The proposed instrument builds on 10 years of development that resulted in the Proof of Concept for a coded aperture mass spectrometer, including development for security applications.
A Solution to the Resolution-Throughput Trade-Off
Miniaturizing instruments for spectroscopic applications requires the designer to confront a trade-off between instrument resolution and instrument throughput (and associated signal-to-background-ratio [SBR]). Our work has demonstrated a solution to this tradeoff by utilizing a computational design approach to the mass spectrometer incorporating an understanding of the underlying mathematical principles of sensors to optimize the instrument using ion coding.
This has enabled the first application of one-dimensional (1-D) and two dimensional (2-D) spatially coded apertures in sector mass spectrometry, similar to those previously demonstrated in optics. This was accomplished by replacing the input slit of a simple custom built, 90-degree magnetic sector mass spectrometer with a specifically designed coded aperture, deriving the corresponding forward mathematical model and spectral reconstruction algorithm, and then utilizing the resulting system to measure and reconstruct the mass spectra of argon, acetone, and ethanol.
Combining Micro Technologies
Ongoing development is aimed at combining the miniaturization-enabling technology of these coded apertures with a microfabricated microelectromechanical systems-based (MEMS) ion source with a carbon nanotube (CNT) field emission cathode and position sensitive Faraday cup array detector with a double focusing sector mass analyzer design.
A practical requirement for an integrated micro ion source platform is the development of cathodes with high current density and long lifetime. Our approach uses cold cathodes based on field emission from CNTs. Cold cathodes are beneficial for an integrated platform because they avoid the thermal management issues of thermionic cathodes, which complicate miniaturization.
CNT emitters in particular are well-suited for integrated MEMS vacuum microelectronics because they can be deposited or grown in situ in a variety of physical configurations. CNT cathodes have been demonstrated in a variety of devices with high emission lifetimes.
The combination of these technologies will provide the disruptive technological improvements to transition the analytical power of mass spectrometry from the lab to the field.