Microfluidic chips polymeric materials

An alternative option to packed channels is the use of monolithic materials, which may have many of the same benefits as packed beds, including high surface area and easily controlled surface chemistry. However, a distinct advantage of monoliths is the ability to prepare them easily and rapidly via polymerization of liquid precursors within the channels of the microdevice without the need for any retaining structures. Despite the popularity of monolithic capillary columns for separations of a variety of low and high molecular weight compounds in HPLC mode, > their first application in microfluidic chips dates back only to 2005. 

As glass and quartz exhibit the same surface property as fused-silica capillary, the monolithic materials could be conveniently prepared in a glass- or quartz-based microfluidic device via the same way of monoliths in the capillary. However, glass/quartz devices are rather expensive, and the need for specialized facilities for their fabrication with conventional photolithography technology hinders any rapid modification of the chip architecture. An attractive alternative is using a variety of polymeric materials, such as poly(dimethylsiloxane) (PDMS), poly(methyl methacrylate) (PMMA), polycarbonate (PC), and cyclic olefin copolymer (COC), to fabricate microchips for their mechanical and chemical properties, low cost, ease of fabrication, and high flexibility. 

The use of polymeric materials in microchips has gained popularity, especially in the fabrication of low-cost, disposable devices [3], It is particularly common to prototype polydimethylsiloxane (PDMS) chips, which can easily be fabricated using the soft lithography technique. This fabrication strategy is considered as a low-expertise route of microscale prototyping. It facilitates creation of micropatterns on a surface or within a microfluidic channel without the need for using photochemical processes [9]. Fabrication... 

The three modes of FP have proven to offer advantages for different applications. Photofrontal polymerization is driven by a continuous flux of energy and has been applied to the preparation of microfluidic chips. It can be applied to any photopolymerization. IFP relies on the gel effect to create a slowly moving localized polymerization through monomers like methyl methacrylate. This method can be used to prepare gradient refractive index materials. 

On-chip waveguides can be fabricated from different types of core materials. Traditionally glass has been a popular choice, but recently polymers have gained popularity due to lower costs and excellent transmittance characteristics [4]. Furthermore, polymeric waveguides can now be easily integrated with microfluidic devices, which are now commonly made in polymers. 

The industrial production of these new materials would require drastic scale-up of the productivity, because the throughput in each microstructured device is very low, typically below a few grams per hour. One promising solution to this issue might be the large-scale parallelization of the 2D microfluidic channels on a chip, which has been successfully demonstrated for the mass production of monodisperse single emulsions and polymeric microparticles [110]. 

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