Complex Fluids Laboratory

Prof. Piotr Habdas, Physics Department, Saint Joseph's University
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colloidal attractive glass If smaller particles are added to the hard-sphere colloidal suspension, a short-range inter-particle attraction is turned on between the large particles. Exclusion of the small particles from the region between the surfaces of two nearby particles creates an unbalanced osmotic pressure pushing the particles together. This is known as the "depletion attraction". The range and the depth of the attraction potential can be varied independently by changing the size and the number of the small particles. Since the "sticky" hard-sphere system takes into account attraction it is a more truthful model of molecular glasses than the hard-sphere system. We are using various microscopy techniques to observe the behavior of the colloidal particles and thus gain more insight into the dynamics of the glass transition.

bentonite and water mixture = mud I taught a Freshman Seminar which introduced students to the physics of squishy materials. To find out more visit our web page about exploring squishy materials.

colloidal glass I just finished working on a project which deals with locally perturbing colloidal glasses. Or actually I finished taking data. Now I have to analyze the data. That will take a while. Still analyzing ...

Me and my daughter, Martyna. Ketchup, toothpaste or mayonnaise are all examples of a Bingham fluid. We use a less "clean" Bingham fluid, mud. Our Bingham liquid is a mixture of bentonite particles dispersed in water. We study the kinematics of a sphere moving through a Bingham liquid. Other project deals with a flow of the Bingham mud down an inclined plane.

sink defect A system know as printer's instability allows to study many interesting 1-dimensional patterns. We study the behavior of source and sink defects in a traveling finger pattern.

binary mixture with upper critical point As a part of my Ph.D. research I studied the behavior of dielectric permittivity in binary mixtures of limited miscibility as a function of temperature and pressure.