Scientists build first self-powered ‘liquibots’ that run continuously without electricity

Inspired by water-walking insects, scientists have built liquid robots that work autonomously and continuously without the need for electrical inputs, transporting chemicals back and forth while partially submerged in solution.

The “liquibot” technology may lead to further developments in automated chemical synthesis or drug delivery systems for pharmaceuticals, say the researchers, including those from Lawrence Berkeley National Laboratory in the US.

Earlier studies had demonstrated the working of liquibots that autonomously perform a task, but just once, and some that can perform a task continuously, but need electricity to do so continuously.

In the new research, published in the journal Nature Chemistry, scientists demonstrated the first self-powered liquid robot – which look like little open sacks just 2mm in diameter – that can run continuously on energy from the chemicals in its surroundings instead of electricity.

“We have broken a barrier in designing a liquid robotic system that can operate autonomously by using chemistry to control an object’s buoyancy,” study co-author Tom Russell from Berkeley Lab’s Materials Sciences Division said in a statement.

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

From a series of experiments, described in the study, the researchers found that “feeding” the liquibots salt makes them heavier than their surrounding solution, causing them to cluster in the middle of the solution where they fill up with select chemicals.

This process triggers a reaction in the liquibots that generates oxygen bubbles, which work like like balloons to lift them up to the surface, where they offload their cargo and repeat the process as long as there is “food” in the system.

“The cyclic buoyancy-induced cargo shuttling occurs continuously, as long as the supply of reactants diffusing to the sac or droplet from the surrounding aqueous phase is not exhausted,” the scientists noted in the study.

In further studies, the researchers hope to assess how liquibots can be applied to carry out a range of tasks such as detecting different types of gas in the environment, or screening chemical samples in drug discovery and drug synthesis.

“By designing the selectivity and functionality of the droplet, the concepts presented here can be extended to other systems for use in chemical or drug delivery and in micro-/milli-robots,” they noted.