Laser-scan lithography and electrolytic etching for fabricating mesh structures on stainless-steel pipes 100 um in diameter

Fine cylindrical micro-components such as stents and micro-needles are required. Here, laser-scan lithography and electrolytic etching were investigated for opening many slits on fine stainless-steel pipes with an outer diameter of 100 μm, a thickness of 20 μm and a length of 40 mm. At first, a pipe coated with a positive resist was exposed to a beam spot of violet laser. Linearly arrayed 22 slit patterns were continuously delineated by scanning and intermittently moving the pipe in the axial direction. The same delineations of 22 slit patterns were repeated four times in every 90-degree circumferential direction. The pipe was exposed to the laser spot in lengths of 170 μm, and interval lengths of 100 μm were located between the exposed lengths. Thus, 88 slit patterns in total were delineated on 8 pipe surfaces. Next, the pipes masked by the resist were electrolytically etched one by one. A pipe was used as an anode, and an aluminum cylinder was set as a cathode around the pipe. As the electrolyte, aqueous solution of NaNO₃ and NH₄Cl was used. Then, the resist was removed by ultrasonic cleaning in acetone. Sizes of etched 22 slits in a line were measured for each pipe using SEM (JEOL, JSM-5510). The average width and length measured at inner surfaces were 25.8 μm (σ=4.7) and 174.8 μm (σ=13.4), respectively. The width and length measured at the outer surface were 54.6 μm (σ=2.6) and 211.4 μm (σ=4.2), respectively. It was demonstrated that aimed mesh structures were successfully fabricated. Keywords: laser-scan lithography, ultra-fine pipe, slit-pattern, electrolytic etching, stent, micro-needle