Conducting polymers such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are increasingly used to interface electronics with biology. Their wettability, however, remains poorly understood. We show that the frequently-used sessile drop technique yields results that are strongly dependent on the experimental conditions (measurement duration and relative humidity), due to the hydrogel-like behavior of PEDOT:PSS. In contrast, the captive bubble technique on a fully wet film overcomes these limitations. Dynamic wettability measurements provide hysteresis values for this polymer and clarify the physical meaning of the static contact angles measured by sessile drop and captive bubble. Finally we show that aging the films in water leads to loss of PSS chains which makes the films more hydrophobic. The addition of a crosslinker reduces and slows down these effects.

Ex vivo explant culture models offer unique properties to study complex mechanisms underlying tissue growth, renewal, and disease. A major weakness is the short viability depending on the biopsy origin and preparation protocol. We describe an interphase microfluidic culture system to cultivate full thickness murine colon explants which keeps morphological structures of the tissue up to 192 h. The system was composed of a central well on top of a porous membrane supported by a microchannel structure. The microfluidic perfusion allowed bathing the serosal side while preventing immersion of the villi. After eight days, up to 33% of the samples displayed no histological abnormalities. Numerical simulation of the transport of oxygen and glucose provided technical solutions to improve the functionality of the microdevice.

In this work, we propose acoustic characterization as a new method to probe wetting states on a superhydrophobic surface. The analysis of the multiple reflections of a longitudinal acoustic wave from solid-liquid and solid-vapor interfaces enables to distinguish between the two well known Cassie-Baxter and Wenzel wetting configurations. The phenomenon is investigated experimentally on silicon micro-pillars superhydrophobic surfaces and numerically using a finite difference time domain method. Numerical calculations of reflection coefficients show a good agreement with experimental measurements, and the method appears as a promising alternative to optical measurement methods.