Ferroelectric polymer-based fully printed flexible strain rate sensors and their application for human motion capture

Abstract

Flexible strain sensors are essential to realizing novel wearable electronics applications that include dynamic human-motion capture sensing devices. Various technologies have been proposed to fabricate flexible strain sensors for motion capture using low-cost printing methods. A new approach utilizing piezoelectric polymers has recently been proposed whereby ferroelectric polymer layers are formed on plastic substrates and employed in wearable sensor devices. However, in printed strain sensor devices using ferroelectric polymers, the influence of layer formulation on sensor properties has not been clear. We have developed fully-printed flexible strain sensors by optimizing the concentration and viscosity of a ferroelectric polymer solution. It was found that the ferroelectric layers using screen printing can be formed with flat morphologies and good crystallinity using solutions with viscosities of over 3.0 Pa s. Moreover, these printed ferroelectric strain sensors achieved practical performance levels, exhibiting ferroelectric characteristics of 6.0 μC cm-2 and 50 MV m−1. The sensors were employed in wearable bending sensors for human fingers to demonstrate their feasibility in motion capture applications. Despite a wide range of operating speeds, the fabricated sensors effectively measured bending rates.