We present the automated design and manufacture of static and locomotion objects in which functionality is obtained purely by the unconstrained 3-D distribution of materials. Recent advances in multimaterial fabrication techniques enable continuous shapes to be fabricated with unprecedented fidelity unhindered by spatial constraints and homogeneous materials. We address the challenges of exploitation of the freedom of this vast new design space using evolutionary algorithms. We first show a set of cantilever beams automatically designed to deflect in arbitrary static profiles using hard and soft materials. These beams were automatically fabricated, and their physical performance was confirmed within 0.5-7.6% accuracy. We then demonstrate the automatic design of freeform soft robots for forward locomotion using soft volumetrically expanding actuator materials. One robot was fabricated automatically and assembled, and its performance was confirmed with 15% error. We suggest that this approach to design automation opens the door to leveraging the full potential of the freeform multimaterial design space to generate novel mechanisms and deformable robots.

We explore vacuum as bonding force for modular robotics. Vacuubes are a set of modules that propagate vacuum across their interfaces in order to generate adhesive forces to form and hold structures. We use analog circuits to simulate vacuum transients and understand critical design parameters and then validate these insights in experiments. A 49-module structure that employs vacuum bonding is demonstrated. We conclude that vacuum offers a relatively strong, simple, reliable, and power-efficient connection principle.

We demonstrate the evolution of locomoting amorphous robots composed of multiple materials. Research in evolutionary robotics has traditionally been limited to morphologies comprising rigid and discrete components, such as links connected with rotational or linear joints and actuators. In the continuous robots presented here, actuation is accomplished by periodic volumetric expansion and contraction of one or more materials composing the body of the robot. The challenges of representing evolvable multi-material freeform shapes and evaluation (simulation) of the resulting soft bodies are discussed. Several genotypic representations are explored which use a level-set threshold to generate the material distribution in the phenotype. Soft body simulation of the robot is accomplished using a relaxation algorithm to model the dynamics of the resulting amorphous machines under the actuation material expansion, gravity forces, and non-linear ground friction. These results open the door to a new design space that more closely mimics the freeform, amorphous and continuous nature of biological systems.

Multi-material 3D-printing technologies permit the freeform fabrication of complex spatial arrangements of materials in arbitrary geometries. This technology has opened the door to a large mechanical design space with many novel yet non-intuitive possibilities. This space is not easily searched using conventional topological optimization methods such as homogenization. Here we present an evolutionary design process for three-dimensional multi-material structures that explores this design space and designs substructures tailored for custom functionalities. The algorithm is demonstrated for the design of 3D non-uniform beams and 3D compliant actuators.