Gait analysis by using electric signals from a triboelectric nanogenerator

Abstract

Gait monitoring is one of important healthcare methods. Gait disorders can be analysed by gait monitoring and related diseases can be further diagnosed. Daily living gait data are obtained by sensors such as accelerometers. In this study, A triboelectric nanogenerator (TENG) which is a well-known energy harvester was assembled into the accelerometer by attaching a drop-cast thin silicone rubber film to the movable mass and a thin nylon film to the fixed base of the accelerometer. Electrical outputs from this prepared TENG based gait monitoring device (TENGAIT) were investigated as the up-and-down reciprocating movement was applied by a Scotch yoke device in which the frequency of the up-and-down movement was controlled by an electric motor. The TENGAIT showed subsequent increase in voltage peaks from 2.5 V to 4 V and in current from 0.3 μA to 0.5 μA as the up-and-down frequency increased from 1 Hz to 5 Hz. The TENGAIT was then installed on a foot to obtain information about gait during walking on the spot in real-time. The voltage and the current showed 2.4 and 2.6 times increase, respectively, comparing the normal walking speed (0.8 Hz) to the fast walking speed (2 Hz). The light running could be distinguished from the fast walking by comparing gait speed and amplitude. And a gait cycle which includes the toe-touch, the heel-touch, the heel-off and the toe-off could be successfully analysed through changes in the shape of the current graph.