The prototype piezoelectric robots respond to different vibration frequencies depending on their configurations, allowing researchers to control individual bots by adjusting the vibration. The 'micro-bristle bot' is roughly 2mm long, 1.8mm wide and 0.8 millimeters thick, and weighs about 5mg. It can cover four times their own length in under a second.
"We are working to make the technology robust, and we have a lot of potential applications in mind," said Azadeh Ansari, an assistant professor in the School of Electrical and Computer Engineering at the Georgia Institute of Technology. "We are working at the intersection of mechanics, electronics, biology and physics. It's a very rich area and there's a lot of room for multidisciplinary concepts."
The bot is built from a piezoelectric actuator glued onto a polymer body that is 3D-printed using two-photon polymerization lithography (TPP). The actuator generates vibration and is powered externally because no batteries are small enough to fit onto the bot. The vibrations can also come from a piezoelectric shaker beneath the surface on which the robots move, from an ultrasound/sonar source, or even from a tiny acoustic speaker.
The vibrations move the springy legs up and down, propelling the micro-bot forward. Each robot can be designed to respond to different vibration frequencies depending on leg size, diameter, design and overall geometry. The amplitude of the vibrations controls the speed at which the micro-bots move.
"As the micro-bristle-bots move up and down, the vertical motion is translated into a directional movement by optimizing the design of the legs, which look like bristles," said Ansari. "The legs of the micro-robot are designed with specific angles that allow them to bend and move in one direction in resonant response to the vibration."
Manufacturing the bots