Engineers from the Massachusetts Institute of Technology developed tiny batteries that deploy autonomous robots by the size of cells for medicine administration within the human body and other uses like identifying gas pipeline leaks. This research was published in the journal Science Robotics.
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The new battery has dimensions of 0.1 mm in length and 0.002 mm in thickness, or about the same as a human hair. It is designed to oxidize zinc by absorbing oxygen from the air and producing a current with a potential of up to 1 volt. The researchers demonstrated that this is sufficient to power a tiny circuit, sensor, or actuator.
We think this is going to be very enabling for robotics. We are building robotic functions onto the battery and starting to put these components together into devices.
Michael Strano, Study Senior Author and Carbon P. Dubbs Professor, School of Chemical Engineering, Massachusetts Institute of Technology
The study’s lead authors are Ge Zhang PhD ’22 and MIT Graduate Student Sungyun Yang.
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 enough power.
Other researchers have demonstrated that solar power can be used to power microscale electronics, but this strategy has the problem of requiring the robots always to have a laser or similar light source aimed 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 small gadgets would allow them to go considerably further.
Strano added, “The marionette systems do not really need a battery because they are getting all the energy they need from outside, but if you want a small robot to be able to get into spaces that you could not access otherwise, it needs to have a greater level of autonomy. A battery is essential for something that’s not going to be tethered to the outside world.”
Strano's lab employed a zinc-air battery to build robots that might grow more independent. These batteries are frequently used in hearing aids because of their high energy density, which gives them a longer lifespan than many other battery types.
Their battery consists of a platinum and zinc electrode embedded in a strip of SU-8 polymer, often used in microelectronics. When these electrodes come into contact with oxygen molecules in the air, zinc oxidizes and releases electrons, which then go to the platinum electrode and produce 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 lifted and lowered. The battery might also power a memristor, which changes electrical resistance to retain memories of events, and a clock circuit, allowing robotic systems to keep track of time.
The battery also supplies enough power to power two separate types of sensors, each of which changes its electrical resistance when exposed to environmental substances. One sensor is made of atomically thin molybdenum disulfide, while the other comprises carbon nanotubes.
“We are making the basic building blocks to build up functions at the cellular level,” Strano added.
Robotic Swarms
In this study, the researchers connected their batteries to an external device via a cable; but, in future work, they intend to construct robots where the battery is integrated into a device.
Strano stated, “This is going to form the core of a lot of our robotic efforts. 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 small robots that can be inserted into the human body and seek out a particular place before releasing a drug like insulin. The researchers imagine that the devices used in the human body would be composed of biocompatible materials that would break down when no longer needed.
The researchers are also raising the battery’s voltage, which might enable additional applications.
The US Army Research Office, the US Department of Energy, the National Science Foundation, and a MathWorks Engineering Fellowship funded the research.
Journal Reference:
Zhang, G., et al. (2024) High energy density picoliter-scale zinc-air micro batteries for colloidal robotics. Science Robotics. doi.org/10.1126/scirobotics.ade4642.