Hollow Hydrogels for Excellent Aerial Water Collection and Autonomous Release

Abstract Air moisture is a valuable and omnipresent resource of fresh water. However, traditional water collectors come with an enduring problem of the water‐release step, which requires special devices and additional energy to remove the water from the adsorbent, such as heat, sunlight, or both. Herein, we report the first composite conical hollow hydrogel architecture fabricated through a film‐ to ‐tube transforming protocol, designed to harvest water from aerial humidity. This hollow hydrogel device can rapidly collect water from humid air to a saturation point, whereupon it automatically and continually releases fresh water at room temperature. The entire water collection and release process does not require any external assistance. Therefore, this device is highly suitable for emergency water collection in arid areas. As an exemplary demonstration, positioning the hollow hydrogel device next to a plant turns into an individualized system for irrigation. Since the device is biodegradable, it eventually decomposes and becomes an organic fertilizer after the water supply is not required. For long‐term application, the water‐release process can be monitored in real time by an electronic device to indicate the amount of collected water. The hollow hydrogel combines the humidity‐adsorbing capacity with autonomous water release that carries the potential for harvesting water from humidity to address the shortage of fresh water, especially in arid locations where other sources of water are scarce or inaccessible.