Aquatic robot powered by light can walk, transport cargo and even dance

Aquatic robot powered by light can walk, transport cargo and even dance.
Aquatic robot powered by light can walk, transport cargo and even dance. Credit: Northwestern University

Northwestern University researchers have developed a first-of-its-kind life-like material that acts as a soft robot. The robot can walk at human speed, pick up and transport cargo to a new location, climb up hills, and even break-dance to release a particle.

The centimeter-sized robot is nearly 90% water by weight and moves without complex hardware, hydraulics, or electricity. It is activated by light and walks in the direction of the external rotating magnetic field.

On the surface of the water, it resembles a tiny four-legged octopus and functions well inside a water-filled tank, making it ideal for use in aquatic environments. It mimics the behavior of marine life and moves at a speed of one step per second.

The aquatic robot is made of a water-filled structure and the embedded skeleton of aligned nickel filaments that are ferromagnetic. Specially designed polymer molecules are added to their structure. Thanks to the combination of materials obtained, the robot can easily move into a water environment. The robot’s soft component is a molecularly designed network with parts that allow it to respond to light, hold or expel water in its interior, and have just the right stiffness to respond rapidly to magnetic fields.

When exposed to light, the robot’s molecules become hydrophobic (repelling water), causing the water molecules to escape. This conversion causes the aquatic robot to come alive by bending from a flat position to standing. This bending enables the material to respond rapidly to rotating magnetic fields, activating its ability to walk fast.

When the light turns off, the molecules revert back to their original state, and the robot goes flat, but it is ready anytime for a new cycle of activity under a magnetic field when prompted by an LED. The rotating field can be programmed to navigate the robot along a pre-determined path.

By combining walking and steering motions together, we can program specific sequences of magnetic fields, which remotely operate the robot and direct it to follow paths on flat or inclined surfaces,” said Monica Olvera de la Cruz, who led the theoretical work. “This programmable feature allows us to direct the robot through narrow passages with complex routes.

The sea creature-inspired robot could also be molecularly designed to recognize and actively remove unwanted particles in specific environments or use their mechanical movements and locomotion to precisely deliver bio-therapeutics or cells to specific tissues.

The inventors plan to improve the technology so that a group of bots can function together as a swarm. Scientists also want to make robots even more compact so that they can be used for the targeted delivery of biotherapeutic drugs to certain human tissues.