Figure 5.

On-body real-time monitoring of sweat during stationary cycling: (a) photograph of a LIG-based sensor attached to the forearm of a subject for continuous monitoring of pH, Na⁺, and K⁺ levels in sweat, and the data were collected with a flexible, printed circuit board (FPCB) and then transmitted wirelessly to the smartphone-based application via Bluetooth; (b) photograph of the FPCB, which consists of (i) microcontroller, (ii) Bluetooth module, (iii) power switch and charging USB, (iv) sensor connector, (v) power management module, and (vi) lithium-ion battery; (c) enlarged photograph of the LIG-based sensor attached to the forearm of a human subject; (d) photograph of the developed Android application; (e) block diagram of FPCB showing the signal transduction from the LIG-based sensor to the custom-developed mobile application; (f) real-time sweat analysis results of pH, Na⁺, and K⁺ concentrations using the integrated wearable sensing system.