Resistive–conductive transitions in the time-dependent piezoresponse of PVDF-MWCNT nanocomposites

Abstract

Nanocomposites were prepared by melt blending of multiwalled carbon nanotubes (MWCNTs) filled with polyvinylidene fluoride. Time-dependent piezoresistance was investigated as a function of concentration. In the quasi-static case, a transition from negative pressure coefficient to positive pressure coefficient (PPC) behavior was observed. The PPC effect was negligible at high concentrations. At short times, the resistive response decreased for all nanocomposites, with the magnitude of the decrease proportionate to the MWCNT concentration. However, long-term creep response was resistive for low concentrations and conductive at high concentrations. A Burgers model based on Maxwell and Kelvin elements in series was used to describe the strain dependence. An equivalent model that uses resistances and capacitances was examined for the time dependence of fractional resisitivity. Results were correlated with Raman mapping-based dispersion analysis. An increased dispersion and an increase in MWCNT-MWCNT contact area resulted in a transition from a matrix-based resistive response to a filler-based conductive response.

Poly(vinylidene fluoride)/poly(acrylonitrile) – based superior hydrophobic piezoelectric solid derived by aligned carbon nanotubes in electrospinning: fabrication, phase conversion and surface energy

“…30, 31 However, superior hydrophobic piezoelectric PVDF coating method, which contains high β – phase content and increased contact angle, are barely reported. Currently some researchers indicated that the induction of nanomaterials could increase the surface roughness and also derive the α – phase of PVDF to β – crystal formation during a chain alignment caused by the electrostatic interaction between the methylene and charged nanoparticles 32-36 . The zigzag carbon atoms on the carbon nanotubes (CNTs) surface could induce β – phase formation during the crystallization of PVDF 37-39 and π conjugated structure of CNTs will attract the F- to CNTs surface.…”

Mechanical and electrical multifunctional poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)—multiwall carbon nanotube nanocomposites

“…In addition to the growing interest in polymers from renewable resources, the importance of multifunctionality from the polymers has grown especially in the field of polymer sensors [14, 15]. The discovery of carbon nanotubes by Iijima in 1991 [16] has resulted in designing novel materials with extraordinary materials with extraordinary combination of mechanical, thermal, and electrical properties [17, 18].…”

Self-Compensated Driving Circuit for Reducing Drift and Hysteresis in Force Sensing Resistors

“…The authors can only hypothesize about the possible source of the noise. The experimental observations from the previous authors' work demonstrated that the effective area for tunneling conduction, A, is modified by the applied stress [19]; see Equation (7). If σ is held constant for an extended period of time, the authors believe that A fluctuates in a random fashion, thus, causing the noise in Figure 9.…”

“…By taking a glance at the datasheets of commercial FSRs [11][12][13], they exhibit from ten to one hundred times more drift and hysteresis error than load cells. Fortunately, a great effort is currently placed on improving the performance of FSRs by investigating multiple trends such as the integration of carbon nanotubes in the polymer matrix [7,14], changing the electrode configuration of the assembled sensor [15,16], testing different types of polymers [17,18], and adding non-conductive nanoparticles to reinforce the polymer matrix with the aim of reducing creep [9].…”

“…FSRs can be fashioned into multiple shapes and dimensions to fulfill the requirements of a given final application [1][2][3]; this can be done by simply cutting the nanocomposite film after the production process is done, followed by electrode positioning and wiring to assemble the final force sensor [4]. The nanocomposite film is obtained by randomly dispersing conductive particles in an insulating polymer matrix [5][6][7]. Finally, when the sensor is assembled, a time-multiplexed circuit is employed to read out the sensor's resistance and provide a pressure profile map [4,8].…”