Flexible tactile sensors for dynamic triaxial force measurement based on piezoelectric elastomer

This paper presents a novel flexible tactile sensor for triaxial force dynamic measurement based on piezoelectric elastomer. The piezoelectric elastomer is flexible composite of polyvinylidene fluoride (PVDF) terpolymer and polydimethylsiloxane (PDMS), and multi-wall carbon nanotubes (MWCNTs) are added into the elastomer to improve the piezoelectricity. The elastomer is placed under a PDMS bump and divided into four sensing units by attaching separated copper electrodes. Electrical charges generated by the sensing units are corresponding to the triaxial contact force and the amplitudes of the component forces in three directions could be obtained via the charge outputs of the proposed sensor. Prototype sensors were validated through dynamic tests and the results showed that the sensitivity of the sensor could be improved by adjusting the content of PVDF (10% to 30%) and MWCNTs (0% to 4%). Specifically, the sensitivity in normal direction would increase by 85% as the content of PVDF increases and increase by over 150% as the content of the MWCNTs increases. Accordingly, the sensitivity in shear direction would increase by 45% and 85%, respectively.