Towards the hand-held mass spectrometer: design considerations, simulation, and fabrication of micrometer-scaled cylindrical ion traps

Abstract Breakthrough improvements in simplicity and reductions in the size of mass spectrometers are needed for high-consequence fieldable applications, including error-free detection of chemical/biological warfare agents, medical diagnoses, and explosives and contraband discovery. These improvements are most likely to be realized with the reconceptualization of the mass spectrometer, rather than by incremental steps towards miniaturization. Microfabricated arrays of mass analyzers represent such a conceptual advance. A massively parallel array of micrometer-scaled mass analyzers on a chip has the potential to set the performance standard for hand-held sensors due to the inherit selectivity, sensitivity, and universal applicability of mass spectrometry as an analytical method. While the effort to develop a complete micro-MS system must include innovations in ultra-small-scale sample introduction, ion sources, mass analyzers, detectors, and vacuum and power subsystems, the first step towards radical miniaturization lies in the design, fabrication, and characterization of the mass analyzer itself. In this paper we discuss design considerations and results from simulations of ion trapping behavior for a micrometer scale cylindrical ion trap (CIT) mass analyzer (internal radius r 0 = 1 μm). We also present a description of the design and microfabrication of a 0.25 cm 2 array of 10 6 one-micrometer CITs, including integrated ion detectors, constructed in tungsten on a silicon substrate.