Proposal of a novel Knudsen pump design benefitting from drilling and 3D printing techniques in low conductivity materials

Over the past two decades a large number of MEMS and micro-devices have been developed. These miniaturized systems, such as lab-on-chip sensors, gas chromatography analyzers, etc., require micro-pumps for air sampling through the testing stages of the device. Additionally, some microscale components such as radio frequency switches, microscopic vacuum tubes and other parts that depend on electron or ion optics, require certain vacuum environment for proper operation. Simply sealing the devices is not sufficient because leaks and outgassing are excessively detrimental in vacuum devices at microscale level. Accordingly, such components may need vacuum pumping to maintain proper functionality. The thermal transpiration phenomenon has been extensively investigated; however, functional prototypes based on this phenomenon have been only recently developed. The Knudsen pump, which is one of the devices exploiting this well-known phenomenon, is able to generate a macroscopic gas flow by solely exploiting a tangential temperature gradient along a surface without requiring any external pressure gradient [1]. Specific geometrical and operational configurations have been investigated to optimize the efficiency of the pump in terms of generated mass flow rate and pressure difference, so analytical and numerical solutions for different configurations have been provided [2] and experimental measurements for thermal transpiration flow through channels have been reported [3]. Still, fabricating a Knudsen pump is not a trivial task mainly due to microfabrication difficulties and constraints linked to the control of local thermal gradients [4, 5].