A study on the fabrication of metal microneedle array electrodes for ECG detection based on low melting point Bi–In–Sn alloys

Figures

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  Figure 1. Images of interface between skin and (a) wet electrode with conductive gel, (b) flat dry electrode, and (c) MAE without conductive gel.

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  Figure 2. A schematic diagram of the fabrication process of the PUA-coated MAE through micromolding of Bi–In–Sn alloy.

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  Figure 3. (a) Image of the fabricated Bi–In–Sn MAE after the micromolding process. The sharpness of the needle tip is around 72 μm when it is fabricated under atmospheric pressure, as shown in the magnified image. (b) After fabricating MAE in a vacuum environment, the sharpness of the needle tip decreases to below 10 μm. (c) Image of Bi–In–Sn MAE before PUA coating, along with its magnified SEM image. (d) Image of Bi–In–Sn MAE after PUA coating, along with its magnified SEM image.

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  Figure 4. (a) Schematic illustration of the skin penetration performance test setup. (b) Stereo microscope image of full porcine skin dyed with 0.25% (v/v) trypan blue after removing the MAE.

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  Figure 5. (a) Impedance change in 0.9% (w/v) NaCl aqueous solution according to PUA coating thickness. (b) Impedance change of Bi–In–Sn MAE according to NaCl electrolyte concentration from 0 to 1.0%. (c) Schematic illustration of the EII test setup. (d) Displacement-Impedance graph of Bi–In–Sn MAE.

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  Figure 6. (a) ECG measurement image using a three-electrode method. Bi–In–Sn MAEs were attached to both wrists, and an Ag/AgCl electrode was attached to the right ankle. ECG graphs obtained using (b) Ag/AgCl electrodes and (c) Bi–In–Sn MAEs.