A zinc-air microbattery has the potential to pave the way for cell-sized, autonomous robots capable of delivering medications inside the human body, as well as performing tasks like detecting gas leaks in pipelines.
Engineers from MIT have developed a small battery that could facilitate the creation of cell-sized, self-sufficient robots for drug delivery within the human body, alongside various applications such as identifying leaks in gas pipelines.
This innovative battery measures 0.1 millimeters long and 0.002 millimeters thick, approximately equivalent to the width of a human hair. It has the ability to absorb oxygen from the air, which it uses to oxidize zinc, generating a current of up to 1 volt. This output is 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 study’s lead author, states, “We believe this will greatly enhance robotics. We are integrating robotic functions into the battery and combining these components into devices.”
Ge Zhang, who earned his PhD in ’22, and Sungyun Yang, an MIT graduate student, are the primary authors of the paper published in Science Robotics.
Battery Powered
For several years, Strano’s laboratory has focused on creating miniature robots that can detect and react to their surroundings. However, one significant hurdle in developing these small robots has been ensuring they have a reliable power source.
While other investigations have shown that microscale devices can be powered by solar energy, this method requires a constant light source, like a laser, to be directed at the robots. These robots are often referred to as “marionettes” since they rely on external power to function. Integrating a battery into these minuscule devices could allow them to operate more independently and travel greater distances.
Strano explains, “Marionette systems don’t need a battery since they draw all their energy externally. If we want a small robot to enter hard-to-reach areas, it must have a higher level of autonomy. A battery is crucial for a device that’s not tethered to an outside source.”
To develop robots with enhanced autonomy, Strano’s team chose to utilize zinc-air batteries. These types of batteries have a longer lifespan than various alternatives due to their high energy density and are commonly found in hearing aids.
The battery they engineered consists of a zinc electrode linked to a platinum electrode, embedded in a strip made from a polymer called SU-8, widely used in microelectronics. When the electrodes interact with oxygen molecules from the air, zinc undergoes oxidation, releasing electrons that flow to the platinum electrode, thus generating a current.
In their study, the researchers demonstrated that this battery could generate sufficient energy to power an actuator, specifically a robotic arm capable of rising and lowering. Additionally, it could power a memristor— an electrical component that retains event memories by altering its electrical resistance— along with a clock circuit that allows robotic devices to track time.
The battery is also capable of running two distinct types of sensors that vary their electrical resistance in the presence of certain chemicals. One sensor is made from atomically thin molybdenum disulfide, while the other is fashioned from carbon nanotubes.
“We are creating essential components to facilitate functions at the cellular level,” remarks Strano.
Robotic Swarms
In their current research, the team connected their battery to an external device using a wire, but they plan to integrate the battery directly into future robot designs.
Strano notes, “This will be foundational for much of our robotic endeavors. You can construct a robot around an energy source, similar to how electric cars are built around their batteries.”
One avenue they’re exploring involves designing tiny robots for injection into the human body. Once inside, these robots could target specific sites and release medications such as insulin. The team envisions using biocompatible materials for the devices, which would disintegrate after their purpose is fulfilled.
The researchers are also working on enhancing the battery’s voltage to enable further applications.
This research received funding from the U.S. Army Research Office, the U.S. Department of Energy, the National Science Foundation, and a MathWorks Engineering Fellowship.
