The development of wearable strain sensors with simultaneous large stretchability (strain >55%) and high sensitivity (gauge factor >100) remains a grand challenge to this day. Drawing on inspiration from nature, nacre has demonstrated outstanding mechanical properties, especially combining high strength and toughness, which is due in part to its delicate hierarchical layered architecture with rich interfacial interactions. We demonstrate that strain sensors based on this nacre-mimetic microscale “brick-and-mortar” architecture can simultaneously achieve ultrahigh sensitivity and large stretchability while performing well in linearity, reliability, long-term durability, and monotonicity. The bioinspired sensor demonstrated a gauge factor >200 over a range of working strains up to 83% and achieved a high gauge factor exceeding 8700 in the strain region of 76–83%. This successful combination of high sensitivity and large stretchability is attributed to (1) the microscale hierarchical architecture derived from the amalgamation of 2D titanium carbide (MXene) Ti3C2T x /1D silver nanowire “brick” and poly(dopamine)/Ni2+ “mortar” and (2) the synergistic toughing effects from interfacial interactions of hydrogen and coordination bonding, layer slippage, and molecular chain stretching. The synergistic behavior of the “brick” and “mortar” allows for controlled crack generation for high sensitivity but can also dissipate considerable loading energy to promote the stepwise propagation of cracks while stretching, guaranteeing the significant comprehensive sensing performance. Moreover, this bioinspired strain sensor is employed to monitor human activities under different motion states to demonstrate its feasibility for wearable, full-spectrum human health and motion monitoring systems.
While stretchable micro‐supercapacitors (MSCs) have been realized, they have suffered from limited areal electrochemical performance, thus greatly restricting their practical electronic application. Herein, a facile strategy of 3D printing and unidirectional freezing of a pseudoplastic nanocomposite gel composed of Ti3C2Tx MXene nanosheets, manganese dioxide nanowire, silver nanowires, and fullerene to construct intrinsically stretchable MSCs with thick and honeycomb‐like porous interdigitated electrodes is introduced. The unique architecture utilizes thick electrodes and a 3D porous conductive scaffold in conjunction with interacting material properties to achieve higher loading of active materials, larger interfacial area, and faster ion transport for significantly improved areal energy and power density. Moreover, the oriented cellular scaffold with fullerene‐induced slippage cell wall structure prompts the printed electrode to withstand large deformations without breaking or exhibiting obvious performance degradation. When imbued with a polymer gel electrolyte, the 3D‐printed MSC achieves an unprecedented areal capacitance of 216.2 mF cm−2 at a scan rate of 10 mV s−1, and remains stable when stretched up to 50% and after 1000 stretch/release cycles. This intrinsically stretchable MSC also exhibits high rate capability and outstanding areal energy density of 19.2 µWh cm−2 and power density of 58.3 mW cm−2, outperforming all reported stretchable MSCs.
The development of strain sensors with both large strain range (>50%) and high gauge factor (>100) is a grand challenge. High sensitivity requires material to perform considerable structural deformation under tiny strain, whereas high stretchability demands structural connection or morphological integrity for materials upon large deformation, yet both features are hard to be achieved in one thin film. A new 0D–1D–2D ternary nanocomposite–based strain sensor is developed that possesses high sensitivity in broad working strain range (gauge factor 2392.9 at 62%), low hysteresis, good linearity, and long‐term durability. The skin‐mountable strain sensor, fabricated through one‐step screen‐printing process, is made of 1D silver nanowire offering high electrical conductivity, 2D graphene oxide offering brittle layered structure, and 0D fullerene offering lubricity. The fullerene constitutes a critical component that lowers the friction between graphene oxide–based layers and facilitates the sliding between adjacent layers without hurting the brittle nature of the nanocomposite film. When stretching, layer slippage induced by fullerene can accommodate partial applied stress and boost the strain, while cracks originating and propagating in the brittle nanocomposite film ensure large resistance change over the whole working strain range. Such high comprehensive performance renders the strain sensor applicable to full‐spectrum human motion detection.
