Abstract
We present the selective laser-induced etching (SLE) process and design guidelines for the fabrication of three-dimensional (3D) microfluidic channels in a glass. The SLE process consisting of laser direct patterning and wet chemical etching uses different etch rates between the laser modified area and the unmodified area. The etch selectivity is an important factor for the processing speed and the fabrication resolution of the 3D structures. In order to obtain the maximum etching selectivity, we investigated the process window of the SLE process: the laser pulse energy, pulse repetition rate, and scan speed. When using potassium hydroxide (KOH) as a wet etchant, the maximum etch rate of the laser-modified glass was obtained to be 166 μm/h, exhibiting the highest selectivity about 333 respect to the pristine glass. Based on the optimized process window, a 3D microfluidic channel branching to three multilayered channels was successfully fabricated in a 4 mm-thick glass. In addition, appropriate design guidelines for preventing cracks in a glass and calibrating the position of the dimension of the hollow channels were studied.
Highlights
IntroductionOver the past 30 years, researches on microfluidic devices using soft lithography have been conducted in a variety of industries including biology, chemistry, medicine, food, energy, and the environment [1–4]
We have studied a rapid fabrication process that can make an all-glass microfluidic device within an hour using ultrafast laser 3D direct writing [9, 10]
We introduced the selective laser-induced etching process using ultrafast laser direct writing and demonstrated the glass 3D micromachining that was highly challenged when using conventional fabrication methods
Summary
Over the past 30 years, researches on microfluidic devices using soft lithography have been conducted in a variety of industries including biology, chemistry, medicine, food, energy, and the environment [1–4]. The development of robust devices that can respond to various samples is essential for the expansion of the microfluidic devices’ capabilities. Most microfluidic devices use polymer materials such as polydimethylsiloxane (PDMS) and polymethymethacrylate (PMMA). Glass can provide many advantages to the microfluidic. Kim et al Micro and Nano Syst Lett (2019) 7:15 processing in glass [11]. Ultrashort laser pulses cause the absorption of photon only in the vicinity of a laser focus enable direct writing of 3D freeform patterns in a transparent material without a mask [12]. Ultrafast laser process has brought the opportunity of rapid and efficient glass microfabrication to microfluidics research [13–15]
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