Opto-biochips for microcytometry

Microscale fluorescence activated cell-sorting (muFACS) by switching of continuous flows in microsystems is a new technology being developed to identify and separate cells. Different elements of the muFACS, fabrication of opto-biochips, particle detection and velocity measurement, and flow switching, are studied in the present work.; Different techniques to fabricate biochips are presented. Masters with inverse patterns of biochips were fabricated by direct laser-writing, and by lithography and dry etching. Biochips were fabricated by casting polydimethylsiloxane (PDMS) on the masters. In a different approach, biochips with integrated waveguides and microchannels were fabricated photolithographically on glass substrates using a negative photoresist, SU-8. The system includes multimode waveguides with combiners and splitters for utilizing lasers of different wavelengths for the identification of different particle types.; Detection of particles in commercial biochips and micropipettes using a custom plastic optical fiber launch-and-detect tip is described. The velocity of the microparticles has been measured by the spatial response of the tip and the dynamic response of the moving microparticles. In a glass biochip with etched microchannels and ion-exchange waveguides, the double peak signal from moving microparticles at the intersection of microchannel and waveguide was used to determine the velocity of the microparticles in an electroosmotic flow. Microparticle flow switching has been realized in PDMS biochips.; In the SU-8 opto-biochips, two excitation waveguides carrying two different wavelengths intersect the microchannel at two points separated by a known distance. One large output waveguide carry fluorescence signals to a single filtered detector. The loss in SU-8 waveguides was measured for two different wavelengths. The velocities of the microparticles were determined by the captured fluorescence from the double peak. Simulations based on beam propagation method were used to predict the performance of the SU-8 waveguides and the intensity at the two intersections has been compared with the experimental results.