Use of flame activation of surfaces to bond PDMS to variety of substrates for fabrication of multimaterial microchannels

Silicones are widely used in industry as sealants, insulation, gaskets, coatings, seals and molds. One variety of silicone, poly dimethyl siloxane (PDMS), has been widely used for rapid prototyping of microfluidic and nanofluidic devices. The bonding of PDMS to other substrates is required to create a sealed microfluidic network. This can be achieved either by using dry bonding (e.g. oxygen plasma treatment) or wet bonding (e.g. microcontact printing) processes. Flame treatment has been used for surface activation of other polymeric materials (e.g. Poloylefin) and wood. This can increase the wettability and improve the adhesion of the coating (e.g. paints, inks and adhesives) with these substrates. In this paper, we present a universal method to bond silicones to other substrates by using flame treatment. We find that the flame treatment could allow one to simply bond PDMS to a variety of substrates including glass, silicon, epoxy (SU8), silicones, polyethylene and even metals such as aluminum. We fully characterize this bonding and find that it is due to the changes in surface property as well as topography on the surface.