X-ray nanotomography of a nanofiber: Quantitative measurement of diameter fluctuations

Imaging nanostructures in three-dimension is beneficial for understanding their formation and interactions. This paper presents application of X-ray imaging as a tool for visualizing the shape fluctuation in polymer nanofibers. Synchrotron X-ray nanotomography is a non-destructive technique that can reveal material internal and surface features at the nanoscale. Diameter fluctuations as a result of processing the polymer nanofiber obtained through forcespinning were imaged using monochromatic synchrotron hard X-rays of 8 keV energy. Reconstructed binary images containing geometric information of the fiber surface were visualized and meshed in 3D. A new approach for processing of the reconstructed data to achieve a quantitative interpretation of 3D results was developed. A local 3D regression approach was developed for tracing the fiber center line, and to determine the minimum distance between triangular surface elements from the center line (radius). Fiber diameter fluctuations measured were presented qualitatively by applying surface coloring to the local fiber diameter information. Nanotomography revealed that the fiber has upto 19% (±43 nm) deviation in fiber radius over the average radius of 221 nm.