Final Report: Acoustically Excited Inertial Tympanum Particulate Matter Nanobalance

EPA Contract Number: 68D02067
Title: Acoustically Excited Inertial Tympanum Particulate Matter Nanobalance
Investigators: May, David F.
Small Business: Analytical Engineering Inc.
EPA Contact: Richards, April
Phase: I
Project Period: September 30, 2002 through July 31, 2003
Project Amount: $100,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2002) RFA Text |  Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , SBIR - Monitoring , Small Business Innovation Research (SBIR)


The goal of this Phase I research project was to develop a proof-of-concept instrument for particulate matter (PM) measurements providing real-time, on-vehicle capability. A critical aspect of the project was to validate that an approved PM collection filter media, when acoustically excited, was capable of providing a measurable proportionate response to PM loading. This component would comprise the core of the acoustically excited paper filter tympanum-based nanobalance.

Summary/Accomplishments (Outputs/Outcomes):

Two mechanical systems were designed and built during this project. In the periods between the mechanical developments, several iterative improvements were made in the transducer types, placements, and methods for excitation. Many improvements also were made to the electronics to increase the sensitivity, improve signal-to-noise ratios, and effectively utilize the transducers for excitation and measurement. These iterative developments were required to exploit the interactions between the electronics, mechanical structure, air-handling subsystems, primary dilution, and transducer enhancements.

Analytical Engineering, Inc., has maintained a research test cell, along with two research engines, to support this endeavor since the initiation of the project. These relatively static development platforms have been critical for effectively reproducing generation rates over periods of several days. A radial inflow minidilution system was developed and built during Phase I to simulate the sample handling system required for a vehicle. This work proved to be very effective in producing a small and lightweight system representative of what will be required for use with SPOT III or other on-vehicle emissions measurement systems, or for stand-alone applications.

The first measurement hardware system utilized a displaced projection system, whereby acoustic excitation was accomplished via air coupling. The measurement subsystem also was air-coupled and the tympanum was supported by a rigid structure with tension adjustment. The results of this hardware were encouraging, but the measurement sensitivity was insufficient to achieve microgram or nanogram precision.

A second hardware system was developed over a period of several months and utilized a direct piezoelectric coupled excitation transducer. This provided exceptional control over acoustic excitation and achieved many improvements in precision and measurement sensitivity. In this system, the measurement transducer resides on the clean side of the barrier filter media. By utilizing very accurate and low-noise amplifiers, many improvements were made with this configuration during the later months of the research. Resonance and intermodal beating patterns have been identified through experimentation, resulting in computational algorithms that predict mass aggregation in low microgram levels and approaches nanogram levels.


This Phase I research project, aimed at demonstrating feasibility of the measurement technology, was very successful. The current prototype is capable of real-time PM measurements, with 5-microgram precision and 2-second integrated measurements. This 10-month effort was conducted by a team of skilled engineers, scientists, and technicians who are confident that further improvements will result in a system that can be commercialized with a high degree of success. The current demand in the industry for such a measurement system, combined with the simultaneous development of SPOT III and the success in this Phase I effort, provide an excellent platform for the successful commercialization of this product. An aggressive program in a Phase II project will be needed to make the system accurate, robust, tolerant of outside influences, easy to install, and above all, affordable.

Supplemental Keywords:

particulate matter, PM, tympanum-based nanobalance, clean air, transducer, signal-to-noise ratio, minidilution system, on-vehicle emissions measurement, SPOT III, acoustic excitation, small business, SBIR., Scientific Discipline, Air, Analytical Chemistry, Environmental Monitoring, Atmospheric Sciences, Engineering, Chemistry, & Physics, Environmental Engineering, particulate matter, atmospheric particles, filter membranes, on-vehicle measurement, air sampling, automotive exhaust, diesel exhaust, emissions, nanobalance, real time monitoring, membrane technology