Manipulation and flow of biological fluids in straight channels micromachined in silicon.

Analysis of minute sample volumes is a major analytical challenge that requires an understanding of fluid flow in microstructures. Accordingly, flow dynamics of biological fluids and cell suspensions in straight glass-capped silicon microchannels (40 to 150 microns wide, 20 and 40 microns deep) were studied. We demonstrated that these microstructures are appropriate components for microfluidic analytical devices. Different fluids were easily manipulated in the microchannels, and measurements of flow rate as a function of pressure for whole human blood, serum, plasma, and cell suspensions revealed non-Newtonian behavior. By means of micromachined filters (5 microns) located in channels, blood cells and microparticles were effectively separated from nanoliter-sized samples, clearly indicating the future role of microstructures for a variety of analytical purposes.

Polarized spectral emittance from periodic micromachined surfaces: V. Undoped silicon: angular measurement in shallow lamellar gratings.

Experimental results of thermal emittance from lamellar gratings in intrinsic silicon are presented along with a theoretical discussion. For azimuthal angular directions in shallow gratings, enhanced thermal emission plateaus and maxima are observed. In the case of p-polarized emission in the Phi = 90 degrees azimuth (parallel to the grating vector), the plateau arises when two diffractive orders can be supported; it lies between the Rayleigh polar angles corresponding to the forbidden zone. The experimentally observed angular dependence of the s-polarized emission for the Phi = 90 degrees azimuth has been compared with a coupled-wave calculation, and a respectable agreement has been obtained. For the experimentally observed s-polarized emission in the Phi = 0 degrees azimuth (perpendicular to the grating vector), there is an onset of enhanced emission at the polar angles that follows a simple empirical relation unrelated to any known diffraction law. By contrast, the p-polarized emission in the Phi = 0 degrees azimuth shows relatively little structure. These data illustrate the value of thermal emission for surveying multivariate absorption processes involving microstructures.

Polarized spectral emittance from periodic micromachined surfaces: IV. Undoped silicon: Normal direction in deep lamellar gratings.

Experimental results of thermal emittance from deep gratings are presented along with a theoretical discussion. We have found that for a certain grating geometry thermal emission peaks coincide with the cutoff frequencies of slab waveguides. The coincidence was found with s- but not p-polarized emission. This suggests that coupling between grating fins for s-polarized emission is small. It was also found that emission peaks do not correlate directly with the well-known grating equation for these deep gratings.