If you're making a 2-mm-long walking robot, it pretty much goes without saying that the thing won't be able to carry much of a battery. That's why Georgia Tech's new "micro-bristle-bots" are instead propelled by vibrations. And someday, they may actually be capable of moving within the human body.
The robots are 3D printed out of polymer resin, via a process known as two-photon polymerization lithography. Each one has either four or six springy "legs," which are really more like bristles – hence the name. Additionally, glued onto the back of each bot is a piezoelectric actuator made of lead zirconate titanate.
When vibrations are delivered to the robot via either a shake table, an external ultrasound/sonar source, or a tiny acoustic speaker, those vibrations cause the angled legs to move up and down, propelling the robot forward. The onboard actuator can also produce the vibrations when subjected to an electrical current, although that current presently has to come from a hard-wired source. Down the road, however, it may be possible to wirelessly activate the actuator using electrical fields.
The amplitude of the vibrations determines the speed at which the robots move. What's more, by tweaking their legs' size, diameter, and overall geometry, the bots can be designed to respond to different vibrational frequencies. Therefore, by linking together two differently-designed robots that respond to different frequencies, it should be possible to steer the two by varying the frequency and amplitude of the vibrations.
Hundreds of the devices have already been created, and the researchers are now looking at ways of scaling up the manufacturing process, so that thousands could be made at once. Possible applications include the movement of materials within tiny spaces, or even the treatment of injuries within the body. And, because the actuators can be tuned to generate an electrical current when exposed to vibrations (the opposite of what they usually do), the robots could also carry environmental sensors that are temporarily powered up as needed.
A paper on the research, which is being led by Asst. Prof. Azadeh Ansari, was recently published in the Journal of Micromechanics and Microengineering. The micro-bristle-bots can be seen in action, in the video below.
Source: Georgia Tech