We have caused natural motion in synthetic robots by using organic elastomers (crosslinked polymers above their glass transition temperature) that deform continuously over large ranges of strain.

• Large shape changes allow easy switching between gaits: walking or undulating.
• The tough materials create robots capable of sustaining large impact forces without damage.
• The robots can be scaled for a mission simply by increasing the size of the mold used to cast the rubber and choosing an appropriate elastic modulus for the material.

Relevant Publications:

• Shepherd, R. F. et al., (2011). Multigait soft robot. PNAS, 108(51), 20400-20403.
• Ilievski, F. et al., (2011). Soft Robotics for Chemists. Angewandte Chemie-International Edition, 50 (8), 1890-1895.
• Shepherd, R. F. et al., (2013). Soft Machines That are Resistant to Puncture and That Self Seal. Advanced Materials, 25(46), 6709-6713.
• Tolley MT et al., (2014). A Resilient, Untethered Soft Robot. Soft Robotics 1(3): 213-223.

We have developed a composite of two entangled foams: an elastomer and a low melting temperature metal, that exhibits dynamic shape morphing and shape memory actuation. Additionally, by melting and freezing the metal foam, the composites can both self-heal and be assembled into larger, continuous structures from smaller sub-components. The composite has been embedded into two soft robotic devices to demonstrate the capability for reversible stiffness in soft robots.

Relevant Publications:

• V. Meerbeek, I. M., MacMurray, B., Kim, J. W., Robinson, S. S., Zou, P., Silberstein, M., Shepherd, R. (2016). Morphing Metal and Elastomer Bicontinuous Foams for Reversible Stiffness, Shape Memory, and Self-Healing Soft Machines. Advanced Materials.

We have developed a hyperelastic light emitting capacitor (HLEC) that can expand its surface area by >635% while actively emitting light and sensing this deformation. The center layer is a thin sheet of silicone with embedded ZnS phosphors that glow under a high electric field. Transparent, ionically conductive hydrogel electrodes sandwich the center dielectric layer.

Relevant Publications:

• C. Larson^†, B. Peele^†, S. Li^†, S. Robinson, M. Totaro, L. Beccai, B. Mazzolai, R. Shepherd (2016). Highly stretchable electroluminescent skin for tactile sensing and optical signaling. Science. (^†First author)

Using our custom DMP-SL printer, we can quickly fabricate high resolution actuators from soft materials. Inspired by the complex three-dimensional arrangement of muscles in octopus tentacles, we have designed soft machines that incorporate multiple actuators into a monolithic, printed structure. These antagonistic pairs allow the printed tentacle to actuate over a wide range of motion. As shown in the video to the right, multiple antagonistic pairs can be combined to create complex, 3D motions.

• High-DOF actuators can be quickly prototyped as a monolithic structure.
• High speed actuation with periods of less than 70ms.
• Working pressures greater than 345 kPa (50 psi).

Relevant Publications:

• Peele, B. N. et al., (2015). 3D printing antagonistic systems of artificial muscle using projection stereolithography. Biomimetics and Bioinspiration, 10(5):055003.