Fig. 2.
Robotic metamaterial with nonreciprocal interactions. a Robotic metamaterial made of 10 unit cells mechanically connected by soft elastic beams (i). Scale bar: 2 cm. (bc) Closeup b and sketch c on two unit cells. Each unit cell is a minimal robot with a unique rotational degree of freedom that comprises an angular sensor (ii), a coreless DC motor (iii), and a microcontroller (iv). Each unit cell communicates with its right neighbor via electric wires (v). These components allow to program a control loop characterized by the feedback parameter α (see main text for definition). d Rescaled torsional stiffnesses CL→R/C (red) and CR→L/C (blue) as a function of the feedback parameter