Fabric-Based Electrochemical Glucose Sensor with Integrated Millifluidic Path from a Hydrophobic Batik Wax

Abstract

In recent years, measuring and monitoring analyte concentrations continuously, frequently, and periodically has been a vital necessity for certain individuals. We developed a cotton-based millifluidic fabric-based electrochemical device (mFED) to monitor glucose continuously and evaluate the effects of mechanical deformation on the device's electrochemical performance. The mFED was fabricated using stencil printing (thick film method) for patterning the electrodes and wax-patterning to make the reaction zone. The analytical performance of the device was carried out using the chronoamperometry method at a detection potential of -0.2 V. The mFED has a linear working range of 0-20 mM of glucose, with LOD and LOQ of 0.98 mM and 3.26 mM. The 3D mFED shows the potential to be integrated as a wearable sensor that can continuously measure glucose under mechanical deformation.

Keywords: chemical and biological sensor; continuous glucose monitoring; fabric-based; millifluidic devices and lab-on-chip devices; sensor testing and evaluation; stencil printing.

Figure A1

Measurement setup for chronoamperometry analysis.

Figure 1

Schematic illustration of the mFED fabrication: (a) Cotton fabrics electrode consists of reference electrode (RE), working electrode (WE), and counter electrode (CE). (b) Wax pattern to create the fluidic chamber, covering the area of RE, WE, and CE. (c) Full mFED design. (d) Vinyl sticker attached to a mat of a digital cutter. (e) Vinyl sticker cut for C-PB stencil. (f) Vinyl sticker cut for Ag/AgCl stencil. (g) C-PB stencil was placed on top of scoured cotton fabric. (h) Applying C-PB ink. (i) Cotton fabric with C-PB ink pattern. (j) Ag/AgCl stencil was placed on top of scoured cotton fabric. (k) Applying Ag/AgCl ink. (l) Cotton fabric with Ag/AgCl and C-PB ink patterns. (m) Paper coated with wax. (n) The fluidic chamber stencil was sandwiched between cotton fabric (with Ag/AgCl and C-PB patterns) and wax-impregnated paper. The wax pattern was transferred to the cotton fabric by using a hot laminator. (o) The finished batch of mFED.

Figure 2

Illustration of the electrochemical measurement setup.

Figure 3

Fabrication of the continuous mFED platform and its evaluations. (a) Electrode patterns on fabric. (b) Wax pattern to be transferred to fabric with electrode patterns. (c) Final design. (d,e) Folding step in an accordion fashion. (f) Fabricated mFED for continuous measurement. (g) Mechanical strain test setup for bending movement. (h) For continuous measurement under folding strain.

Figure 4

Cyclic voltammograms of C-PB electrodes on various scan rates in 6 $\mathsf{\mu }$L 0.1 M PBS.

Figure 5

(a) CVs of the glucose mFED as obtained in the absence and presence of ${\mathrm{H}}_2{\mathrm{O}}_2$. (b) Effect of applied potential on the glucose mFED extracted from data in part (a). (c) Signal-to-background ratio extracted from the data shown in part (b).

Figure 6

(a) Chronoamperograms of glucose with different concentrations ranging from 0–20 mM. (b) Linear calibration curve of glucose detection.

Figure 7

Results on continuous glucose evaluations: (a) Chronoamperograms of continuous dynamic measurement of mFED under three different solutions: 0.1 M PBS, five mM glucose, and ten mM glucose. (b) Continuous measurement using a real sample (Chemistry Control Level I) for three hours. (c) Chronoamperograms of enzyme retention experiment using 2D µFED for three hours using intermittent sampling with 15 min intervals.

Figure 8

(a) The anodic current responses of the 3D mFED during normal (planar) position and under mechanical strain using flowing 5 mM glucose solution in the reservoir. (b) The anodic current response of the 3D mFED during normal (planar) position and under different folding conditions using a flowing five mM glucose solution in the reservoir.