These little robots are powered by an electromagnetic field, similar to how you would wirelessly charge a cell phone. By changing the frequency of the magnetic field, the researchers are able to precisely control the exact movement of their prototype.
For instance, one triangular robot that’s no bigger than a quarter is composed of three triangular pieces of thin plastic, attached with hinges to a middle triangle that has a circuit. The hinges are controlled by coils of a metal called “shape-memory alloy,” which changes its form when it’s exposed to heat. When an electric current starts running through the central circuit, these coils heat up and contract, causing the three triangles to fold up toward the center of the robot. When the current stops, the hinges return to their flat state.