Tiny robots from “Galinstan” can run faster than a (miniature) cheetah

Scientists at the Johannes Kepler University (JKU) have developed steerable soft robots that can run, swim and jump at high speeds. During the test, the robots reached a speed of 70 BL/s (body lengths per second). These results are remarkable since even a cheetah (the fastest land animal on earth) can only run up to 23 BL/s. But don’t expect any absolute speed records, as the robots have millimeter-sized bodies – although these tiny machines are probably the world’s fastest soft-robots.

Soft robots are different from the traditional robots you see in factories, restaurants, and science exhibitions. They are made of flexible materials such as polymers and shape memory alloys (these alloys change shape with changes in temperature). Soft materials allow the robots to function much like a living organism (or living tissue). In contrast, conventional robots are made of rigid materials such as plastic, aluminum and metal.

Scientists have long tried to create soft robots fast enough to work in extreme environments where no other machines would work. Such robots could play an important role in the medical field. For example, ultra-fast robots could replace invasive methods such as colonoscopy. Doctors could use fast soft robots to examine abnormalities in body organs (like the stomach) that are difficult to examine with traditional diagnostic robots.

Build ultra-fast robots

The ultra-fast robots are made from a liquid metal alloy called Galinstan. It consists of tin (Sn), gallium (Ga) and indium (In). Galinstan is not typically used to create soft robots. They are mostly made of silicone-based elastomers. When asked why, the study’s first author and soft matter physicist at JKU, Dr. Guoyong Mao, told Ars Technica: “The most important property of this material is that it is liquid at room temperature. It also has high conductivity, making it useful for building soft and deformable coils.”

The researchers used liquid metal 3D printing technology to form the Galinstan coils. These 3D-printed coils were then encased in elastomeric sleeves that hold them together with an actuator that controls their state. This creates a coil-shaped soft electromagnetic robot (SEMR) capable of delivering high-speed actuation and drive. Researchers are also equipping the robots with L-shaped or sawtooth-shaped feet based on the substrates they will move across.

The SEMRs are powered by lithium-polymer batteries, and their ultra-fast movement is powered by electromagnetic actuators (components that convert electrical energy into mechanical energy). The actuators are magnetically responsive components and therefore the fast moving robots can be easily controlled with a static magnetic field. During testing, the tethered robots could move at 35 BL/s in an airplane and 70 BL/s on a folded 3D surface. In addition, they swam at 4.8 BL/s in water tests. “We think this is a new and promising technology in the field of robotics that has great potential for the future. We couldn’t find a similar technology using a soft functional material that can do so many tasks at such a high speed,” Mao said.

Future of ultra-fast soft robots

The researchers also ran speed tests on prototype untethered soft robots and achieved a swimming speed of 1.8 body lengths per second (BL/s) and a maximum running speed of 2.1 BL/s. The researchers now plan to improve the efficiency and performance of the untethered robots.

Mao and his team also say that developing millimeter-scale SERMs with liquid 3D printing could pave the way for larger, ultra-fast robots in the future.

There are different types of soft robots; Some could help us remove plastic debris from the oceans, and others could allow us to study the hot deserts of the Moon and Mars. Speed ​​is a big limiting factor for all of these soft machines. The technology behind ultra-fast SEMRs has the potential to break this limit.

Nature Communications, 2022. DOI: 10.1038/s41467-022-32123-4 (About DOIs)

Rupendra Brahambhatt is an experienced journalist and filmmaker. He covers science and culture news and for the past five years has been actively collaborating with some of the most innovative news outlets, magazines and media brands operating in different parts of the world.