Carnegie Mellon University Website Home Page


A lattice-style modular robot, the 22-cubic-centimeter Cube, which has been developed in the Carnegie Mellon-Intel Claytronics Research Program, provides a base of actuation for the electrostatic latch that has also been engineered as part of this program.   The Cube (pictured below, right) also models the primary building block in a hypothetical system for robotic self-assembly that could be used for modular construction and employ Cubes that are larger or smaller in scale than the pictured device.

Elecrostatic Latches    

The design of a cube, which resembles a box with starbursts flowering from six sides, emphasizes several performance criteria: accurate and fast engagement, facile release and firm, strong adhesion while Cube latches clasps one module to another.   Its geometry enables reliable coupling of modules, a strong binding electrostatic force and close spacing of modules within an ensemble to create structural stability.

Designed to project angular motion from the faces of its box-like shape, the Cube extends and contracts six electrostatic latching devices on stem assemblies.   By this mechanism, the latches of a Cube integrate with latches on adjacent Cubes for construction of larger shapes.

With extension and retraction of stem-drive arms that carry the latches, the module achieves motion, exchanges power and communicates with other Cubes in a matrix that contains many of these devices.   Combining these forces of motion, attachment and data coupling, Cubes demonstrate a potential to create intricate forms from meta-modules or ensembles that consist of much greater numbers of Cubes; numbers determined by the scale of Cubes employed in an ensemble of self-construction.  

To create motion for a Cube in a matrix of many cubes, a direct-current motor inside the Cube 's central frame actuates expansion and contraction of electrostatic latches fixed to the ends of independent worm-drive assemblies.   Housed in individual tubes, the assemblies provide arms to support the motion of latches from six sides of the central frame.   Linear motion enables the Cube to exploit considerable lateral flexibility for forming shapes within a matrix.   The Cube measures 22 cm between faces when fully contracted and 44 cm when fully expanded.  

The worm-drive assembly extends the face of one cube to create contact with the face of an adjacent cube.   The electrodes on each face create one-half of a capacitor.   When the two "genderless, " star-shaped faces of adjacent Cubes integrate their combs, they complete a capacitor and form an electrostatic couple from the contact of electrodes, which binds the faces as a completed latch.  

Cube with Extended Worm-Drives
The capacitive couple, which forms the electrostatic latch, provides within an ensemble of Cubes not only adhesion and structural stability but also the transmission of power and communication.   In a meta-module of many cubes, power would move in discrete packets rather than as a continuous current, in a mode similar to data moving through a network in discrete packets of bytes that reassemble into larger packages of information at the point of delivery.   This packet delivery of energy would enable the meta-module or ensemble to move power from cubes that have a surplus to others that require more of it.  

Four sub-circuits within the capacitive couplings of these electrostatic latches make possible this system of power transfer.   With these circuits, the simultaneous transfer of data would follow an even simpler scheme.

Cubes reconfigure by expanding the connected faces of two neighboring modules so that one is pushed one block length across the assembly.   Then by contracting its extended arm, it pulls the next module forward.   Such motion within a meta-module consisting of sufficiently large numbers of cubes could form any conceivable shape.

This micro-electro-mechanical device thus presents a model for a type of robotic self-assembly of complex structures at both macro and micro scales.

Publications and Documents

Electrostatic Latching for Inter-module Adhesion, Power Transfer, and Communication in Modular Robots,
    Mustafa Emre Karagozler, Jason D. Campbell, Gary K. Fedder, Seth Copen Goldstein, Michael Philetus Weller, and Byung W. Yoon. In Proceedings of the IEEE International Conference on Intelligent Robots and Systems (IROS '07), October, 2007. See karagozler-msreport07.
Movement Primitives for an Orthogonal Prismatic Closed-Lattice-Constrained Self-Reconfiguring Module,
    Michael Philetus Weller, Mustafa Emre Karagozler, Brian Kirby, Jason D. Campbell, and Seth Copen Goldstein. In Workshop on Self-Reconfiguring Modular Robotics at the IEEE International Conference on Intelligent Robots and Systems (IROS) '07, October, 2007.