| Recent research has shown that the atomic force microscope (AFM) can be used as a tool to draw suspended sub-micron polymer fibers into different three-dimensional geometries from a solvated polymer droplet. Different forces interact during the formation or pulling of these fibers. Hence, the purpose of this study is to investigate the force response of the AFM cantilever when an attempt is made to pull a polymer fiber from a droplet of solvated polymer. This study also attempts to interpret events that occur during the interaction of the AFM cantilever with the solvated polymer droplet in terms of the forces acting between the two.; In this study, poly-(methyl methacrylate) (PMMA) was dissolved in a low vapor pressure dibasic ester. The low volatility of the solvent, dibasic ester, makes it impossible to pull an actual free-standing fiber with the AFM tip, but the forces involved prior to fiber formation are investigated with the idea of eventually forming fibers from more volatile solvated polymers. The AFM cantilever is lowered into and removed from the PMMA droplet at a selected velocity while the force response of the AFM cantilever is recorded. A force-distance curve, showing the tip-sample interaction during the approach and retraction, is recorded for every trial. These force-distance curves were obtained and analyzed for different PMMA concentrations, molecular weights, and retraction velocities.; The results of this study show that there is a signature point where nano-scale forces recorded by the AFM are indicative of the time at which a fiber is about to be pulled from a polymer droplet before it rapidly thins and breaks. |
