Stretchable fingernail sensors for measurement of fingertip force

This paper describes a novel stretchable fingernail sensor for measuring fingertip forces for human-computer interaction. The fingernail sensor uses photoplethysmography to measure the change in blood perfusion in the fingernail bed when the fingerpad touches a surface with various forces. The original fingernail sensor was rigidly attached to the human fingernail, necessitating a customized fabrication for each individual user. Using novel fabrication techniques, a new stretchable sensor has been developed, where optoelectronic components are embedded within a soft rubber substrate, connected by stretchable conductors. This stretchable sensor can conform to the two-dimensional curvature of any human finger, eliminating the need for individual customization. In this paper, we demonstrate the successful fabrication of a prototype sensor with two LEDs and two photodetectors.