Development of adhesive bonding and functional testing systems for in-process inspection of hot embossed microfluidic devices

Abstract

Microfluidics has emerged as an increasingly popular field with a wide-variety of applications such as medical diagnostics, drug development, and DNA analysis. The transition of microfluidic devices from research to industry has stimulated interest in producing them at low costs and high volumes. Hot embossing has been of interest lately as a low-cost, high quality, and flexible manufacturing method that is ideal for medium-volume production. This project focuses on the continued development of a tabletop microfactory that can be used to study the control of a novel hot embossing machine. By incorporating an in-line measurement system, it would be possible to add feedback control to improve the process. This led to the design of an automated testing machine that uses an optical inspection of the microfluidic channel widths to determine embossing quality and a flow test to verify device functionality.

The total cycle time of the testing machine is 85 seconds, which is well within the time of one embossing cycle (110 seconds). In order to produce complete devices for testing, an automated taping machine was also designed to seal the embossed channels. This machine took 15 seconds to complete its cycle. These two machines were integrated with the microfactory, which is currently capable of producing an embossed, sealed, and tested device every 170 seconds. The taping and width measurement processes have an error of 0.63 μm with a standard deviation of 0.82 [mu]m. The mixing length test has an accuracy of 72.8 [mu]m. A preliminary test demonstrated the ability to generate credible run data, and the effect of embossing temperature on width was detected to a resolution of 2 [mu]m. The system is now able to characterize the embossing process and the effects of various embossing parameters on the final product.

Closed-loop cycle-to-cycle process control can then be implemented, which will create a robust production cell that is capable of adapting to a variety of conditions.