Perfusable multi-scale channels fabricated by integration of nanoimprint lighography (NIL) and UV lithography (UVL)

Numerous microfluidic devices have been applied to bioassays. Decreasing amount of liquid solutions helps to reduce sample waste and reagent consumption. Increasing sensitivity with fast reactions is another advantage. However, further downsizing of microfluidic devices brings difficulties in perfusing solutions due to a pressure drop, which is essential in bioassays. Here, we report a perfusable channel array in submicrometer to micrometer scale fabricated by integrating nanoimprint lithography (NIL) and UV lithography (UVL). Two lithography techniques are used to fabricate multiscale SU-8 mother mold for poly(dimethylsiloxane) (PDMS) replicas. SU-8 is an appropriate material as a mold due to mechanical stability and chemical resistance. However, it causes problems in a NIL process such as SU-8 residue on a silicon mold after demolding from a patterned SU-8 surface. To keep the compatibility of SU-8 in NIL process, UV-assisted NIL is employed to fabricate the line-and-space pattern for the channel array and microscale structures for microchannels were defined by UVL. NIL provides high throughput and high resolution patterns for the channel array, while UVL defines micrometer scale channels as interface between a user and the channel array. The fabricated device consists of a channel array (w = 0.5-2 mu m, h = 1-2 mu m, l = 200 mu m) and 2 mu m scale channels (w = 250 mu m, h = 50 mu m, l = 5 mm). These micrometer scale channels are used for inlet or outlet of the channel array to deliver solutions. We demonstrated exchanging solutions using fluorescent solutions. Repetitive increase and decrease of fluorescent intensity proved the solution exchange in channel array. (C) 2012 Elsevier B.V. All rights reserved.