Microfluidic chips fabrication from UV curable adhesives for heterogeneous integration

Conventional fabrication of microfluidic chips is based on silicon, glass, PDMS and various other polymeric materials (COC, polycarbonate, PMMA etc). Silicon and glass processing technologies are highly developed and the chips can be fabricated with ease. Polymeric microfluidic chips have become very common in recent years due to the demand for the cheap and disposable devices. New entrants in to the field are UV curable adhesives which are gaining recognition as promising players in microfluidics. UV curable adhesives are generally used in various applications ranging from usage in the manufacture of parts of an aircraft to sealing/packaging of microfluidic chips. Unlike any other previously discussed materials UV curable adhesives have the flexibility in alignment and bonding during fabrication process. These adhesives can be applied in between two surfaces which are to be glued and can be left like that for hours to days without bonding them as long as the glue is not exposed to UV light. In this paper we explain the detailed fabrication of microfluidic chips (100μm wide and 3μm (NOA74), 22μm (NOA 68) deep) completely made from UV curable adhesives having better chemical resistance, permeability and flexible surface treatments compared to other known polymeric materials. Firstly the patterns were etched on silicon, followed by PDMS molding and subsequently UV curable adhesives were casted and cured on structured PDMS master. After unmolding the stamps were mounted on a glass substrate and permanent bonding was achieved by further UV treatment and/or oxygen plasma treatment. The final devices were successfully tested for any leakage. These microfluidic chips will be integrated with a sensor and antenna for further biological studies. UV curable adhesives are also used for permanent/temporary sealing of microfluidic channels. These adhesives, which are still new to the fluidics branch can functionally and economically, have a greater impact on microfluidics.