Optimization of selective laser-induced etching (SLE) for fabrication of 3D glass microfluidic device with multi-layer micro channels

Abstract

We present the selective laser-induced etching (SLE) process and design guidelines for the fabrication of threedimensional (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.

3D Manufacturing of Glass Microstructures Using Femtosecond Laser

“…SLE provides a relatively easy and highly controllable method for producing both surface and embedded channels. Here, SLE allows to form even complicated, curved, embedded 3D structures in glass [ 132 , 137 , 154 , 155 ]. It is demonstrated such channels ability to focused particles in the loops of the channels [ 137 ].…”

Merits and advances of microfluidics in the pharmaceutical field: design technologies and future prospects

“…Microfluidic fabrication methods are classified according to the microfluidic fabrication material, silicon/glass, or polymer. Glass/silicon-based microfluidic devices are fabricated using lithography and etching techniques (Kim et al., 2019 ; Vasilescu et al., 2020 ). Polymer-based microfluidics are fabricated using lithography (Mukherjee et al., 2019 ; Kajtez et al., 2020 ), laser ablation (Shaegh et al., 2018 ; Gao et al., 2019 ; Hu et al., 2020 ), injection molding (Li et al., 2020 ; Ma et al., 2020 ), hot embossing (Lin et al., 2017 ; Lauri et al., 2019 ) and 3D printing (Macdonald et al., 2017 ; Romanov et al., 2018 ; Vasilescu et al., 2020 ).…”

Monolithic 3D micromixer with an impeller for glass microfluidic systems

“…The aforementioned design rule for fused silica was empirically confirmed in our prior work on the fabrication of 3D multi-layer microfluidic channels. 49 Therefore, the blade was designed with a width of 750 μm and a height of 380 μm so as to have a clearance of 15 μm from the walls and bottom of the mixing tank (width: 780 μm, height: 410 μm), thus minimizing the effects of wear and friction during rotation. A cross-shaped cap was added to prevent the impeller from moving from its original position.…”

“…The etching rate of the laser-modified area is much higher than that of the unexposed area, enabling us to obtain sufficient etching selectivity beyond 300 : 1. 49 An ultrafast laser-based (Satsuma HP2, Amplitude laser) 3D laser structuring system was used to directly write microchannels inside a glass substrate (fused silica, JMC glass), with dimensions of 10 mm × 10 mm × 2 mm. The laser beam, deflected using a two-axis (XY) Galvano scanner (DynAXIS, SCANLAB GmbH), was finally focused through an objective lens (NA 0.42, Mitutoyo M plan Apo 50×).…”

“…The laser modification parameters (wavelength: 1030 nm, repetition rate: 500 kHz, pulse energy: 400 nJ, scan rate: 200 mm s −1 , slicing and hatching size: 10 μm and 15 μm, respectively) were optimized as described in our previous research. 49 The modified substrate was immersed in an ultrasonic bath of potassium hydroxide (8 mol L −1 ) at 90°C, and finally cleaned with isopropyl alcohol, deionized (DI) water, and nitrogen gas.…”