Air Entrainment upon Drop Impact on Liquid-infused Surfaces
Liquid-infused surfaces have attracted great interest in recent years due to their super slippery properties upon drop impact and potential benefits in self-cleaning and anti-fouling applications without much understanding of the underlying physics. This project seeks to examine the drop impact dynamics on lubricated and liquid-infused surfaces, with a focus on probing the role of the entrained air layer prior to drop-film contact and during drop-film interactions. Understanding the air film dynamics underneath the droplet allows for the better tuning of the liquid film properties in the lubricating layer, designing more robust nanostructures, and ultimately enhancing the performance of liquid-infused surfaces for applications ranging from anti-fouling and anti-icing to phase separation and thermal management. By integrating the total internal reflection microscopy, reflection interference microscopy, and high-speed imaging, the air film evolution and post-rupture liquid-liquid contact dynamics are directly visualized for different impact conditions and drop/film/substrate properties with nanometer spatial and microsecond temporal resolution. This unique capability enables direct probing of air film profile at thickness where the liquid-liquid intermolecular interactions become important.
Indirect Dry Cooling of Power Plants
Thermal management systems for electric power plants account for approximately 40% of total fresh water withdrawals in the US. Due to dwindling access to fresh water resources worldwide, continued operation of these systems poses a significant engineering challenge. As such, this project aims to develop transformative “dry-cooling” technologies completely eliminating the use of water for cooling steam condensers in modern electric power plants. This will be achieved using phase-change materials (PCM) to decouple the condensation and heat rejection processes, reducing steam condensation temperature, pressure drop, and system size as compared to current air-cooled condensers.
Inkjet Printing of 3D Heterogeneous Nanostructures
This project conducts fundamental research on integrating inkjet printing of functional materials with nanoporous structures for high-throughput manufacturing of 3D heterogeneous nanostructures for energy, biomedical, and sensing applications. Specifically, the research will combine in-situ imaging, multi-scale modeling, and advanced characterization to examine the simultaneous wetting, infiltration, and evaporation of inkjet-printed functional inks onto nanoporous substrates and the subsequent particle self-assembly and deposition processes both inside and through nanopores. A synchronized high-speed camera, confocal microscope, and laser interferometry setup will directly observe the complex transport phenomena during the 3D nanoprinting process. A multi-scale approach, integrating a mesoscale lattice Boltzmann model at the entire drop level and a molecular dynamics model for probing interactions of nanoparticles with the contact line inside a single pore, will be developed to capture the radial-dependent infiltration process in nanopores. The project goal is to build the structure-process-property relationship for nanoporous-templated 3D nanoprinting.
Electrode Microstructure and Peroxide Growth in Li-air Battery
Li-air battery, with its usable energy density close to 1,700Wh/kg, has captured worldwide attention as a promising battery solution for electric vehicles. However, current Li-air technology suffers from low round-trip efficiency and rate capacity. The cathode microstructure and the Li2O2 formation can have a significant influence on the performance of the non-aqueous Li-air battery. Our objective is to examine the effect of electrode microstructure and Li2O2 growth morphology on Li-air cell performance via combined multi-scale modeling and experiments. Most efforts attempt to design electrode microstructures for enhanced round-trip efficiency through costly and time-consuming experiments and highly empirical knowledge. Our integrated program includes novel electrode fabrication, high fidelity multi-scale modeling, post-mortem and in-situ characterization, electrochemical testing, and high performance computing to probe the effects of electrode microstructure and Li2O2 growth morphology on cell performance.