It would be naive of me to say a straight yes, but this is of course the work we are doing. I strongly believe with the development of new materials that will help with the energy density. We are at a stage where we have done some groundbreaking research using 3D printed electric materials as a low cost scalable technology. There is a lot to say about the functionalization of the electrodes that enables colonization from the microbes in making sure all the progeny cells colonize and the ceramic separators that allows for target ion transfer that makes the whole operation smarter and more efficient.” In thinking more about his work, he declared, “We have yet to see the full potential of Microbial Fuel Cells. I do think one day we will have a ‘Back to the Future’ scenario, feeding your food scraps to your car,”
Pressing Leropoulos on how he envisions robot-charging stations working in a factory or home in the near future, he illustrated it best, “with a Roomba example its actually picking of food scraps in the kitchen that would be a very nutritious source of fuel for the Microbial Fuel Cell, but that’s a few steps down the line.” He continued, “a straightforward application for something like a Roomba is to leave the charging station where it is and connect it to the toilet or kitchen sink. The fuel cycle would be continuous as the robot would not be drawing energy from the house, but the wastewater.” Processing the impact of his vision, it took me back to the early days of the global pandemic shutdown with animals returning to ancient grazing areas and pollution clouds clearing over heavily populated areas with many seeing for the first time distant mountains and blue skies. Innovations like MFCs are part of a new wave of mechatronic environmentally-focused solutions. Before parting, I asked Leropoulos how hopeful is he about the environment, “I do feel optimistic, I have more faith in the the younger generation that they will do things better. The shock we sustained as a society [this past year] is a lesson in seeing the true color of our natural world, if we learn from this then I think the future is a good one.”
By Anthony King
Doctors know that we need smarter medicines to target the bad guys only. One hope is that tiny robots on the scale of a billionth of a metre can come to the rescue, delivering drugs directly to rogue cancer cells. To make these nanorobots, researchers in Europe are turning to the basic building blocks of life – DNA.
Today robots come in all shapes and sizes. One of the strongest industrial robots can lift cars weighing over two tons. But materials such as silicon are not so suitable at the smallest scales.
While you can make really small patterns in solid silicon, you can’t really make it into mechanical devices below 100 nanometres, says Professor Kurt Gothelf, chemist and DNA nanotechnologist at Aarhus University in Denmark. That’s where DNA comes in. ‘The diameter of the DNA helix is only two nanometres,’ says Prof. Gothelf. A red blood cell is about 6,000 nanometres across.
Lego
Dr Tania Patiño, a nanotechnologist at the University of Rome in Italy, says DNA is like Lego. ‘You have these tiny building blocks and you can put them together to create any shape you want,’ she explained. To continue the analogy, DNA comes in four different coloured blocks and two of the colours pair up opposite one another. This makes them predictable.
Once you string a line of DNA blocks together, another line will pair up opposite. Scientists have learnt how to string DNA together in such a way that they introduce splits and bends. ‘By clever design, you branch out DNA strands so that you now have three dimensions,’ said Prof Gothelf. ‘It is very easy to predict how it folds.’
Dr Patiño is developing self-propelled DNA nanorobotics in her project, DNA-Bots. ‘DNA is highly tuneable,’ she said. ‘We can have software that shows us which sequences produce which shape. This is not possible with other materials at this tiny scale.’
While DNA nanorobots are a long way from being used in people, with Prof. Gothelf saying that ‘we won’t see any medicines based on this in the next ten years,’ progress is being made in the lab. Already scientists can obtain a string of DNA from a virus, and then design using software shorter stretches of DNA to pair with and bend the string into a desired shape. ‘This amazing technique is called DNA origami,’ said Prof. Gothelf. It allows scientists to create 3D bots made from DNA.
In an early breakthrough, Prof. Gothelf’s research lab made a DNA box with a lid that opened. Later, another group built a barrel-shaped robot that could open when it recognised cancer proteins, and release antibody fragments. This strategy is being pursued so that one day a DNA robot might approach a tumour, bind to it and release its killer cargo.
