Digital Clay modules being manipulated.

There are two approaches to understanding digital clay:

At Xerox PARC it is a subset of the modular robotics project.  As such it is a stripped down version of a modular robot.  That is, there is a) no active coupling and b) no actuation for producing module to module motions. Changes to an assembly of modules is made by a user.  But it embodies one very important aspect—that the modules have some capacity to sense or know their own orientation in space with respect to other modules. As such it may be a useful hardware system for testing software, communications, power distribution for physically modular and reconfigurable systems.

The other approach is to see it as a 3 dimensional human-computer interface.  A structure where physical changes made to the structure are represented in a computer model.  There are plenty of gross structures with this quality, animation armatures, or robots for example. This structure might be composed of tiny elements. So what you would have would be glob of material, highly structured at a small scale but relatively unstructured at a normal scale. Conventional robots by contrast are highly structured at a normal scale. As with clay the user shapes the material into some form or orientation The orientation or distribution of the inherently regular structure is sensed and directly represented in the computer. It is not as though this in and of itself would be a groundbreaking advance; laser imaging can relatively easily generate a 3d computer representation of a model. What is possible is a smart material or structure that a user (designer?) can actually experience in real 3d space,  and yet has a direct representation in a cad program.  You can further imagine that the material might be specialized for different uses or different structural properties. Material as Interface--Definitions

There are two kinds of structures you can imagine.  The first is made up of permanently connected modules.   Below is a prototype of such a structure.  It is made up of tetrahedral nodes connected by several right angle links which are free to rotate.  The overall topology is similar to the molecular structure of diamond.  The resulting structure can be freely molded.   Angle sensors at each joint could provide the information necessary for a computer model of the structure.  Obviously for such a structure to be useful would require a large number of nodes and a very large number of calculations.

The second type which I have called Digital Clay, and which is the main focus of my work at Xerox PARC, is made up of an assembly of individual modules.  Below is a solid model of such an assembly made up of rhombic dodecahedral  modules.

Future Link: Why a rhombic dodecahedron?

Each individual module must be able to sense to which other modules it is connected as well as its orientation with respect to the other modules; i.e. which face is connected to which.  Thus each module must have its own identity within the assembly, and each of the 12 faces must have a unique identity within a module.

Future Link: Method for cataloguing the coordinates and orientations of rhombic dodecahedrons within a regular assembly.

Below are first generation prototypes of Digital Clay modules.  Each face has two NdFeB magnets (so that they adhere to one another), a power and ground connection, as well as a communication line unique to each face. 

The current generation of digital clay has modules the size of a large marble (1" Diameter).

Each module is made of a flex circuit with 12 rigid backer boards and a single component sheet which folds into the center of the module.  Each module has an 8 MHz PIC processor with 6 serial ports communicating in pairs to each of the twelve faces.  Each face has 4 sets of three connection pads--power, ground, and communication.  Each group of connection pads is backed by a NdFeB magnet (2 north, 2 south) one of which is attached to the center of a spiral cut in the Kapton to insure a good connection.