According to the developers, the swarm of robots can maintain cohesion, support substantial weight and self-heal, taking inspiration from biological processes in embryonic development, wherein a collection of simple cells transforms into tissues and organs via coordinated movements and alterations in mechanical properties.
Source: Brian Long/UCSB
In a press release, the team explained, “Living embryonic tissues are the ultimate smart materials. To sculpt themselves, cells in embryos can make the tissues switch between fluid and solid states.”
To mimic the fluidity and movement of the embryonic cells, the team identified three biological processes that occur during embryonic development: fluidization, polarization and adhesion.
The scientists added that embryonic tissues are capable of switching from a fluid-like to a solid state thanks to internal forces in the cells that enables them to move past each other like a fluid and then subsequently reorganize and stabilize like a solid — a process dubbed fluidization.
The polarization process enables embryonic cells to organize in a specific direction, thus enabling directional forces to be applied in a directional manner. Meanwhile, embryonic cells maintain adhesion with other cells — even while rearranging — and eventually offer structural strength as the organs are formed.
Together, the three processes were key to building a robot swarm that can rearrange and form complex shapes.
The team noted that the individual robots are shaped like circular discs, measuring 5 cm wide, and they are powered by an internal lithium-ion battery, reportedly enabling 30 minutes of uninterrupted operation.
Additionally, eight gears are located along the perimeter of the robots to encourage movement that have the individual robots pushing against each other while rotatable magnets placed along the perimeter allow for adhesion with their neighboring robots.
Each robot features a light sensor with polarized filters on top that detects the direction of the polarized light — otherwise known as light waves that vibrate in a specific direction but not all directions — and instructs each robot what direction to rotate its gears.
The team noted that each robot is programmed on two parameters — the direction of the polarized light, which determines what direction to move in, and the intensity of the polarized light, which controls how forcefully to move and how much to apply those forces.
Using an “if-then” ruleset, the flexible control system allowed the researchers to guide the collective behavior of the robots without programming new instructions for each desired movement or shape.
During trials of the system, the 20-robot collective alternated between solid and fluid states via controlled light intensity fluctuations, which reportedly improved efficiency over steady signals.
In additional trials, two groups of robots demonstrated that they could stretch toward each other and then connect in the middle, forming a bridge capable of bearing roughly 5 kg, while other configurations could bear the weight of a human weighing up to 70 kg.
Further, the collective robots flowed around objects, creating shapes like wrenches, and repaired defects.
The study, "Material-like robotic collectives with spatiotemporal control of strength and shape," appears in the journal Science.
