Utilizing zinc-air technology, these miniature power sources capture oxygen from the environment to oxidize zinc, creating an electrical current1. The batteries boast an impressive energy density of 760 to 1070 watt-hours per liter, despite their minuscule dimensions of less than 100 micrometers wide and 2 micrometers thick2. Each unit, with a volume of only 2 picoliters, can produce voltages around 1.05 volts and store total energies between 5.5 to 7.7 microjoules, with a maximum power output close to 2.7 nanowatts2. This innovative design allows for the integration of power sources directly into microscale devices, potentially eliminating the need for external power tethers and enhancing the autonomy of tiny robotic systems13.

These microscopic power sources open up a wide range of innovative applications across various fields. In medicine, they could enable the development of injectable robots for targeted drug delivery within the human body, revolutionizing treatment methods1. Environmental monitoring could benefit from these batteries powering tiny sensors capable of detecting chemical changes or locating gas leaks in pipelines2. The batteries have already demonstrated their ability to power:

• Micrometer-sized memristor circuits for nonvolatile memory

• Microscale actuators that bend back and forth at 0.05 hertz, useful for robotic movement

• Two different types of nanosensors

• A clock circuit for timekeeping in robotic devices3

These applications showcase the versatility and potential of MIT's hair-thin batteries in advancing fields such as microelectronics, robotics, and sensor technology.

Photolithography, a technique commonly used in microelectronics, enables the efficient production of these miniature power sources. A single 2-inch silicon wafer can yield an impressive 10,000 batteries, demonstrating the scalability of the manufacturing process1. This high-volume production capability is crucial for the widespread adoption of microscale robotic devices. The batteries are embedded in a polymer called SU-8, which is widely used in microelectronics, and consist of a zinc electrode connected to a platinum electrode2. Once fabricated, these tiny power units can be suspended in liquid as colloidal particles, each carrying its own energy storage, making them versatile for various applications and environments.

Researchers at MIT are actively working to integrate these miniature power sources directly into autonomous robotic systems, aiming to eliminate the need for external tethers1. This advancement could pave the way for fully self-contained microscopic robots with unprecedented mobility and functionality. Future developments include:

• Increasing the battery's voltage output to expand potential applications

• Designing biocompatible versions for use within the human body that can safely degrade after completing their tasks

• Exploring the use of these batteries in swarm robotics for complex, coordinated operations

As the technology progresses, these hair-thin batteries are expected to become a cornerstone of future robotic innovations, enabling a new generation of microscale devices with enhanced autonomy and capabilities12.