Abstract-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 electric fields and capacitive coupling. Our design provides not only significant adhesion forces, but can also be used for inter-module power transmission and communication. The key insight presented in this paper, and the factor that enables electrostatic adhesion to be effective at the macroscale, is the use of electric field attraction to generate frictional shear forces rather than electric field attraction alone. A second important insight is that a specific degree of flexibility in the electrodes is essential to maximize their mutual coupling and the resulting forceselectrodes which are too flexible or too rigid will perform less well. To evaluate the effectiveness of our latch we incorporate it into a cubic module 28cm on a side. The result is a latch which requires almost zero static power and yet can hold 0.6N/cm 2 of latch area.

In this article we describe a concept for a new type of material, which we call claytronics , made out of very large numbers-potentially millionsof submillimeter-sized spherical robots. While still only a concept, we have completed a considerable amount of initial design and experimentation work, enough at this point to allow us to understand what is readily achievable within a short time frame (less than a decade) and also to identify some of the most significant technical challenges yet to be overcome. To date, we have developed and analyzed several promising engineering designs, conducted numerous large-scale experiments on a high-fidelity physics-based simulator, and successfully carried out several prototype three-dimensional (3D) microelectromechanical systems (MEMS) manufacturing runs. These experiences lead us to believe that there are no fundamental software or hardware barriers to realizing claytronics on a large scale and within a few years.While the most fundamental purpose of our research on claytronics is to understand manufacturing and programming of very large ensembles of independently actuated computing devices, it is also clear that such a material would have numerous practical applications, ranging from shape-shifting radio antennas (important for software-defined radios) to 3D fax machines. Perhaps our most fanciful-sounding application, however, is motivated by one of the most basic of human needs: to communicate and interact with others. Two centuries ago, the only practical way to carry on a real-time conversation with

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Figure 1. Sketching a woolly dinosaur with Posey Puppet Show.Posey is a physical construction kit that is instrumented to capture assembly and configuration information and convey it to a host computer. We have used Posey to build applications that deploy a reconfigurable physical model as a tangible interface for various domains. We demonstrate these applications to support a case for computationally enhanced construction kits as a semigeneral interaction modality.

We describe Posey, a computationally-enhanced hub-and-strut construction kit for learning and play. Posey employs a ball and socket connection that allows users to move the parts of an assembled model. Hubs and struts are optocoupled through the ball and socket joints using infrared LEDs and photosensors. Wireless transmitters in the hubs send connection and geometry information to a host computer. The host computer assembles a representation of the physical model as the user creates and configures it. Application programs can then use this representation to control computational models in particular domains.