Mini-robots, smaller than ants, printed in 3D

Researchers at Georgia Tech in the US have created a new type of tiny robot powered by ultrasonic vibrations or miniature speakers. Printed in 3D, this mini robot is only two millimeters long and weighs 5 milligrams.

A team of researchers from the Georgia Institute of Technology in the United States has developed tiny robots that work through vibration. In an article published in the Journal of Micromechanics and Microengineering, scientists describe a "vibrobot" or "bristle bot," a tiny robot whose legs are made of bristles and an oscillating actuator that generates vibrations.

This kind of robot is already known and can be manufactured, for example, with a toothbrush head, a small motor, and an electric battery. The vibrations of the engine deform the flexible legs, which is enough to advance these little robots. The researchers' version differs in size, weighing only five milligrams and measuring two millimeters long, the size of the smallest of the ants. These robots have four or six legs, and titanium leads zirconate actuator with a thickness of 0.3 millimeters.

The robot's structure is created using a 3D lithography printing technique called two-photon polymerization (TPP). This technology uses a photopolymerizable material, which hardens in contact with a sufficiently strong light. A cube of this material in resin form is placed on the 3D printer. A laser moves to perform the printing, and the material polymerizes at the focal point of the laser. Once the structure is created within the cube, wash it to remove the excess, and discover the printed product. The process is fast enough to test many different configurations, but researchers would like to find a more efficient way to create hundreds or thousands of them.

These tiny robots are only two millimeters long, 1.8 millimeters wide, and 0.8 millimeters thick, for a weight of 5 milligrams. The size is not limited by the printer, capable of making smaller robots, but by the strength of adhesion. Smaller robots may adhere to the surface on which they are laid and may be impossible to separate from the forceps used to catch them.

They are so small that there is no suitable battery.

In this configuration, the actuator inside the robots could be used to produce an electric current, for example, to onboard power sensors.

They resonate at a vibration frequency around 6.3 kHz, but the size and shape of the robots influence the exact rate.

The researchers can, therefore, vary the frequency and amplitude of the vibrations to order more specifically individual robots. Researchers want to create a control system by combining two sensors of unequal sizes that would respond to different frequencies.

The team of scientists also wants to develop robots that can jump and swim so that they can face the real conditions outside the laboratory.