Lightweight and robust cellulose/MXene/polyurethane composite aerogels as personal protective wearable devices for electromagnetic interference shielding.

The increasing electromagnetic pollution is urgently needed as an electromagnetic interference shielding protection device for wearable devices. Two-dimensional transition metal carbides and nitrides (MXene), due to their interesting layered structure and high electrical conductivity, are ideal candidates for constructing efficient conductive networks in electromagnetic interference shielding materials. In this work, lightweight and robust cellulose/MXene/polyurethane composite aerogels were prepared by mixing cellulose nanofiber (CNF) suspensions with MXene, followed by freeze-drying and coating with polyurethane. In this process, CNF effectively assembled MXene nanosheets into a conductive network by enhancing the interactions between MXene nanosheets. The prepared aerogel exhibited the shielding effectiveness of 48.59 dB in the X-band and an electrical conductivity of 0.34 S·cm-1. Meanwhile, the composite aerogel also possessed excellent thermal insulation, infrared stealth, mechanical and hydrophobic properties, and can be used as a wearable protective device to protect the human body from injuries in different scenarios while providing electromagnetic interference shielding protection.

Mussel-inspired adhesive gelatin-polyacrylamide hydrogel wound dressing loaded with tetracycline hydrochloride to enhance complete skin regeneration.

Even though the global wound care market size was valued at USD 19.83 billion in 2020, it is still a challenge to develop a hydrogel-based wound dressing with a good mechanical property, adhesiveness and antibacterial property. This study established and validated a mussel-inspired adhesive hydrogel wound dressing with antibacterial activity by dispersing tetracycline hydrochloride into hydrogel based polydopamine, gelatin and polyacrylamide. A tough hydrogel with a fracture stress of 0.42 MPa was prepared by changing the contents of the gelatin and polyacrylamide. With the addition of polydopamine and tetracycline hydrochloride, the hydrogel was endowed with an adhesive property (with a tissue adhesive strength of 4.13 kPa) and antibacterial activity against both Escherichia coli and Staphylococcus aureus. Finally, a rat full-thickness skin defect wound model was used to evaluate the performance of the hydrogels in wound repair. The hydrogel group showed a significantly reduced wound area (95.72%) compared with the blank group (86.34%) on day 14. The hydrogel promoted the collagen deposition, weakened the inflammatory response and enhanced wound healing. Therefore, the hydrogel with multifunctional properties is a promising candidate for complete skin regeneration.

Nanocellulose-mediated transparent high strength conductive hydrogel based on in-situ formed polypyrrole nanofibrils as a multimodal sensor.

A simple method was provided to prepare a transparent, highly conductive, mechanically reinforced, stretchable, and compressible hydrogel. In this system, pyrrole (Py) monomers were gently polymerized and uniformly deposited on the surface of cellulose nanofiber (CNF) via the improved in-situ polymerization. In the opaque PPy@CNF suspension, acrylamide monomers (AM) were dissolved and radical-polymerized to construct the PPy@CNF-PAM hydrogel with the in-situ formation of PPy nanofibrils in the presence of excess ammonium persulfate (APS). The in-situ formed PPy nanofibrils were well intertwined with the CNF and PAM chains, and a highly conductive path was established and permitted visible light to pass through. The amphipathic CNF took along and dispersed PPy aggregates well, and reinforced the hydrogel after formation of PPy nanofibrils. In view of the improved mechanical compressive, stretchable properties and excellent electrical conductivity (4.5 S/m), the resulting hydrogels could serve as a potential electrical device in a range of applications.

The fabrication of polylactide/cellulose nanocomposites with enhanced crystallization and mechanical properties.

Polylactide/cellulose nanocomposites were fabricated by blending of commercial polylactide (PLA) and modified cellulose nanocrystals (CNCs). Modified CNCs were prepared via the in situ polymerization of CNCs and L-lactic acid (CNCs-PLLA) or D-lactic acid (CNCs-PDLA). The actual occurrence of chemical bond between CNCs and PLA segment was confirmed by Fourier transform infrared, nuclear magnetic resonance, X-ray diffraction and solubility tests. Differential scanning calorimetry and X-ray diffraction characterization indicated that CNCs-PDLA better improved the crystallization ability of PLA matrix compared with CNCs-PLLA. Furthermore, compared with the neat PLA (60.0 MPa), the tensile strength of resulting nanocomposites showed an enhancement of up to 36% (81.65 MPa). And the nanocomposites with CNCs-PDLA exhibited both high crystallinity and improved mechanical properties.