Interfacial control of transport applications

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This Discovery program is directed towards creating a new class of interfacial manipulation for three transport applications: evaporation, (slippery) electro-osmosis, and electrodialysis. These processes are omnipresent and fundamental, influencing applications in technology of water and sustainable energy. ******Concerning heat transport, the first project aims at controlling particle arrangement in a drying droplet by varying substrate properties of wetting and (thermal) conductivity. Systematic experimental measurements of temperature profiles and 3D flow fields induced by evaporation in a sessile drying droplet on a surface will be carried out. This crucial data, which is currently lacking, would shed light on optimal design for sorting and arranging materials on surfaces, using the simple and powerful method of evaporation.******To enhance momentum and charge transport, in the second project, a new type of modified superhydrophobic surfaces will be designed and generated for drag reduction in microfluidics, which is a long-standing challenge. Hydrophobic micro-channels with longitudinal microgrooves will be fabricated to entrap gas phase fluid-creating shear-free interfaces-upon the microstructures, resulting in the reduction of wall-friction. The high-resolution of flow field will be probed; the effect of geometry of gas-liquid interfaces on microfluidic slippage will be experimentally investigated. Under a similar physical mechanism, enhancement of charge/ion transport on charged gas-liquid interface is expected. However, no such experimental verification exists. I will hence examine the associated electrical and fluid dynamical effects by modifying the superhydrophobic channels to be charge-selective with electrodes.******Employing ion transport, various water and energy technologies are operated using charge selective surfaces or membranes. For instance, electrodialysis is a widely used method for desalination and water purification. In electrodialysis, ions develop concentration gradients adjacent to a charge selective surface under an electrical forcing, which in turn limits the ion transport. The third project tackles this limiting step of electrodialysis, by experimentally examining the hydrodynamic processes triggered by the gradient of ion concentrations. High-resolution measurements of electrical, ion concentration and flow fields will be conducted to understand their complex interplay for efficient electrodialysis performance. **