Bioinspired waterproof, breathable materials: How does nature transport water across its surfaces and through its membranes?

The controlled transport of water vapor and liquid water across membranes is a crucial biological process observed in natural systems for over 460 million years. Through evolution, plants have developed various methods to regulate water gradients between their internal structures and the external environment. The primary natural mechanisms used to modulate the water gradient effectively involve integrating specialized organs, like those responsible for gas exchange, in tandem with developing impermeable outer surfaces. Several applications in engineered materials – including rainwear, wound dressings, textiles, packaging, and building materials require breathability and waterproofing properties. Breathable materials can enable water vapor movement within their structure, while waterproof materials effectively resist the penetration and absorption of liquid water. Developing materials that can simultaneously exhibit waterproofness, and breathability presents a significant scientific and engineering challenge due to the inherent conflict between these properties. This review aims to delve into the physicochemical mechanisms governing plant water transport and establish a connection with developing bio-based and bio-inspired materials. We explore how plant components can give rise to hydrophobic, hydrophilic, porous, and responsively porous bio-inspired materials, addressing challenges encountered in the waterproof-breathable textile industry.