| This research study is primarily concerned with the underlying mechanisms of the adhesion, friction, elasticity, and functional behavior of polymer particles and fibers at the micro/nanoscale, which have been used in a wide range of industrial applications. There are multiple issues to be addressed in order to study such mechanisms in fine scale. First, calibration errors in micro/nanoscale force measurement devices such as Atomic Force Microscope (AFM) should be corrected to enable reliable force characterization. Therefore, we propose a calibration procedure that can be used in most AFM systems to compensate for the crosstalk problem on the cantilever bending and twisting signals. By accurately calibrating the AFM signals, it is possible to investigate the modes of motion (sliding, spinning, or rolling) of micro/nanoscale particles while pushing them laterally using an AFM probe. Such particle pushing experiments enable the characterization of frictional behavior of micro/nanoscale particles, which is important for micro/nano-particle based manipulation, lubrication, aggregation and dispersal of powders and polishing studies. Additionally, micro/nanoscale fiber networks are also investigated as a part of this thesis study. Mechanical and adhesive properties of individual fibers are the key components that determine the failure of fiber networks due to external perturbations such as vibration, air flow, and impact forces. We propose experimental methods to determine the mechanical properties of individual fibers by bending or breaking them laterally using an AFM. Moreover, in order to avoid complexity of the tensile test in AFM, the tensile strength of the fibers is found using a custom designed experimental setup to measure the corresponding stress values using a stochastic approach. In addition, we propose a custom adhesion measurement setup to determine the stress, contact area, and adhesion between two contacting fibers in random orientations for the design of fiber networks. Depending on the fiber orientation, the contact area takes different shape which determines the adhesive strength of the fibers. The approximate Johnson-Kendall-Roberts (JKR) theory for elliptical contacts will be taken as basis for the experimental data analysis, and the deviation of the experiments from this theory will be discussed in detail. Finally, we demonstrate the fabrication, characterization and functionalization of novel piezoelectric poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) microfiber arrays, which feature high strength, sensing, and actuation capabilities. These highly ordered piezoelectric fiber arrays mimics the hair cell receptors found in the animal kingdom. The microfiber arrays are produced using two distinct methods, and the fabrication procedures and parameters are identified in detail. Furthermore, the microfiber arrays are tested for their sensing and actuation capabilities. |
