Hygroscopic and Photothermal All-Polymer Foams for Efficient Atmospheric Water Harvesting, Passive Humidity Management, and Protective Packaging

Abstract

Environmental humidity and thermal control are of primary importance for fighting global warming, growing energy consumption, and greenhouse gas emissions. Sorption-based atmospheric water harvesting is an emerging technology with great potential in clean water production and passive cooling applications. However, sorption-based humidity management and their hybrid applications are limited due to the lack of energywise designs of hygroscopic materials and devices. Herein, all polymeric 3D foams are developed and evaluated as hygroscopic and photothermal materials. The gas-foaming method generates closed-cell structures with interconnected hydrophilic networks and wrinkled surfaces, expanding hygroscopic, photothermal, and evaporating areas of the 3D foams. These unique advantages lead to efficient water vapor sorption in a wide broad relative humidity (RH) range of 50−90% and efficient water release in a wide solar intensity (0.4−1 sun) and temperature range (27−80 °C). The reversible moisture sorption/release in 50 adsorption/desorption cycles highlights the excellent durability of the 3D foams compared to conventional inorganic desiccants. The 3D foams disclose passive and efficient apparent temperature regulation in warm and humid environments. Moreover, the use of the 3D foams as loose fill for fruit preservation and packaging is demonstrated for the first time by taking the merit of the 3D foams' moisture-absorbing, quick-drying, cushioning, and thermal-insulating properties. This work presents an integrated design of polymeric desiccants and scaffolds, not merely delivering stable water adsorption/desorption but also discovering innovative hybrid applications in humidity management and protective packaging.

Self‐Contained Moisture Management and Evaporative Cooling Through 1D to 3D Hygroscopic All‐Polymer Composites

“…Multiphysics was assigned to the model and the physics boundary conditions were defined, considering water vapor diffusion and liquid movement inside the porous medium (Brinkman equation), water vapor transportation in the closed space (Navier−Stokes equation), and heat transfer of humid air. [ 61,70 ] The meshes were created and the boundaries of hygroscopic fabrics, air and the closed space were refined (Figure S16, Supporting Information). The simulation of humid air movement surrounding HNF‐2 and HNF‐3 was conducted from 0 to 9 s (Figure S17, Supporting Information).…”

“…To tackle this, the design of "all-polymer" hygroscopic composites and crosslinked networks presents a potential solution to prevent material solvation and sorbent leaks. [35,61] However, waterinduced swelling is ubiquitous in many hydrophilic polymers. The porous morphologies of fabrics are highly susceptible to swelling-controlled deformation (i.e., stretching, wrinkling, and delamination) at multiple length scales, limiting the processing, mechanical strength and breathable functionalities of swollen fabrics.…”

Alginate Biopolymeric Coated Heat Exchanger for Atmospheric Water Harvesting

“…To address the challenge of producing water in dry climates, materials scientists have been investigating the synthesis and processing of various types of sorbent materials, including minerals such as clays, − silica gel, − metal–organic-frameworks (MOFs), − and polymers. − When exposed to ambient humidity, sorbent materials can absorb water vapor molecules through chemisorption and/or physisorption mechanisms. , The sorbent materials reported in the literature typically require high regeneration temperatures of up to 120 °C in some cases to release water molecules from the sorbent. During the regeneration process, these free water vapor molecules (at higher temperatures and pressures) undergo condensation as they contact colder surfaces with a dew point above that during the water capture stage.…”

Multi-bioinspired hierarchical integrated hydrogel for passive fog harvesting and solar-driven seawater desalination

“…Extracting fresh water from the atmosphere and seawater is a good choice. On the one hand, water harvesting technologies from the atmosphere include raindrop, dew, and fog collection as well as adsorption [19] , [20] , [21] , [22] , [23] , [24] , [25] . In addition, in virtue of the moisture in the air contains less bacteria and impurities, the collected water could be generally ready for further use without complicated sterilization and purification processes [25] , [26] .…”