Authors: Masoumeh Nazari, Sina Nazifi, Zixu Huang, Tian Tong, Habilou Ouro-Koura, Jiming Bao, Kausik Das, Hadi Ghasemi
Summary: Capillary wicking drives liquid motion in miniature channels and capillaries, which are omnipresent in the human body, nature, and technology; examples include the brain’s capillary network, plants, power systems, nanofluidics devices, and cooling systems for electronics/photonics. Capillary force is inversely proportional to the radius of confinement and becomes the dominant driving force for mass transport at smaller scales. Here, we demonstrate that capillary wicking breaks down at a sub-10 nm scale for some fluids, changing the governing physics of the mass transport and leading to a quasi-static liquid–vapor interface experiencing the dynamic process of wetting and liquid fracture in a cyclic manner. The scale of capillary breakdown is a function of interfacial tension of the liquid and could be tuned based on the system requirements. Capillary breakdown results in surface tension nanogates that are turned on/off via external stimuli such as minimal temperature actuation or applied voltage. These nanogates are highly effective and tunable for ion transport, playing a critical role in the functionality of biological systems. The surface tension nanogates promise platforms to govern nanoscale functionality of a wide spectrum of systems, and applications can be foreseen in drug delivery, energy conversion, power generation, seawater desalination, and ionic separation.
Source: ACS Applied Nano Materials, 2020; 3 (7): 6979