Design, Development and Characteristics of an In-Shoe Triaxial Pressure Measurement Transducer Utilizing a Single Element of Piezoelectric Copolymer Film

In gait analysis, there is growing awareness of the

need to simultaneously measure shear and vertical forces for the

diagnosis and treatment assessment of pathological foot disorders.

This is especially the case in the measurement of the forces

between the plantar surface of the foot and the shoe. Although

clinical awareness of the need to simultaneously measure shear

and vertical forces under the foot has increased little has been done

to provide the technology. This is mainly due to the difficulty in

constructing devices capable of carrying out this task in the in-shoe

environment. The aim of this paper is to describe the development

and characteristics of a miniature triaxial transducer measuring

10 10 2.7 mm and a weight of only 2 g. This transducer

is capable of simultaneously measuring three orthogonal forces

under any location of the plantar surface of the foot utilizing a

single element piezoelectric copolymer P(VDF-TrFE). Transducer

sensitivity, linearity, hysteresis, cross-talk and temperature dependence

is presented. As well as in-shoe force measurement, this

triaxial transducer could have other biomedical and general engineering

applications, e.g., prosthetic interface forces, handgrip

forces, sport, robotics, etc.