High conductivity and stability of polystyrene/MXene composites with orientation-3D network binary structure

Flexible Silica/MXene/Natural rubber film strain sensors with island chain structure for Healthcare monitoring

The demand for flexible strain sensors with high sensitivity and durability has increased significantly. However, traditional sensors are limited in terms of their detection ranges and fabrications. In this work, a space stacking method was proposed to fabricate natural rubber (NR)/ Ti3C2Tx (MXene)/silica (SiO2) films that possessed exceptional electrical conductivity, sensitivity and reliability. The introduction of SiO2 into the NR/MXene composite enabled the construction of an "island-chain structure", which promoted the formation of conductive pathways and significantly improved the conductivity of the composite. Specifically, the electrical conductivity of the NR/MXene/10 wt%SiO2 composite was enhanced by about 200 times compared to that of the NR/MXene composite alone (from 0.07 to 13.4 S/m). Additionally, the "island-chain structure" further enhanced the sensing properties of the NR/MXene/10 wt%SiO2 composite, as evidenced by its excellent sensitivity (GF = 189.2), rapid response time (102 ms), and good repeatability over 10,000 cycles. The fabricated device demonstrates an outstanding mechanical sensing performance and can accurately detect human physiological signals. Specifically, the device serves as a strain detector, recognizing different strain signals by monitoring the movement of fingers, arms, and thighs. This study provides critical insights into composite manufacturing with exceptional conductivity, flexibility and stability, which are essential properties for creating high-performance flexible sensors.

Multi-Pleated Alkalized Ti3 C2 Tx MXene-Based Sandwich-Like Structure Composite Nanofibers for High-Performance Sodium/Lithium Storage

The volume expansion of CoFe2 O4 anode poses a significant challenge in the commercial application of lithium/sodium-ion batteries (LIBs/SIBs). However, metal-organic-frameworks (MOF) offer superior construction of heterostructures with refined interfacial interactions and lower ion diffusion barriers in Li/Na storage. In this study, the CoFe2 O4 @carbon nanofibers derived from MOF are produced through electrospinning, in situ growth followed by calcination, which are then confined within an MXene-confined MOF-derived porous CoFe2 O4 @carbon composite architecture under alkali treatment. The CoFe2 O4 nanofibers anchor on the alkalized MXene that is decorated with the NaOH solution to form a multi-pleated structure. The sandwich-like structure of the composite effectively alleviates the volume expansion and shortens the Li/Na-ion diffusion path, which displays high capacity and outstanding rate performance as anode materials for LIBs/SIBs. As a consequence, the obtained CoFe2 O4 @carbon@alkalized MXene composite anode shows satisfied rate performance at current density of 10 A g-1 for LIBs (318 mAh·g-1 ) and 5 A g-1 for SIBs (149 mAh g-1 ). The excellent cycling performance is further demonstrated at a high current density, where it maintains a discharge capacity of 807 mAh g-1 at 2 A g-1 after 400 cycles for LIBs and 130 mAh g-1 at 1 A g-1 even after 1000 cycles for SIBs.

MXene-Embedded Electrospun Polymeric Nanofibers for Biomedical Applications: Recent Advances

Recently MXenes has gained immense attention as a new and exciting class of two-dimensional material. Due to their unique layered microstructure, the presence of various functional groups at the surface, earth abundance, and attractive electrical, optical, and thermal properties, MXenes are considered promising candidates for various applications such as energy, environmental, and biomedical. The ease of dispersibility and metallic conductivity of MXene render them promising candidates for use as fillers in polymer nanocomposites. MXene-polymer nanocomposites simultaneously benefit from the attractive properties of MXenes and the flexibility and facile processability of polymers. However, the potentiality of MXene to modify the electrospun nanofibers has been less studied. Understanding the interactions between polymeric nanofibers and MXenes is important to widen their role in biomedical applications. This review explores diverse methods of MXene synthesis, discusses our current knowledge of the various biological characteristics of MXene, and the synthesis of MXene incorporated polymeric nanofibers and their utilization in biomedical applications. The information discussed in this review serves to guide the future development and application of MXene-polymer nanofibers in biomedical fields.

