Electrospun carbon nanofiber (CNF) has been demonstrated to possess outstanding physical properties with relatively low fabrication cost. In this work, CNFs with controllable waviness are made through shrinkage-induced micro buckling of polymeric precursors inside amorphous PMMA matrix. Compared with the existing releasing prestrained poly(dimethylsiloxane) (PDMS) substrate induced nanofiber buckling, this method provides a more simple process suitable for large scale production of buckled CNF without introducing defects as stretchable conductor. To fabricated the wavy and coiled CNFs, the as-electrospun polyacrylonitrile (PAN) precursor nanofiber was first dip-coated with PMMA to form a nanocomposite containing PAN nanofiber and PMIVIA matrix. The obtained nanocomposite was then hot-drawn to different draw ratios. During the stabilization process, the entropic and chemical reaction induced shrinkage of hot-drawn PAN nanofiber provides the compressive force for the nanocomposite to shrink, which generates compressive stresses on the PAN nanofibers causing them to buckle. In the following carbonization process, the PMMA phase will be fully decomposed and PAN nanofiber will be transferred to CNF at 1400 °C. The waviness of CNF is demonstrated to be tunable through controlling the hot-drawing ratio of the precursor nanofiber. The CNF mat electrical resistance change with applied strain was measured to show its stability and repeatability in application of stretchable conductors.
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