Mini-robots, smaller than Ants

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 small 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 comprise four or six legs, and an actuator zirconate titanate of the lead having a thickness of 0.3 millimeters.

Tiny robots printed in 3D

The structure of the robot is created through a technique of 3D printing by lithography called polymerization two photons (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, simply 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.

Robots capable of feeding sensors

They are so small that there is no suitable battery. The vibrations are therefore provided for the moment by an external piezoelectric actuator which duplicates the effects of the one integrated into the robots, but they also work with a loudspeaker. In this configuration, the actuator inside the robots could be used to produce an electric current, for example to power onboard sensors.

They resonate at a vibration frequency around 6.3 kHz, but the size and shape of the robots influence the exact frequency. The researchers can, therefore, vary the frequency and amplitude of the vibrations to order more specifically certain robots.

Researchers want to create a control system by combining two sensors of slightly 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.