Dry film microchips for miniaturised separations

In this work microfluidic devices were made from the dry film photoresist Ordyl SY330, characterised by optical and electron microscopy and used for electrophoretic separations. A simple and fast microfabrication process was developed for the fabrication of channels that are 50 pm wide and 30 pm in height, requiring only the use of an office laminator, a hot plate, an exposure source and mask and an electric drill to make four microdevices in less than 1 h. The optical properties of the photoresist were studied and the resist showed significant absorbance below 370nm and 570-630 nm, and had an optical transmission of 80% between 400 and 550 nm. Fluorescence emission over the region of maximum transmission was low allowing these devices to be used for fluorescence detection at 488/512 nm. Electrophoretic separation of APTS and three derivatised sugars was performed in 20 mM phosphate buffer, pH 2.5 with efficiencies of the three sugars of 40 000 plates (2 100 000 plates/m) within 30 s at a field strength of 500 V/cm. The simple fabrication process also allowed microchannels to be easily filled with chromatography particles before sealing, avoiding the challenging task of slurry packing, and the potential of these devices for liquid chromatography was demonstrated by the extraction of fluorescein onto anion exchange particles.