Water transport through hydrogel membranes at low relative humidities*

Atmospheric water harvesting is an emerging research area focusing on ways to tap into the water vapor around us as a new water resource. Capturing that water vapor is thermodynamically challenging in low humidity environments. We envision a way to capture and transport that water through a thin polymeric membrane. We hypothesize that the performance of such membranes is dictated by a combination of hydrogel microstructure, hygroscopic functionalities, crosslinking, and the gradient in chemical potential. Through systematic experiments of measuring water fluxes while varying these parameters, we elucidate how transport properties such as diffusivity and permeability can be affected, especially in the context of low humidities. The results of this work will pave the way for more informed design of atmospheric water harvesting and related applications such as dehumidification.