Particulate Matter Sensors: Industrial Sensor Development at Lawrence Berkeley National Laboratory

Description:
The Miniaturized System for Particle Exposure Assessment (MSPEA) device monitors fine respirable particulate matter (PM) mass concentrations, and it differentiates between various PM types in real time. MEMS-PEA, now in development, is a smaller, more sensitive and cost-effective MSPEA using micro-electro-mechanical systems.

MSPEA sensor fixture with heating wire shown in yellow. Components not shown include the collection crystal which
rests on the posts that hold the wire, the quartz slide that is held by the notches below the wire, and the optical reflectance probe which
passes through the hole centered beneath the wire.

Figure 1. MSPEA sensor fixture with heating wire shown in yellow. Components not shown include the collection crystal which rests on the posts that hold the wire, the quartz slide that is held by the notches below the wire, and the optical reflectance probe which passes through the hole centered beneath the wire.

Broad Fields of Use:
These particle measurement devices are intended for use in environmental health research and for low-cost monitoring of PM concentrations and source identification. In addition to research applications, is anticipated that commercialization of these low-cost devices will provide local organizations and private citizens with a means of verifying particulate air pollutant levels within their communities.

Comparison with Current Technologies:
No commercial particle monitoring system exists now that can directly measure particle mass and quantify particle source contributions simultaneously, at any price. Current methods of PM exposure monitoring are too expensive. They are also limited by size, weight, noise, and power constraints. Total costs must be reduced by one to two orders of magnitude for monitoring within populations to be affordable. Simultaneous measurements of several species by a single PM device are not typically available in current sensors. The MEMS-PEA sensor under development would address all of these issues with a device that is easy to use, portable, inexpensive, and provides on-board particle source identification for at least three of the major disease causing particle sources: diesel exhaust, environmental tobacco smoke, and woodsmoke.

Description of Current Application:
Lawrence Berkeley National Laboratory's Environmental Energy Technologies Division has recently fabricated and tested a low-power Miniaturized System for Particle Exposure Assessment (MSPEA). The device is the next generation of miniaturized particulate matter (PM) exposure assessment instrumentation. It monitors fine respirable particulate matter (PM_2.5 or PM₁₀) mass concentrations, and it differentiates between various PM types in real time. It can provide population-based exposure assessment for PM epidemiology studies, with no special training required for data retrieval.

Berkeley Lab has teamed with UC Berkeley Sensor and Actuator Center (BSAC) and the UC Berkeley Microfabrication Facility (Microlab) as well as the Lab for Ultra Small Technology Engineering Research (LUSTER) in the Engineering Division to miniaturize MSPEA, in a project funded by the Innovative Clean Air Technologies program of the California Air Resources Board. Using micro-electro-mechanical systems (MEMS) based fabrication techniques, the team's goal is to produce a smaller, more sensitive and cost-effective MSPEA that is ready for commercialization. The device is called the MEMS-PEA.

This technology will contribute to meeting critical needs of the current national effort to understand the links between particle exposure and human health.

Figure 2. Schematic diagram of the prototype MSPEA with integration of major components.

Benefits:
Particulate matter exposure and health effects have become top U.S. environmental research agenda items over the last decade. Environmental epidemiological studies rely on information from both sides of the dose-response equation: risk factor measures and health outcome data. The ability to resolve relationships from environmental data depends upon the quantity, accuracy, specificity and precision of both. Although health surveillance and data collection methods have improved dramatically through database system advances, PM exposure assessment methods are woefully deficient.

A significant benefit of the miniaturized samplers is the ability to use them in mail-out surveys where they are deployed in-home, or on-person, by survey participants, reducing the need for trained field personnel.