Goal
Collect liquid water from ambient air without external energy input
Problem
Scarcity of fresh water and need for low-energy water harvesting from low-humidity environments
Concept Summary
A nanostructured film that combines hydrophilic nanopores with a hydrophobic polymer matrix (amphiphilic nanopores). Capillary condensation in the nanopores pulls water vapor into liquid form even at undersaturated humidity, and the hydrophobic polymer drives the condensate to exude onto the surface as droplets, providing a passive water-harvesting material.
Detailed Description
The material consists of a polymer-infiltrated nanoparticle film where amphiphilic molecules are partially cross-linked, creating a network of nanopores. Hydrophilic nanoparticles (e.g., silica) attract water vapor, while the surrounding hydrophobic polymer (e.g., polyethylene) repels water, creating a balance that enables capillary condensation. As vapor pressure rises, voids fill with liquid water; the hydrophobic domains then push the liquid out of the pores, forming microscopic droplets on the surface. The process operates isothermally and requires no external heat or power. The patent (US2024392117) describes a method of forming a barrier layer, inserting nanopores, and further cross-linking amphiphilic molecules to stabilize the structure.
Principles
- Capillary condensation
- Amphiphilicity
- Surface energy balance
- Isothermal water collection
Scientific Domains
Materials
- Hydrophilic nanoparticles (e.g., silica, alumina)
- Hydrophobic polymer (polyethylene or similar)
- Amphiphilic cross-linkable molecules
- Cross-linking agents
Mechanisms of Action
- Condensation of water vapor in nanoscopic pores
- Droplet exudation driven by hydrophobic polymer matrix
Applications
- Emergency water supply
- Irrigation in arid regions
- Off-grid water harvesting
- Heat-management surfaces that also collect moisture
Experimental Evidence
The researchers observed water droplets forming on the material's surface when exposed to air with relatively low humidity, demonstrating capillary condensation and droplet exudation without external energy input.
Limitations
- Performance depends on ambient relative humidity
- Scaling the nanostructured film to large areas may be challenging
- Potential fouling or clogging of nanopores over time