Development of PVDF nanocomposite with single-walled carbon nanotubes (SWCNT) and boron nitride nanotubes (BNNT) for soft morphing actuator

Soft morphing actuators can deliver a range of displacements whilst being flexible and lightweight, making them advantageous over traditional mechanical actuators. Piezoelectric polymer polyvinylidene fluoride (PVDF) is combined with nanofillers to achieve superior soft actuator with the nanocomposite than with solely the polymer. This paper investigates and compares the distinctive effects of 1D nanofillers: single-walled carbon nanotubes (SWCNTs) and boron nitride nanotubes (BNNTs), through the promotion of crystal structures and polar beta crystals of PVDF, and consequently its actuation ability. Results showed that 80 mu m thick 2 wt.% SWCNT/PVDF clamped at both ends with a 10 mm span achieved a high deflection per applied electric field of 414 mu m (V mm(-1))(-1) and deflection of 570 mu m. This was due to a combination of fabrication method, physical geometry, and large surface area of SWCNTs leading to enhanced degree of crystallinity, beta crystals, dielectric constant, and conductivity. The increase in both overall crystal formation and targeted beta crystals lead to a high total beta crystal content of 35%, and the conductivity lead to a low applied electric field of 1.3 V mm(-1). BNNT/PVDF was able to undergo electric poling due to its insulating nature. BNNT/PVDF achieved a deflection magnitude per applied electric field of 2.9 mu m (V mm(-1))(-1), due to a much higher electric field (90-150 V mm(-1)). This corresponded to a deflection magnitude of 260 mu m, which was a 520% increase from only stretched BNNT/PVDF samples. Both nanocomposites displayed large scale actuation that is greater than the 70 mu m deflection (0.9 mu m (V mm(-1))(-1)) observed for pure PVDF of same geometry and setup.

Automated summary

Soft morphing actuators made of piezoelectric polymer PVDF combined with nanofillers, such as SWCNTs and BNNTs, demonstrate superior performance compared to pure PVDF. SWCNT/PVDF exhibits high deflection with a low applied electric field, while BNNT/PVDF requires a higher electric field for deflection. Both nanocomposites show large-scale actuation capabilities that outperform pure PVDF.