This Small Business Innovation Research (SBIR) Phase II project supports development of a nanoparticle characterization instrument that will fill the critical unmet need to rapidly and accurately measure the size and distribution of nanoparticles from 30 nanometers to 1 micron. Initially the technology will target two applications: protein aggregation in biopharmaceuticals, and nanoparticles in medicine (e.g., tumor-targeted drug delivery). The importance of nanoparticle analysis, however, goes well beyond therapeutics. Currently the market for nanoparticle analysis instrumentation across the life sciences is $5.6 billion, and there are increasing concerns about nanoparticles in consumer products such as food and cosmetics, as well as in drinking water, effluents, and the environment. A major challenge in understanding the health impacts of nanoparticles is simply in accurately and easily detecting their presence and size distribution. Additionally, improved nanoparticle instrumentation will enable new discoveries in biotechnology and environmental and health sciences.<br/><br/>This challenge can be met by developing a practical method for counting and sizing submicron particles in polydisperse mixtures. NSF Phase I/IB funds supported development of a prototype instrument that detects individual nanoparticles and accurately measures their size, at very high count rates. This instrument has successfully demonstrated robust detection of individual particles as small as 60 nm in diameter at rates approaching 10,000 particles per second, and has already begun to deliver useful information to particle manufacturers in the pharmaceutical industry, with on-going measurements of actual customer samples. The Phase II support will considerably enhance the utility of this instrument by addressing several outstanding technical challenges; most significantly, by extending the range of detectable particles to span the full range from 30 nm to 1000 nm, and by further maximizing the range of measurable particle concentrations. In addition, the Phase II work will drive significant improvements in functionality and ease of use, driven by innovations in its control software. Finally, the instrument will be further validated using a wide variety of particle types relevant beyond the pharmaceutical space.