Super-Hydrophobic Surface Enabled Microfluidic Energy Conversion

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Currently, rechargeable batteries are widely used to power electronic devices. The use of batteries is increasing significantly to meet the demand of the rapidly growing number and density of portable electronic devices. Such rapid growth results in major challenges in recycling and replacement of batteries, and environmental concerns related both to manufacturing and disposal of batteries. Therefore, the development of an eco-friendly alternative energy harvesting method to effectively extend the lifetime of batteries or even replace them becomes increasingly urgent. To meet this urgent need, the research project is investigating a new high-power high-efficiency microfluidic energy scavenging technology to convert mechanical energy into electricity. The proposed method can operate virtually in any situation having a pressure difference. The proposed eco-friendly method is envisioned to recover electricity from human locomotion. Human power is ubiquitous and abundant, environmentally friendly and independent of climate and environment. Such applications are of high interest to military for the usage on the battlefield or emergency and law enforcement personnel as well as civilians to power a broad range of portable electronic devices. This technology has the potential of translating into critical social and environmental benefits, such as decreased pollution due to the reduction in the amount and capacity of batteries. In partnership with local high schools, the PI has developed an already successful summer camp. Results from the project will be used in educational modules for a camp used to attract high school students to engineering at the University of Nevada in Las Vegas, which has a large Latino population. This project explores the application of super-hydrophobic surfaces for energy conversion. Using a combined theoretical and experimental approach, the central goals of the project are to: (1) fundamentally understand electrokinetics over super-hydrophobic surfaces, and (2) explore these phenomena in order to design new microfluidic energy-conversion devices with high efficiency and high power density, using super-hydrophobic surfaces. This proposed technology capitalizes on the finding that conversion efficiency and power density over a super-hydrophobic surface can be greatly enhanced compared to a traditional smooth surface. However, very little work has been reported on energy conversion over super-hydrophobic surfaces. In this project, a program integrating theory, computation and experiment is employed with the aim of bridging this fundamental knowledge gap. The PI will employ a mathematical model accounting for surface conduction and concentration polarization. These factors have been neglected in previous modeling efforts but are essential for practical applications. In addition, the PI will measure the power density over super-hydrophobic surfaces to directly test theories. In turn, the validated model will guide the experimental design as well as engineer the performance of energy conversion. The proposed coordinated theoretical and experimental approach will allow the PI to explore the rich behavior of a variety of physical phenomena (non-uniform surface conduction, concentration polarization, and associated diffusio-osmotic flows) over super-hydrophobic surfaces. Understanding of these important phenomena will surely advance the fundamental knowledge in electrokinetics and lay a solid foundation for the rational design of super-hydrophobic-surface-enabled systems. Equipped with a much improved understanding, the PI also proposes to use the microfluidic large-scale integration method to integrate thousands of channels into a microfluidic chip to demonstrate the feasibility of the conversion method in powering small electronic devices.