Paul V. Braun

Research

Our research program covers a wide range of materials science disciplines, with a general focus on the formation and study of nano and microstructures through self and directed assembly. Materials containing structure on these length scales have been found to exhibit interesting and important electrical, optical, mechanical and biological properties. We often use and develop new materials chemistry approaches to the synthesis of these materials, which allows us to create novel structures and materials including photonic bandgap structures, conducting polymers, nanostructured ceramics, semiconductors, biomaterials and metals. An important nanostructured system we study is liquid crystals, which can be designed to contain periodic structure ranging from one nanometer to greater than 100 nanometers. We are exploring multiple methodologies to use the periodic structure of these and other self-organized matrices to create new materials.

The liquid crystal mediated synthesis of materials could provide many yet unseen properties. One group objective is to use liquid crystals to create chemically functionalized hollow nanospheres, which would serve as site-specific drug delivery agents. Another application for hollow nanospheres is to form low dielectric constant materials for high-speed microelectronics. Liquid crystal mediated synthesis of materials is a new field, and very few of the basic principles are known or understood. We are attempting to quantify the important parameters, such as the liquid crystal ­ product interaction, and the effect of the liquid crystal's structure. Along with hollow nanoobjects, we are also studying the liquid crystal templating of such materials as conducting polymers and metals.

Another component of our research is the formation and characterization of photonic bandgap structures. Structures exhibiting photonic bandgaps have very interesting and potentially important optical properties. For example, waveguides formed from photonic bandgap materials can execute a 90 degree turn over a few microns, which is necessary for the on-chip integration of optical devices. One way to form the periodic structure necessary to realize a photonic bandgap is through templating with self-organized colloidal crystals. We are developing new routes to the formation of such structures, as well as modeling and measuring their optical response.

Publications

Stephanie A. Rinne, Florencio García-Santamaría and Paul V. Braun : Embedded cavities and waveguides in three-dimensional silicon photonic crystals, Nature Photonics, 2, 52-56 (2008).

Y. C. Chen, J. B. Geddes III, J. T. Lee P. V. Braun and P. Wiltzius: Holographically fabricated photonic crystals with large reflectance, Applied Physics Letters, 91, 241103 (2007).: Holographically fabricated photonic crystals with large reflectance, Applied Physics Letters, 91, 241103 (2007).

Erik C. Nelson and Paul V. Braun: Enhancing Colloids Through the Surface, Science, 318, 924-925 (2007).

W.-S. Chae and P. V. Braun: Templated mesoporous silica colloids with controlled internal structures, Chemistry of Materials, 19, 5593-5597 (2007).

F. García-Santamaría, E. C. Nelson, and P. V. Braun: Optical surface resonance may render photonic crystals ineffective, Physical Review B, 76, 075132(1-6), (2007).

C. Rau, W. Liu, V. Crecea, K.M. Peterson, P.R. Jemian, C.-P. Richter, U. Neuhäusler, G. Schneider, X. Yu, P. V. Braun, I. K. Robinson: Synchrotron-based imaging and tomography with hard X-rays, Nucl. Instrum. Methods Phys. Res., Sect. B, 261, 850-854 (2007).

Wonmok Lee, and Paul V. Braun: Epitaxially grown colloidal crystals of silica microspheres on patterned substrate of triangular arrays, Materials Science and Engineering C, 27, 961-967 (2007).

X. Yu, Y.-J. Lee, R. Furstenberg, J. O. White, and P. V. Braun: Filling fraction dependent properties of inverse opal metallic photonic crystals, Advanced Materials, 19, 1689-1692 (2007).

F. García-Santamaría, M. Xu, V. Lousse, S. Fan, P. V. Braun and J. A. Lewis: A germanium inverse woodpile structure with a large photonic band gap, Advanced Materials, 19, 1567-1570 (2007).

F. García-Santamaría and P. V. Braun: Are artificial opals non-close-packed fcc structures? Applied Physics Letters, 90, 241905 (1-3) (2007).

C. Rau, V. Crecea, K.M. Peterson, P.R. Jemian, C.-P. Richter, U. Neuhäusler, G. Schneider, X. Yu, P. V. Braun, T. C. Chiang, I. K. Robinson: Imaging of micro- and nano-structures with hard X-rays, Micro and Nano Letters, 2, 1-5 (2007).

R. G. Shimmin, R. Vajtai, R. W. Siegel, and P. V. Braun: Room-temperature assembly of germanium photonic crystals through colloidal crystal templating, Chemistry of Materials, 19, 2102-2107 (2007).

H. Tu, L. Hong, S. M. Anthony, P. V. Braun and S. Granick: Brush-sheathed particles diffusing at brush-coated surfaces in the thermally-responsive PNIPAAm system, Langmuir, 23, 2322-2325 (2007).

T. A. Berfield, J.K. Patel, R.G. Shimmin, P.V. Braun, J. Lambros, and N.R. Sottos: Micro- and Nanoscale Deformation Measurement of Surface and Internal Planes via Digital Image Correlation, Experimental Mechanics, 47, 51-62 (2007).

For the complete list of Dr. Braun's publications, please visit http://braungroup.beckman.uiuc.edu/publications.html

Awards

• 2007 Accenture Multi-year Faculty Achievement Award, College of Engineering, UIUC
• 2007 Accenture Engineering Council Award for Excellence in Advising
• 2006-2009 University Scholar, University of Illinois Urbana-Champaign
• 2006 Accenture Engineering Council Award for Excellence in Advising
• 2005 Named on An Incomplete List of Teachers Ranked as Excellent by Their Students
• 2005 Burnett Teaching Award, Department of MatSE, UIUC
• 2004 Xerox Award for Faculty Research, College of Engineering, UIUC
• 2003 Accenture Engineering Council Award for Excellence in Advising
• 2002-present Willett Faculty Scholar Award, College of Engineering, UIUC
• 2002 The 2002 Robert Lansing Hardy Award of the TMS (annually awarded to one young materials scientist whose career shows exceptional promise)
• 2001, -02, -03, -04 3M Nontenured Faculty Award
• 2001 Beckman Young Investigator Fellowship from the Arnold and Mabel Beckman Foundation
• 1999-2001 Racheff Assistant Professorship, University of Illinois, Dept. of Materials Science and Engineering
• 1997 Mavis Memorial Fund Scholarship, University of Illinois
• 1996-1997 Beckman Institute for Advanced Science and Technology Research Assistantship
• 1996 Racheff Award for Outstanding Graduate Research in Materials Science and Engineering
• 1995-1996 Beckman Institute for Advanced Science and Technology Research Assistantship
• 1993 Graduated with Distinction, Cornell University
• 1992 Inducted, Alpha Sigma Mu (Materials Honor Society)
• 1992-1993 American Electroplaters and Surface Finishers Society Scholarship
• 1991-1992 American Electroplaters and Surface Finishers Society Scholarship
• 1991 Inter-Industry Alliance Electronic Materials and Electronic Packaging Fellowship

Highlights