Contact Information:
e-mail:
phone: (217) 333-5720
fax: (217) 333-5052
1022 F. Seitz Materials Research Laboratory
MC-230,
Urbana, IL 61801
We are an experimental group interested in the interface between disciplines. We have strong collaborations, within UIUC and also with colleagues in industry and in government labs. Students in this group include chemical engineers, materials scientists, chemists, and physicists. This diversity of background and perspective helps to maintain a particularly stimulating environment. On our group webpage, each student explains his/her own work, in his/her own words.
We are interested in "soft materials" fluid membranes, liposomes, polymers, colloids, and other structured liquids, and presently focus on their behavior at surfaces. This is important because the structure, properties, and reactivity of matter at a surface can be very different from that in bulk. Thin films and interfaces of these complex fluids are at the heart of an enormous range of scientific and technological problems: drug delivery, colloidal stability and flocculation, coatings, lubrication, adhesion, polymer reinforcement with nanoparticles, and biocompatibility. Students in the research group thus gain broad training in a variety of subjects. The strengths of this group are in creatively devising new experimental approaches, using new experimental tools, to ask (and answer) new questions about these important problems.
One research theme is imaging sometimes by single-molecule fluorescence microscopy, sometimes by Raman spectroscopy and other confocal methods. We make much use of these optical methods to track single molecules and nanoparticles, as well as to study how to induce them to self-assemble in novel, interesting ways. Femtosecond laser fluorescence spectroscopy is used to probe the surface diffusion rates, rotational relaxation times, surface conformations, and binding-unbinding rates of polymers, polyelectrolytes, DNA and proteins. These questions of the surface mobility of polymers and biopolymers, and how and why the relaxation between states is different from in the bulk, form the basis of many significant scientific problems to whose solution we would like to contribute -- in areas from tribology to biology.
Imaging is often combined with nanorheology experiments. We measure equilibrium forces of interaction between surfaces and have also devised a new device, a molecular tribometer, to measure dynamical responses over a wide range of excitation frequency and shear rate. A key point of this work is that interfacial forces depend strongly on time and rate. We would like to understand these rates, and learn how to control them. This research gets down to the fundamentals of surface-surface interactions, adhesion, friction, and surface recognition, at the direct level of molecular forces.
S. Jiang and S. Granick, "Janus Balance of Amphiphilic Colloidal Particles," J. Chem. Phys. 127, 161102 (2007).
S. Granick and S. C. Bae, "Molecular Motion at Soft and Hard Interfaces: from Phospholipid Bilayers to Polymers and Lubricants", Annu. Rev. Phys. Chem. 58, 353 (2007).
A. Poynor, L. Hong, I. K. Robinson, S. Granick, Z. Zhang, P. A. Fenter, "How Water Meets a Hydrophobic Surface," Phys. Rev. Lett. 97, 266101 (2006).S. Granick, H. Lee, and Y. Zhu, "Slippery Questions of Stick When Fluid Flows Past Surfaces," Nature Materials 2, 221 (2003).
X. Zhang, Y. Zhu, and S. Granick, "Hydrophobicity at a Janus Interface," Science 295, 663 (2002).