Cliff I. Davidson, Daniel P. Y. Chang, Adam Dalis, Sheryl H. Ehrman, Steven L. Heisler, George M. Hidy, Anshuman A. Lall, Thomas Lesniewski, Peter H. McMurry, Sotiris E. Pratsinis, Daryl L. Roberts, Paul T. Roberts, Weizhi Rong, Patrick Sislian, Chandra Venkataraman, Chiu-Sen Wang, Robert S. Windeler, and Cheng Xiong 1 Department of Civil & Environmental Engineering and Engineering & Public Policy, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA 2 Department of Civil & Environmental Engineering, University of California—Davis, Davis, California, USA 3 Intel Corporation, Portland Technology Department, Hillsboro, Oregon, USA 4 Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland, USA 5 ENSR Corporation, Camarillo, California, USA 6 Envair/Aerochem, Placitas, New Mexico, USA 7 Department of Mechanical Engineering, University of Maryland, College Park, Maryland, USA 8 Northrup Grumman Corporation, San Diego, California, USA 9 Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota, USA 10 Particle Technology Laboratory, Swiss Federal Institute of Technology, Zurich, Switzerland 11 MSP Corporation, Shoreview, Minnesota, USA 12 Sonoma Technology, Inc., Petaluma, California, USA 13 UCLA BH5531, Los Angeles, California, USA 14 Department of Chemical and Biomolecular Engineering, University of California—Los Angeles, Los Angeles, California, USA 15 Department of Chemical Engineering, India Institute of Technology—Bombay, Powai, Mumbai, India 16 124 Idaho Avenue, Unit 304, Santa Monica, CA, USA 17 OFS Laboratories, Murray Hill, New Jersey, USA 18 Intel Corporation, DC1 Lithography, RA2, Hillsboro, Oregon, USA