Capacitive Heart-Rate Sensing on Touch Screen Panel with Laterally Interspaced Electrodes

Abstract

It is demonstrated that the heart-rate can be sensed capacitively on a touch screen panel (TSP) together with touch signals. The existing heart-rate sensors measure blood pulses by tracing the intensity of optically reflected light and this process requires considerable amounts of power and area. It is noticed that the variation of the effective dielectric constant of finger stemming from the difference of systolic and diastolic blood flows can be measured with laterally interspaced top electrodes of TSP. The spacing between a pair of non-adjacent top electrodes is found to be wide enough to distinguish heart-rate signals from noises. With the aid of Fast Fourier Transform, the heart-rate can be extracted reliably which matches with the one obtained by actually counting heart beats on the wrist.