Selective chemical surface modification of fluidic microsystems and characterization studies

Control of wetting behaviour of fluidic microsystems was achieved by selective chemical surface modification using either a solution-based procedure or micro-contact printing. The modification procedures were designed in such a way as to obtain optimum wetting in fluid channels, sample reservoirs and nozzles, while at the same time preventing intermixing of fluids from different nozzle exits and thus enabling multiple long-term stable delivery of nano-litre droplets. Analysis included thickness measurements by ellipsometry, contact angle measurements and fluorescence microscopy. Selectively coated TopSpot dosage chips as are used for the fabrication of DNA and protein micro-arrays exhibit superior performance over uncoated dosage chips. Mixed and back-filled silane coatings show enhanced stability versus hydrolysis in basic and acidic solutions, as has been determined from measurements of contact angle as a function of immersion time.