One of the primary impediments to building ensembles with many modular robots is the complexity and number of mechanical mechanisms used to construct the individual modules. As part of the Claytronics project?-which aims to build very large ensembles of modular robots?-we investigate how to simplify each module by eliminating moving parts and reducing the number of mechanical mechanisms on each robot by using force-at-a-distance actuators. Additionally, we are also investigating the feasibility of using these unary actuators to improve docking performance, implement intermodule adhesion, power transfer, communication, and sensing.

A simple and robust inter-module latch is possibly the most important component of a modular robotic system. This paper describes a latch based on capacitive coupling which not only provides significant adhesion forces, but can also be used for inter-module power transmission and communication. The key insight that enables electrostatic adhesion to be effective at the macroscale is to combine flexible electrodes with a geometery that uses shear forces to provide adhesion. To measure the effectiveness of our latch we incorporated it into a 28cm x 28cm x 28cm modular robot. The result is a latch which requires almost zero static power and yet can hold over 0.6N/cm^2 of latch area.