Numerical and experimental investigaton of ultrasonic embossing technique for fabrication of thermoplastic microfluidic devices

Çoğun, Ferah
In this study, numerical models and experimental results were presented to describe mechanisms of hot embossing (HE) and ultrasonic embossing (UE) for fabrication of thermoplastic microfluidic chips. The substrates were embossed using micromilled aluminum molds in both techniques. Effects of embossing temperature, time, and force on performance outputs (replication rates and channel symmetry) were investigated numerically and experimentally in HE. Experimental results revealed the importance of temperature on performance outputs, whereas time and force have less effect. The experimental and finite element (FE) analyses emphasized the strong dependency of the channel skewness on substrate flow characteristics. In this study UE is considered as an alternative to HE since microfluidic channel embossing time is few seconds. The substrate deformation and temperature distribution across the mold and the substrate in UE were investigated using an FE model. The findings were verified with experiments using 3 mm thick PMMA substrate and a mold with straight channels. The mold pattern was replicated in 5 s at room temperature with high replication rates (99.5% in width and 100% in depth). A process-affected zone in the shape of a semi-circle observed in the experiments was proven by FE and thermal camera analyses to be bounded by the isothermal surface at the glass transition temperature of the substrate (107oC). Sealing of the fabricated channels were achieved by solvent-assisted thermo-compressive bonding in HE and UE. A hydrogel droplet generator chip was designed and fabricated to demonstrate the suitability of the UE and micromilled mold for microfluidic device fabrication.


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Citation Formats
F. Çoğun, “Numerical and experimental investigaton of ultrasonic embossing technique for fabrication of thermoplastic microfluidic devices,” Ph.D. - Doctoral Program, Middle East Technical University, 2018.