Abstract
Conventional manufacturing of glass microfluidic devices is a complex, multi-step process that involves a combination of different fabrication techniques, typically photolithography, chemical/dry etching and thermal/anodic bonding. As a result, the process is time-consuming and expensive, in particular when developing microfluidic prototypes or even manufacturing them in low quantity. This report describes a fabrication technique in which a picosecond pulsed laser system is the only tool required to manufacture a microfluidic device from transparent glass substrates. The laser system is used for the generation of microfluidic patterns directly on glass, the drilling of inlet/outlet ports in glass covers, and the bonding of two glass plates together in order to enclose the laser-generated patterns from the top. This method enables the manufacturing of a fully-functional microfluidic device in a few hours, without using any projection masks, dangerous chemicals, and additional expensive tools, e.g., a mask writer or bonding machine. The method allows the fabrication of various types of microfluidic devices, e.g., Hele-Shaw cells and microfluidics comprising complex patterns resembling up-scaled cross-sections of realistic rock samples, suitable for the investigation of CO2 storage, water remediation and hydrocarbon recovery processes. The method also provides a route for embedding small 3D objects inside these devices.
Highlights
Conventional manufacturing of glass microfluidic devices is a complex, multi-step process that involves a combination of different fabrication techniques, typically photolithography, chemical/dry etching and thermal/anodic bonding
The devices are typically made of two plates, one of which has a microfluidic pattern generated on its surface, whereas the other has a set of inlet/outlet ports and is used as a lid to enclose the microfluidic pattern from the top
The mean depth (D) and surface roughness (Sa) of the patterns generated using the 515 nm wavelength were observed to depend on many laser machining parameters, such as the laser spot size (2ω), pulse energy (EP), pulse repetition frequency (PRF), scan velocity (v), hatch distance (ΔH), and number of laser passes
Summary
Conventional manufacturing of glass microfluidic devices is a complex, multi-step process that involves a combination of different fabrication techniques, typically photolithography, chemical/dry etching and thermal/anodic bonding. The lid is transparent and must be properly bonded to the other plate such that the device is leak-proof and the injected fluids can flow only within the area of a microfluidic pattern Such microfluidic devices enable various complex physical and chemical operations to be performed on small amounts of liquids, gases and solids, including small particles, colloids, living cells and microbes. Microfluidic patterns can be generated directly on a glass surface using a CO2 or ultrashort pulsed laser[43,44,45,46,47], or inside the material using so-called a selective laser etching (SLE) process[48,49,50] The latter method is attractive because it eliminates additional fabrication steps related to the bonding of two glass plates together, but it still requires the use of etchants. In contrast to the other fabrication methods described earlier, this technique does not use any dangerous etchants (e.g. hydrofluoric acid) and additional expensive equipment, and it can be carried out in normal laboratory environment (i.e. without being in a cleanroom)
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