Spontaneously oriented receding on superhydrophobic bundles for high- efficiency enrichment of airborne microdroplets

S Peng and PB Liang and MZ Wang and Z Li and HH Dong and XJ Zhang and A Hubao and S Zheng and YY Zhao, CHEMICAL ENGINEERING JOURNAL, 523, 168438 (2025).

DOI: 10.1016/j.cej.2025.168438

Realization of precise manipulation of microdroplets on solid surfaces is highly needed but proves particularly difficult in many fields, including printing, diagnostics, drug delivery, and water collection. This difficulty arises primarily due to the adhesion or friction between the solid and liquid, a phenomenon referred to as contact angle hysteresis. Here, we reported a design using intrinsically superhydrophobic nanowire bundles, shaped as mountains, which were found to guide spontaneous movement of microdroplets. Our unique "mountain" formation was formed asymmetrically, with ridges mimicking the form of the papillae of a tongue, and slopes containing nanowires arranged parallel on an angle. This configuration created differential receding contact angles during microdroplets evaporation, encouraging their spontaneously directional movement along the slopes towards the ridges, thus continually concentrating the droplets. A key application of the design is on realizing efficient capture of over six times the number of virus-laden airborne microdroplets that flat surfaces could. This demonstrates significant potential for enhancing real-time surveillance and control of respiratory pathogen.

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