Mit Engineers Develop Small Batteries To Power Cell-Sized Robots
A tiny battery developed by MIT engineers could enable the deployment of cell-sized, autonomous robots for medicine delivery within the human body, as well as other uses such as detecting leaks in gas pipelines.
The new battery, which is 0.1 millimeters long and 0.002 millimeters thick—roughly the thickness of a human hair—can absorb oxygen from the air and utilize it to oxidize zinc, generating a current with a potential of up to 1 volt. The researchers demonstrated that this is sufficient power for a small circuit, sensor, or actuator.
“We think this is going to be very enabling for robotics,” says Michael Strano, senior author of the paper and the Carbon P. Dubbs Professor of Chemical Engineering at MIT. “We’re building robotic functions onto the battery and starting to put these components together into devices.”
Ge Zhang, PhD ’22, and Sungyun Yang, an MIT graduate student, are the principal authors of the research, which appears in Science Robotics.
Powered by batteries
Strano’s lab has spent several years developing tiny robots that can detect and respond to events in their surroundings. One of the most difficult issues in constructing such small robots is ensuring that they have enough power.
Other researchers have demonstrated that solar power can be used to power microscale devices, but this strategy has the problem of requiring the robots to always have a laser or another light source pointed at them. These gadgets are referred to as “marionettes” since they are powered by an external source. Placing a power source, such as a battery, within these tiny devices would allow them to travel considerably further.
“The marionette systems don’t really need a battery because they’re getting all the energy they need from outside,” according to Strano. “However, if you want a small robot to be able to enter spaces that would otherwise be inaccessible, it must have a higher level of autonomy.” A battery is necessary for something that will not be connected to the outside world.”
Strano’s lab chose to employ a zinc-air battery to make robots more autonomous. Because of their high energy density, these batteries last longer than many other types of batteries and are commonly used in hearing aids.
The battery they devised consists of a zinc electrode connected to a platinum electrode embedded in a strip of SU-8 polymer, which is extensively used in microelectronics. When these electrodes interact with oxygen molecules in the air, the zinc oxidizes and releases electrons, which travel to the platinum electrode, resulting in a current.
In this study, the researchers demonstrated that this battery could deliver enough energy to power an actuator, namely a robotic arm that can be raised and lowered. The battery might also power a memristor, which changes electrical resistance to retain memories of events, as well as a clock circuit, which allows robotic systems to keep track of time.
The battery also provides enough power to power two separate types of sensors, each of which vary their electrical resistance when exposed to substances in the environment. One of the sensors is built of atomically thin molybdenum disulfide, while the other is created from carbon nanotubes.
“We’re making the basic building blocks in order to build up functions at the cellular level,” Strano explains.
Robotic swarm
In this investigation, the researchers utilized a wire to connect their battery to an external device; however, in the future, they intend to develop robots with the battery integrated.
“This is going to form the core of a lot of our robotic efforts,” according to Strano. “You can build a robot around an energy source, sort of like you can build an electric car around the battery.”
One of these efforts is to develop tiny robots that can be put into the human body and seek out a particular place before releasing a medicine like insulin. The researchers imagine that the devices used in the human body would be made of biocompatible materials that would break down when no longer needed.
The researchers are also working on raising the battery’s voltage, which could enable new applications.
The Army Research Office, the Department of Energy, the National Science Foundation, and a MathWorks Engineering Fellowship all contributed to the study’s funding.
