Control Underwater Robots With Light

2023 Author: Hannah Pearcy | [email protected]. Last modified: 2023-05-24 11:12

A robot that can move freely under water is not easy to construct. A research team from the Max Planck Institute for Intelligent Systems and the University of Tampere in Finland has now succeeded in doing this by using a material that has never been used in the construction of soft robots: the Snail-o-Bot is made of light-sensitive materials Liquid crystal gels (LCGs).

Water snails as a role model

Most of the known soft materials are difficult to deform and operate efficiently under water. When looking for a suitable material, the researchers were inspired by nature: "We examined various animals that can move easily in the water," explains Hamed Shahsavan, a post-doctoral student in the Department of Physical Intelligence.

“The animals that can move very well in liquid are the ones that have a very soft and gel-like body. Our heroine was the Spanish dancer, who can both move on the sea floor and swim freely. But other invertebrate, soft animals have also inspired us, such as snails.

Robot crawls, runs, jumps and swims under light

A gel-like body as the main requirement - soon they agreed on LCGs as building materials, as they have several advantages. First , they respond to light. This means that Snail-o-Bot can be moved on board without drive, sensor and actuation components. Even with little energy, the robot can carry out various types of movement.

The second advantage is that by arranging the gel molecules in a certain pattern, the overall construction can change its shape by only a few millimeters when light illuminates certain parts of the robot. Because of this targeted alignment of the gel molecules, the researchers speak of "programmable shape changes".

As soon as the light-sensitive, flaccid, rubber-band-like material is exposed to light, it can make rapid and reversible changes in shape: it can crawl, run, jump and swim. This is because LCGs reduce their density when exposed to light by 7 to 8 percent. With light, the individual LCGs become lighter and float upwards. The robot is actuated photothermally by the buoyancy of the illuminated parts and by switching the light on and off at certain intervals.

Soft robots for medicine

Advantage of the small robot: It has a low energy requirement (20 to 30 times less energy than non-gel constructions, according to the researchers) and the shape change can be preprogrammed due to the molecular orientation. Shahsavan explains: “This is a solution for remote control and movement of soft materials under water quickly, efficiently and in a controlled manner. We hope to inspire other robotics who, like us, are trying to design wireless and soft robots that can move freely in fluid ".

Soft robots are particularly in demand in minimally invasive, robot-based medicine and biotechnology. One day the snail-o-bot could also be used here. But the researchers still have to develop further: "In the future we will try to operate this material with energy sources other than light, since light from outside cannot penetrate through the human body. We hope that one day we will be able to use ours to make the soft construction so small that we can move and control it through the body with near infrared light, acoustic waves, electric or magnetic fields."

The researchers published their work “Bioinspired underwater locomotion of light-driven liquid crystal gels” in the Proceedings of the National Academy of Sciences PNAS in February 2020.