The microscopic robots measure just 5 microns thick, 40 microns wide and 40 to 70 microns long, which are too small to be seen by the naked eye. (Image Credit: Criss Hohmann)
Researchers at Penn Engineering and Cornell University have developed an army of microscopic robots that are powered by lasers and could potentially walk inside a human body. The researchers hope these machines can be built into more complex systems, allowing them to be controlled by computer chips. These robots could improve the future of medicine. The team published their findings in the journal Nature on August 26th, 2020.
Measuring 5 microns thick, 40 microns wide, and 40 to 70 microns long, the robots are too tiny to be seen by the naked eye. They leverage new actuators. Each robot is comprised of a circuit made from silicon photovoltaics that serves as the brain and torso and four electrochemical actuators (0.1mm in size), which are used for the legs.
The platinum strips on the microscopic robots function as legs, allowing the microscopic robots to move forward when a laser is toggled onto the different photovoltaics. (Image Credit: Penn Engineering)
The researchers constructed the robots using lithography techniques to etch the brain and torso onto silicon. The legs, which contain platinum strips, are then added via atomic layer deposition. Rigid panels are placed on top of the strips since the platinum curls up due to applied voltage. These panels act as joints for the legs, determining how the strips bend when actuated.
Controlling the robot's movement is done by beaming laser pulses on different photovoltaics, which causes their legs to become activated. Switching the laser back and forth causes the robot to walk. These robots are designed to operate in all types of environments, including high temperatures and extreme acidity. They can also be injected through hypodermic needles, allowing it to investigate the inside of an animal's or a human body.
Scientists behind this study believe these robots are the first to be produced that are smaller than 0.1mm that can be controlled via onboard electronics. Even more impressive is that robots can be mass-produced. The researchers created over one million of the robots on a 4-inch piece of silicon.
The robots are capable of walking at a top speed of 30 microns per second, which is still pretty slow. However, the team believes their gaits can be optimized to imitate the motion of biological microorganisms, making them move more efficiently.
"While these robots are primitive in their function — they're not very fast, they don't have a lot of computational capability — every single one of the innovations that we made in creating them blows open the door to making these things smart, fast and mass-producible," says Itai Cohen, professor of physics. "This is really just the first shot across the bow that, hey, we can do electronic integration on a tiny robot."
There are still some limitations with these robots. For example, they can't sense the environment around them, have to be controlled from an external source, and they are slower than other tiny robots. The researchers also say they can improve the microscopic robots by adding more capabilities. In such circumstances, they can be used for biological applications, such as sitting on leaves to fight agricultural pests or sitting in the bloodstream to detect infections or cancer.
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