Analytical, numerical, and experimental studies of viscoelastic effects on the performance of soft piezoelectric nanocomposites

Abstract

Piezoelectric composite (p-NC) made of a polymeric matrix and piezoelectric nanoparticles with conductive additives is an attractive material for many applications. As the matrix of p-NC is made of viscoelastic materials, both elastic and viscous characteristics of the matrix are expected to contribute to the piezoelectric response of p-NC. However, there is limited understanding of how viscoelasticity influences the piezoelectric performance of p-NC. Here we combined analytical and numerical analyses with experimental studies to investigate effects of viscoelasticity on piezoelectric performance of p-NC. The viscoelastic properties of synthesized p-NCs were controlled by changing the ratio between monomer and cross-linker of the polymer matrix. We found good agreement between our analytical models and experimental results for both quasi-static and dynamic loadings. It is found that, under quasi-static loading conditions, the piezoelectric coefficients (d) of the specimen with the lowest Young's modulus (∼0.45 MPa at 5% strain) were ∼120 pC N, while the one with the highest Young's modulus (∼1.3 MPa at 5% strain) were ∼62 pC N. The results suggest that softer matrices enhance the energy harvesting performance because they can result in larger deformation for a given load. Moreover, from our theoretical analysis and experiments under dynamic loading conditions, we found the viscous modulus of a matrix is also important for piezoelectric performance. For instance, at 40 Hz and 50 Hz the storage moduli of the softest specimen were ∼0.625 MPa and ∼0.485 MPa, while the loss moduli were ∼0.108 MPa and ∼0.151 MPa, respectively. As piezocomposites with less viscous loss can transfer mechanical energy to piezoelectric particles more efficiently, the dynamic piezoelectric coefficient (d') measured at 40 Hz (∼53 pC N) was larger than that at 50 Hz (∼47 pC N) though it has a larger storage modulus. As an application of our findings, we fabricated 3D piezo-shells with different viscoelastic properties and compared the charging time. The results showed a good agreement with the predicted trend that the composition with the smallest elastic and viscous moduli showed the fastest charging rate. Our findings can open new opportunities for optimizing the performance of polymer-based multifunctional materials by harnessing viscoelasticity.

Chitosan-ZnO Nanocomposites Assessed by Dielectric, Mechanical, and Piezoelectric Properties

“…Such a high piezoelectric coefficient can be related to elastic properties of the CS matrix because the viscous and elastic properties play an important role in the piezoelectric performance of piezoelectric polymer composites [ 58 ].…”

“…There have been several reports that proposed different models, for instance Refs. [ 58 , 74 , 75 , 76 ] reported an increase of d 33 with the volume fraction of the piezoelectric NPs. Moreover, in polymer nanocomposites with NPs with high dielectric constant (such as PZT, BaTiO 3, BZT) there is an increase of d 33 with an increase of the dielectric constant with NPs content [ 74 , 75 , 76 ].…”

“…40 nm the size of the nanodomains must be less than 40 nm that can increase d 33 in CS-ZnO nanocomposite. Furthermore, high value of d 33 in CS-ZnO nanocomposite films can be related to their elastic properties that play an important role in the piezoelectric performance of piezoelectric polymer composites [ 58 ]. Additionally, refs.…”

Soft Piezoionic/Piezoelectric Nanocomposites Based on Ionogel/BaTiO3 Nanoparticles for Low Frequency and Directional Discriminative Pressure Sensing

“…The soft nanocomposites exhibited elastomeric-like properties, which are beneficial to enhance their electromechanical response under low frequency stimulations in the quasi-static regime. 43 The nanoparticles size and crystallinity are very important features to confer piezoelectric behavior to polymer-based nanocomposites. 44,45,16 In the present study, BaTiO 3 NPs were synthesized according to the literature with small modifications 46 via the sol-precipitation method at atmospheric pressure (see Supporting Information for details) and were obtained as a fine white powder.…”

“…The optimal formulation and synthesis procedure were determined empirically, by qualitatively evaluating the uniaxial stretching of the material. The soft nanocomposites exhibited elastomeric-like properties, which are beneficial to enhance their electromechanical response under low frequency stimulations in the quasi-static regime …”