Battery-free devices that have skin-like properties can be realized using a soft laminating strategy. Small, wearable sensors that monitor health offer opportunities for improving personalized care, but powering these systems remains a challenge. Instead of applying rigid batteries, John Rogers at the University of Illinois at Urbana-Champaign and his colleagues from the United States and China developed a wearable device that captures far-field radio frequency (RF) power from sources such as cell-phone signals. Biological tissues have changeable dielectric properties that make it tricky to optimize RF energy harvesting. Switching from typical monolithic fabrications to a modularized approach in which components such as ultrathin antennas and voltage doublers are produced and tested separately proved successful. To avoid damaging their elastomeric substrates, the team laminated components together with soft wetting techniques and cold welding of gold electrodes.
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