Interest in additive manufacturing has recently been spurred by the promise of multi-material printing and the ability to embed functionality and intelligence into objects. Here, we present an alternative to additive manufacturing, introducing an end-to-end workflow in which discrete building blocks are reversibly joined to produce assemblies called digital materials. We describe the design of the bulk-material building blocks and the devices that are assembled from them. Further, we detail the design and implementation of an automated assembler, which takes advantage of the digital material structure to restore positioning errors within a large tolerance. To generate assembly sequences, we use a novel CAD/CAM workflow for designing, simulating, and assembling digital materials. Finally, we evaluate the structures assembled using this process, showing that the joints perform well under varying conditions and that the assembled structures are functionally precise.

We introduce a discrete approach to robotic construction that enables the integration of structure, mechanism, and actuation and offers a promising route to on-demand robot fabrication. We demonstrate this with the assembly of two centimeter-scale electromechanical systems: a Discretely Assembled Walking Motor (DAWM) capable of producing large scale linear or rotary motion from five millimeter-scale part types as well as a Modular Tiny Locomoting Element (MOTILE) that can locomote on a variety of ferrous surfaces. The five part types each embody a limited capability including rigid (strut and node), flexural, magnetic, or coil. Through their arrangement in a three-dimensional lattice, we demonstrate the assembly of actuated mechanical degrees-of-freedom in useful small-scale machines. This work extends prior research in discrete material systems with the inclusion of flexural and actuation components. Actuation is accomplished with the use of voice coil actuator components that produce up to 42 mN of force and strokes of 2 mm. This performance compares well with other millimeter scale actuators and provides sufficient force to lift 28 connected nodes in our assembled lattice, or 7 other actuator components. DAWM is capable of stepping at rates of up to 35 Hz, resulting in velocities of up to 25 mm/s. Multiple DAWM systems can be stacked to add force and can be driven in-phase or out-of-phase to produce intermittent or continuous force, respectively. MOTILE can climb vertical surfaces at speeds of 2.46 body-lengths per second, representing the fastest vertical climbing robot in recently reported research. This approach to robot fabrication discretizes robotic systems at a much finer granularity than prior work in modular robotics and demonstrates the possibility of assembling useful small-scale machines from a limited set of standard part types.

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