John C. Crocker

Assitant Professor of Applied Physics

B.A. -   University of Chicago, 1990 
M.A. -  University of Chicago, 1992 
Ph. D. - University of Chicago, 1996
(626) 395-3989 (voice)
(626) 793-8675 (fax)

Research Interests:

My research interests lie in biophysics, specifically at the border of molecular and cellular biology with soft condensed matter physics.  One the one hand, we use the power of biological systems to build interesting physics experiments, and on the other, we test physical models which describe complex biological systems such as the cytoskeleton and single macromolecules.  Ultimately, we will use that knowledge to engineer useful devices for medicine and bioengineering.

In practice this research amounts to measuring the tiny forces acting between single biological molecules or tiny probe particles floating in some sort of complex gooey material.  To do this, we infer the forces by watching how the probe particles move, and then applying physical models to deduce the driving force.  The main tools we employ are optical and fluorescence microscopies, novel optical tweezer setups, and lots of image processing to follow the motion of the probes or molecules.

If you'd like more details as to how we can track hundreds of bacteria-sized particles to better than a few nanometers, my colleague Eric Weeks has set up a nice page here.


"Two-Point Microrheology of Inhomogeneous Soft Materials" 
Crocker JC, Valentine MT, Weeks ER, Gisler T, Kaplan PD, Yodh AG, Weitz DA,  Download PDF

Selected papers:

"Three-dimensional direct imaging of structural relaxation near the colloidal glass transition"  Weeks ER, Crocker JC, Levitt AC, Schofield A, Weitz DA  Science 287 627-631 (2000).  Download PDF

"Attractions between hard colloidal spheres in semiflexible polymer solutions"
Verma R, Crocker JC, Lubensky TC, Yodh AG, Macromolecules  33 177-186 (2000). 
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"Entropic colloidal interactions in concentrated DNA solutions"
Verma R, Crocker JC, Lubensky TC, Yodh AG, Phys Rev Lett  81 4004-4007 (1998). 
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"Entropic attraction and repulsion in binary colloids probed with a line optical tweezer"
Crocker JC, Matteo JA, Dinsmore AD, Yodh AG, Phys Rev Lett  82 4352-4355  (1999). 
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"When like charges attract: The effects of geometrical confinement on long-range colloidal interactions"  Crocker JC, Grier DG, Phys Rev Lett  77 1897-1900  (1996). 
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"Microscopic Measurement of the Pair Interaction Potential of Charge Stabilized Colloid"   Crocker JC, Grier DG, Phys Rev Lett  73 352-355 (1994). 
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"Comment on `Monte Carlo study of structural ordering in charged colloids using a long-range attractive interaction'"  Grier DG, Crocker JC,  Phys Rev E  61  980-982 (2000). Download PDF

"Measurement of the hydrodynamic corrections to the Brownian motion of two colloidal spheres"  Crocker JC,  J. Chem Phys 106  2837-2840 (1997). 
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"Origin of stratification in creaming emulsions" 
Mueth DM, Crocker JC, Esipov SE, Grier DG,  Phys Rev Lett 77 578-581 (1996). 
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"Methods of digital video microscopy for colloidal studies"
Crocker JC, Grier DG,  J. Colloid Interface Sci.  179  298-310 (1996). 
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