# Facile Access to Salt‐Resistant Polyzwitterionic Hydrogel Evaporator via In Situ Frontal Curing‐3D Printing Strategy

## TL;DR

A new 3D printing method creates salt-resistant hydrogel evaporators that efficiently produce freshwater even in highly saline conditions.

## Contribution

The in situ frontal curing-3D printing strategy enables efficient fabrication of salt-tolerant polyzwitterionic hydrogel evaporators.

## Key findings

- The hydrogel shows a high evaporation rate of 4.02 kg·m−2·h−1 in 15 wt.% NaCl solution.
- The material exhibits a higher intermediate water/free water ratio and lower evaporation enthalpy.
- Macro-channels from 3D printing and microchannels in the hydrogel enhance water transport performance.

## Abstract

Freshwater crisis has emerged as a global problem, which has significant negative impact on human production and life. Thus, material design and fabrication are extremely necessary for high salt tolerance and highly efficient evaporation in freshwater production. In this work, polyzwitterionic hydrogel is designed by an in situ frontal curing‐3D printing strategy, which greatly saves times and energy, while ensuring high fidelity and integrity of the printed structure. The polyzwitterionic hydrogel has anti‐polyelectrolyte effect and boosted hydration, showing a higher intermediate water/free water ratio and lower evaporation enthalpy. Meanwhile, the macro‐channels formed by 3D printing and inherent microchannels in hydrogels are synergistically enhancing the water transport performance. As a consequence, the hydrogel exhibits a high evaporation rate of 4.02 kg·m−2·h−1 in 15 wt.% NaCl solution with excellent salt tolerance. This work provides an in situ frontal curing‐3D printing strategy for the preparation of highly efficient and salt‐tolerant polyzwitterionic hydrogel evaporator, which would guide the development of advanced hydrogel evaporator in a facile fashion.

Polyzwitterionic hydrogel evaporator is developed by a facile in situ curing 3D printing strategy. It shows higher intermediate water/free water ratio in high‐salinity brine, leading to increased amount of activated water and lower evaporation enthalpy, which exhibits high evaporation efficiency and satisfactory salt tolerance.