Although lithium (Li)-ion batteries have achieved great success in commercialization for sustainable and clean energy applications including portable electronics, electric transportation, and grid-scale energy storage, existing battery systems of graphitebased anodes and transition metal oxide-based cathodes hardly meet the increasing requirements for higher energy and power densities.  Li metal has a high theoretical capacity Metallic lithium (Li) is a promising anode for next-generation high-energydensity batteries, but its applications are still hampered due to the limited charging/discharging rate and poor cycling performance. Here, a hierarchical 3D porous architecture is designed with a binary network of continuous silver nanowires assembled on an interconnected 3D graphene skeleton as the host for Li-metal composite anodes, which offers a significant boost in both charging/discharging rates and long-term cycling performance for Li-metal batteries. This unique hierarchical binary network structure in conjunction with optimized material combination provides ultrafast, continuous, and smooth electron transportation channel and non-nucleation barrier sites to direct and confine Li deposition. It also offers outstanding mechanical strength and toughness to support massive Li deposition and buffer the internal stress fluctuations during long-term repeated Li stripping/plating thereby minimizing fundamental issues of dendrite formation and volume change even under ultrafast charging/discharging rates. As a result, the composite anode using this hierarchical host can work smoothly at an unprecedented high current density of 40 mA cm -2 over 1000 plating/stripping cycles with low overpotential (<120 mV) in symmetric cells. The as-constructed full cell, paired with LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode, also exhibits excellent rate capability and high-rate cycling stability.(3860 mAh g −1 ) and low electrochemical potential (−3.04 V vs the standard hydrogen electrode) and is thus perceived as an ideal anode for next-generation rechargeable batteries-especially for Li-sulfur and Li-oxygen battery systems.  However, the use of a Li-metal anode in advanced battery systems for stable and ultrafast charging/discharging is severely restricted by safety and cyclability concerns caused by dendritic Li formation, infinite volume change, and instability of solid electrolyte interphase (SEI). This has limited the practical use of Li-metal batteries for many decades.  Several strategies focused on constructing stable and uniform SEI layer on Li anode have been explored to tolerate the huge volume change and suppress the formation of dendritic Li. Examples include optimizing the electrolyte contents, modifying he Li anode surface, and developing artificial coatings on the anode surface. [10, Despite the great success achieved on the rational design of SEI layer, the nature of Li dendrite formation arising from inhomogeneous Li-ion flux distribution on planar Li foil or copp...
A solar-thermal water evaporation structure that can continuously generate clean water with high efficiency and good salt rejection ability under sunlight is highly desirable for water desalination, but its realization remains challenging. Here, a hierarchical solar-absorbing architecture is designed and fabricated, which comprises a 3D MXene microporous skeleton with vertically aligned MXene nanosheets, decorated with vertical arrays of metalorganic framework-derived 2D carbon nanoplates embedded with cobalt nano particles. The rational integration of three categories of photothermal materials enables broadband light absorption, efficient light to heat conversion, low heat loss, rapid water transportation behavior, and much-improved corrosion and oxidation resistance. Moreover, when assembling with a hydrophobic insulating layer with hydrophilic channel, the MXene-based solar absorber can exhibit effective inhibition of salt crystallization due to the ability to advect and diffuse concentrated salt back into the water. As a result, when irradiating under one sun, the solar-vapor conversion efficiency of the MXene-based hierarchical design can achieve up to ≈93.4%, and can remain over 91% over 100 h to generate clean vapor for stable and continuous water desalination. This strategy opens an avenue for the development of MXenebased solar absorbers for sustainable solar-driven desalination.
Lithium-iodine (Li-I 2 ) batteries are promising candidates for next-generation electrochemical energy storage systems due to their high energy density and the excellent kinetic rates of I 2 cathodes. However, dissolution of iodine and iodide has hindered their widespread adoption for practical applications. Herein, a Ti 3 C 2 T x MXene foam with a three-dimensional hierarchical porous architecture is proposed as a cathode-electrolyte interface layer in Li-I 2 batteries, enabling high-rate and ultrastable cycling performance at a high iodine content and loading mass. Theoretical calculations and empirical characterizations indicate that Ti 3 C 2 T x MXene sheets with high metallic conductivity not only provide strong chemical binding with iodine species to suppress the shuttle effect but also facilitate fast redox reactions during cell cycling. As a result, the Li-I 2 battery using a cathode with 70 wt % I 2 cycled stably for over 1000 cycles at a rate of 2 C, even at an ultrahigh loading mass of 5.2 mg cm −2 . To the best of the authors' knowledge, this is the highest reported loading at such a high iodine content. This work suggests that using a Ti 3 C 2 T x MXene interface layer can enable the design and application of high-energy Li-I 2 batteries.
Traditional covalent organic frameworks (COFs) are prepared via polymerization based on small molecular monomers. However, the employment of polymers as building blocks to construct COFs has not been reported yet. Herein, we create a new concept of polymer covalent organic frameworks (polyCOFs) formed by linear polymers as structural building blocks, which inherit the merits from both COFs and linear polymers. PolyCOFs represent a new category of porous COF materials that demonstrate good crystallinity and high stability. More importantly, benefiting from the flexibility and processability of a linear polymer, polyCOFs can spontaneously form defect-free, flexible, and freestanding membranes that exhibit excellent mechanical properties and undergo reversible mechanical transformation upon exposure to various organic vapors. For the first time, we demonstrated that polyCOF membranes can be used as artificial muscles to perform various complicated motions (e.g., lifting objects, doing “sit-ups”) triggered by vapors. This study bridges the gap between one-dimensional amorphous linear polymers and crystalline polymer frameworks and paves a new avenue to prepare stimuli-responsive actuators using porous COF materials.
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