Electrostatically Enhanced Microbe Collection in the Troposphere and Stratosphere

The proposed work will modify the proof of concept ESP to be optimized for future aerobiology studies. The electronics hardware will be upgraded to include power interfaces enabling power from either an 18- volt battery pack or 110-volt outlet to allow the ESP to operate on any of the candidate research platforms. The key technical challenge in this technology development is achieving electrostatic precipitation in the reduced atmospheric pressures in the troposphere and stratosphere. Operating in low atmospheric pressure environments can be challenging due to the Paschen minimum, an electrostatic phenomenon that dictates the maximum voltage that can be achieved without arcing. However, the Electrostatics and Surface Physics Laboratory (ESPL) at Kennedy Space Center has experience developing ESPs in reduced atmospheric pressure environments as they are currently developing an ESP to operate in Mars atmosphere. This knowledge will be adapted to develop this technology for high altitudes on Earth. The team will use on-site vacuum chambers in the ESPL to simulate the high altitude environment of Mt. Bachelor and high altitude balloon flights. This laboratory has the capability to simulate the atmospheric pressure and temperature of the candidate platforms and sites shown in Figure 2. This work is complimentary to the work in ESP development for standard atmosphere conditions that is currently underway in academia [5-6] and is also complimentary to the bioaerosols research underway at NASA ARC and the USGS.

This project will develop an ESP optimized for use in a reduced atmospheric pressure environment to collect microbes in the troposphere and stratosphere. While benchtop studies have shown viability of ESPs at 1 atm, optimization is required for this technology to be successful at lesser pressures. This technology is currently TRL 3 for troposphere and stratosphere bioaerosol studies. Severely limited access to air samples above the boundary layer (> 1-2 km above sea level) has prevented systematic studies across time and space. Some of the most basic questions in the field of aerobiology remain wide open. What are the primary sources and sinks of microorganisms in the atmosphere? How long can cells remain aloft before returning to the surface? How does the atmospheric environment influence the survival of transported microorganisms and the ecology of downwind habitats? New experimental approaches and sampling platforms may provide an improved understanding of distantly transported microbes in Earth's atmosphere. The biggest challenge in aerobiology is collection inefficiency due to low microbe concentrations [1]. There are many air sampling methods that can be used to collect microbes for aerobiology studies. Gravity based deposition is simple and inexpensive but tends to only collect larger particles, as fluid flow forces from air currents dominate gravitational forces for sub-micron particles. Centrifugation can support high flow rates and can result in high collection efficiencies, but the high impact stress results in a loss of viability of the microbes [2]. However, a relatively new type of air sampling method shows great promise. Electrostatic precipitation is used by manufacturing industries to reduce pollution emissions but the method has not been adopted by scientists studying aerosols. Electrostatic precipitators (ESPs) have demonstrated 90% capture rates of particles in the size range of 0.3 to 0.5 um and are potentially an order of magnitude more efficient than liquid impingement at recovering airborne bacteria and fungi [2]. Electrostatic precipitation works on the basis of corona discharges. Corona discharges generate ions and free electrons that attach to particles. These charged particles are driven to a grounded surface by a strong electric field.

This is early/mid-stage (TRL 4) — 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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