Innovative Zinc-Air Battery for Autonomous Cell-Sized Robots in Medical Applications

Engineered by a team at MIT, a groundbreaking miniaturized battery could pave the way for the development of cell-sized, autonomous robots, capable of performing tasks like targeted drug delivery within the human body or detecting leaks in gas pipelines.

Revolutionizing Power for Tiny Robots

This innovative battery measures just 0.1 millimeters in length and 0.002 millimeters in thickness—comparable to the diameter of a human hair. It harnesses oxygen from the air to oxidize zinc, generating a current with a potential of up to 1 volt, sufficient to power small circuits, sensors, or actuators, as demonstrated by the researchers.

Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT and the lead author of the study, emphasizes its potential: “We believe this technology will greatly enhance the capabilities of robotics. We are integrating robotic functions into the battery and assembling these components into cohesive devices.”

Challenges of Miniature Robotics Power

For several years, Strano’s lab has been focused on creating tiny robots that can react to environmental stimuli. A significant hurdle in advancing these miniature robots has been ensuring they have a reliable power source.

While some researchers have managed to power microscale devices using solar energy, this method requires a constant light source, making the robots reliant on external control, similar to marionettes. In contrast, incorporating a battery allows these tiny robots to operate independently and explore areas that are otherwise inaccessible.

Strano notes, “Marionette systems don’t require batteries as they derive all their energy externally. However, for a small robot to navigate freely, it must possess a higher level of autonomy, which necessitates an internal power source.”

Zinc-Air Battery Design and Function

To foster this autonomy, Strano’s team opted for a zinc-air battery—a type known for its longevity and high energy density, commonly found in hearing aids. The designed battery comprises a zinc electrode connected to a platinum electrode within a polymer strip called SU-8, frequently utilized in microelectronics. When these electrodes interact with oxygen molecules in the air, the zinc undergoes oxidation and releases electrons that flow to the platinum electrode, generating a current.

In their study, researchers demonstrated that this compact battery could power an actuator—a robotic arm capable of movement. Additionally, it could energize a memristor, which alters its electrical resistance to retain memory of events, and a clock circuit that enables robotic devices to keep track of time.

“We are creating fundamental building blocks aimed at establishing functions at the cellular level.”

Expanding Applications and Future Directions

The battery also has the capability to operate two types of sensors that change their electrical resistance in response to chemicals in their environment; one sensor is composed of atomically thin molybdenum disulfide, while the other utilizes carbon nanotubes.

While the current study involved connecting the battery to an external device via a wire, future work aims to fully integrate the battery within autonomous robots. Strano anticipates that this will form the foundation for numerous robotic innovations: “You can design a robot around an energy source much like you would design an electric vehicle around its battery.”

One exciting application under consideration is the creation of miniature robots that could be injected into the human body to locate specific sites and administer medications like insulin. For biocompatibility, these devices would ideally be constructed from materials that disintegrate once their purpose is fulfilled.

Researchers are also focused on increasing the voltage output of the battery to expand its potential applications.

This research received funding from various institutions including the U.S. Army Research Office, the U.S. Department of Energy, and the National Science Foundation.