Biomedical Engineering
Soft robots take on hard tasks
Soft, robust miniature robots powered by fluid kinetic energy can traverse tricky terrains at impressive speeds, offering a valuable new tool for search and rescue operations.
Tiny robots can be just as useful as their larger cousins. Imagine smallscale robots, equipped for precision tasks, navigating confined spaces within the human body to inspect and treat tissues or zooming through challenging terrains for reconnaissance in search and rescue operations.
Issue 04 | January 2025
At the Department of Biomedical Engineering, College of Design and Engineering, National University of Singapore, Associate Professor Raye Yeow and his team are making huge leaps in the world of miniature robots. Their latest creation is a completely soft, amphibious crawling robot powered by electrohydraulic kinetic energy. No larger than the palm of a hand and weighing as little as a few paperclips, this robot can move in multiple directions — forward, backward and even turn — thanks to its flexible design.
From inspecting underwater objects or performing delicate tasks in hard-to-reach spaces, such as the narrow crevices, the team’s adaptable, durable robot thrives in scenarios where precision and versatility are paramount.
The team’s findings were published in Advanced Science on 1 February 2024.
Associate Professor Raye Yeow pioneered a soft, miniature robot powered by electrohydraulic kinetic energy, capable of traversing tricky terrains at impressive speeds.
Great things come in small packets
Traditional rigid robots excel in many tasks — manufacturing cars, assembling circuit boards, packaging electronics — but they are not naturally geared to be flexible enough to navigate through confined, unstructured environments. Soft robots, with their squishier, flexible bodies, are far better suited for such situations.
“One major challenge in designing soft robots is controlling how they stretch and deform, which governs how they move about.”
Like our joints, all robots rely on components called actuators to generate movement. Unlike rigid robots that move in fixed ways depending on their joints, soft robots can bend, stretch and expand in multiple ways depending on the materials used.
“One major challenge in designing soft robots is controlling how they stretch and deform, which governs how they move about,” says Assoc Prof Yeow. “Traditional soft actuators often face limitations such as slower speeds or difficulty in scaling down for practical applications.”
Issue 04 | January 2025
To tackle these limitations, Assoc Prof Yeow’s team designed a soft miniature robot that harnesses electrohydraulic fluid kinetic energy. Underpinning the movement of the robot is an electrohydraulic actuator, composed of two flexible electrodes and a membrane filled with dielectric fluid. When a high voltage is applied, the electrodes compress the fluid within the membrane, transforming electrical energy into mechanical motion that drives the robot’s movements.
This fluid-driven mechanism creates a continuous crawling motion. By controlling how the fluid flows inside the membrane, the robot can move in multiple directions — not just forward and backward, but also turn. This is achieved by deploying four electrodes on the robot that, when activated, direct the fluid to specific areas of the robot’s body, enabling it to pivot on command in up to eight directions.
“This allows the robot to manoeuvre accurately — even through gaps as narrow as one centimetre,” adds Assoc Prof Yeow. “Such capability could, for example, enable the robot to inspect confined spaces or ferry small payloads in challenging environments.”
Speed, robustness and adaptability are also defining features of the robot. Despite its small size, it can crawl up to 16 millimetres per second — a rate nearly 290 times faster than other soft miniature crawling robots powered by hydraulically amplified self-healing electrostatic actuators. Its fully waterproof body enables it to operate on both land and underwater, while its durability allows it to recover quickly from severe compression, such as being stepped on.
Small robot, big dreams
The versatile capabilities of the soft robot make it well-suited for a range of specialised tasks. Its current applications could include exploration in narrow gaps, underwater inspection and small-scale reconnaissance, making it a valuable tool in areas such as disaster management, underwater exploration and industrial maintenance. With improvements, such as better water-to-land transitions and reduced power requirements, its utility could expand further to areas like medical robotics and environmental monitoring.
With that in mind, the team plans to improve how the robot transitions between land and water. For instance, it could be given soft paddles to help it swim better. In addition, the researchers are also exploring alternative dielectric materials to reduce the robot’s power requirements. A fully untethered version is also in the works, which would provide greater autonomy for real-world applications.