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Freshwater scarcity has become a critical global challenge affecting some of the most vulnerable populations. In response, significant effort has focused on ways to increase access to this precious resource. Within the context of geographical, cultural, political, and technological factors governing freshwater availability, atmospheric water harvesting (AWH) has demonstrated tremendous promise to help address these shortages. Specifically, mesh‐based fog harvesters have received considerable attention for their passive qualities compared with their energy‐dependent technological siblings (sorbents, condensation, etc.), yet their specific water yield (SY) has developed only modestly in recent decades. While the plant and animal kingdom provide diverse examples of passive fog collection, and science has developed a remarkable understanding of these processes, much of this knowledge has yet to be translated practically at scale. This is partially due to challenges in mass‐producing complex (often micro‐scale) structures observed in nature. Fortunately, manufacturing technology is catching up with scientific understanding, especially at the scale of mesh design. To this end, the review begins by surveying bioinspired research in fog harvesting. Afterward, this study identifies milestones in developing bioinspired fog harvesting meshes, concluding in a discussion of future mesh research opportunities connecting bioinspiration and emerging advanced manufacturing techniques. [ABSTRACT FROM AUTHOR]

When microdroplets with quasi‐spherical contact angles coalesce together on a low‐adhesion substrate, the capillary‐inertial expansion of the liquid bridge induces a dramatic out‐of‐plane jumping event due to symmetry breaking. From the onset of merging, droplet jumping initiates after a capillary‐inertial time scale of tci∼1–100 ${t}_{\text{ci}}\sim 1\mbox{--}\,100$ μs with characteristic jumping speeds of order vj∼0.1 ${v}_{{\rm{j}}}\sim 0.1$ m/s. This coalescence‐induced jumping‐droplet effect is most commonly observed among a population of growing dew droplets on a superhydrophobic condenser, but can also occur by colliding deposited droplets together or during droplet sliding on fog harvesters. In this review, we cover the historical development of capillary‐inertial jumping droplets, summarize the decade‐long effort to rationalize the ultra‐low energy conversion efficiency and critical droplet size of the phenomenon, and then present 15 variations on a theme of jumping. Capillary‐inertial jumping droplets are not only a visceral illustration of the surprising power of surface tension at the microscale but they also have the potential to enhance phase‐change heat transfer, enable self‐cleaning surfaces, combat frost formation, harvest energy, and govern the rate of disease spread for wheat crops. [ABSTRACT FROM AUTHOR]

Surfaces with micro/nano‐structures significantly enhance the critical heat flux of nucleate boiling by increasing the wickability of the liquid phase to delay film boiling. An alternative strategy, of removing surface bubbles at smaller sizes, is largely ignored. Here, they fabricate a rationally designed micro‐structured surface that enables the coalescence‐induced departure of microscopic vapor bubbles during the pool boiling of water at diameters an order of magnitude smaller than single‐bubble buoyant departure. Arrays of micro‐cavities or micro‐grooves serve as tailored nucleation sites to nucleate close‐packed vapor bubbles, which coalesce at unusually small sizes compared to a homogeneous surface. Two different modes of coalescence‐induced bubble departure are observed and modeled: capillary‐inertial jumping for smaller micro‐bubbles and buoyant‐inertial liftoff for larger micro‐bubbles. Capillarity‐enhanced pool boiling on micro‐structured surfaces has the potential to dramatically enhance the heat transfer coefficient and critical heat flux of pool boiling. [ABSTRACT FROM AUTHOR]

Fog Harps harvest substantially more water than conventional mesh‐based harvesters. However, to date, all large‐scale Fog Harps have been impractically hand‐wound at low wire tensions and suffer from elastocapillary wire tangling. Here, we develop large‐scale and high‐tension Fog Harps that are manufacturable and antitangling. These Fog Harps retain the record‐setting fog harvesting efficiency (η≈17 $\eta \approx 17$%) of their optimized scale‐model counterparts, while uniquely enabling practical real‐life implementation. Manufacturability was achieved by adapting the industrial process for making harp screens, a pre‐existing technology used for screening solid materials. The critical tension required to minimize wire tangling was rationalized by an improved elastocapillary tangling model. [ABSTRACT FROM AUTHOR]

Phase‐change thermal diodes effectively transport heat unidirectionally, but are currently constrained by either a gravitational dependence, a 1D configuration, or poor durability. Here, a novel bridging‐droplet thermal diode which uniquely bypasses all of these existing constraints is developed. The diode is comprised of two opposing copper plates separated by an insulating gasket of micrometric thickness; one plate contains a superhydrophilic wick structure while the other is smooth and hydrophobic. In the forward mode of operation, water evaporates from the heated wicked plate and condenses on the hydrophobic plate. The large contact angle of the dropwise condensate enables bridging across the gap to replenish the wicked evaporator, providing sustained phase‐change heat transfer. Conversely, in the reverse mode, the heat source is now on the hydrophobic plate, resulting in dryout and excellent thermal insulation across the gap. An orientation‐independent heat transfer ratio (i.e., diodicity) as high as 85 was measured. [ABSTRACT FROM AUTHOR]

Fog harvesting is useful for passively collecting fresh water in arid regions, but the efficiency of current mesh‐based harvesters is compromised by their poor drainage. Inspired by the linear needles of redwood trees, "fog harps" are developed whose array of vertical wires enables an unobstructed drainage pathway. A full‐scale (1 m2 frame) fog harp is fabricated by winding a stainless steel wire around a spinning aluminum frame featuring threaded rods. The fog harp is field tested for a full year at a local farm (Blacksburg, VA, USA), alongside the control case of a mesh harvester. Under moderate fog conditions, the fog harp collects anywhere from 2 to 78 times more water compared to the mesh harvesters. Under light fog conditions, the fog harp collects up to several hundred milliliters of water per day while the mesh is unable to collect any water at all. The water harvesting performance of fog harps is therefore unprecedented in two ways: they substantively elevate the performance ceiling when exposed to healthy fog while also enabling, for the first time, appreciable water harvesting under light fog. [ABSTRACT FROM AUTHOR]