Design and process optimization of a hot embossing machine for microfluidics with high aspect ratios

Abstract

Microfluidics is a growing technology in the field of medical diagnostics. Daktari Diagnostics is a startup located in Cambridge, MA that seeks to introduce a lab-on-a-chip device for monitoring HIV in patients. This work investigates hot embossing as a prototyping process for Daktari's microfluidic device. A hot embossing system was designed and built for the purpose of prototyping a critical feature of their microfluidic network. The machine was designed for an embossing area of 6 square inches, and was found to have a maximum positional repeatability of 43 microns. The purpose of this research was to find the capabilities of the system used for hot embossing and optimize the process for maximizing the performance. The system was validated for alignment, measurement procedure and the process control. The measuring procedure was analyzed to find the best possible metric which could serve as a response variable for the performance of the process. The 'Fill ratio' of height and width were chosen as metrics for the experimental design which had precision to tolerance ratios of 0.44 and 0.33 respectively. An analysis of the factors affecting the hot embossing process was carried out using experimental design and the optimal parameters were identified. The tool temperature, pressure and the holding time were the most significant in that order. The Cp for the process with respect to the height fill was found to be 4.71 and for the width fill ratio was found to be 1.97. Using the optimal parameters the process variation of six standard deviations was found to lie within the specification limits. Hot embossing was recommended as a possible method for rapid prototyping of the assay channel and the complete cartridge at Daktari Diagnostics.