Cactus‐Inspired Conical Spines with Oriented Microbarbs for Efficient Fog Harvesting

Abstract

and joints can efficiently transport and collect water from moisture. [4] The tenebrionid beetle with hydrophilic/hydrophobic patterned structures can collect drinking water from foggy air. [5] Many Cactaceae species living in highly arid deserts are extremely drought-tolerant owing to their excellent fog harvesting ability and minimal water loss. [6] Cacti uses conical spines with oriented microbarbs and hydrophilic trichomes as a continuous and effective fog harvesting system that relies on the cooperation effect of the Laplace pressure gradient and wettability difference. [6a,7] The Laplace pressure gradient generated from the conical shape of spines produces a unidirectional transport of water drops. Oriented microbarbs on spines have an asymmetrical morphology, which aids the unidirectional transport of drops. The wettability difference between spines and trichomes facilitates the rapid absorption and preservation of water drops. This multi structural and multifunctional integrated fog collection system can achieve spontaneous and continuous fog collection, transport, and preservation.Inspired by this superior fog collection system of cacti, several artificial spine-based fog collectors have been developed. [1b,8] However, these spine-based fog collectors are rarely integrated with oriented microbarbs for the fog harvesting owing to the fabrication limitation of microbarbs on the curved spine surface. Heng et al. [7] fabricated a branched ZnO wire structure using a two-step vapor-phase approach for the fog harvesting. The stem wire and branched wires were used to imitate the conical spine and microbarbs, respectively. This artificial branched wire structure collected more water compared with the cactus structure owing to relatively larger surface areas of the branched wires. However, the orientation of branched wires on the stem wire was random. Thus, it is still a challenge to construct oriented microbarbs on curved surfaces, and the effect of oriented microbarbs on the fog harvesting process lacks a systematical investigation.Herein, we propose the magnetorheological drawing lithography (MRDL) method to fabricate cactus-inspired conical spines with/without oriented microbarbs on the superhydrophilic porous substrate for efficient fog harvesting. MRDL is an effective additive manufacturing technique that can easily form 3D conical spines with/without oriented microbarbs on a porous substrate with the assistance of an external magnetic field. [9] The water collection behavior and the underlying In nature, cacti use conical spines with oriented microbarbs and hydrophilic trichomes as an effective fog harvesting system. However, the fabrication dilemma of complex cactus-inspired conical spines with oriented microbarbs limits their applications. Here, a magnetorheological drawing lithography (MRDL) method is developed to additively manufacture 3D cactus-inspired conical spines with/without oriented microbarbs on a superhydrophilic porous substrate for efficient fog harvesting. Cactus-inspired conical spin...

Special Wettability Materials Inspired by Multiorganisms for Fog Collection

“…The complex and directional structure of microbarbs restricts the manufacturing of conical materials. Yi et al [87] used magnetorheological drawing lithography (MRDL) method to fabricate conical materials with different orienting microspines on a superhydrophilic porous substrate (Figure 3e-g). The strategy of a conical material with backward barbs can significantly speed up the directional transport of water droplets and achieve higher fog collection efficiency.…”

“…e,f) Reproduced with permission. [87] Copyright 2019, Wiley-VCH. Scale bars (e) 1 mm, (f) 1 mm, (g) 1 mm.…”

“…g) The process of creating forward microspines on the curved surfaces of conical spines. e,f) Reproduced with permission [87]. Copyright 2019, Wiley-VCH.…”

Bioinspired materials for water-harvesting: focusing on microstructure designs and the improvement of sustainability

“…In order to achieve the same water collection function, scientists have prepared a series of cactus-inspired conical structures. [71][72][73] Cao et al 74 have developed an improved organic solvent-free magnetic particle-assisted molding (MPAM) technology that can mass produce cactus-like microtips in a short period of time. The array of hydrophobic conical tips composed of PDMS and MP, together with the hydrophilic cotton fabric, constitutes a mist collection system.…”

Tailoring silicon for dew water harvesting panels

“…Another issue is that the expected wetting properties heavily rely on specific surface morphologies. No matter biomimetic structures (Mele et al, 2012;Barthlott et al, 2010;Schulte et al, 2011;Yi et al, 2019;Kuru et al, 2011;Gao et al, 2005), anisotropic sliding surfaces (Kang et al, 2013;Wu et al, 2011;Zhang et al, 2014), or hierarchical architectures (Yan et al, 2020;Chen et al, 2007;Rykaczewski et al, 2013), they require relatively complicated fabrication steps involving lithography or chemical synthesis, which is challenging for large-area production and seriously restricts their applications.…”