Nano-Porous Thermoelectric Based Knudsen Gas Pumps

University Of Louisville Research Foundation Inc, Louisville KY

Investigators

Abstract

Shamus McNamara, University of Louisville Proposal #1133877 The Knudsen pump is a thermally driven gas pump which features no moving parts, potentially providing very high reliability. For MEMS devices, the lack of seals is especially attractive. The Knudsen pump uses the principle of thermal transpiration as the basis of its operation, and thus must operate in either the free molecular flow regime or near the free molecular flow regime in the transitional flow regime. For operation at atmospheric pressure, sub-micron channel cross-sections are required for operation, with channel diameters on the order of 100 nm commonly utilized. The objectives of this research project are to (1) improve the efficiency of the Knudsen gas pump, (2) develop a method to integrate the Knudsen pump with microfluidic applications in a simple, efficient manner, (3) better model and understand gas pumps based upon the thermal transpiration effect through unobstructed channels, (4) explore efficient methods of using the Knudsen Pump to generate pneumatic energy from heat sources, such as body heat and solar thermal energy. New thermoelectric materials will be investigated for use in the Knudsen pump, and prototype pumps using these materials will be tested. Studies on the effects of surface roughness of the channels making up the Knudsen pump will be performed, as there is experimental evidence to suggest that the tangential momentum accommodation coefficient (TMAC) can have a significant impact on the performance of the Knudsen pump. The expected outcomes include a smaller, more efficient Knudsen pump with better pump performance, a better understanding of the limitations of the Knudsen pump, a better theoretical model describing how the Knudsen pump operates, a better understanding of how microfluidic devices can incorporate the Knudsen pump, and a demonstration of the Knudsen pump used to generate pneumatic energy from heat sources. Because the Knudsen pump features no moving parts, an efficient Knudsen pump has many applications where pump size, noise, or reliability is a concern. It can also be integrated with microfluidic devices, providing a key component for many lab-on-a-chip devices that are under development for medical diagnostics and fast, efficient drug and materials research. As a passive device, the Knudsen pump has the potential to generate pneumatic energy from waste heat, such as the catalytic converter of an automobile or manufacturing plant. It can be powered from the sun, generating pneumatic power than can be used to run a generator. And it can be powered from human heat, opening up applications for biomedical devices.