Optically encoded silicon microbeads: Detection and characterisation in a microfluidic system

A novel microbead encoding and detection technology platform is presented. This system will provide new opportunities for assay development. Distinctive silicon microbeads have been fabricated using conventional MEMS fabrication technologies. The microfluidic transport and behaviour of these microbeads has been observed and characterized in several different microfluidic structures. These observations established that microbeads adopt almost 100% of the average fluid velocity when transported in a pressure driven fluid flow. For this reason the viscosity has only a minimal influence on the microbead velocity. Experimental results also confirm that the observed microbead velocity was independent of the channel width for equal microbead dimensions. The optical signature has been effectively detected and decoded in situ with a customized laser identification system. Incorporation of a real time decoding algorithm and associated Labview™ software facilitated continuous identification of microbeads at a maximum velocity of 10 cm/s.