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Spotted: A Cornell research team led by Mingming Wu has created cell-sized robots inspired by the way that bacteria and sperm move. One limiting factor in the creation of very small robots is a power source. To solve this problem, the team found a way to use high-frequency sound waves as an energy source. 

The team used a laser lithography system called a NanoScribe, which creates 3D nanostructures on a photosensitive resin. This resin also happens to be hydrophobic. After several months of experimentation, the team created a micro-robot with a pair of precisely placed cavities etched on it, each one with a different diameter. 

When submerged, a tiny air bubble is trapped in each cavity. These air bubbles can be made to oscillate using an ultrasound transducer. As the air bubbles move, vortices are created in the liquid, and these propel the robot. Because the cavities have differently-sized openings, the researchers can control which direction the robot moves by exciting one bubble more than the other. 

Wu explains how another challenge is to use the right number of bots, explaining that “you could have a group of micro-robotic swimmers, and if one failed during the journey, that’s not a problem. That’s how nature survives. In a way, it’s a more robust system. Smaller does not mean weaker. A group of them is undefeatable. I feel like these nature-inspired tools typically are more sustainable, because nature has proved it works.” 

The Cornell micro-robot is the first we have seen to use bubbles and ultra-sound for propulsion, but it is not the first micro-robot that we have seen at Springwise. This is not surprising, given their promise for drug delivery. So far, we have seen a micro-robot that can be directed by magnets and a micro-robot that uses electro-adhesion to climb walls. 

Written By: Lisa Magloff

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