Electrostatic Force Microscopy of Electrospun Polymer Nanofibers with Embedded Carbon Nanotubes
Rahamim, Joseph M.
- In order to study the electric characteristics of polymer nanofibers with embedded nanotubes, Elec- trostatic Force Microscopy (EFM) was conducted on both embedded nanofibers and neat polymer nanofibers. This project studies electrospun nanofibers of polylactic acid (PLLA) with embedded mul- tiwall nanotubes, as well as the case without nanotubes, using techniques in atomic force microscopy (AFM). ... read moreThe distribution of fibers spun on a silicon substrate is observed by means of an optical microscope. The topography of the nanofibers is then studied using AC mode AFM, and physical characteristics such as the distribution of fiber diameters are studied. Next, electrostatic force microscopy (EFM) is used to measure the dielectric properties of the fibers, and using some modeling of the tip-substrate system, a value for the dielectric constant of the fibers is measured, however the model is found not to apply. Accurate knowledge of the AFM-tip physical parameters (such as tip radius, spring constant etc.) is required for precise measurement of fiber dielectric constants. To achieve this, a novel technique is explored to find the tip/cantilever spring constant. Finally deviations from the modeled tip-sample interactions as proposed by this paper are discovered. Transient effects on the cantilever motion as the cantilever measures the edges of fibers breaks the simple harmonic motion analysis employed by AFM. Furthermore, evidence of permanent partial polarization of the dielectric fibers due to the EFM measurement is observed, resulting in long range forces that cause the AFM tip to interact with the fiber even when it is a considerable distance away.read less