Developed by a team from the University of Pennsylvania and University of Michigan, the microscopic swimming machines can independently sense and respond to their surroundings, operate for months and cost a US penny each.<\/p>\n
Measuring about 200 by 300 by 50 micrometers, the robots could advance medicine by monitoring the health of individual cells and manufacturing by helping construct microscale devices.<\/p>\n
Powered by light, the robots carry microscopic computers and can be programmed to move in complex patterns, sense local temperatures and adjust their paths accordingly.\u00a0<\/p>\n
Described in\u00a0Science Robotics<\/a>\u00a0and\u00a0Proceedings of the National Academy of Sciences<\/a>\u00a0(PNAS), the robots operate without tethers, magnetic fields or joystick-like control from the outside, making them the first truly autonomous, programmable robots at this scale.<\/p>\n \u201cWe\u2019ve made autonomous robots 10,000 times smaller,\u201d said senior author\u00a0Marc Miskin, Assistant Professor in Electrical and Systems Engineering at Penn Engineering. \u201cThat opens up an entirely new scale for programmable robots.\u201d<\/p>\n Swimming Solution<\/p>\n To move, the new robots generate an electrical field that nudges ions in the surrounding solution. Those ions then push on nearby water molecules, animating the water around the robot\u2019s body.<\/p>\n The robots can adjust the electrical field that causes the effect, allowing them to move in complex patterns and even travel in coordinated groups at speeds of up to one body length per second.\u00a0<\/p>\n The electrodes that generate the field have no moving parts, making the robots extremely durable. \u201cYou can repeatedly transfer these robots from one sample to another using a micropipette without damaging them,\u201d said Miskin.<\/p>\n Giving Robots Brain Power<\/p>\n For full autonomy, a robot needs a computer to make decisions, electronics to sense its surroundings and control its propulsion, and solar panels for energy. The package then needs to fit on a chip that is a fraction of a millimetre in size.<\/p>\n David Blaauw\u2019s team at the University of Michigan were able to assist in overcoming this challenge as Blaauw\u2019s lab holds the record for the world\u2019s smallest computer.\u00a0<\/p>\n Blaauw said: \u201cWe saw that Penn Engineering\u2019s propulsion system and our tiny electronic computers were just made for each other. \u00a0The key challenge for the electronics is that the solar panels are tiny and produce only 75nW of power. That is over 100,000 times less power than what a smart watch consumes.\u201d<\/p>\n To run the robot\u2019s computer, the Michigan team developed special circuits that operate at extremely low voltages and bring down the computer\u2019s power consumption by more than 1000 times.\u00a0<\/p>\n Another challenge was to force the processor and memory to store a program in the little space that remained.<\/p>\n \u201cWe had to totally rethink the computer program instructions, condensing what conventionally would require many instructions for propulsion control into a single, special instruction to shrink the program\u2019s length to fit in the robot\u2019s tiny memory space,\u201d said Blaauw.\u00a0<\/p>\n Robots that Detect, Recall, and Respond<\/p>\n To the researchers\u2019 knowledge, no one has previously put a processor, memory and sensors \u00a0into a robot as small as theirs. According to the team, that breakthrough makes these devices the first microscopic robots that can sense and act for themselves.\u00a0<\/p>\n The robots have electronic sensors that can detect the temperature to within a third of a degree Celsius. This lets robots move towards areas of increasing temperature, or report the temperature – a proxy for cellular activity – allowing them to monitor the health of individual cells.<\/p>\n \u201cTo report out their temperature measurements, we designed a special computer instruction that encodes a value, such as the measured temperature, in the wiggles of a little dance the robot performs,\u201d said Blaauw. \u201cWe then look at this dance through a microscope with a camera and decode from the wiggles what the robots are saying to us. It\u2019s very similar to how honey bees communicate with each other.\u201d<\/p>\n The robots are programmed by pulses of light that also power them. Each robot has a unique address that allows the researchers to load different programs on each robot. \u201cThis opens up a host of possibilities, with each robot potentially performing a different role in a larger, joint task,\u201d said Blaauw.\u00a0\u00a0<\/p>\n According to the team, future versions of the robots could store more complex programs, move faster, integrate new sensors or operate in more challenging environments.<\/p>\n