Fig. 2: Mechanical engineering designs for the creation of flexible and stretchable devices that adapt to the body’s movements.

a Textile-based EBFCs integrated with socks for self-powered lactate sensors, subjected to mechanical resilience tests during twisting deformations. Adapted with permission from ref. 79 © 2016, Royal Society of Chemistry. b Wearable diabetes monitoring utilizing silicon film attached to human skin. Adapted with permission from ref. 80 © 2016, Springer Nature Limited. c Printed devices for electrochemical sensors and EBFCs based on stretchable CNT-based ink. Adapted with permission from ref. 81. © 2016, American Chemical Society. d Skin-mountable wearable EBFC device with an “island-bridge” design capable of harvesting sweat energy to power a light-emitting diode (LED). Adapted with permission from ref. 82. © 2019, WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.