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A novel approach for multisensing has been developed based on the integration of a parallel-channel microfluidic module with a surface acoustic wave (SAW) sensor chip. The microfluidic module was used to compartmentalize the surface of a single SAW sensor into N equal subareas in order to deliver and detect multiple samples on the sensor. The design concerns and fabrication procedure using soft lithography of polydimethyisiloxane are described. Successful demonstration of a four-channel module is reported, along with a sensitivity evaluation and comparison with a standard flow cell used so far. Very promising results were revealed during the tests concerning the system's operation with liquid samples. The reliability and reproducibility of the results in all four subareas render the proposed setup very suitable for biological testing and screening of various biomolecules in an array format. Index Terms--Microfluidics, polydimethylsiloxane (PDMS), soft lithography, surface acoustic waves (SAWs).

The issue of controlled modification of the surface topography of polydimethylsiloxane (PDMS) when subjected to oxygen-based plasma treatments is addressed. The resulting enhanced surface area is investigated as a means of controlling the surface wetting properties.

Two-photon-allowed laser-induced fluorescence of a 10MHz parallel-plate rf discharge facilitates determination of spatial distribution and O2 atom evolution through detection of atomic oxygen. The production of oxygen atoms in the interelectrode space is regular, as revealed by uniform spatial oxygen distribution. The increase in O concentration implies the dependence of production on time, while the decrease in concentration of O indicates a reaction between the O atoms and surface materials in the plasma.

A method which employed two-photon absorption laser-induced fluorescence was used to achieve spatial distribution of H atoms in the rf reactor's interelectrode space. The surface loss coefficients of H atoms that were generated at the sheath boundary ranged from 0.1% to 20%. This method was also used to evaluate real-time and in situ energetic plasma-induced surface alterations.

Absolute H-atom concentration profiles in continuous and pulsed rf discharges were investigated. The results showed that two-photon absorption laser-induced fluorescence in a pure hydrogen rf discharge determined the absolute concentrations of ground state atomic hydrogen. A constant concentration in the region around the center of the discharge was observed. Diffusion originating from the source regions towards the electrode space determined the distribution of the plasma produced hydrogen.