Properly controlling the rheological properties of nanoparticle inks is crucial to their printability. Here, it is reported that colloidal gels containing a dynamic network of graphene oxide (GO) sheets can display unusual rheological properties after high‐rate shearing. When mixed with polyaniline nanofiber dispersions, the GO network not only facilitates the gelation process but also serves as an effective energy‐transmission network to allow fast structural recovery after the gel is deformed by high‐rate shearing. This extraordinary fast recovery phenomenon has made it possible to use the conventional air‐brush spray technique to print the gel with high‐throughput and high fidelity on nonplanar flexible surfaces. The as‐printed micro‐supercapacitors exhibit an areal capacitance 4–6 times higher than traditionally spray‐printed ones. This work highlights the hidden potential of 2D materials as functional yet highly efficient rheological enhancers to facilitate industrial processing of nanomaterial‐based devices.

Evaporative pre-concentration is energy conserving and benefits from minimal intervention in environmental monitoring for sustainability.Drops of specific volume falling cleanly through the superhydrophobic hole method here are found to work on woven mesh (wire diameter ¼ 57 mm, pitch ¼ 125 mm) but not on plate substrates. Their conception as solid spheres was not borne out in volume to hole diameter trends, and they can also be retained on the substrate despite high levels of inclination.

Drops with larger volumes placed over a superhydrophobic (SH) surface with a hole do not fall through unless they are evaporated to a size that is small enough. This feature offers the ability to preconcentrate samples for biochemical analysis. In this work, the influence of pinning on the behavior of drops placed on a 0.1 mm thick SH substrate with a 2 mm diameter hole as they evaporated was investigated. With 16 μL of water dispensed, the sessile drop component volume was initially higher than that of the overhanging drop component and maintained this until the later stages where almost identical shapes were attained and full evaporation was achieved without falling off the hole. With 15 μL of water dispensed, the volume of the sessile drop was initially higher than that of the overhanging drop component but the liquid body was able to squeeze through the hole after 180 s due to the contact line not having sufficient pinning strength when it encountered the edge of the hole. This resulted in the liquid body either falling through the hole or remaining pinned with an oval-like shape. When it did not fall-off, the liquid body had volume and contact angle characteristics for the sessile drop and overhanging drop components that were reversed. In the later stages, however, nearly identical shapes were again attained and full evaporation was achieved without falling off the hole. The effects of pinning, despite the substrate being SH, offer another path toward achieving practical outcomes with liquid bodies without the need for chemical surface functionalization. Similarities and differences could be seen in the behavior of a sessile drop on a SH plate that was inclined at 30° to the horizontal and evaporated.

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