Monitoring the Degree of Comfort of Shoes In-Motion Using Triboelectric Pressure Sensors with an Ultrawide Detection Range.

Shoes play an important role in sports and human daily life. Here, an in-shoe sensor pad (ISSP) attached to the vamp lining is based on a triboelectric nanogenerator (TENG) for monitoring the real-time stress distribution on the top side of a foot. Each sensor unit on this ISSP is an air-capsule TENG (AC-TENG) consisting of activated carbon/polyurethane (AC/PU) and microsphere array electrodes. The detection range of each AC-TENG reaches 7.27 MPa, which is enough for monitoring the pressure change during different sports. This multifunctional ISSP can realize many typical functions of conventional smart shoes, including step counting and human-machine interaction. Moreover, it can also reveal special information, including the fitness of shoes, the stress concentration on toes, and the in-motion comfort degree. The signal processing and data transmission modules in the system have a hybrid power supply with wireless power transfer, while the real-time information about feet can be observed on a cell phone. Hence, this ISSP provides a potential approach to study the feet motion and comfort degree of shoes in long-term operations, which can guide both athlete training and the customized design of shoes.