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
Recently, it is required to develop a method for fabricating cylindrical micro-components in the field of measurement
and medical engineering. Here, electrolytic etching of fine stainless-steel pipes patterned by laser-scan lithography was
researched. The pipe diameter was 100 μm. At first, a pipe coated with 3-7 μm thick positive resist (tok, PMER P
LA-900) was exposed to a violet laser beam with a wavelength of 408 nm (Neoark,TC20-4030-45). The laser beam was
reshaped in a circle by placing a pinhole, and irradiated on the pipe by reducing the size in 1/20 using a reduction
projection optics. Linearly arrayed 22 slit patterns with a width of 25 μm and a length of 175 μm were delineated in
every 90-degree circumferential direction. That is, 88 slits in total were delineated at an exposure speed of 110 μm/s. In
the axial direction, patterns were delineated at intervals of 90 μm. Following the pattern delineation, the pipe masked by
the resist patterns was electrolytically etched. The pipe was used as an anode and an aluminum cylinder was set as a
cathode around the pipe. As the electrolyte, aqueous solution of NaCl and NH4Cl was used. After etching the pipe, the
resist was removed by ultrasonic cleaning in acetone. Although feasibility for fabricating multi-slit pipes was
demonstrated, sizes of the etched slits were enlarged being caused by the undercut, and the shapes were partially
deformed, and all the pipes were snapped at the chuck side.
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