Researchers have discovered that a tiny battery the thickness of a human hair could be used to power autonomous robots to deliver drugs inside the human body.
A team at the Massachusetts Institute of Technology (MIT) has developed a cell-sized battery that is only 0.1 mm long and 0.002 mm thick.
It works by taking oxygen from the air and using it to oxidize zinc, which can produce a current of up to 1 volt – enough to power a small circuit, sensor or actuator.
“We believe this will advance robotics tremendously,” said Professor Michael Strano, lead author of the study. “We are building robotic functions into the battery and starting to assemble these components into devices.”
While other researchers have developed microrobots that use solar power, these require a laser or other light source to be constantly connected. Such devices are called “puppets” because they are controlled by an external power source. Equipping these tiny devices with a power source such as a battery would allow them to travel much greater distances.
“The puppet systems don’t actually need a battery because they get all the power they need from the outside,” Strano said. “But if you want a small robot to be able to go into areas you couldn’t otherwise reach, it needs to have a higher level of autonomy. A battery is essential for something that isn’t connected to the outside world.”
The zinc-air batteries commonly used in hearing aids have a longer lifespan than many other battery types due to their high energy density.
The battery they developed consists of a zinc electrode connected to a platinum electrode embedded in a strip of a polymer called SU-8, which is commonly used in microelectronics. When these electrodes come into contact with oxygen molecules from the air, the zinc oxidizes and releases electrons that flow to the platinum electrode, creating a current.
In this study, the researchers showed that this battery could provide enough energy to power an actuator – in this case, a robotic arm that can be raised and lowered. The battery could also power a memristor, an electrical component that can store memories of events by changing its electrical resistance, and a clock circuit that allows robotic devices to measure time.
The battery also provides enough power to run two different types of sensors that change their electrical resistance when they encounter chemicals in the environment. “We’re making the basic building blocks to build functions at the cellular level,” Strano said.
In this study, the researchers used a cable to connect their battery to an external device, but in future work they plan to build robots where the battery is integrated into a device.
These include efforts to develop tiny robots that could be injected into the human body, where they could seek out a target site and then release a drug such as insulin. For use in the human body, researchers envision devices made of biocompatible materials that decompose once they are no longer needed.
In addition, the researchers are working on increasing the voltage of the battery, which could enable further applications.
