Effect of aligned ferromagnetic particles on strain sensitivity of multi-walled carbon nanotube/polydimethylsiloxane sensors

A strain sensor using chain-structured ferromagnetic particles (FPs) in a multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) nanocomposite was fabricated under a magnetic field and its strain sensitivity was evaluated at different material proportions. When the proportion of MWCNTs that are well dispersed in PDMS is higher than the percolation threshold, the strain sensitivity reduces with the increase of MWCNTs, in general; whereas a higher volume fraction of FPs produces a higher strain sensitivity when the chain-structure of FPs sustains. The mechanisms causing this interesting phenomenon have been demonstrated through the microstructural evolution and micromechanics-based modeling. These findings indicate that an optimal design of the volume fraction of FPs and MWCNTs exists to achieve the best strain sensitivity of this type of sensors. It is demonstrated that the nanocomposites containing 20 vol. % of nickel particles and 0.35 wt. % MWCNTs exhibit a high strain sensitivity of ∼80.