  A novel, highly flexible, conductive polymer-based fiber with high electric
capacitance is reported. In its crossection the fiber features a periodic
sequence of hundreds of conductive and isolating plastic layers positioned
around metallic electrodes. The fiber is fabricated using fiber drawing method,
where a multi-material macroscopic preform is drawn into a sub-millimeter
capacitor fiber in a single fabrication step. Several kilometres of fibers can
be obtained from a single preform with fiber diameters ranging between 500um
-1000um. A typical measured capacitance of our fibers is 60-100 nF/m and it is
independent of the fiber diameter. For comparison, a coaxial cable of the
comparable dimensions would have only ~0.06nF/m capacitance. Analysis of the
fiber frequency response shows that in its simplest interrogation mode the
capacitor fiber has a transverse resistance of 5 kOhm/L, which is inversely
proportional to the fiber length L and is independent of the fiber diameter.
Softness of the fiber materials, absence of liquid electrolyte in the fiber
structure, ease of scalability to large production volumes, and high
capacitance of our fibers make them interesting for various smart textile
applications ranging from distributed sensing to energy storage.
