Scientists Create Self-Powered, Aqueous Robot That Runs Without Electricity

Scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of Massachusetts Amherst have developed the first self-powered, aqueous robot that can run continuously without electricity. 

The research was published in the journal Nature Chemistry.

“Water-Walking” Robots

These “water-walking” liquid robots can dive below water to retrieve precious chemicals before resurfacing to deliver them repeatedly. 

This is the first technology of its kind to run continuously without electrical input. It could potentially be used as an automated chemical synthesis or drug delivery system for pharmaceuticals.

Tom Russell is senior author of the research, a visiting faculty scientist, and professor of polymer science and engineering from the University of Massachusetts Amherst. He leads the Adaptive Interfacial Assemblies Towards Structuring Liquids program in Berkeley Lab’s Materials Sciences Division.

“We have broken a barrier in designing a liquid robotic system that can operate autonomously by using chemistry to control an object's buoyancy,” Russell said.

According to Russell, the technology helps significantly advance “liquibots,” which are a family of robotic devices. Previously, researchers have demonstrated that these liquibots can autonomously perform a task, but just once. Others can perform a task continuously, but they require electricity to operate.

“We don’t have to provide electrical energy because our liquibots get their power or ‘food’ chemically from the surrounding media,” Russell said.

Running the Experiments

Russell and first author Ganhua Xie ran a series of experiments in Berkeley Lab’s Material Sciences Division. Xie is a former postdoctoral researcher at Berkeley Lab and currently a professor at Hunan University in China. 

Through these experiments, the pair learned that “feeding” the liquibots salt makes them heavier or denser than the liquid solution surrounding them.

Co-investigators Paul Ashby and Brett Helms at Berkeley Lab’s Molecular Foundry carried out additional experiments that demonstrated how liquibots transport chemicals back and forth.

The liquibots are only 2 millimeters in diameter, and since they are denser than the solution, they cluster in the middle of it and fill up with selected chemicals. This results in a reaction that generates oxygen bubbles, which lift the liquibot to the surface. Another reaction takes place which pulls the liquibots to the rim of the container, where they can offload their cargo.

This process takes place over and over again.

The liquibots could complete a variety of tasks simultaneously depending on their formulation. While some could detect different types of gas in the environment, others could react to specific types of chemicals. 

Besides these applications, liquibots could also enable autonomous, continuous robotic systems that are applied in drug discovery or drug synthesis applications. 

The team will now look to scale up the technology for larger systems while exploring how to make it operate on solid surfaces.