Flexible micro thermoelectric generators with high power density and light weight

Body heat as a sustainable energy source can be harvested for wearable and implantable devices. Flexible micro thermoelectric generators (TEGs) show great promise for converting body heat into electricity for wearable applications owing to their compact structure, light weight, and flexibility. Here, we report on flexible micro TEGs with high power density and light weight fabricated via pulse electroplating. Through tuning the electroplating conditions of thermoelectric pillars and improving the electrical contact between pillars and electrodes, an optimized flexible micro TEG achieves maximum areal and gravimetric power densities as high as 14.3 mW cm-2 and 189 mW g-1, respectively, under a temperature difference of 29.9 degrees C. As a result, our flexible micro TEG demonstrates a device-level voltage factor of 65.2 mV cm-2 K-1, a power factor of 16.0 mu W cm-2 K-2, and a normalized power to weight ratio of 212 mu W g-1 K-2. The voltage factor and normalized power to weight ratio of our flexible micro TEG are over three times higher than the counterparts of cross-plane flexible TEGs in the literature, which opens new opportunities for flexible TEGs to be applied in self-powered wearable electronics.