Influence of zinc oxide nanofillers on the mechanical properties of PDMS

Zinc oxide (ZnO) is a piezoelectric material, which can be used for sensors and actuators. The piezoelectric feature combined with the flexibility of a polymer offers novel opportunities to develop flexible force or pressure... [ view full abstract ]

Zinc oxide (ZnO) is a piezoelectric material, which can be used for sensors and actuators. The piezoelectric feature combined with the flexibility of a polymer offers novel opportunities to develop flexible force or pressure sensors for wearable health-care systems, electronic skins, and nanogenerators. In these applications, flexibility, high strain and robustness to repeated flexing and bending are crucial characteristics which can be enhanced by adding ZnO nanofillers to the flexible polymer. In this work, we analyse the mechanical properties of a nanocomposite formed of polydimethylsiloxane (PDMS), used as a polymer matrix, and ZnO piezoelectric nanofillers. PDMS nanocomposites were fabricated using two types of ZnO nanofillers: nanoparticles (NPs) and nanorods (NRs), in different concentrations (0.1 – 5 %w/w). The influence of shape and size of the nanofillers on the mechanical properties of the PDMS matrix is investigated. Tensile testing is carried out to determine the Young’s modulus (E), ultimate tensile strength (UTS), elongation at break (%Eb) as function of particle concentration and after thermal ageing (24 hours at 200 °C).

E is found to decrease from 1.42 ± 0.21 MPa to 0.77 ± 0.015 MPa and 1.13 ± 0.02 MPa when loading with high concentrations (5 %w/w) of NRs and NPs, respectively (Fig. 2a). In general, the nanocomposite showed an increased %Eb when compared to the unloaded PDMS. Thermal ageing resulted in an increase of E (Fig. 2b) and decrease of % Eb. Overall, the incorporation of ZnO nanofillers affects the crosslinked network with the filler’s geometry influencing the mechanical properties of the nanocomposite. Dynamic mechanical analysis (DMA) of nanocomposites was performed to investigate the mechanical behaviour in a range of temperatures from -150 to 200° C. In this paper, we will present the details of the obtained results and in-depth analysis of the mechanical properties of the nanocomposites. The current results show that the nanocomposites retain a very good degree of flexibility regardless particle geometry, can possibly withstand microfabrication processing conditions and therefore are excellent materials for flexible sensor technology.