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8-Aminoquinoline (8AQ) is the building block for many medicinal molecules. However, the redox properties of 8AQ, which are important for understanding the redox stability of drugs based on 8AQ in the human body, have not been studied in detail before. We have used cyclic voltammetry and pulse voltammetric techniques to investigate the anodic as well as the cathodic electrochemical behavior of 8AQ in a wide pH range. We have also applied UV–Vis spectroscopy to get a better understanding of the deprotonation of 8AQ due to pH changes. In addition, quantum chemical studies exploring the energy landscapes of the possible oxidations and reductions were performed, advancing our understanding of the electrochemical phenomena. The results indicate that the oxidation pathway of 8AQ strongly depends on the pH of the solution while reduction occurs according to a single pathway.

We have investigated the compatibility of some organic solvents commonly used in electrochemistry with microfluidic channels based on poly(dimethylsiloxane) (PDMS) and compared the stability of electrochemical measurements over several hours with how much PDMS swells when immersed in these solvents. Lee et al. (Anal Chem 75: 6544–6554. doi: 10.1021/ac0346712 , 2003 ) have shown that there is a good correlation between swelling of PDMS and the solubility parameter ( δ H ) of the various solvents and suggested that δ H can function as an indication of PDMS compatibility. We show that solvents with a very high swelling ratio can give stable voltammetry over several hours, and thus, we do not find that swelling is a good measure for compatibility with PDMS in electrochemical experiments.

Since the pioneering works of Wenzel and Cassie Baxter in the 1930s, and now with the trivialization of the micro- and nanotechnology facilities, superhydrophobic surfaces have been announced as potentially amazing components for applications such as fluidic, optical, electronic, or thermal devices. In this paper, we show that using superhydrophobic surfaces in digital microfluidic devices could solve some usual limitations or enhance their performances. Thus, we investigate a specific monophasic (air environment) microfluidic device based on electrowetting integrating either a hydrophobic or a superhydrophobic surface as a counter-electrode. The droplet transport using a superhydrophobic surface compared with a classical hydrophobic system led to some original results. Characterization of the dynamic contact angle and the droplet shape allows us to get new insight of the fluid dynamics. Among the remarkable properties reported, a 30 % lower applied voltage, a 30 % higher average speed with a maximum instantaneous speed of 460 mm/s have been measured. Furthermore, we have noticed a huge droplet deformation leading to an increase by a factor 5 of the Weber number (from 1.4 to 7.0) on SH compared to hydrophobic surfaces. Finally, we discuss some of the repercussions of this behaviour especially for microfluidic device.