A novel three-electrode electrolyte supercapacitor (electric double-layer capacitor [EDLC]) architecture in which a symmetrical interdigital "working" two-electrode micro-supercapacitor array (W-Cap) is paired with a third "gate" electrode that reversibly depletes/injects electrolyte ions into the system controlling the "working" capacity effectively is described. All three electrodes are based on precursor-derived nanoporous carbons with welldefined specific surface area (735 m 2 g −1 ). The interdigitated architecture of the W-Cap is precisely manufactured using 3D printing. The W-Cap operating with a proton conducting PVA/H 2 SO 4 -hydrogel electrolyte and high capacitance (6.9 mF cm −2 ) can be repeatedly switched "on" and "off ". By applying a low DC bias potential (−0.5 V) at the gate electrode, the AC electroadsorption in the coupled interdigital nanoporous carbon electrodes of the W-Cap is effectively suppressed leading to a stark capacity drop by two orders of magnitude from an "on" to an "off " state. The switchable micro-supercapacitor is the first of its kind. This general concept is suitable for implementing a broad range of nanoporous materials and advanced electrolytes expanding its functions and applications in future. The integration of intelligent functions into EDLC devices has extensive implications for diverse areas such as capacitive energy management, microelectronics, iontronics, and neuromodulation.

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A three‐step fabrication process for optically transparent, conducting ITO thin films with an intrinsic inverse opal structure is described. The preparation is based on colloidal crystal templating using polystyrene microspheres (100 nm–600 nm). For the realization of varying periodicities in this structure, different sphere sizes were assembled to monolayers on a substrate by spin coating and infiltrated afterwards similarly. The influence of rotation parameters as well as dispersion concentration was studied. Using this approach different geometries of the surface are accessible by systematically varying the rotation parameters and infiltration volume. The thin films show excellent anti‐reflection behavior, good transmission (>80% in the visible range) as well as a low resistance of 200 Ω/sq compared to other porous ITO interfaces. The properties are very promising for several optoelectronic applications such as in‐ or out‐coupling structures in solar cells and organic light emitting diodes.

Dropwise condensation (DWC) has the potential to enhance heat transfer compared to filmwise condensation. The heat transfer rates achieved by DWC depend on the drop size distribution, which is influenced by nucleation processes of newly formed drops. In DWC modeling, the nucleation site density Ns is used as an input parameter to obtain the drop size distribution of small drops. However, due to the small scale of the condensate nuclei, direct observation is difficult and experimental data on the nucleation site density is scarce. In the literature, values in the range of 109 m-2 to 1015 m-2 can be found for Ns. In this paper, we report dropwise condensation experiments on SiO2 and PFDTES thin hydrophobic coatings that show significantly different nucleation site densities. Nucleation site densities are estimated from high speed imaging of small drops during initial condensation and from model calibration using established DWC theory. We have found the values for Ns to be in the range from 1.1⋅1010 m-2 to 5.1⋅1011 m-2 for the SiO2 coating and 1011 m-2 to 1013 m-2 for the PFDTES coating. Our results show that there can be large differences in the nucleation site density under similar conditions depending on the surface properties. This underlines the importance of investigating nucleation site density specifically for each surface and under consideration of the specific process conditions used for DWC.

Organic light-emitting diodes (OLEDs) have successfully entered the display market and continue to be attractive for many other applications. As state-of-the-art OLEDs can reach an internal quantum efficiency of almost 100%, light outcoupling remains one of the major screws left to be turned. The fact that no superior outcoupling structure has been found underlines that further investigations are needed to understand their prospect. In this paper, we use two-dimensional titanium dioxide block arrays as a model of an internal light outcoupling structure and investigate the influence of its geometrical parameters on achieving the highest external quantum efficiency (EQE) for OLEDs. The multivariable problem is evaluated with the visual assistance of scatterplots, which enables us to propose an optimal period range and the block width-to-distance ratio. The highest EQE achieved is 45.2% with internal and external structures. This work contributes to the highly desired prediction of ideal light outcoupling structures in the future.