Fig. 3: Design and characterization of the wearable analog processor for core-body temperature (CBT) monitoring.
From: All-printed chip-less wearable neuromorphic system for multimodal physicochemical health monitoring
a Schematic of the wearable CBT sensing mechanism based on a single-heat flux model. Tskin, temperature of skin-device interface; TAI, temperature of device-ambient interface; Rskin and Rdevice, thermal resistances of the skin and the device, respectively. Inset, optical image highlighting key components including Au reference lines and temperature-sensitive MXene lines. Similar morphological features are observed at more than five locations in each of the three independently prepared samples. Scale bar, 200 μm. b Detailed schematic of the wearable CBT monitoring system with operational details. Input voltages are set at Vskin = − 7.5 V and VAI = 7.5 V. VOUT+ and VOUT- represent the synaptic inputs corresponding to Tskin and TAI. c SEM images of the inkjet-printed MXene line surface. Scale bars, 200 μm (Left) and 1 μm (Right). d Thermal and optical (inset) images of the wearable CBT monitor attached to human skin. Scale bars, 2 cm. e The resistance variation of the Au and MXene lines as a function of temperature. f Output voltage from the voltage divider circuit, comprising Au and MXene lines, under varying temperatures with a supply voltage of 7.5 V. g LTP/D characteristics of the synapse under different voltage amplitudes. h Plots of PSC change per single weight update as a function of the voltage amplitude. Vamp, voltage amplitude. Redline, exponential growth fitting. Error bars represent s.d. of the mean from 5 synaptic transistors. i Additive and subtractive characteristics of the synaptic calculator with two biosignal input terminals. j Real-time biosignal input plots obtained from attaching CBT sensors to various body parts in different environments. k Dynamic temperature plots recorded over a 2 h period, including Tskin, TAI, mathematically calculated CBT based on sensor readings (Tcal), and synaptic CBT output (Tsynapse), and CBT values measured using a medical-grade armpit thermometer (Tref).
