Equipment Proposal: Integrated Optical Force and Near-Field Scanning-Probe Microscope for Polymer Interfaces

University Of Florida, Gainesville FL

Investigators

Abstract

NSF CTS 0083258 Equipment Proposal: Integrated Optical-Force and Scanning-Probe Microscope Raj Rajagopalan, University of Florida Abstract The funds requested through this proposal will be used to construct an optical-tweezer-probe for a scanning optical microscope and to add dynamic light scattering peripherals to the instrument. The resulting optical force microscope will be used to study polymer-induced forces at solid-liquid interfaces and to develop techniques for measuring dynamic compliance of polymer layers. The requested additions will enhance the capability of the basic instrument so that a number of related problems, such as mechanical response of oil-surfactant-water interfaces and fluorescent microscopy on single polymer chains, can be studied. The overall objective of this grant is to incorporate a device for "optical manipulation" of small particles in a microscope. A tightly focused laser beam trained on a small particle allows one to manipulate and move the particle using the forces generated by the light beam. The combination of such a "laser tweezer" with a scanning optical microscope allows one to use the optically held particle as a "probe" to study local interactions on a surface. The laser beam holding the particle behaves like an invisible spring on the particle, and the stiffness of this "spring" can be changed easily by adjusting the laser power. Therefore, the optically held probe allows one to study very soft surfaces such as polymer chains on a surface or a liquid/liquid interface. This opens up new ways to study the mechanical and dynamic properties of polymer layers, single polymer chains, surfactants at interfaces, and the like. The implications of such phenomena extend to a number of important problems in engineering and the sciences, such as stability of biological and pharmaceutical dispersions, polymer compatibility with biomedical surfaces, and environmental separation processes involving particulates.