Design considerations for photovoltaic energy harvesting in wearable devices.

Wearable technology is emerging as a solution for various bio-mechanic and health-metric applications. Solar photovoltaic energy is a viable supplemental power source that can reduce battery size requirements in wearables. This study outlines the considerations for a wearable sleeve device and its associated power converter system using commercially-available flexible photovoltaic panels located on the forearm. Investigation of the effects of curvature shows that while curvature of the panel around a forearm does reduce output power, the angle relative to the light source has a more pronounced effect on both output power and voltage characteristics. Among various panel arrangements on the forearm, that with five individual panels of smaller width provided the highest output power after the boost converter power stage. Testing under various static positions, the PV sleeve provided up to 94 mW outdoors, which can effectively reduce the battery size while maintaining user safety.

Electronics-free soft robot has a nice ring to it.

A fluidic ring oscillator provides timing to soft robots, thus enabling complex locomotion and load carrying.

Ultra-sensitive and resilient compliant strain gauges for soft machines.

Soft machines are a promising design paradigm for human-centric devices1,2 and systems required to interact gently with their environment3,4. To enable soft machines to respond intelligently to their surroundings, compliant sensory feedback mechanisms are needed. Specifically, soft alternatives to strain gauges-with high resolution at low strain (less than 5 per cent)-could unlock promising new capabilities in soft systems. However, currently available sensing mechanisms typically possess either high strain sensitivity or high mechanical resilience, but not both. The scarcity of resilient and compliant ultra-sensitive sensing mechanisms has confined their operation to laboratory settings, inhibiting their widespread deployment. Here we present a versatile and compliant transduction mechanism for high-sensitivity strain detection with high mechanical resilience, based on strain-mediated contact in anisotropically resistive structures (SCARS). The mechanism relies upon changes in Ohmic contact between stiff, micro-structured, anisotropically conductive meanders encapsulated by stretchable films. The mechanism achieves high sensitivity, with gauge factors greater than 85,000, while being adaptable for use with high-strength conductors, thus producing sensors resilient to adverse loading conditions. The sensing mechanism also exhibits high linearity, as well as insensitivity to bending and twisting deformations-features that are important for soft device applications. To demonstrate the potential impact of our technology, we construct a sensor-integrated, lightweight, textile-based arm sleeve that can recognize gestures without encumbering the hand. We demonstrate predictive tracking and classification of discrete gestures and continuous hand motions via detection of small muscle movements in the arm. The sleeve demonstration shows the potential of the SCARS technology for the development of unobtrusive, wearable biomechanical feedback systems and human-computer interfaces.