Theoretical considerations suggest that the strength of carbon nanotube (CNT) fibers be exceptional; however, their mechanical performance values are much lower than the theoretical values. To achieve macroscopic fibers with ultrahigh performance, we developed a method to form multidimensional nanostructures by coalescence of individual nanotubes. The highly aligned wet-spun fibers of single- or double-walled nanotube bundles were graphitized to induce nanotube collapse and multi-inner walled structures. These advanced nanostructures formed a network of interconnected, close-packed graphitic domains. Their near-perfect alignment and high longitudinal crystallinity that increased the shear strength between CNTs while retaining notable flexibility. The resulting fibers have an exceptional combination of high tensile strength (6.57 GPa), modulus (629 GPa), thermal conductivity (482 W/m·K), and electrical conductivity (2.2 MS/m), thereby overcoming the limits associated with conventional synthetic fibers.

Here, we studied the triboelectric properties of structurally controlled laser-induced graphene (LIG) to clarify the key factors for improving the energy harvesting performance. With a facile defocusing method, the LIG morphology was modulated in porous LIG, in short carbon fiber combined LIG (SF-LIG) and in long carbon fiber-dominant LIG (LF-LIG). Through correlation analysis of the triboelectrification characteristic according to the material properties of LIG, it was found that asymmetric defects as well as the graphitic-N configuration within the fibrous LIG structure can significantly improve the triboelectric effectiveness by supplying trap sites and lowering the work function, respectively. The vertically aligned fibrous structure also increases the structural contact area, contributing to the improvement in the charge transfer efficiency. As a result, it was demonstrated that the long carbon fiber structure of LF-LIG can improve the performance by 130 times (512 mW m⁻²) compared with porous LIG-based triboelectric nanogenerators (TENGs) (3.9 mW m⁻²). As a feasible application, all LIG-based flexible triboelectric touch sensors are fabricated, which are composed of LF-LIG active matrices (4 × 4) and LIG electrodes through a one-step laser writing process. The demonstrated touch sensor independently addressed each pixel for tracking the location of the human touch, showing self-powering capabilities. This work presents a facile strategy for surface morphology modification of LIGs and investigates their triboelectric charging effect, which might promote the development of practical flexible TENGs for wearable electronic devices.

Microneedles (MNs) are a new system of effective drug delivery that create micron-sized pathways to the epidermis or upper dermis regions of the skin. In this study, we developed coated-type microneedles for direct hispidin delivery to the skin. Hispidin is a well-known plant-derived antioxidant component showing antitumor, anti-inflammatory, antiallergic, antiangiogenic, antioxidant, hypoglycemic, hypolipidemic, and immunomodulatory activities. Polymeric blends of polylactic acid (PLA) and polycaprolactone (PCL) were casted as MNs to enhance skin permeability. PLA/PCL MNs exhibited the highest strength of 51.26 MPa with a width of ~200 ųm. Hispidin was directly coated onto the MNs with PLA/PCL blends to form delivery layers. Compared to the hispidin-only delivery layer, skin permeability of hispidin increased by over 50% when using agarose gel in in vitro tests. In a dose-dependent manner, hispidin coated on PLA/PCL MNs also showed a brightening effect, as well as anti-inflammatory activity at the gene and protein level in skin cell culture experiments. It also demonstrated antimicrobial activity, and showed no cytotoxicity to skin cells. These results suggest that the PLA/PCL MN system with hispidin may have great potential as a prototype platform for various drug delivery systems, allowing the development of more effective subcutaneous delivery of vaccines, oligonucleotides, insulin, and many other cosmetic applications.

Owing to the increasing generation of waste coffee powder and the biochar from this waste being considered as alternative conductive carbon fillers, we developed eco-friendly and electrically conductive cementitious composites using biochar from waste coffee beans, which were directly pyrolyzed into eco-friendly and electrically conductive biochar. Via carbonization and graphitization, cyclic organic carbon precursors were transformed into sp2-bonded carbon structures and then functionalized with melamine. The non-covalent functionalization process driven by the electromagnetic process accelerated the mass production and enhanced the monodispersive properties of the cementitious composites. Thus, the melamine-functionalized biochar cementitious composites exhibited an electrical conductivity of 3.64 × 10⁻⁵ ± 1.02 × 10⁻⁶ S/cm (n = 6), which corresponded to an improvement of over seven orders of that of pure concrete. Furthermore, the percolation threshold of biochar was between 0.02 and 0.05 wt.%; thus, an effective conductive network could be formed using low additions of functionalized biochar. As a result, in this study, electrically conductive cementitious composites were developed using waste coffee powder converted into carbon nanomaterials through a newly introduced process of non-covalent functionalization with melamine.