Dynamic mechanical thermal analysis, forming and mold fabrication studies for hot-embossing of a polyimide microfluidic platform

In this study, we have explored the hot-embossing of polyimide films through dynamic mechanical thermal analysis (DMTA), forming and mold fabrication studies. First, the relationship between the formability and the temperature for the polyimide film was investigated by DMTA and hot-embossing tests. The DMA results represented that, as a polyimide goes through its glass transition, it exhibited dramatic decreases in storage elastic modulus, storage shear modulus and viscosity as well as the peak of tangent delta, and continued to show strong dependence on frequency and temperature. The filling characteristics of the polyimide film investigated by hot-embossing tests showed a sharp increase in the replicated depth near the glass transition temperature. Second, silicon microfluidic platforms and molds were prepared by electron beam lithography (EBL) combined with inductively coupled plasma (ICP). An ICP etching condition to prevent reverse taper of a microstructure was investigated, and Si microfluidic channels and high aspect-ratio microstructures with nearly vertical sidewall were structured. Finally, the channel structures could be successfully replicated on the polyimide surface by hot-embossing with the Si mold prepared by using EBL combined with ICP plasma etching.