In most climatic conditions, radiative cooling of typical surfaces results in only a few degrees of subcooling, and dew only forms a few hours per night on some nights. [3,4] Even so, dew is considered an important source of water for basic sustenance of plants and animals, especially in arid and semiarid regions. [11,12] In the past 20 years, research has been dedicated to obtaining design principles that lead to the most efficient dew water collection on artificial surfaces. [3,[13][14][15] The efficiency of atmospheric water collection (as well as the efficiency of processes of industrial relevance, such as heat transfer in cooling towers) depends on the ability of a surface to first nucleate water droplets at a high rate, and shed those droplets at low volumes, so they can be collected. [16][17][18][19] Classical nucleation theory teaches that the free energy barrier for nucleation ΔG is lower for ideal planar surfaces that are highly wettable by water (low water contact angle), and can be estimated by the following equation [20]

An experiment which investigates the wettability of natural surfaces was developed for undergraduate students, which allows them to explore concepts of surface structure, wettability, superhydrophobic surfaces, and self-cleaning. The students choose their own samples of leaves and flowers present in their local environment, examine their surface structure and chemistry by microscopy and contact angle measurements, and, using their understanding of the literature on the wettability of rough surfaces, relate the two. The experiment is student-focused in that it gives students agency in choosing the samples to study, increases their confidence, and develops curiosity in their local environment.

The capture of moisture from the atmosphere through condensation has the potential to provide a sustainable source of water. Here, we investigate the condensation of humid air at low subcooling condition (11 °C), similar to conditions for natural dew capture, and explore how water contact angle and contact angle hysteresis affect the rates of water capture. We compare water collection on three families of surfaces: (i) hydrophilic (polyethylene oxide, MPEO) and hydrophobic (polydimethylsiloxane, PDMS) molecularly thin coatings grafted on smooth silicon wafers, which produce slippery covalently attached liquid surfaces (SCALSs), with low contact angle hysteresis (CAH = 6°); (ii) the same coatings grafted on rougher glass, with high CAH (20°–25°); (iii) hydrophilic polymer surfaces [poly(N-vinylpyrrolidone), PNVP] with high CAH (30°). Upon exposure to water, the MPEO SCALS swell, which likely further increases their droplet shedding ability. MPEO and PDMS coatings collect similar volume of water (around 5 l m−2 day−1), both when they are SCALS and non-slippery. Both MPEO and PDMS layers collect about 20% more water than PNVP surfaces. We present a basic model showing that, under low heat flux conditions, on all MPEO and PDMS layers, the droplets are so small (600–2000 µm) that there is no/low heat conduction resistance across the droplets, irrespective of the exact value of contact angle and CAH. As the time to first droplet departure is much faster on MPEO SCALS (28 min) than on PDMS SCALS (90 min), slippery hydrophilic surfaces are preferable in dew collection applications where the collection time frame is limited.

This study demonstrates the feasibility of molecular imprinting using a functional chain transfer agent sans a functional monomer. Ethylene glycol dimethacrylate (EGDMA)-based MIPs were synthesised in the presence of thioglycolic acid (TGA) possessing a carboxylic acid group, capable of interacting with the chosen test template R,S-(±)-propranolol (PNL) and a labile S-H bond to facilitate an efficient chain transfer reaction. Quantitative 1H NMR measurements showed high PNL and TGA incorporation within the MIP, indicating an efficient chain transfer process and a favourable interaction between PNL and TGA. TGA-50, with the lowest amount of CTA, showed the largest imprinting effect and an imprinting factor (IF) of 2.1. The addition of MAA to the formulation improved the binding capacity of PNL to the MIP but also increased NIP binding, resulting in a slightly decreased IF of 1.5. The Kd for the high-affinity sites of the TGA/MAA MIP were found to be two times lower (10 ± 1 μM) than that for the high-affinity sites of the TGA-only MIPs, suggesting that the incorporation of the functional monomer MAA increases the affinity towards the PNL template. Selectivity studies, cross-reactivity as well as binary competitive and displacement assays showed the TGA-based MIPs to be highly selective towards PNL against pindolol and slightly competitive against atenolol. The morphologies of the polymers were shown to be affected by the concentration of the TGA, transforming into discrete macrospheres (from small aggregates) at a higher TGA concentration.