Soft robots move with a tiny, soft pump

Soft robots have a “cardiovascular” problem: while their bodies can deform and bend, their hearts, the pumps that keep them moving, have remained bulky and rigid. Researchers at the University of Bristol have created a “soft” miniature pump that weighs about as much as a single dried pumpkin seed but can generate enough hydraulic pressure to power soft robotic systems without bulky compressors or rigid mechanical pumps.

One of the biggest challenges in soft robotics, the field of robotics that says robots can be flexible and/or squishy, is that while the robots themselves can be made from lightweight, flexible materials that stretch and deform like living organisms, the systems required to power and control them remain rigid and bulky. Although there have been recent developments in soft robotics that use heat, most soft robots rely on hydraulic and pneumatic systems to move fluid through their artificial muscles and actuators.

These components are often much larger and heavier than the robots they control, forcing many designs to remain tethered to stationary equipment via tubes and cables. This severely limits portability and real-world usability, making it difficult to deploy soft robots in applications such as wearable assistive devices, medical implants, haptic feedback systems, search-and-rescue robots, and miniature inspection machines.

Existing attempts to miniaturize these pumping systems often involve compromises, such as rigid mechanical components, high operating voltages, complex fabrication processes, or sacrifices in pumping performance. Roboticists have long sought a compact, energy-efficient pumping technology that can be fully integrated into soft robotic systems without undermining the flexibility and adaptability that make soft robotics attractive in the first place.

This is exactly what the researchers have developed. Their technology, christened the Liquid Metal Magnetohydrodynamic Actuator (LIMA) pump, is a miniature soft pump designed to replace bulky compressors and rigid pumping systems that currently limit soft robotic technologies. At the astonishing size of a pea and weighing just 0.2 g, the pump serves as a compact, self-contained fluid power source capable of generating hydraulic pressure and fluid flow while operating at less than 0.1 volts.

Unlike conventional pumps, which rely on mechanical components to physically push fluid through a system, the LIMA pump uses electromagnetic forces acting on a droplet of liquid metal to create motion. This feature eliminates many of the rigid moving parts that make traditional pumps difficult to integrate into flexible robotic systems.

“It’s a really exciting development, which overcomes the existing barriers of stiff bulkiness and offers something miniature, portable and more adaptable. These enhanced characteristics mean it could be deployed to better effect in existing uses like lab-on-a-chip devices for disease diagnosis and also with new ones, ranging from micro pumps for robotic clothing to tiny actuators environmental sampling. The sky really is the limit,” says Saba Firouznia, study lead author.

A paper on the research was published in the journal Nature Communications.