Size and arrangement of elementary fibrils in crystalline cellulose studied with scanning tunneling microscopy

Abstract
Scanning tunneling microscopy (STM) was used to investigate the ultrastructure of cellulose. The materials used in the experiments were cotton fiber, dewaxed cotton fiber, and microcrystalline cellulose. The results showed that the elementary fibrils in all these kinds of cellulose could be directly observed from the surface and cross-sectional view with high resolution. The elementary fibrils assembled together in parallel, and their lateral dimension showed a great variability in different kinds of cellulose, but was uniform in the same kind of cellulose. Elementary fibrils were the smallest structural units of cellulose, and they further aggregated into microfibrils, and the microfibrils constituted fibrils. In each gradation, the fibers piled up in parallel. STM was useful in studying the fine structure of cellulose.