Electrical and piezoresistive properties of multi-walled carbon nanotube/polymer composite films aligned by an electric field

Aligned multi-walled carbon nanotube (MWCNT)/polymer composite films are prepared by solution casting in the presence of an alternating electric field. Application of 7 kV/m at a frequency of 60 Hz to the polymer composite melt induces MWCNT alignment in the direction of the applied field, which is maintained after polymer crystallization. The electrical conductivity and piezoresistive response of electric-field-aligned and randomly oriented 0.1–0.75 wt% MWCNT/polysulfone films are evaluated. Electrical conductivity is 3–5 orders of magnitude higher for composites with electric-field-aligned MWCNTs than for randomly oriented composites. MWCNT alignment inside the polymer matrix also increases the film piezoresistive sensitivity, enhancing the strain sensing capabilities of the composite film.