A stainless steel (SUS304) material with a thickness of 200 µm was cleaned and dried using ethanol according to the design shown in Fig. 1b . A microneedle sheet with a conductive lead was cut using a laser machine, after which the lead of the microneedle sheet was bent at 90°, degreased, and washed. The oxidized layer on the surface was removed using acidic detergent, followed by the formation of a protective layer via electrochemical Au plating.
The laser used in the fabrication process was a YLP-F Series Optical Fiber Laser marking machine, with the following conditions: laser wavelength 1.06 μm, engraving line speed 2000 mm/s, power 16 W, and engraving 1000 times. The microneedles could be fabricated by Huasheng Precision Hardware Co., Ltd. The acidic detergent contained 24% zinc oxide, 30% ammonium chloride, 6% hydrochloric acid, 30% acetic acid, 12% deionized water, and 3% surfactant and was provided by the company Yuncaitaotao.
The conditions of gold plating were as follows: the modified electrode was used as the working electrode, the pure gold electrode was used as the counter electrode, and silver chloride was used as the reference electrode, forming a three-electrode system. The three electrodes were immersed in 0.2 mmol/L gold sulfite solution, and a constant voltage of −0.3 V was applied and maintained for 1200 s. A uniform layer of gold atoms was coated on the electrode surface. The thickness of the gold plating was not characterized in this work.
The laser used in the fabrication process was a YLP-F Series Optical Fiber Laser marking machine, with the following conditions: laser wavelength 1.06 μm, engraving line speed 2000 mm/s, power 16 W, and engraving 1000 times. The microneedles could be fabricated by Huasheng Precision Hardware Co., Ltd. The acidic detergent contained 24% zinc oxide, 30% ammonium chloride, 6% hydrochloric acid, 30% acetic acid, 12% deionized water, and 3% surfactant and was provided by the company Yuncaitaotao.
The conditions of gold plating were as follows: the modified electrode was used as the working electrode, the pure gold electrode was used as the counter electrode, and silver chloride was used as the reference electrode, forming a three-electrode system. The three electrodes were immersed in 0.2 mmol/L gold sulfite solution, and a constant voltage of −0.3 V was applied and maintained for 1200 s. A uniform layer of gold atoms was coated on the electrode surface. The thickness of the gold plating was not characterized in this work.
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