5/16/2023 0 Comments Smaller particles![]() ![]() The researchers also showed that they could use the rhythmic beating of these particles to generate an oscillating electric current. Using this approach, the researchers found they could create oscillators containing up to at least 11 particles.ĭepending on the number of particles, this oscillator beats at a frequency of about 0.1 to 0.3 hertz, which is on the order of the low-frequency oscillators that govern biological functions such as walking and the beating of the heart. This allows this particle to move to the center of the group, where it coordinates the oscillations of all of the other particles. This leader particle is the same size as the other particles but has a slightly larger platinum patch, which enables it to create a larger oxygen bubble. However, if they added one particle that was slightly different from the others, that particle could act as a “leader” that reorganized the other particles back into a rhythmic oscillator. The researchers found that two particles could make a very reliable oscillator, but as more particles were added, the rhythm would get thrown off. “One particle by itself stays still and doesn’t do anything interesting, but through teamwork, they can do something pretty amazing and useful, which is actually a difficult thing to achieve at the microscale,” Yang says. Then, they begin forming new bubbles, and the cycle repeats over and over. Each particle produces its own tiny bubble of oxygen, and when two particles come close enough that their bubbles interact, the bubbles pop, propelling the particles away from each other. At this liquid-air interface, they interact with any other particles found there. When the particles are placed at the surface of a droplet of hydrogen peroxide on a flat surface, they tend to travel to the top of the droplet. The discs, made from a polymer called SU-8, have a platinum patch that can catalyze the breakdown of hydrogen peroxide into water and oxygen. The simple particles that the researchers designed for this study are discs as small as 100 microns in diameter. Until now, building low-frequency micro-oscillators has required sophisticated electronics that are expensive and difficult to design, or specialized materials with complex chemistries. In this study, the researchers wanted to design particles that could generate rhythmic movements, or oscillations, with a very low frequency. ![]() “Physicists and engineers like myself want to understand these rules because it means we can make tiny things that collectively do complex tasks.” They can forage for food and build these elaborate tunnel structures,” Strano says. “Ants have minuscule brains and they do very simple cognitive tasks, but collectively they can do amazing things. Along with Yang, Thomas Berrueta, a Northwestern University graduate student advised by Professor Todd Murphey, is a lead author of the study.ĭemonstrations of emergent behavior can be seen throughout the natural world, where colonies of insects such as ants and bees accomplish feats that a single member of the group would never be able to achieve. Strano is the senior author of the new paper, which appears today in Nature Communications. Dubbs Professor of Chemical Engineering at MIT. “We're trying to look for very simple rules or features that you can encode into relatively simple microrobotic machines, to get them to collectively do very sophisticated tasks,” says Michael Strano, the Carbon P. Under the right conditions, these interactions create an oscillator that behaves similar to a ticking clock, beating at intervals of a few seconds. ![]() The particles used to create the new oscillator perform a simple chemical reaction that allows the particles to interact with each other through the formation and bursting of tiny gas bubbles. There are a lot of electrical components that require such an oscillatory input,” says Jingfan Yang, a recent MIT PhD recipient and one of the lead authors of the new study. “In addition to being interesting from a physics point of view, this behavior can also be translated into an on-board oscillatory electrical signal, which can be very powerful in microrobotic autonomy. These oscillations can then be harnessed to power tiny robotic devices, the researchers showed. Working together, the microparticles can generate a beating clock that oscillates at a very low frequency. Taking advantage of a phenomenon known as emergent behavior in the microscale, MIT engineers have designed simple microparticles that can collectively generate complex behavior, much the same way that a colony of ants can dig tunnels or collect food. ![]()
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