Fluorescence microscope for particle-tracking microrheology

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This is a proposal to purchase a fluorescence microscope that will be used to study the small-scale structure of complex fluids. The materials and phenomena to be studied include the formation of structure in clay suspensions as they undergo a transition from liquid to gel, and diffusion in porous gels which may find application in synthetic heart valves. We will use this microscope to track the diffusion of small fluorescent spheres suspended in the materials. The suspended particles are illuminated at one wavelength by a light source in the instrument, and imaged by the microscope at a different wavelength which is characteristic of the fluorescent dye being used. The particle trajectories will be obtained from sequences of stored images using particle-tracking software. The structure in the material restricts the motion of the particles, and analysis of the trajectories of individual particles and of correlations between the motions of pairs of particles provides information about that structure.