A highly sensitive polydopamine@hybrid carbon nanofillers based nanocomposite sensor for acquiring high-frequency ultrasonic waves

Nanocomposite strain sensors have shown application prospect in a wide range of applications. However, the sensitivities of the existing nanocomposite strain sensors to high-frequency, microscope dynamic strains are rather unsatisfactory. Herein, we fabricate a highly sensitive nanocomposite sensor for acquiring micro-vibrations generated by ultrasonic waves, from polydopamine(PDA)-coated hybrid carbon nanofillers. First, multi-walled carbon nanotubes (MWCNTs) are coated by 10s nm thick viscous PDA to improve their compatibility with polyvinylidene fluoride substrates. Compared to uncoated MWCNTs, the use of 15 wt% PDA-coated MWCNTs leads to a 40% increase in sensitivity. Then, one-dimensional PDA@MWCNTs are mixed with two-dimensional single-layer graphene to enhance the geometric contact between nanofillers. The sensitivity of sensors with hybrid nanofillers far exceeds that of PDA@MWCNT sensors. Also, as the mass fraction of graphene within hybrid nanofillers expands from 33% to 66%, the sensitivity of the proposed sensor improves by approximately 120%, surpassing that of pure graphene sensors. The high sensitivity of the proposed sensor, which actually utilizes a lower graphene content, was shown to be derived from the synergy between the two types of nanofillers which are of different dimensionalities. This study presents a novel approach for optimizing the sensitivity of nanocomposite strain sensors to high-frequency micro-vibrations.