Enhancing solar steam generation in hydrogel evaporator by bio-based microfluidic component

The hydrogel-based evaporator exhibits exceptional water activation capabilities, enabling it to surpass the previously established upper limits of evaporation rates in interfacial solar steam generation (ISSG). Although hydrogels possess a pronounced affinity for water, this characteristic could result in temporary expansion and heat loss, which hinder their capacity to sustain rapid and efficient evaporation over prolonged durations. Herein, polyacrylamide-based photothermal hydrogel with customized microfluidic components achieved long-term operation. The photothermal hydrogel showed high sunlight absorbance (∼95.5%) and its surface temperature spontaneously could reach 44.1 °C under one sun simulated irradiation (1.0 kW/m2). The efficient regulation of water transport was accomplished by Nafion-modified corn straw, i.e., a microfluidic component. This hydrogel-based evaporator demonstrated an increasing evaporation rate from 2.03 to 2.42 kg/m2/h during 12 h of continuous solar illumination. Notably, the microfluidic component resulted in controlled water transport enabling programmable adjustment of the hydrogel evaporator, allowing it to be reused multiple times in practical applications around the clock. The daily potable freshwater production amount reached 7.84 kg/m2/h in outdoor seawater desalination experiments. This research provides a paradigm approach to address freshwater scarcity on a global scale by using waste biomass to fully compensate for the shortcomings of hydrogels in ISSG systems.