Meet the Portable Aerosol Imager—Transforming How We Measure Coarse Mode Aerosols

When people discuss aerosols, much attention focuses on ultrafine or PM2.5 particles—yet coarse mode particles are equally critical to environmental science. From desert dust and volcanic ash to pollen and spores, these larger aerosols carry significant implications for climate, weather, ecology, and public health. At CloudSci, we’ve been pushing ahead with a unique sensor: our Portable Aerosol Imager (PAI). The project is supported by a Department of Energy Phase II SBIR grant awarded to CloudSci last year. It’s a next-generation holographic instrument designed to capture high-quality images of coarse-mode particles in their natural state.

Why Coarse Mode Matters

1. Climate & Weather: Coarse dust and sea spray can scatter sunlight, interact with clouds, and deposit nutrients (and contaminants) across continents and oceans.
2. Air Quality & Health: Fungal spores, pollen, and dust can trigger or exacerbate respiratory illnesses, yet remain under-measured by standard urban monitoring stations.
3. Agricultural Impacts: Elevated dust levels, spore-borne plant diseases, and even insect-scale particles can affect crop yields and food security.

Despite their importance, coarse particles are notoriously difficult to measure accurately. Traditional instruments can be bulky, prone to particle losses, or require carefully designed inlets. Enter the PAI.

The PAI Difference

1. Digital Inline Holography (DIH)
   • Instead of deducing size from scattered light alone, DIH directly images each particle in three dimensions. This allows us to easily distinguish between, say, an oddly-shaped piece of dust versus a spherical pollen grain.
2. Open-Path Design
   • The PAI doesn’t require active flow through a nozzle. Instead, it leverages the surrounding wind or ambient airflow, resulting in a larger sampling volume. That’s crucial for coarse particles, often present in lower concentrations but with major environmental impacts.
3. Triggering & Efficiency
   • Our system uses a trigger laser to sense a particle’s presence. Only then do we capture a hologram, yielding high-resolution images without wasting processing cycles. This on-demand imaging ensures we see coarse particles even if they appear sporadically, like during a pollen release or dust event.
4. Built for Field Use
   • In parallel with lab tests, we’re designing the PAI enclosure to handle outdoor conditions. We aim to make it low-maintenance, with an internal purge or cleaning system to keep optical surfaces clear over extended deployments.

Prototyping & Testing

• Lab Validation: Using test materials in the lab, we’re verifying PAI’s ability to size-check everything from glass beads around 10 µm to larger pollen above 50 µm. These “stress tests” help us refine algorithms for size and shape retrieval.
• Software: Real-time hologram reconstruction isn’t trivial. Our next step is employing both numerical methods and machine learning, reducing the heavy-lift from raw images to actionable data.
• Field Deployments: We’re partnering with researchers who want to measure dust storms, track pollen plumes in urban corridors, and evaluate local air-quality strategies. PAI is set to provide new insights on how these aerosols evolve over time and space.

Potential Applications

• Urban Air Quality: Municipalities can integrate PAI sensors into monitoring networks, closing gaps in coarse-particulate data, especially for a size range that can vary substantially over space and time.
• Agricultural Monitoring: By placing a PAI near fields or orchards, farmers may detect fungal spore outbreaks sooner—or measure how wind-borne dust travels. We’re in early conversations with USDA scientists about how we might deploy our prototype systems to examine this application.
• Public Health & Allergy Research: Real-time observation of pollen bursts could improve allergen forecasts and help clinicians advise patients more effectively. Our team is exploring potential collaborations with health researchers as to how we might tailor the measurement system for these types of applications.
• Climate & Environmental Studies: From local dust storms to broadscale climate modeling, the size, shape, and concentration of coarse aerosols feed into climate models and satellite validation.

Looking Ahead

As we finalize the PAI prototype, our objectives remain twofold. On the technical side, we’re committed to ensuring accurate, reliable data in a rugged enclosure that can endure a variety of weather conditions. On the collaboration side, we’re seeking researchers, cities, and industry partners interested in pushing the boundaries of coarse-mode aerosol measurements. Expect more updates on our laboratory testing benchmarks, field deployment strategies, and (of course) new revelations about the coarse aerosols floating in the air around us. If you’re intrigued by the potential of holography for real-time aerosol imaging, we’d love to talk—just reach out through our website or drop us a message on LinkedIn. Thank you for joining us on this journey. The Portable Aerosol Imager is poised to become a valuable asset in understanding a dimension of air quality and climate science that has long been overlooked.