Optimization of Buckypaper-enhanced Multifunctional Thermoplastic Composites

Intrinsic carbon nanotube liquid crystalline elastomer photoactuators for high-definition biomechanics

Photoresponsive soft actuators with the unique merits of flexibility, contactless operation, and remote control have huge potential in technological applications of bionic robotics and biomedical devices. Herein, a facile strategy was proposed to prepare an intrinsically-photoresponsive elastomer by chemically grafting carbon nanotubes (CNTs) into a thermally-sensitive liquid-crystalline elastomer (LCE) network. Highly effective dispersion and nematic orientation of CNTs in the intrinsic LCE matrix were observed to yield anchoring energies ranging from 1.65 × 10^-5 J m^-2 to 5.49 × 10^-7 J m^-2, which significantly enhanced the mechanical and photothermal properties of the photoresponsive elastomer. When embedding an ultralow loading of CNTs (0.1 wt%), the tensile strength of the LCE increased by 420% to 13.89 MPa (||) and 530% to 3.94 MPa (⊥) and exhibited a stable response to repeated alternating cooling and heating cycles, as well as repeated UV and infrared irradiation. Furthermore, the shape transformation, locomotion, and photo-actuation capabilities allow the CNT/LCE actuator to be applied in high-definition biomechanical applications, such as phototactic flowers, serpentine robots and artificial muscles. This design strategy may provide a promising method to manufacture high-precision, remote-control smart devices.

Synthesis of polyvinyl alcohol (PVA) infiltrated MWCNTs buckypaper for strain sensing application

Buckypaper (BP)/polymer composites are viewed as a viable option to improve the strain transfer across the buckypaper strain sensor by means of providing better interfacial bonding between the polymer and carbon nanotubes (CNTs). Multiwall carbon nanotubes (MWCNTs) BP/polyvinyl alcohol (PVA) composites were fabricated by a sequence of vacuum filtration and polymer intercalation technique. The optimized conditions for achieving a uniform and stable dispersion of MWCNTs were found to be using ethanol as a dispersion medium, 54 μm ultrasonic amplitude and 40 min sonication time. FTIR analysis and SEM spectra further confirmed the introduction of oxygenated groups (-COOH) on the surface of MWCNTs BP and the complete infiltration of PVA into the porous MWCNTs network. At MWCNTs content of 65 wt. %, the tensile strength, Young's modulus and elongation-at-break of PVA-infiltrated MWCNTs BP achieved a maximum value of 156.28 MPa, 4.02 GPa and 5.85%, improved by 189%, 443% and 166% respectively, as compared to the MWCNTs BP. Electrical characterization performed using both two-point probe method and Hall effect measurement showed that BP/PVA composites exhibited reduced electrical conductivity. From the electromechanical characterization, the BP/PVA composites showed improved sensitivity with a gauge factor of about 1.89-2.92. The cyclic uniaxial tensile test validated the high reproducibility and hysteresis-free operation of 65-BP/PVA composite under 3 loading-unloading cycles. Characterization results confirmed that the flexible BP/PVA composite (65 wt. %) with improved mechanical and electromechanical properties is suitable for strain sensing applications in structural health monitoring and wearable technology, as an alternative choice to the fragile nature of conventional metallic strain sensors.

Mechanically Robust Magnetic Carbon Nanotube Papers Prepared with CoFe2O4 Nanoparticles for Electromagnetic Interference Shielding and Magnetomechanical Actuation

The introduction of inorganic nanoparticles into carbon nanotube (CNT) papers can provide a versatile route to the fabrication of CNT papers with diverse functionalities, but it may lead to a reduction in their mechanical properties. Here, we describe a simple and effective strategy for the fabrication of mechanically robust magnetic CNT papers for electromagnetic interference (EMI) shielding and magnetomechanical actuation applications. The magnetic CNT papers were produced by vacuum filtration of an aqueous suspension of CNTs, CoFe₂O₄ nanoparticles, and poly(vinyl alcohol) (PVA). PVA plays a critical role in enhancing the mechanical strength of CNT papers. The magnetic CNT papers containing 73 wt % of CoFe₂O₄ nanoparticles exhibited high mechanical properties with Young's modulus of 3.2 GPa and tensile strength of 30.0 MPa. This magnetic CNT paper was successfully demonstrated as EMI shielding paper with shielding effectiveness of ∼30 dB (99.9%) in 0.5-1.0 GHz, and also as a magnetomechanical actuator in an audible frequency range from 200 to 20 000 Hz.