Surface modifications, microfluidic

Hu SW, Ren X, Bachman M, Sims CE, Li GP, Allbritton NL (2002) Surface modification of poly(dimethylsiloxane) microfluidic devices by ultraviolet polymer grafting. Anal Chem 74 4117 Hunter RJ (1981) Zeta potential in colloid science. Academic Press, London Jensen KF (2001) Microreaction engineering is small better Chem Eng Sci 56 293... 

Xiao, D., Le, T.V., Wirth, M.J., Surface modification of the channels of poly(dimethylsiloxane) microfluidic chips with polyacrylamide for fast electrophoretic separations of proteins. Anal. Chem. 2004, 76, 2055-2061. 

Soper, S. A. Henry, A. C. Vaidya, B. Galloway, M. Wabuyele, M. McCarley, R. L., Surface modification of polymer-based microfluidic devices, Anal. Chim. Acta 2002, 470, 87-99. 

Stachowiak TB, Mair DA, Holden TG, Lee LJ, Svec F, Frechet JMJ. Hydrophilic surface modification of cyclic olefin copolymer microfluidic chips using sequential photografting. J Separation Sci 2007 30(7) 1088-93. 

Brown, L., Koemer, T., Horton, J. H., and Oleschuk, R. D., Fabrication and characterization of poly(methyhnethacrylate) microfluidic devices bonded using surface modifications and solvents. Lab... 

Luo N, Hutchinson JB, Anseth KS et al (2002) Integrated surface modification of frilly polymeric microfluidic devices using living radical photopolymerization chemistry. J Polym Sci A Polym Chem 40 1885-1891... 

Surface modification for microchannels in microfluidic and nanofluidic devices. 

The CVD method is an important method for the deposition of highly pure thin-layer films for microfluidic and nanofluidic devices. The most common use of CVD techniques in microfluidic and nanofluidic devices is for surface modification. With the rapid development in microfluidic... 

Chang et al. [5] utilized microtubes to generate micro-segmented flow. Upon surface modification, the prepared nanoparticles were mixed with a monomer and emulsified into uniform droplets in a capillary-based microfluidic device. The microchannel-based reactor offered reliable control over the nanocomposite products by precisely adjusting the interfacial tension. 

In 2004, Hisamoto and coworkers [19] have presented a simple approach, called capillary-assembled microchips (CAs-CHIP), for assembling a commercial square fused-silica capillaiy into a PDMS microfluidic device. The capUlaiy could be completely functionalized off-chip and cut into required size and then integrated raito a chip without any solution leakage (as shown in Fig. 3). As many methods for surface modification of capillary have been well established, the CAs-CHIP method offered a way to fabricate different microfluidic devices having various functions for analytical applications including sample pretreatment, biochemical sensors, and so on. 

Microchannels that range in diameter from tens to hundreds of microns have emerged as potentially powerful tools for a variety of biomedical applications. They can be used to minimize sample volume and reduce costs, as well as to increase throughput and analysis sensitivity. Since microfluidic devices operate at small length scales, their functionality is greatly dependent on their surface properties, which vary depending on the type of material that is used to fabricate the channel and the subsequent surface modifications. 

The materials used for the fabrication of most microfluidic chips include glass, silicon, quartz, and plastics ( Materials Used in Microfluidic Devices) In addition to cost and optical, electric, and physical properties, careful consideration must be given to the surface chemistry of the material ( Surface Modification, Methods). In fact, surface chemistry plays a major role in chemical cytometry, as protein adsorption to the channel walls can degrade the separation performance and make the electroosmotic flow unreproducible. 

The surfaces of devices often exhibit different wettability characteristics, depending on the manufacturing approach adopted. Surface modification techniques can be used to alter the wettability behavior of microfluidic devices. This difference in wettability can be used to control the flow rate in devices. There are many other benefits of hydrophilic surface treatments, including the ability to increase adhesion and capillary effects [2]. Irrespective of the material used in the device, the primary requirement that a material needs to fulfill is biocompatibifity in various applications. Therefore, it is also necessary to use surface modification techniques to render materials biocompatible. It is believed that future devices of increasing sophistication will often require programmable surface properties, including control of the spatial distribution of charge and polarity [3]. 

Conventional polymers do not always possess the combination of desired bulk and surface properties for a specific application. The polymer materials used for microfluidic devices are innately hydrophobic, low-surface-energy materials and thus do not adhere weU to other materials brought into contact with them. This necessitates their surface modification/treatment to render them adhesive. This has prompted the development of a variety of polymer modification techniques, with the aim of developing new materials from known and commercially available polymers that have desirable bulk properties (elasticity, thermal stability, permeability, etc.) in conjunction with newly tailored surface properties (adhesion, biocompatibUity, optical reflectivity, etc.). 

Some commercially available protein-inert polymers commonly used in microfluidic applications, all of which require permanent surface modification, are polyacrylamide, poly (N-hydroxyethyl acrylamide), poly(N,N -dimethyl acrylamide) (PDMA), polyvinylpyrrolidone (PVP), poly(vinyl alcohol) (PVA), hydroxyethyl cellulose (HEC), and hydroxypropyl methylceUulose (HPMC). To permanently attach protein-resistant materials to the channel sinface, high-energy sources, special chemistries, or even strrMig physical adsorption have been employed to introduce reactive functionalities. After activatirm, protein-resistant polymers can be anchored via UV-initiated free-radical polymerization. Polymeric materials... 

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