Viscoelastic solid-repellent coatings for extreme water saving and global sanitation

Abstract

Water scarcity threatens over half of the world population, yet over 141 billion liters of fresh water is used globally each day for toilet flushing. This is nearly 6 times the daily water consumption of the population in Africa. The toilet water footprint is so large primarily because large volumes of water are necessary for the removal of human feces; human feces is viscoelastic and sticky in nature, causing it to adhere to conventional surfaces. Here, we designed and fabricated the liquid-entrenched smooth surface (LESS), a sprayable non-fouling coating that can reduce cleaning water consumption by ~90% compared to untreated surfaces due to its extreme repellency towards liquids, bacteria, and viscoelastic solids. Importantly, LESS-coated surfaces can repel viscoelastic solids with dynamic viscosities spanning over 9 orders of magnitude, i.e., three orders of magnitude higher than previously reported for other repellent materials. With an estimated >~1 billion toilets and urinals worldwide, incorporating LESS coating into sanitation systems will have significant implications for global sanitation and large-scale wastewater reduction for sustainable water management.

Lubricant Depletion‐Resistant Slippery Liquid‐Infused Porous Surfaces via Capillary Rise Lubrication of Nanowire Array

“…Silicone oil‐infused ZnO NW arrays were also prepared by a general procedure in which silicone oil was coated onto the surface of ZnO NW arrays using a spin coater (1000 rpm for 60 s). [ 2,10b ] After the spin‐coating step, the surface of ZnO NW arrays was infused and covered by a smooth silicone oil layer.…”

“…[ 1 ] The physical origin of the liquid repellency of SLIPS comes from a lubricant film within and above the surface of the porous template. [ 2 ] However, the lubricant film can be lost because of lubricant evaporation, shear force/frost induced lubricant loss, and movement of liquid droplets on the infused surface. [ 3 ]…”

Faeces – Urine separation via settling and displacement: Prototype tests for a novel non-sewered sanitation system

“…While the use of a conical tank in the NMT is likely to reduce the risk of plugs forming, there is still a chance for ‘bridging’ to occur, a type of clogging observed for example in grain silos ( Wu et al, 2009 ). This could be exacerbated by the high stickiness of faeces, and their tendency to adhere to even smooth surfaces ( Wang et al, 2019 ). Therefore, it may be worth investigating whether a higher liquid content would reduce the risk of bridging.…”

Rational Design of Transparent Nanowire Architectures with Tunable Geometries for Preventing Marine Fouling

“…Other alternative biocompatible surface modifications can also be applied to make NWs superhydrophobic, for example, the grafting of polydimethylsiloxane (PDMS) chains. [ 31 ]…”