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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. ? 1997 American Vacuum Society.
@S0734-211X~97!12704-4#