Knudsen pump for atmospheric and over-atmospheric pressure applications: System design, fabrication procedure and performance evaluation

Knudsen pumps are promising candidates for vibration-free gas pumping in a variety of scientific and industrial applications, particularly where miniaturization is required. Based on thermal transpiration flows induced by temperature gradients along microchannels, they operate without moving parts and therefore offer high reliability. However, current fabrication techniques limit the realization of submicron channels needed for high performance operation at atmospheric and over-atmospheric pressures. To address this challenge, the present study investigates the feasibility of using Bessel beam technology for channel fabrication, enabling the creation of dense arrays of nanochannels with diameters of only a few nanometers at writing speeds of up to 1 kHz. Numerical simulations of gas flow and heat transfer were performed to design and optimize a single-stage, parallelchannel architecture while accounting for microfabrication constraints. The proposed design consists of 294,294 parallel nanochannels arranged within a 1 × 1 cm$^2$ glass substrate, each with a diameter of 600 nm and a length of 500 μm. Under simulated atmospheric operating conditions with moderate heating up to 100 ◦C, an average temperature difference of approximately 46.8 ◦C across the channels is predicted, resulting in a thermomolecular
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pressure difference of 1575 Pa and a maximum mass flow rate of 3.43 × 10$^{-10}kg s${-1}$ . When normalized by the total channel area, the predicted mass flow rate is much higher than that of previously reported Knudsen pumps, while maintaining a pressure difference among the highest values reported in the literature. The results demonstrate the potential of Bessel beam microfabrication for future high-performance Knudsen pumps operating at over-atmospheric pressures.