Oxidation-Resistant MXene-Based Melamine Foam with Ultralow-Percolation Thresholds for Electromagnetic-Infrared Compatible Shielding

To effectively avoid the drawbacks of conventional metal-based electromagnetic interference (EMI) shielding materials such as high density and susceptibility to corrosion, a multifunctional melamine foam (MF) consisting of MXene/polydimethylsiloxane (PDMS) layers with ultralow percolation thresholds was designed through the electrostatic self-assembly and impregnation strategies. The prepared lightweight foams simultaneously show multifunctional properties including EMI shielding, infrared (IR) stealth, oxidation-resistance, and compression stability. Typically, this multifunctional foam exhibits an excellent EMI shielding efficiency (EMI SE) of 45.2 dB at X-band (8.2-12.4 GHz) with only 1.131 vol % MXene filler. Moreover, the temperature difference between the upper and lower surfaces of the foam can be maintained at 45 °C due to its unique three-dimensional (3D) porous structure and low infrared emissivity. The MF skeleton with MXene/PDMS (MFMXP) displays high hydrophobicity, which remains stable in EMI SE after 60 days of exposure to air. Additionally, it shows outstanding mechanical stability after 100 cycles of compression experiments. The lightweight stealth nanocomposite foams can operate stably in complex environments and show high potential for applications in high-tech fields such as wearable electronics, the military, and semiconductors, etc.

Electrically conductive porous MXene-polymer composites with ultralow percolation threshold via Pickering high internal phase emulsion templating strategy

HYPOTHESIS

Constructing a segregated network in electrically conductive polymer composites (ECPCs) is an effective method to lower the electrical percolation threshold. The segregated network structure can be formed naturally via polymerizing Pickering high internal phase emulsions (HIPEs) because solid particles are assembled at water-oil interfaces. However, most Pickering stabilizers show poor electrical conductivity. In this work, we propose a facile method to prepare lightweight ECPCs with well-controlled segregated structure via Ti₃C₂T_x-stabilized HIPE templating.

EXPERIMENTS

Hydrophilic Ti₃C₂T_x flakes are delicately hydrophobized with a double-chain cation surfactant. The morphology of Ti₃C₂T_x flakes is investigated by transmission electron microscopy (TEM) and atom force microscopy (AFM). The surface properties of modified Ti₃C₂T_x are characterized by zeta potential and water contact angle tests. The stability of Ti₃C₂T_x-stabilized emulsions, and the structure of prepared ECPCs are systematically investigated.

FINDINGS

Surface modified Ti₃C₂T_x flakes are used to stabilize water-in-oil (w/o) HIPEs for the first time. After the polymerization of continuous oil phase, ECPCs are successfully prepared with closed-cell porous structure. The pore size and size distribution of porous composites can be tailored by varying the content of Ti₃C₂T_x flakes. The Ti₃C₂T_x flakes are mainly immobilized at the water-oil interface and eventually form the segregated network in composites. Combining the unique segregated network and the outstanding metallic conductivity of Ti₃C₂T_x, the prepared porous polymer composites exhibit good conductivity even with ultralow Ti₃C₂T_x content of 0.016 vol%.

Anisotropic conductive networks for multidimensional sensing

In the past decade, flexible physical sensors have attracted great attention due to their wide applications in many emerging areas including health-monitoring, human-machine interfaces, smart robots, and entertainment. However, conventional sensors are typically designed to respond to a specific stimulus or a deformation along only one single axis, while directional tracking and accurate monitoring of complex multi-axis stimuli is more critical in practical applications. Multidimensional sensors with distinguishable signals for simultaneous detection of complex postures and movements in multiple directions are highly demanded for the development of wearable electronics. Recently, many efforts have been devoted to the design and fabrication of multidimensional sensors that are capable of distinguishing stimuli from different directions accurately. Benefiting from their unique decoupling mechanisms, anisotropic architectures have been proved to be promising structures for multidimensional sensing. This review summarizes the present state and advances of the design and preparation strategies for fabricating multidimensional sensors based on anisotropic conducting networks. The fabrication strategies of different anisotropic structures, the working mechanism of various types of multidimensional sensing and their corresponding unique applications are presented and discussed. The potential challenges faced by multidimensional sensors are revealed to provide an insightful outlook for the future development.