Low-temperature Polymer Bonding Using Surface Hydrophilic Treatment for Chemical/bio Microchips

Polymer materials have been used for electronic, optical and bio micro/nano devices. Polymer device fabrication technologies based on replication methods including hot embossing (Becker & Heim, 2000; Park et al., 2003; Shinohara et al., 2007b), injection molding (Becker et al., 1986; Svedberg et al., 2003), ultraviolet (UV) imprinting (Haisma et al., 1996; Kawaguchi et al., 2007; Shinohara et al., 2008d) and casting (Duffy et al., 1998; Slentz et al., 2001) can reduce costs. Polymer bonding technologies have also been required for sealing or stacking the devices. Some examples of bonding methods have been reported, including thermal direct bonding (Spierings & Haisma, 1994; Chen et al., 2004; Shinohara et al., 2007b), solvent bonding (Wang et al., 2002; Lin et al., 2007), and bonding using other intermediate layer (Graß et al., 2001; Lei et al., 2004). Low-temperature bonding technologies are required with deformation of the previous surface structures as small as possible. On the other hand, surface modification for biocompatibility is one of the most important processes for biochips. Polymer surface modification methods are classified into two categories. One is modification of the original surface (e.g., plasma treatment (Lianos et al., 1994; Kamińska et al., 2002; Chai et al., 2004; Lai et al., 2006), UV irradiation (Peeling & Clark, 1981; Murakami et al., 2003; Hozumi et al., 2004; Diaz-Quijada et al., 2007; Kim et al., 2009). The other is coating with other materials (Ratner, 1995; Oehr, 2003; Liu et al., 2004; Bi et al., 2006). In this chapter, two low-temperature bonding technologies are described. Section 2 introduces low-temperature direct bonding methods of poly (methyl methacrylate) (PMMA) or cyclo-olefin polymer (COP), and their applications of microchannel devices. Section 3 describes surface hydrophilic treatment method using aromatic polyurea film, and bonding method using the polyurea film.