Multifunctional Environmental Digital Scanning Electron Microprobe (MEDSEM)

Chromologic (CL) and the California Institute of Technology (Caltech) propose to develop and demonstrate a Multifunctional Environmental Digital Scanning Electron Microprobe (MEDSEM) instrument that transmits high-energy beams of electrons sequentially from a two-dimensional array of miniaturized electron probes into a planetary atmosphere, and these electrons will strike solid or liquid planetary surfaces to simultaneously generate a wealth of spatially-mapped compositional information. MEDSEM will simultaneously measure X-ray Fluorescence (XRF), Backscattered Electron Spectra, Optical Spectra and Mass Spectra. Caltech will transfer to CL the microfabrication technology for vacuum-encapsulating, electron-transmissive SiN membranes, the key enabling component without which MEDSEM would not be possible. Caltech will also transfer the results of electron-optic simulations performed for optimizing the MEDSEM instrument configuration. The 12-month Phase I effort will be aimed at demonstrating the proof-of-principle for MEDSEM via an experimental setup made up of mostly commercial-off-the-shelf (COTS) parts: miniature electron sources, an x-ray detector and a double-chambered test setup. High-energy electrons will be generated in the first, evacuated chamber, and these electrons will pass through the Caltech-fabricated SiN membrane into the second chamber (maintained at Martian ambient pressure), to strike planetary analog samples thereby generating characteristic XRF. The XRF spectra will be captured by a COTS x-ray detector which is present in the second chamber. Contingent on a successful, follow-on, Phase II effort, the proof-of-principle experiment will be expanded to demonstrate the remaining simultaneous measurement modalities, namely the acquisition of Backscattered Electron Spectra, Optical Spectra and Mass Spectra. Microfabrication of the fully-integrated, field-emitter array of miniaturized electron probes will be pursued during Phase II.

MEDSEM satisfies NASA's stated need for new and innovative scientific measurements for in situ planetary exploration. To date, although miniaturizing scanning electron microscopes has been a "holy grail" for developers of planetary instruments, an in situ electron microprobe instrument has never flown. Once successfully demonstrated, MEDSEM would be a strong candidate for planetary instrument payloads for NASA's future landed missions, as described by the National Research Council Committee on the Planetary Science Decadal Survey for future NASA missions from 2013 – 2022. According to the Decadal Survey, primary planetary targets for landed missions include the moon, Mars, Venus and Europa.

In the field of materials science and engineering outside of NASA, there is a great need for capable, field-portable instruments that are rugged and reliable. As with NASA missions, size, weight and power consumption are of concern for humans transporting these instruments into remote locations for geological studies, environmental monitoring and oil exploration. An added concern is the overall cost of the instrument, especially for widespread acceptance and use. A successful MEDSEM instrument would open up numerous applications in the educational arena. At both the K-12 and college level, MEDSEM could be used for science demonstrations as well as for hands-on experimentation and research in chemistry, solid-state physics, geology and materials science laboratories. Although MEDSEM cannot match the spatial resolution of terrestrial laboratory instruments such as scanning electron microscopes (mm vs nm), still it could serve as a rapid screening device with the ability to answer basic composition-related questions. MEDSEM's primary advantage, of course, is its ability to simultaneously make multiple, different measurements on the samples being studied in ordinary room air. It is anticipated that MEDSEM will continue to evolve as an instrument, incorporating the latest advancements in micro- and nanotechnology.

This is early/mid-stage (TRL 6) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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