Evolution of Computer Controlled Scanning Electron Microscopy for Characterization of Atmospheric Particles

GARY CASUCCIO, Traci Lersch, Kristin Bunker, Roger West, Long Li, RJ Lee Group, Inc.

     Abstract Number: 241
     Working Group: History of Aerosol Science

Abstract
Scanning electron microscopy (SEM) has been used to characterize atmospheric particles since the 1960s. Combined with an energy dispersive X-ray spectroscopy (EDS) detector, the SEM has evolved into a powerful tool that can provide high-resolution images and elemental composition at the nanoscale, allowing for the collection of detailed information on individual particles. However, although a powerful analytical tool, its application in environmental studies has been limited compared to bulk analytical techniques, due in part, to being perceived as primarily a research tool and not capable of providing quantitative data on particle populations. This limitation was realized early in the development of the SEM and led researchers in the late 1970s to begin exploring the potential of integrating computers and developing software to ‘control’ the SEM/EDS systems to enable particles to be detected and characterized rapidly and in sufficient numbers to be representative of the entire sample. Over the past four decades, automated SEM analysis, which is often referred to as computer-controlled SEM (CCSEM), has evolved from hybrid ‘one-off’ research systems to fully integrated systems used routinely in a variety of industrial applications. The evolution of CCSEM parallels advancements in computer technology from mainframe computers to minicomputers to PCs. It also dovetails with the evolution in air quality sampling and analysis, from total suspended particles (TSP) to PM₁₀ to PM_2.5. This presentation will provide an overview of the key developments associated with CCSEM from the perspective of environmental analysis of ambient samples from TSP to PM_2.5 and will provide a glimpse of where the technology is headed in the not too distant future.