‘With nanorobots we could have more specific delivery to a tumour,’ said Dr Patiño. ‘We don’t want our drugs to be delivered to the whole body.’ She is in the lab of Professor Francesco Ricci, which works on DNA devices for the detection of antibodies and delivery of drugs.
Meanwhile, the network Prof. Gothelf heads up, DNA-Robotics, is training young scientists to make parts for DNA robotics that can perform certain actions. Prof. Gothelf is working on a ‘bolt and cable’ that resembles a handbrake on a bike, where force in one place makes a change in another part of the DNA robot. A critical idea in the network is to ‘plug and play,’ meaning that any parts built will be compatible in a future robot.
This has the potential to make a completely new generation of drugs.
Prof. Kurt Gothelf, Aarhus University, Denmark
Bloodstream
As well as carrying out specific functions, most robots can move. DNA robots are too miniscule to swim against our bloodstream, but it is still possible to engineer into them useful little engines using enzymes.
Dr Patiño previously developed a DNA nanoswitch that could sense the acidity of its environment. Her DNA device also worked as a self-propelling micromotor thanks to an enzyme that reacted with common urease molecules found in our bodies and acted as a power source. ‘The chemical reaction can produce sufficient energy to generate movement,’ said Dr Patiño.
Movement is important to get nanorobots to where they need to be. ‘We could inject these robots in the bladder and they harvest the chemical energy using urease and move,’ said Dr Patiño. In future such movement ‘will help them to treat a tumour or a disease site with more efficiency that passive nanoparticles, which cannot move.’ Recently, Patiño and others reported that nanoparticles fitted with nanomotors spread out more evenly than immobile particles when injected into the bladder of mice.
Rather than swim through blood, nanobots might be able to pass through barriers in our body. Most problems delivering drugs are due to these biological barriers, such as mucosal layers, notes Dr Patiño. The barriers are there to impede germs, but often block drugs. Dr Patiño’s self-propelled DNA robots might change these barriers’ permeability or simply motor on through them.
Stability
Nanoparticles can be expelled from a patient’s bladder, but this option isn’t as easy elsewhere in the body, where biodegradable robots that self-destruct might be necessary. DNA is an ideal material, as it is easily broken down inside of us. But this can also be a downside, as the body might quickly chew up a DNA bot before it gets the job done. Scientists are working on coating or camouflaging DNA and strengthening chemical bonds to boost stability.
One other potential downside is that naked pieces of DNA can be viewed by the immune system as signs of bacterial or viral foes. This may trigger an inflammatory reaction. As yet, no DNA nanobot has ever been injected into a person. Nonetheless, Prof. Gothelf is confident that scientists can get around these problems.
Indeed, stability and immune reaction were obstacles that the developers of mRNA vaccines – which deliver genetic instructions into the body inside a nanoparticle – had to get over. ‘The Moderna and the Pfizer (BioNTech) vaccines (for Covid-19) have a modified oligonucleotide strand that is formulated in a nano-vesicle, so it is close to being a small nanorobot,’ said Prof. Gothelf. He foresees a future where DNA nanorobots deliver drugs to exactly where needed. For example, a drug could be attached to a DNA robot with a special linker that gets cut by an enzyme that is only found inside certain cells, thus ensuring that drug is set free at a precise location.
But DNA robotics is not just for nanomedicine. Prof. Gothelf is mixing organic chemistry with DNA nanobots to transmit light along a wire that is just one molecule in width. This could further miniaturise electronics. DNA bots could assist manufacturing at the smallest scales, because they can place molecules at mind bogglingly tiny but precise distances from one another.
For now though, DNA robotics for medicine is what most scientists dream about. ‘You could make structures that are much more intelligent and much more specific than what is possible today,’ said Prof. Gothelf. ‘This has the potential to make a completely new generation of drugs.’
The research in this article was funded by the EU. If you liked this article, please consider sharing it on social media.
This post Foldable, organic and easily broken down: Why DNA is the material of choice for nanorobots was originally published on Horizon: the EU Research & Innovation magazine | European Commission.