Simulation and Development of an Ion Funnel for Miniature Mass Spectrometers

Rationale

Miniature mass spectrometers are increasingly used in portable and on-site analysis due to their compact size and light weight. However, miniaturization, higher operating gas pressure, and complex airflow movement have significantly reduced ion transmission efficiency. Conventional ion guide devices are unsuitable under these conditions, severely limiting the performance and practicality of such spectrometers. Thus, developing a novel ion guiding device to improve ion transmission and detection performance is urgently needed.

Methods

We designed a miniature ion funnel with isobaric, tapered, and widened exit electrodes. Using SIMION and AXSIM software, we systematically studied the impact of radio frequency (RF) and direct current (DC) voltages, radial displacement, ion kinetic energy, mass-to-charge ratios, and gas pressure on ion transmission. Additionally, computational fluid dynamics simulations with Virtual Device software visualized temperature, velocity, and pressure fields in subvacuum regions.

Results

Based on simulation results, we precisely manufactured the ion funnel, measuring 6.2 × 3.4 × 3.2 cm³ and weighing 51.4 g. Tested on a continuous atmospheric pressure interface (CAPI) miniature mass spectrometer at 5.34 Torr, the new ion funnel showed a 44.3% increase in intensity compared to the previous version, validating its effectiveness.

Conclusions

The proposed ion funnel enables efficient ion focusing and transfer, overcoming miniaturization-related limitations. It enhances the detection performance of miniature mass spectrometers, offering a practical solution with important implications for the development of portable analytical instruments.