Smart Stretchable Janus Membranes with Tunable Collection Rate for Fog Harvesting

Water scarcity is one of the severest global resource shortages because freshwater plays a vital role in human existence. Fog harvesting is a promising approach to alleviate freshwater shortage, but most existing strategies based on rigid materials suffer from the shortage of nontunable fog collection rate. Herein, a smart Janus membrane with a tunable fog collection rate via uniaxially stretching a flexible polydimethylsiloxane sheet fabricated by ultrafast laser drilling is reported. Compared to its original form, the maximum strain of 200% shows up to 67% enhancement in its fog collection efficiency. Further theoretical calculation demonstrates that the increase of fog collection rate along with uniaxially stretching is estimated to be approximate to 79% for 200% strain sample based on the cooperation between the wetting driving force and Laplace pressure, which is in well agreement with the experimental result. It is believed that this smart Janus membrane would operate not only in the field of fog harvesting, but also in specific scenarios, such as dynamic fog-flux regulators.