Inspired by biological cells, researchers have developed computationally simple robots that connect in large groups to move around, transport objects, and complete other tasks. This “particle robotics” system comprises many individual disc-shaped units referred to as “particles.” The particles are loosely connected by magnets around their perimeters and each unit can only do two things: expand and contract. (Each particle is about 6” in its contracted state and about 9” when expanded.) That motion, when carefully timed, allows the individual particles to push and pull one another in coordinated movement. Onboard sensors enable the cluster to gravitate toward light sources.
Researchers demonstrated a cluster of two dozen real robotic particles and a virtual simulation of up to 100,000 particles moving through obstacles toward a light bulb. The demonstration also showed that a particle robot can transport objects placed in its midst.
Particle robots can form into many configurations and fluidly navigate around obstacles and squeeze through tight gaps. None of the particles directly communicate with or rely on one another to function, so particles can be added or subtracted without any impact on the group. The particle robotic systems can complete tasks even when many units malfunction. Robots made up of these simplistic components could enable more scalable, flexible, and robust systems.
The researchers chose disc-shaped mechanisms that can rotate around one another. They can also connect and disconnect from each other and form into many configurations. Each unit of a particle robot has a cylindrical base, which houses a battery, a small motor, sensors that detect light intensity, a microcontroller, and a communication component that sends out and receives signals. Mounted on top is a children's toy called a Hoberman Flight Ring that consists of small panels connected in a circular formation that can be pulled to expand and pushed back to contract. Two small magnets are installed in each panel.
To program the robotic particles to expand and contract in an exact sequence to push and pull the whole group toward a destination light source, the researchers equipped each particle with an algorithm that analyzes broadcasted information about light intensity from every other particle, without the need for direct particle-to-particle communication. The sensors of a particle detect the intensity of light from a light source; the closer the particle is to the light source, the greater the intensity. Each particle constantly broadcasts a signal that shares its perceived intensity level with all other particles.
This creates a mechanical expansion-contraction wave, a coordinated pushing and dragging motion, that moves a big cluster toward or away from environmental stimuli. The key component is the precise timing from a shared synchronized clock among the particles that enables movement as efficiently as possible. Simulated clusters of up to 10,000 particles maintain locomotion, at half their speed, even with up to 20 percent of units failed.
The next step is miniaturizing the components to make a robot composed of millions of microscopic particles.