A team from the University of Pennsylvania and the University of Michigan made what it calls the smallest fully programmable, autonomous robots ever created: tiny machines capable of swimming, sensing their surroundings and reacting independently. Each robot measures approx 200 by 300 by 50 micrometerssmaller in size than a grain of salt and comparable to many biological microorganisms. The platform is designed to be produced at extremely low costs: a single robot can cost around a cent of a dollar, paving the way for entire fleets of microscopic devices. According to the researchers, the reduction in scale is significant: compared to existing autonomous robots, these systems are approximately 10,000 times smaller.
Architecture: Computers, sensors, and micrometer-scale actuation
The result arises from the integration between the expertise of the University of Pennsylvania in the creation of active structures at the micrometric scale and the work of the University of Michigan on very low-power microcomputers. At the center of the robot is a microcomputer about 100 micrometers largeequipped with processing capacity and programmable memory, sufficient to store elementary commands and control logic. The components for locomotion and sensors are integrated around the electronics, creating a complete system capable of “feeling”, processing and acting autonomously.
To ensure operation with available power in the order of tens of nanowatts, the University of Michigan group designed circuits capable of operating at extremely low voltages, reducing computer consumption by more than a thousand times compared to conventional solutions. The very particular chip integrates small solar cells that generate about 75 nanowattsa value over 100,000 times lower than the typical consumption of a smartwatch, but sufficient to power the optimized electronics and control logic of the robot.
The implementation of the movement is based on an electrokinetic mechanismin which applied electric fields generate forces on the surrounding fluid, allowing the robot to swim without moving mechanical parts. This architectural choice aims to maximize robustness: the electrodes that generate the field do not suffer wear and the devices can be repeatedly transferred between different samples using micro-pipettes without significant damage.
Programming through light and sensory capabilities
As we said microrobots are powered by light, which is also used as a control system: The same light pulses that provide energy are used to send programs to the on-board memory.
Each unit has a unique address, which allows it to load different command sequences on different robotsmaking it possible to create swarms in which each element plays a specific role within a common task. Once programmed, the devices can perform complex movements, track defined paths and change their trajectory in response to conditions in the surrounding environment. Demonstrated capabilities include the ability to measure local temperature and react accordingly, for example by changing direction along a thermal gradient.
The integration between sensors and control logic allows robots to operate for extended periods of time, up to several months, as long as a sufficient light source such as a simple LED is available. Thanks to fine control of the electric field that generates propulsion, robots can move up to approximately one body length per second and
organize themselves into coordinated groups, similar to a school of fish.
Possible applications in medicine and manufacturing
Operating on a scale comparable to that of many cellular structures, these microrobots are thought of as potential tools for monitor the health of individual cells, intervene on tissues or support the targeted administration of therapies. The possibility of programming autonomous behaviors, such as tracking temperature gradients or other environmental parameters, makes their use plausible in scenarios where it is necessary to follow complex paths in biological or fluidic environments. In industrial and manufacturing fields, researchers point to the use of fleets of robots to build microscopic devices or perform assembly operations at a scale unachievable by traditional robotic systems as a prospect.
The work is part of a line of research that has been trying for years combine microelectronics technologies and micrometer-scale locomotion systems to bring robotics closer to the scale of biological systems. According to the team, having overcome the millimeter barrier with truly autonomous and programmable robots can represent a reference platform for further developments, including the integration of new sensors and communication capabilities between robots. The technical details of the project are described in a series of articles published in the journals Science Robotics and Proceedings of the National Academy of Sciences, which illustrate the electronic architecture, propulsion system and demonstrations of autonomous behavior of the microrobots.
