Imparting dexterity, touch, and visual expression in soft robotics

Supplemental file(s) description: Supplemental MoviesAs robots transition from industrial automation tools to devices that interact directly with humans, new hardware is needed to ensure that these interactions are safe and comfortable for the user. Soft robots use elastomeric materials with low mechanical compliance to create systems that are intrinsically safe for human interaction. This work develops fabrication techniques and materials systems that impart soft robotics with dexterous movement, tactile sensing and visual expression. A digital mask projection stereolithography (DMP-SL) system is developed to directly 3D print soft, pneumatic actuators. The mechanical properties of a commercially available, photopolymerizable elastomeric material are characterized and numerical simulations are used to design pleated actuators that achieve large overall deformations with small local strains. Antagonistic pairs are combined to achieve high degree of freedom (DOF) actuators with cycle times that rival high speed contraction in animal muscle. In order to enable feedback control and visual expression, an electroluminescent skin is developed using hyperelastic light emitting capacitors (HLECs). The HLEC is composed of transparent hydrogel electrodes that sandwich a ZnS phosphordoped dielectric elastomer layer. Under a high electric field, the HLEC emits light while stretching uniaxially to >480% strain. This deformation results in a measureable change in capacitance. The HLEC is integrated into the skin of a soft robot, providing it with dynamic coloration and sensory feedback from external and internal stimuli. To enable applications in human-computer interaction, a portable, battery-powered control system is developed for four HLECs embedded in a flat sheet. This sheet turns into a dome when pressurized, forming a tactile interface with dynamic coloration. The co-located touch sensing and light-emitting capabilities of this system are demonstrated by developing an interactive memory game