A double crosslinking MXene/cellulose nanofiber layered film for improving mechanical properties and stable electromagnetic interference shielding performance

With the discovery of the two-dimensional(2D) MXene, it shows a great application potential in the field of electromagnetic interference(EMI) shielding, but the mechanical brittleness and easy oxidation of MXene limit its wide application. For this reason, a double crosslinking strategy is provided to solve the above problems in a nacre-like “brick-mortar” layered MXene/cellulose nanofiber(MXene/CNF) film.Typically, the film was firstly suffered by dopamine modification, then was further reinforced by secondary Ca^(2+)bridging, so as to obtain excellent mechanical properties and antioxidative EMI shielding performance. Comparing with the single crosslinking, the double crosslinking strategy reveals a higher efficiency in improving the mechanical property. The mechanical strength and toughness of the double crosslinking MXene/CNF film can increase to 142.2 MPa and 9.48 MJ/m^(3), respectively. More importantly, while achieving good mechanical properties, the MXene composite film still holds a very stable EMI shielding performance of more than 44.6 dB when suffering from the oxidation treatment of hightemperature annealing, showing excellent anti-oxidation ability and environment tolerance. Therefore,this work provides a universal but effective double crosslinking strategy to solve the mechanical brittleness and easy oxidation of MXene-based composites, thus showing a huge potential in flexible EMI shielding applications.

Dual cross-linked MXene/cellulose nanofiber/nickel alginate film with improved mechanical properties and electromagnetic interference shielding performance

Electromagnetic interference pollution has raised urgent demand for the development of electromagnetic interference shielding materials.Transition metal carbides(MXenes)with excellent conductivity have shown great potential in electromagnetic interference(EMI)shielding materials,while the poor mechanical strength,flexibility,and structural stability greatly limit their further applications.Here,cellulose nanofibers and sodium alginate are incorporated with MXene nanosheets as flexible matrices to construct strong and flexible mussellike layered MXene/Cellulose nanofiber/Sodium Alginate composite films,and nickel ions are further introduced to induce metal coordination crosslinking of alginate units.Benefited from the dual-crosslinked network structure of hydrogen bonding and metal coordination,the tensile strength,Young’s modulus,and toughness of the MXene/cellulose nanofiber/nickel alginate composite film are significantly increased.After subsequent reduction by ascorbic acid,excess nickel ions are reduced to nickel nanoparticles and uniformly dispersed within the highly conductive composite film,which further improved its hysteresis loss effect toward the incident electromagnetic waves.Consequently,the MXene/cellulose nanofiber/nickel alginate-Ni composite film presents a considerably enhanced electromagnetic interference shielding effectiveness(47.17 dB)at a very low thickness of 29μm.This study proposes a feasible dual-crosslinking and subsequent reduction strategy to synergistically enhance the mechanical properties and electromagnetic interference shielding performance of MXene-based composite materials.

Preparation,Mechanical and Biological Properties of Inkjet Printed Alginate/Gelatin Hydrogel

3D printing has made remarkable progress in soft tissue reconstruction enabling the custom design of complex material implants with patient specific geometry.The aim of this study was to inkjet print mechanically reinforced biocompatible hydrogels.Here,we developed a double crosslinked ink by optimizing the rheological properties of solutions of sodium alginate(NaAlg),NaAlg/transglutaminase(TG),CaCl_(2)and gelatin/CaCl_(2).The results showed that a two-component ink system comprising NaAlg(4%w/v)/TG(0.8%w/v)and gelatin(4%w/v)/CaCl_(2)(3%w/v)gave optimum printability.The mechanical and biological properties of printed alginate/gelatin hydrogels prepared from inks with different gelatin contents,and incorporated fibroblasts,were characterized by Scanning Electron Microscope(SEM),mechanical testing and laser confocal microscopy.The compressive moduli of alginate/gelatin hydrogels could be adjusted from 19.2 kPa±1.2 kPa to 65.9 kPa±3.3 kPa by increasing the content of gelatin.After incubation for 7 d,fibroblasts had permeated all printed hydrogels and the rate of proliferation increased with increasing gelatin content.The highest cell proliferation rate(497%)was obtained in a hydrogel containing 4.5%(w/v)gelatin.This study offers a new strategy for the fabrication of 3D structures used to mimic the function of native tissues.