In this work, a microfluidic system to investigate the flow behavior of red blood cells in a microcirculation-mimicking network of PDMS microchannels with thickness comparable to cell size is presented. We provide the first quantitative description of cell velocity and shape as a function of the applied pressure drop in such devices. Based on these results, a novel methodology to measure cell membrane viscoelastic properties in converging/diverging flow is developed, and the results are in good agreement with data from the literature. In particular, in the diverging channel the effect of RBC surface viscosity is dominant with respect to shear elasticity. Possible applications include measurements of cell deformability in pathological samples, where reliable methods are still lacking.

Relying on the water-dependent hybrid conductor properties of eumelanin biopolymers, a structurally controlled melanin thin film that can be reversibly switched-on and off by hydration–dehydration cycles and used as a biocompatible platform for stem cell growth and differentiation up to 11 days is reported. A key feature of the new eumelanin-based bioelectronic interface is its remarkable structural regularity and integrity, as the result of an ad hoc fabrication protocol involving ammonia-induced solid state polymerization (AISSP) technology of a 5,6-dihydroxyindole thin film. The AISSP technology is operationally simple and versatile, enabling the preparation of device-quality thin films (AFM and MALDI-MS evidence) on various substrates with efficient chemical control over molecular complexity. Overall the results of this study pave the way for the implementation of tailored eumelanin thin films for bioelectronic devices, e.g., in organic electrochemical transistors (OECTs).