Tuning the fabrication parameters of multi-walled carbon nanotubes-epoxy based flexible strain sensitive composites

Over the past two decades, carbon nanotubes (CNTs) have attracted a great deal of interest owing to their superior electrical properties and they are being used in many engineering applications including highly sensitive strain sensors. However, realization of well-dispersed CNTs within the polymer matrix is challenging due to the strong tendency of carbon nanotubes to form bundles. Therefore, each processing parameters should be well characterized. In this work, the optimization of the processing parameters for synthesizing viable dispersions of multi-walled carbon nanotubes (MWCNTs)/epoxy based films was performed. Dispersions ranging from 0.3 wt.% to 1 wt.% MWCNTs were synthesized and deposited on flexible substrate by the stencil printing technique at different deposition speeds up to 90 mm/s. The scanning electron microscopy (SEM) images confirmed that MWCNTs are homogeneously dispersed within the epoxy matrix. Furthermore, the piezoresistive properties of composites for optimized deposition speed were also analyzed by electrochemical impedance spectroscopy (EIS). It was observed that, sensors at low concentrations shows higher sensitivity (13.6 at 0.3 wt.%). A non-linear piezoresistivity was observed at low concentrations due to dominant effect of tunneling and in contrast with that, at high concentrations sensor shows higher linearity.

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