Cephalopods such as octopuses have a combination of a stretchable skin and color-tuning organs to control both posture and color for visual communication and disguise. We present an electroluminescent material that is capable of large uniaxial stretching and surface area changes while actively emitting light. Layers of transparent hydrogel electrodes sandwich a ZnS phosphor-doped dielectric elastomer layer, creating thin rubber sheets that change illuminance and capacitance under deformation. Arrays of individually controllable pixels in thin rubber sheets were fabricated using replica molding and were subjected to stretching, folding, and rolling to demonstrate their use as stretchable displays. These sheets were then integrated into the skin of a soft robot, providing it with dynamic coloration and sensory feedback from external and internal stimuli.

The detailed mechanical design of a digital mask projection stereolithgraphy system is described for the 3D printing of soft actuators. A commercially available, photopolymerizable elastomeric material is identified and characterized in its liquid and solid form using rheological and tensile testing. Its capabilities for use in directly printing high degree of freedom (DOF), soft actuators is assessed. An outcome is the ∼40% strain to failure of the printed elastomer structures. Using the resulting material properties, numerical simulations of pleated actuator architectures are analyzed to reduce stress concentration and increase actuation amplitudes. Antagonistic pairs of pleated actuators are then fabricated and tested for four-DOF, tentacle-like motion. These antagonistic pairs are shown to sweep through their full range of motion (∼180°) with a period of less than 70 ms.

Although soft robotics promises a new generation of robust, versatile machines capable of complex functions and seamless integration with biology, the fabrication of such soft, three dimensional (3D) hierarchical structures remains a significant challenge.

An intrinsically soft and stretchable multicolor display and touch interface is reported. Red, green, and blue pixels are formed separately by photopatterning transition-metal-doped ZnS embedded in silicone gels and transfer printing onto an elastomeric dielectric sheet. The device shows stable illumination while being stretched up to 200% area strain or under different deformation modalities. It also introduces capabilities for dynamic colorations and multipoint capacitive touch sensing.

Human skin contains highly specialized deformation receptors that allow us to intuitively and effortlessly interpret our surroundings. These sensors help us to localize touch and determine the degree of contact pressure. In addition, the innate understanding of our own body posture is also due to these mechanoreceptors. This work demonstrates a synthetic sensory-motor analog that can be 3D printed, using direct ink writing (DIW) onto soft, fluidic elastomer actuators (FEAs). This 3D printing technique uses two inks-one that is an ionically conductive hydrogel and another that is an electrically insulating silicone-which is then patterned and photopolymerized into stretchable capacitive sensors. In this paper, these sensors are used to enable tactile sensing and kinesthetic feedback in a pneumatically actuated haptic device. This capacitive skin enabled the device to detect a compressive force from a finger press of ~2 N, and an internal pressurization of as low as ~ 10 kPa.