Berkeley Lab Presents Tiny Liquid Robots that Work Continuously Without Electricity

When one thinks of a robot, images of R2-D2 or C-3PO might enter one’s mind. But robots can offer more than basic entertainment on the big screen.

In a laboratory, for example, robotic systems can enhance efficiency and safety by doing repetitive activities and handling harmful chemicals.

But before a robot can begin working, it requires energy — usually from electricity or a battery. Yet, even the most advanced robot stops when the juice is depleted. For a number of years, researchers have desired to create a robot that can function autonomously and uninterruptedly, without requiring electrical input.

At present, as reported recently in the journal Nature Chemistry, researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of Massachusetts Amherst have shown precisely that — through “water-walking” liquid robots, like miniature submarines, dive below water to reclaim valuable chemicals, and then surface to supply chemicals “ashore” repeatedly.

The technology is the first self-driven, aqueous robot that works nonstop without electricity. It could potentially be used as an automated chemical synthesis or drug delivery mechanism for pharmaceuticals.

We have broken a barrier in designing a liquid robotic system that can operate autonomously by using chemistry to control an object’s buoyancy.

Tom Russell, Senior Study Author and Visiting Faculty Scientist, Lawrence Berkeley National Laboratory

Tom Russell is a professor of polymer science and engineering from the University of Massachusetts Amherst who leads the Adaptive Interfacial Assemblies Toward Structuring Liquids program in Berkeley Lab’s Materials Sciences Division.

Russell states that the technology considerably advances a group of robotic devices known as “liquibots.” In earlier studies, other scientists have presented liquibots that autonomously accomplish a task, but merely once; and some liquibots that can accomplish an activity continuously, but require electricity to keep working.

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

Tom Russell, Senior Study Author and Visiting Faculty Scientist, Lawrence Berkeley National Laboratory

Through a succession of experiments in Berkeley Lab’s Materials Sciences Division, Russell and first author Ganhua Xie, a former postdoctoral researcher at Berkeley Lab who is currently a professor at Hunan University in China, discovered that “feeding” the liquibots salt makes the liquibots denser or heavier than the liquid solution encompassing them.

Further experiments by co-investigators Paul Ashby and Brett Helms at Berkeley Lab’s Molecular Foundry showed how the liquibots carry chemicals to and fro.

Since they are denser than the solution, the liquibots — which resemble small open sacks, and are only 2 mm in diameter — group in the middle of the solution where they fill up with preferred chemicals. This activates a reaction that produces oxygen bubbles, which like tiny balloons lift the liquibot back to the surface.

Another reaction tugs the liquibots to the rim of a container, where they “land” and offload their contents.

The liquibots travel to and fro, similar to the pendulum of a clock, and can work nonstop, provided there is “food” in the system.

Based on their formulation, a collection of liquibots could accomplish a range of tasks concurrently. For example, some liquibots could identify various types of gas in the air, while others react to particular types of chemicals.

The technology may also facilitate independent, continuous robotic systems that monitor drug discovery and drug synthesis applications or small chemical samples for clinical applications.

Russell and Xie’s subsequent plan is to examine how to expand the technology for larger systems and investigate how it would function on solid surfaces.

In this short video, liquid robots just 2 millimeters in diameter transport chemicals back and forth while partially submerged in solution. (Video Credit: Ganhua Xie and Tom Russell/Berkeley Lab).

Journal Reference:

Xie, G., et al. (2021) Continuous, autonomous subsurface cargo shuttling by nature-inspired meniscus-climbing systems. Nature Chemistry. doi.org/10.1038/s41557-021-00837-5.

Source: https://www.lbl.gov/