Design and measurement analysis of hot embossing system for high aspect ratio microfluidics

Abstract

Microfluidics is a growing technology in the arena 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 machine 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 microfluidic feature that was prototyped is known as the assay channel. This feature is a high aspect ratio channel with a depth of 50 microns and width of 4 mm. A 10- micron ridge is adjacent to the channel. Several measurement methods were evaluated with gage repeatability and reproducibility studies to determine the methods most capable of quantifying the quality of embossed parts. The end determination was that quality of parts should be defined by the completeness of formation of the ridge lining the channel. The height and width measurements of the ridge were used as quality metrics. The precision to tolerance ratio (P/T ratio) of the measurement method used for finding ridge height was found to be 0.44 and the P/T ratio of the ridge width measurement method was found to be 0.33.