Researchers from Japan’s Osaka University have found how the thermoelectric effect, or converting temperature differences into electricity, can be best used to power small, flexible devices, reports the journal Advanced Materials Technologies. Future healthcare applications will require internet connectivity between billions of sensors, and the devices that enable them must be small, flexible, reliable and environmentally sustainable. Batteries are not optimal because continually replacing them is inconvenient and expensive. Many researchers have optimized device performance solely from the standpoint of the thermoelectric materials themselves. “Our approach is to also study the electrical contact, or the switch that turns the device on and off,” explains Tohru Sugahara, the corresponding author of the study. “The efficiency of any device critically depends on the contact resistance.” Thermoelectric power generators are self-sustaining, self-powered and have no moving parts. Solar power and vibrational power do not have all of these advantages.