The orientation and inhomogeneous distribution of carbon nanofibers and distinctive internal structure in polymer composites induced by 3D-printing enabling electromagnetic shielding regulation

Foaming ink for 3D-printing of ultralight and hyperelastic graphene architectures: Multiscale design and ultra-efficient electromagnetic interference shielding

Extrusion-based printing of macroscopic architectures layer-by-layer offers new opportunities for constructing customized electromagnetic interference (EMI) shielding materials. However, current research primarily focuses on improving the printability of material inks by increasing contents and adding various modifiers, controllable construction of ultralight and robust macro-architectures with structural design at both macro- and micro-scales is still challenging. Herein, we develop a graphene oxide foaming ink enriched with air bubbles for direct-ink writing, enabling the creation of macroscopic graphene architectures with arbitrary geometries. Meanwhile, air bubbles guide the self-assembly of nanosheets into a unique closed-cellular structure, which plays a critical role in enhancing EMI shielding performance. The resulting bubble-derived graphene aerogels (BGAs), fabricated through lyophilization and reduction of the foaming inks, exhibit ultralow densities of 0.0033-0.0045 g·cm-3, superior resilience even at cryogenic temperatures (-196 °C in liquid nitrogen), high compressive strength, and a negative Poisson's ratio. Remarkably, these BGAs achieve exceptionally high EMI shielding effectiveness (SE), reaching 103.2 dB with a low SE reflection of merely 4.8 dB. The specific SE (SSE/t), an absolute measure considering density and thickness, reaches an impressive value of 52,252 dB·cm2·g-1, ranking among the highest reported for synthetic foams. The desirable nanosheets-wrapped closed bubble-shaped cells, well-connected porous and conductive networks, and abundant interfaces in the BGAs collectively contribute to the intense interference and multireflection of electromagnetic waves, driving their outstanding shielding performance. This study presents a straightforward and practical approach to construct ultralight and resilient graphene architectures with multiscale designs, offering a promising solution for advanced EMI shielding applications.

Reduction of amylose/amylopectin ratio improves the molecular orientation and performance of three-dimensional-printed thermoplastic starch/polylactic acid intestinal stents

Three-dimensional (3D)-printed intestinal stents based on thermoplastic starch (TPS)/polylactic acid (PLA) are a promising biodegradable alternative to conventional metal stents. However, the influence of the structure and conformation of starch on the properties of 3D-printed TPS/PLA intestinal stents requires clarification. This study evaluated the effects of the amylose/amylopectin ratio of starch on the molecular orientation, molecular interactions, crystallization behavior, microstructure, and thermodynamic, mechanical and hydrolysis performance of 3D-printed TPS/PLA intestinal stents. The molecular orientation of starch was determined during the preparation of the filaments for 3D printing. The 3D printing process promoted intermolecular interactions by further improving the molecular orientation, and enhanced the short-range order and crystallinity of the starch molecules. Decreasing the amylose/amylopectin ratio enhanced the short-range order of the starch molecules by increasing molecular orientation, which improved the circumferential compression performance of the 3D-printed intestinal stents but not the axial compression performance. However, the reduction in plasticized starch particles and improved PLA continuity caused by decreasing the amylose/amylopectin ratio contributed to improving the circumferential and axial compression performance as well as the anti-hydrolysis performance. These findings highlight the potential of starch to replace PLA as an inexpensive raw material for the development of high-performance biodegradable 3D-printed intestinal stents.

Optimization of CoFe2O4 nanoparticles and graphite fillers to endow thermoplastic polyurethane nanocomposites with superior electromagnetic interference shielding performance

The rapid growth, integration, and miniaturization of electronics have raised significant concerns about how to handle issues with electromagnetic interference (EMI), which has increased demand for the creation of EMI shielding materials. In order to effectively shield against electromagnetic interference (EMI), this study developed a variety of thermoplastic polyurethane (TPU)-based nanocomposites in conjunction with CoFe2O4 nanoparticles and graphite. The filler percentage and nanocomposite thickness were tuned and optimized. The designed GF15-TPU nanocomposite, which has a 5 mm thickness, 15 weight percent cobalt ferrite nanoparticles, and 35 weight percent graphite, showed the highest total EMI shielding effectiveness value of 41.5 dB in the 8.2-12.4 GHz frequency range, or 99.993% shielding efficiency, out of all the prepared polymer nanocomposites. According to experimental findings, the nanocomposite's dipole polarization, interfacial polarization, conduction loss, eddy current loss, natural resonance, exchange resonance, multiple scattering, and high attenuation significantly contribute to improving its electromagnetic interference shielding properties. The created TPU-based nanocomposites containing graphite and CoFe2O4 nanoparticles have the potential to be used in communication systems, defense, spacecraft, and aircraft as EMI shielding materials.

Three-Dimensional-Printed Carbon Nanotube/Polylactic Acid Composite for Efficient Electromagnetic Interference Shielding

High-performance electromagnetic interference (EMI) shielding materials with ultralow density and environment-friendly properties are greatly demanded to address electromagnetic radiation pollution. Herein, carbon nanotube/polylactic acid (CNT/PLA) materials with different CNT contents, which exhibit characteristics of light weight, environmental protection and good chemical stability, are fabricated using 3D printing technology, where CNTs are evenly distributed and bind well with PLA. The performances of 3D-printed CNT/PLA composites are improved compared to pure 3D-printed PLA composites, which include mechanical properties, conductive behaviors and electromagnetic interference (EMI) shielding. The EMI shielding effectiveness (SE) of CNT/PLA composites could be improved when the content of CNTs increase. When it reaches 15 wt%, the EMI SE of 3D-printed CNT/PLA composites could get up to 47.1 dB, which shields 99.998% of electromagnetic energy. Meanwhile, the EMI shielding mechanism of 3D-printed CNT/PLA composites is mainly of absorption loss, and it generally accounts for more than 80% of the total shielding loss. These excellent comprehensive performances endow a 3D-printed CNT/PLA composite with great potential for use in industrial and aerospace areas.