Passive alignment of micro-fluidic chips using the principle of elastic averaging

This thesis presents a novel design for a passive alignment feature for vertically stacking chips in a micro fluidic device. Each chip is the size of a standard microscopic slide (75mm—25mm) and is a highly specialized functional unit designed and fabricated to process fluidic samples. The fluidic samples in the device flows from one chip to another using inter connecting holes 500μm-100μm in diameter. Hence an alignment of better than 100μm between chips is necessary to allow for the interconnecting holes to overlap so as to provide with a path for the fluid to flow. The feature to be used for alignment consists of v-grooves and dowel pins. Five v-grooves are hot embossed to each longer side walls of the chip such that the groove runs along the thickness of the chip. The dowel pins are fixed to a base and equal the number of v-groves. An elastic fit in between the groove and the pin provide the necessary alignment. A mathematical model has been developed and is used to predict the alignment of the method. The results from the model have been further verified experimentally.