Fig. 4: Design and characterization of the wearable processor for heart rate (HR) monitoring.
From: All-printed chip-less wearable neuromorphic system for multimodal physicochemical health monitoring
a Schematic illustration of the wearable HR monitoring system, which translates cardiovascular signals into synaptic currents. b Schematics of the HR processing module components, comprising the receptor (pressure-sensitive sensor) and processor (synaptic device). c Optical images of a wearable HR processing module, showing the integration of skin-attached receptors and processors. Scale bar, 1 cm. d Calibration plot of the conductive sponge-based pressure sensor under varying pressure levels. I and I0 represent the current responses under applied pressure load and baseline (no pressure load), respectively. Error bars represent s.d. of the mean from 5 different samples. VD = 1 V, I0 ~ 26 μA. e Resistance variations of the conductive sponge under different body conditions. R and R0 represent the resistance under exercise and at rest, respectively. R0 ~ 38 kΩ. BPM, beats per min. f Voltage signal output after processing the resistance changes through the amplifier circuit. g Calibration curve correlating the frequency of the amplified voltage pulses with a commercial HR monitor. h Characterization of the PSC changes during HR module operation, with readings taken after 3 s of biosignal input, followed by a reset. i Real-time PSC changes updated under varying body conditions. Inset numbers were collected using a commercial HR monitor. j Calibration curve comparing PSC changes from the synaptic HR processor with readings from the commercial HR monitor. Error bars represent s.d. of the mean from 5 repeated measurements. k Continuous 2 h HR monitoring with a commercial HR monitor (black) and the wearable synaptic HR processor (red) during various activities performed by the subject.
