SHPF

Scalable Hygroscopic Polymer Film Shpf Action Principles

Described in Nature Communications in may 2022, Super Hygroscopic Polymer Films (SHPF) is a newly invented composite biopolymer. It’s high efficiency of water uptake in arid climates, aswell as it’s cheap and available material components and potential scalability make it relevant to atmospheric water harvesting all over the world.

SHPF has great vapor absorption traits (speed of absorption and absorption amount) and the energy it requires to release captured vapor is low. It achieves these properties by distributing hygroscopic lithium chloride salt molecules in a thin and highly porous fiber matrix made up of plant fibers. Material appears like a thin film, and it is produced by mixing the ingredients into a hydrogel, freezing the hydrogel and drying the material (through sublimation) in a freeze dryer.

SHPF works by taking advantage of specific chemical properties of 3 different material ingredients:

1) The emulsifying properties and the low temperature hydrophilicity-tohydrophobicity transition of hydroxypropyl cellulose (HPC).

2) The fiber strength and high viscosity, water solubility and hydrophilicity of konjac glucomannan fiber (KGM).

3) The good solubility and great hygroscopic potential of lithium chloride (LiCl).

As such, SHPF is preferable for scaling, when compared to other AWH substrate materials such as zeolites like silica gel, metal organic frameworks and pure hygroscopic salts.

MAPPING PRODUCTION SUPPLYCHAIN FOR THE SAMPLE MATERIAL.

Organic binding agent with low temperature hydrophiliv/hydrophobic transition.

Highly viscous organic fiber, used as emulsifyer for forming strong uniform gels.

Alkali metal salt with exceptional hygroscopic properties and great soluability.

ForestryAgriculture

Produced with short wood fiber from gum trees and long wood fibers from pine trees when made in european factories. Both lengths of wood fiber can be sought out in alternative species lik

Highly viscous organic fiber, used as emulsifyer for forming strong uniform gels.

Salt refinement

Alkali metal salt with exceptional hygroscopic properties and great soluability.

Mix

2 minutes

Precursor ingedrients are measured out, mixed untill even and set for 5 minutes, while the cellulose and konjac fibers form hydrogen bonds, until the gelation formation process is complete.

Mold

15 minutes

The hydrogel is poured into prepared acrylic molds. At this stage, the gel is shaped into the required surface area and thickness. The gel is set for 15 minutes to even equalize and even out.

Freeze

3 hours / 15 minutes

The molds are pre-frozen at -4OC for 3 hours. It's important that the samples don't freeze solid at this stage. The Lithium Chloride dissolved lowers the eutectic freezing point of the solution. After this, the samples are rapidly frozen with liquid nitrogen bath for 15 minutes. This rapid and powerful freeze helps the water in the hydrogel freeze form small homogeneous ice crystals.

Freezedry

6 - 9 hours

The molds with the frozen samples are put in a lyophilizer, to remove the ice from the samples via sublimation. This is the gentlest way of removing water from the samples, and it helps maintain the pourous structure of the samples that makes SHPF able to absorb water vapor rapidly.

DEPLOY

30 minutes / 2 hours

After drying the fiber matrix of the SHPF is cured and fully bonded. The dry samples are hard and brittle, but will resaturate with atmospheric moisture from ambient air over the course of 30 min / 2 hours, depending on the relative humidity of ambient air, and become soft and workable, at which point they can be lifted from the molds and deployed.