Flexible and durable fluorine-free superhydrophobic films through sustainable approach

The performance of multiple engineering systems including solar panels, flexible electronics, optical equipments and devices is limited due to atmospheric contamination. Pollutant and salt-laden aerosol and rain causes enourmous loss of functionality to multiple engineering systems. In the present work, we developed flexible, semi-transparent and durable superhydrophobic films for complex geometrical shapes. We showed that an environmental and simple biofuel-based flame treatment can be effectively tailored to develop durable superhydrophobic polydimethylsiloxane (PDMS) films within a minute through tuned motion, without any pre-treatment. The treatment of PDMS results in the formation of Coral-like wrinkled morphology decorated with in-situ synthesized functionalized nano silica particles. The processing conditions are tuned to generate a hierarchically structured surface with utmost dewetting to water (θ > 160°), and other liquids including blood, with low hysteresis (<5°) and sliding angles (<5°). The adhesion with water is extremely low (∼2 μN) and better than that of the Lotus leaf (∼10 μN). This extreme dewetting and low adhesion characteristics are attributed to the Coral-like structures formed from agglomerated nano silica particles endowing negative capillary pressure of more than 14 MPa. The developed films showed excellent resistance to harsh physical and chemical environments with no signs of severe damage, sustaining more than 20,000 droplet impacts and more than one year weathering. The developed superhydrophobic flexible, durable, and semi-transparent films can be used for devising non-wettable self-cleaning structures, even with intricate shapes.