New approaches to realize silicon-based microfluidic systems are demonstrated and used to fabricate biological and biochemical research instrumentation. By using combinations of silicon fusion bonding (SFB), deep reactive ion etching (DRIE), anodic bonding, adhesive bonding, and wet anisotropic etching, microfluidic instruments are fabricated that have high geometric versatility and modularity. DRIE facilitates the fabrication of single and multiple channel levels with high density interconnect and photo-lithographically defined geometries. This geometrical structuring enables the development o f an instrument for endothelial cell shape and function studies, elongating cells under both static and flow conditions, and a micromixer that uses multiple levels of interconnected channels to manipulate laminar fluid streams resulting in improved mixing. In addition, fluidic microinstrument boards are fabricated and used to demonstrate surface-mount interconnection and plug-in components. A manifold with multiple pressure sensors is used to demonstrate measurement in buried microchannels using surface-mount components. Novel cylindrical and grooved “fin”-type joints fabricated by DRIE are used to “plug-in” component packages to a microinstrument board. A new type of coupler fabricated by DRIE that accurately fits the inner and outer diameter of capillary tubing with a “sleeve”-like cylindrical structure is used to couple off-chip devices to the mixer and pressure sensor manifold.

The mixer was tested using streams of differently dyed water, and found to mix the two fluids faster than diffusion in a simple, straight channel The microinstrument for endothelial cell research was used to induce elongation in microchannels and study various aspects of elongated and non-elongated cells under static and flow conditions. The manifold with pressure sensors was tested using both air and water at different flow rates, and pressure drop along the microchannel was found to be in close agreement with theoretical results. The “sleeve”-type couplers were used to interface external components to the mixers up to pressures of 200 psi (1.38 MPa). Cylindrical and fin-type vertical interconnect structures were tested up to pressures of 70 kPa and 100 kPa, respectively.