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Spin-coating process of a commercially available soft thermoplastic elastomer (sTPE) is demonstrated for the realization of microfluidic prototypes. It is a reliable, wrinkling-free, and high-yield holding and transfer methodology for single and multilayered devices fabrication. Complex microfluidic systems including embedded microlenses array, dilutor-like chip for stable capillary filling, and pneumatically drive valve confirms the performances and quality of the process. The dissolved sTPE, a soft styrenic-block polymer-based material, is flexible in its raw state as poly(dimethylsiloxane) and thermoformable as classical thermoplastics. Depending on the solvent evaporation rate, two stable morphologies of the block nanodomains are revealed: either a nanocylinder or hexagonal nanospheres pattern. Both are evenly distributed over the whole surface and account for a uniform and convenient surface at a “microfluidic scale device.” Plasma hydrophilization allows a stable and hydrophilic surface (≈20° after 7 d). The biocompatibility is assessed through the cell culture proliferation assay of progenitor endothelial cells. This sTPE solution displays fast and reliable fabrication and assembly performances, it can achieve strong and stable hydrophilicity within a low level of initial equipment investment.

Here we demonstrate the ability to characterize microporous scaffolds and evaluate cell concentration variation via the utilization and interpretation of complex permittivity measurements (CP), a direct and nondestructive method. Polymer-based microporous scaffolds are of importance to tissue engineering, particularly in the promotion of cell adhesion, proliferation, and differentiation in predefined shapes. Chitosan gel scaffolds were seeded with increasing concentrations of macrophages to simulate cell growth. Complex permittivity measurements were performed using a dielectric probe and a vector network analyzer over a frequency ranging from 200 MHz to 2 GHz. An effective medium theory was applied to interpret the data obtained; respectively, Looyenga and Maxwell-Wagner-Hanai functions were used to retrieve the porosity and the variation of the cell concentration from the CP measurements. Calculated porosities were in agreement with experimental evaluation—porosity ranged from 81–96%. Changes in cell concentration inside the scaffolds upon injection of differing cell concentrations into the scaffold were detected distinguishably. Variations resulting from the cumulative injection of 400–1800 μL of 106 cells/mL solution into the scaffold were monitored. Results suggest that CP measurements in combination with an appropriate effective medium approximation can enable on-line monitoring of cell growth within scaffolds. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 343–350, 2003.