LIG-Based High-Sensitivity Multiplexed Sensing System for Simultaneous Monitoring of Metabolites and Electrolytes

Abstract

With improvements in medical environments and the widespread use of smartphones, interest in wearable biosensors for continuous body monitoring is growing. We developed a wearable multiplexed bio-sensing system that non-invasively monitors body fluids and integrates with a smartphone application. The system includes sensors, readout circuits, and a microcontroller unit (MCU) for signal processing and wireless communication. Potentiometric and amperometric measurement methods were used, with calibration capabilities added to ensure accurate readings of analyte concentrations and temperature. Laser-induced graphene (LIG)-based sensors for glucose, lactate, Na⁺, K⁺, and temperature were developed for fast, cost-effective production. The LIG electrode's 3D porous structure provided an active surface area 16 times larger than its apparent area, resulting in enhanced sensor performance. The glucose and lactate sensors exhibited high sensitivity (168.15 and 872.08 μAmM^-1cm^-2, respectively) and low detection limits (0.191 and 0.167 μM, respectively). The Na⁺ and K⁺ sensors demonstrated sensitivities of 65.26 and 62.19 mVdec^-1, respectively, in a concentration range of 0.01-100 mM. Temperature sensors showed an average rate of resistance change per °C of 0.25%/°C, within a temperature range of 20-40 °C, providing accurate body temperature monitoring.

Keywords: K+ sensor; Na+ sensor; glucose sensor; lactate sensor; laser-induced graphene; wearable biosensor.

Figure 2

FE-SEM images of LIG electrode. (a) Top view. (b) Cross-sectional view.

Figure 3

(a) Raman spectrogram of PI film and LIG. (b) Raw CV plot and (c) peak current plot of LIG electrode according to scan speed. (d) Plot of potential difference with and without PVB coating Ag/AgCl RE vs. commercial Ag/AgCl at various NaCl concentrations.

Figure 1

(a) Left: Multisensor array Right: Passivation layer. (b) Laser irradiation process of LIG-based electrodes. (c) Picture of the multisensor array. (d) Structure of multisensor array. (e) Picture of multisensor and multiplexed sensing system board. (f) Block diagram of multisensor and multiplexed sensing system board.

Figure 4

Plot of (a) glucose and (b) lactate sensor’s amperometric current depending on glucose and lactate concentration. (c) Plot of lactate sensor’s sensitivity in the lactate concentration range between 0.1 mM and 10 mM. (d) Plot of lactate sensor’s amperometric current in 0–0.5 mM lactate concentration range. Sensitivity and LOD comparison plot of enzymatic electrochemical.

Figure 5

Sensitivity and LOD comparison plot of enzymatic electrochemical (a) glucose and (b) lactate sensors. Plot of (c) Na⁺ and (d) K⁺ sensor’s potential according to Na⁺ and K⁺ concentration.

Figure 6

Selectivity plot of (a) glucose, (b) lactate, (c) Na⁺, and (d) K⁺ sensor.