Science & Technology (Commonwealth Union) – A small battery formed by MIT engineers could pave the way for cell-sized autonomous robots to be used in various applications, such as delivering drugs within the human body or detecting leaks in gas pipelines.
This innovative battery measures just 0.1 millimeters in length and 0.002 millimeters in thickness—about the thickness of a human hair. It works by capturing oxygen from the air to oxidize zinc, generating a current with a potential of up to 1 volt. This is sufficient to power a tiny circuit, sensor, or actuator, as demonstrated by the researchers.
Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT and the study’s senior author indicated that it has the potential to significantly advance robotics. He further pointed out that they are integrating robotic functions with the battery and assembling these components into functional devices.
Ge Zhang, Ph.D. ’22, and Sungyun Yang, an MIT graduate student, are the lead authors of the paper, which was published in Science Robotics.
For years, Strano’s lab has been developing tiny robots that can detect and respond to environmental stimuli. A key challenge has been ensuring these miniature robots have sufficient power.
While some researchers have powered microscale devices using solar energy, this approach requires the robots to be continuously illuminated by a laser or other light source. These devices, often referred to as “marionettes,” are controlled by an external power source. Integrating a battery within these small devices could enable them to operate independently and explore much larger areas.
“The marionette systems don’t really need a battery because they’re getting all the energy they need from outside,” added Strano. “But if you want a small robot to be able to get into spaces that you couldn’t 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.”
To advance the development of more autonomous robots, Strano’s lab opted to use a zinc-air battery. These batteries, which are often employed in hearing aids due to their high energy density and extended lifespan compared to many other battery types, were the focus of their design efforts.
The team created a battery featuring a zinc electrode linked to a platinum electrode, both embedded within a strip of SU-8 polymer, a material frequently used in microelectronics. When these electrodes interact with oxygen molecules from the air, the zinc undergoes oxidation, releasing electrons that travel to the platinum electrode, thereby generating an electrical current.
In their research, the scientists demonstrated that this battery could supply sufficient energy to power an actuator—specifically, a robotic arm capable of moving up and down. Additionally, the battery could power a memristor, a component that stores information by altering its electrical resistance, and a clock circuit, which enables robotic devices to measure time.
The battery also delivers enough power to operate two different types of sensors that change their electrical resistance in response to environmental chemicals. One sensor is made from atomically thin molybdenum disulfide, while the other is constructed from carbon nanotubes.
Strano stated that they are creating the fundamental building blocks necessary to establish functions at the cellular level.
The study had the researchers utilize a wire for the linking of their battery to an external device, they indicated however that for their future work they intend to form robots in which the battery is already in the device.
“This is going to form the core of a lot of our robotic efforts,” said Strano. “You can build a robot around an energy source, sort of like you can build an electric car around the battery.”
One of the initiatives focuses on developing miniature robots that could be injected into the human body, where they would navigate to a specific target and then deliver a drug, such as insulin. For application inside the human body, the researchers anticipate that these devices would be constructed from biocompatible materials designed to disintegrate once their task is complete.
