Researchers at the University of Pennsylvania and the University of Michigan recently collaborated to develop the smallest, fully programmable autonomous robots ever made. These tiny machines are only one-tenth the width of a millimeter and can think, swim and survive for months.
The robots measure approximately 200 microns by 300 microns by 50 microns, smaller than a grain of salt, and cost only about a penny to manufacture. Despite their tiny size, they can move, sense, compute and respond to their environment without the need for external connections, magnetic fields or controllers. Mark Miskin, assistant professor of electrical and systems engineering at the University of Pennsylvania, said that such robots are 10,000 times smaller than existing microrobots, opening up a new scale for programmable robots.
The research team published their results in Science Robotics and Proceedings of the National Academy of Sciences, envisioning its application in single-cell health tracking or microscopic machine assembly. Since robots are about the same size as microorganisms, they could one day shuttle through organizational environments or microscopic production lines that are difficult to reach with traditional robots.
At the sub-millimeter scale, gravity and inertia give way to forces such as surface tension, resistance and viscosity, making traditional mechanical limbs prone to failure. The team's innovative propulsion system uses induced electric fields to control ions in the surrounding liquid and push water molecules forward, just like a robot driving itself in a "moving river".
The robots can travel along complex trajectories at speeds of one body length per second and coordinate their movements like a school of fish. A simple LED light provides power, and a design with no moving parts ensures the machine is robust, can repeatedly transfer samples without damage, and can run for months.
To achieve autonomy, the researchers integrated ultra-small computer technology from David Blau's group at the University of Michigan, which was presented as complementary at a DARPA conference. The solar panel only produces 75 nanometers of electricity - more than 100,000 times less than a smart watch - but the circuit can run at extremely low voltages. The processor, memory, sensors and motors are all integrated in a structure of hundreds of microns. It can sense temperature accurately to one-third of a degree Celsius, and track thermal gradients to report real-time data.
Humans communicate with robots through movement: the computer encodes temperature and other data into "dance" jitters, which are decoded by cameras under the microscope, similar to the way bees communicate. Light pulses can be powered and programmed individually to support division of labor and collaboration among robots.
Miskin and Blau regard this as a starting point. This platform combines mechanical simplicity, efficient electronics and scalable manufacturing. It is suitable for fields that require distributed microscopic intelligence, marking the beginning of a new era of microscopic robots.