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Granular Materials: The Unusual Properties of Powders, Ball-Bearings, and M&Ms

Granular Materials
Reported by
Angelo DePalma

Posted March 11, 2008


Everyone is familiar with granular materials—sand, powders, and collections of even larger particles. Yet these materials behave differently from other forms of matter such as gases, solids, and liquids, leading some scientists to believe that granularity may represent an additional state of matter. This is more than an academic argument. Understanding granular materials carries implications in fields ranging from civil engineering to pharmaceutical manufacturing.

The speakers in a symposium held at the Academy on January 23, 2008, represent a cross-section of research on granular materials. Bruno Hancock of Pfizer provided an overview of segregation and handling issues for granular pharmaceutical ingredients. Mark Shattuck of the City College of New York took the discussion to a more theoretical level, describing the behavior of granular "gases" and "crystals" under various stresses. Paul Chaikin of New York University presented an amazing finding in an unusual granular system—containers of M&M's candies.

Web Sites

An Introduction to Granular Physics
This Web site built by the University of Chicago contains an introduction to granular materials.

Center for Complex Fluids Engineering
The Pharmaceutical Solids Formulation and Processing Consortium of Carnegie Mellon University is a technology-driven scientific research consortium focused on liquid-contacting granular materials.


Antony SJ, Hoyle W, Ding Y. 2004. Granular Materials: Fundamentals and Applications. Royal Society of Chemistry, Cambridge, UK.

Oda M, Iwashita K. 1999. Mechanics of Granular Materials: An Introduction. Taylor and Francis, London.

Kolymbas D. 2000. Constitutive Modelling of Granular Materials. Springer, New York.

Journal Articles

Angelescu DE, Harrison CK, Trawick ML, et al. 2005. Two-dimensional melting transition observed in a block copolymer. Phys. Rev. Lett. 95: 025702.

Cao X, Leyva N, Anderson SR, Hancock BC. 2007. Use of prediction methods to estimate true density of active pharmaceutical ingredients. Int. J. Pharm. Dec. 23 [Epub ahead of print].

Dutta M, Hancock B, Benthamb C et al. 2005. An implementation of granular dynamics for simulating frictional elastic particles based on the DL_POLY code. Computer Physics Communications 166: 26-44.

Huntley JM, Martin TW, Mantle MD, et al. 2007. NMR measurements and hydrodynamic simulations of phase-resolved velocity distributions within a three-dimensional vibrofluidized granular bed. Proceedings of the Royal Society A Volume 463, Number 2086.

Man WN, Donev A, Stillinger FH, et al. 2005. Experiments on random packings of ellipsoids. Phys. Rev. Lett. 94: 198001.

Reis PM, Ingale RA, Shattuck MD. 2007. Forcing independent velocity distributions in an experimental granular fluid. Phys. Rev. E 75: 051311.

Reis PM, Ingale RA, Shattuck MD. 2006. Crystallization of a quasi-two-dimensional granular fluid. Phys. Rev. Lett. 96: 258001.

Sullivan MT, Zhao K, Hollingsworth AD, et al. 2006. An electric bottle for colloids. Phys. Rev. Lett. 96: 015703.

Wua C-Y, Ruddy O, Bentham A, et al. 2005. Modelling the mechanical behaviour of pharmaceutical powders during compaction. Powder Technology 152: 107-117. (PDF, 2.14 MB) FULL TEXT


Bruno Hancock, PhD

Pfizer, Inc
e-mail | web site | publications

Bruno Hancock is a senior research investigator at Pfizer where he works on developing techniques to characterize the physical and mechanical properties of powdered and compacted pharmaceutical materials. Hancock's research career has been focused on amorphous pharmaceutical systems and the mechanical properties of pharmaceutical solids. He has published more than 45 research papers and several patents. He also serves on the editorial board of the Journal of Pharmacy and Pharmacology.

Mark Shattuck, PhD

The City College of New York
e-mail | web site | publications

Mark Shattuck is an associate professor of Physics at the Benjamin Levich Institute and the City College of New York. He received his PhD in Physics from Duke University in 1995. He was a postdoctoral fellow at the University of Texas from 1996–1998. He is a member of the American Physical Society, the Society of Industrial and Applied Mathematics, and Sigma Xi.

Paul Chaikin, PhD

New York University
e-mail | web site | publications

Paul Chaikin is a professor of Physics at New York University. Previous professorships include the University of California, Los Angeles; University de Paris, Sud. Orsay; the University of Pennsylvania and Princeton. Chaikin has also worked as a research associate and consultant for Exxon Research and Engineering Co and the NEC Institute. He cowrote the textbook Principles of Condensed Matter Physics with Tom Lubensky. Among Chaikin's awards are a Sloan Fellowship (1979–1981), a Guggenheim Fellowship (1997), and election to both the American Academy of Arts and Sciences (2003) and the National Academy of Sciences (2004). Paul Chaikin received his PhD in Physics from the University of Pennsylvania in 1971.

Angelo DePalma

Angelo DePalma is a freelance science writer living in Newton, New Jersey. His e-mail address is