Rectifying Directional Liquid Transport for the Thermal Diode Application Using the Bio-inspired Approach

Project: Research

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Achieving the directional and long-range mass, momentum and energy transport on solid hydrophobic surfaces is highly desired for practical applications, but has proven to be challenging. Particularly, directionality and long-range droplet transport on hydrophobic surfaces are mutually exclusive. Such a tradeoff is further complicated at harsh environments, where the notorious liquid flooding is induced by the collapse of hydrophobicity. Recently we observed a peculiar ballistic droplet transport phenomenon on a ubiquitous insect which can maintain non-wetting property even in very high humidity. The drain fly serves as a flexible fluid rectifier to allow a directional and long-range droplet propagation as well as self-removal without the need of the driving forces dictated on natural hydrophilic surfaces such as gradients in surface energy or Laplace pressure. Moreover, the directional and long-range droplet transport is against gravity, and does not require any additional energy input.The objectives of the proposed project are to probe the fundamental mechanism underlying the unique ballistic droplet transport manifested on the drain fly, and to translate the directional liquid transport to thermal diode application. We will first experimentally investigate how the localized droplet nucleation on the surface of drain fly is rectified to a directional and global migration, and analytically elucidate the effect of structural topography, in particular the nanoscale ratchet arrays, on the droplet transport dynamics. We will also explore the feasibility of achieving such a preferential liquid transport on micro-patterned ratchets to demonstrate the generality of this peculiar transport. As an extension of the fundamental understanding, we will further design a bio-inspired liquid rectifier that promotes the droplet nucleation, growth and directional droplet movement and collection. By integrating with the wicking structure recently developed in our lab which allows for the directional liquid spreading for efficient thin film evaporation, we will translate the directional liquid motion into a novel thermal diode with high rectification coefficient. We believe that this new liquid transport mechanism to be identified in this project will dramatically advance our fundamental understanding of the droplet dynamics as well as open up a new avenue for the design of liquid rectifiers for a wide range of applications.?


Project number9042533
Grant typeGRF
Effective start/end date1/09/17 → …