Tracing Immunological Interaction in Trimethylamine N-Oxide Hydrogel-Derived Zwitterionic Microenvironment During Promoted Diabetic Wound Regeneration.

The diabetic wound healing is challenging due to the sabotaged delicate balance of immune regulation via an undetermined pathophysiological mechanism, so it is crucial to decipher multicellular signatures underlying diabetic wound healing and seek therapeutic strategies. Here, this work develops a strategy using novel trimethylamine N-oxide (TMAO)-derived zwitterionic hydrogel to promote diabetic wound healing, and explore the multi-cellular ecosystem around zwitterionic hydrogel, mapping out an overview of different cells in the zwitterionic microenvironment by single-cell RNA sequencing. The diverse cellular heterogeneity is revealed, highlighting the critical role of macrophage and neutrophils in managing diabetic wound healing. It is found that polyzwitterionic hydrogel can upregulate Ccl3+ macrophages and downregulate S100a9+ neutrophils and facilitate their interactions compared with polyanionic and polycationic hydrogels, validating the underlying effect of zwitterionic microenvironment on the activation of adaptive immune system. Moreover, zwitterionic hydrogel inhibits the formation of neutrophil extracellular traps (NETs) and promotes angiogenesis, thus improving diabetic wound healing. These findings expand the horizons of the sophisticated orchestration of immune systems in zwitterion-directed diabetic wound repair and uncover new strategies of novel immunoregulatory biomaterials.

Biobased Inks Based on Cuttlefish Ink and Cellulose Nanofibers for Biodegradable Patterned Soft Actuators.

Soft actuators with stimuli-responsive and reversible deformations have shown great promise in soft robotics. However, some challenges remain in existing actuators, such as the materials involved derived from nonrenewable resources, complex and nonscalable preparation methods, and incapability of complex and programmable deformation. Here, a biobased ink based on cuttlefish ink nanoparticles (CINPs) and cellulose nanofibers (CNFs) was developed, allowing for the preparation of biodegradable patterned actuators by direct ink writing technology. The hybrid CNF/CINP ink displays good rheological properties, allowing it to be accurately printed on a variety of flexible substrates. A bilayer actuator was developed by printing an ink layer on a biodegradable poly(lactic acid) film using extrusion-based 3D printing technology, which exhibits reversible and large bending behavior under the stimuli of humidity and light. Furthermore, programmable and reversible folding and coiling deformations in response to stimuli have been achieved by adjusting the ink patterns. This work offers a fast, scalable, and cost-effective strategy for the development of biodegradable patterned actuators with programmable shape-morphing.

Multistimuli-Responsive Actuators Derived from Natural Materials for Entirely Biodegradable and Programmable Untethered Soft Robots.

Untethered soft robots have attracted growing attention due to their safe interaction with living organisms, good flexibility, and accurate remote control. However, the materials involved are often nonbiodegradable or are derived from nonrenewable resources, leading to serious environmental problems. Here, we report a biomass-based multistimuli-responsive actuator based on cuttlefish ink nanoparticles (CINPs), wood-derived cellulose nanofiber (CNF), and bioderived polylactic acid (PLA). Taking advantage of the good photothermal conversion performance and exceptionally hygroscopic sensitivity of the CINPs/CNF composite (CICC) layer and the opposite thermally induced deformation behavior between the CICC layer and PLA layer, the soft actuator exhibits reversible deformation behaviors under near-infrared (NIR) light, humidity, and temperature stimuli, respectively. By introducing patterned or alignment structures and combining them with a macroscopic reassembly strategy, diverse programmable shape-morphing from 2D to 3D such as letter-shape, coiling, self-folding, and more sophisticated 3D deformations have been demonstrated. All of these deformations can be successfully predicted by finite element analysis (FEA) . Furthermore, this actuator has been further applied as an untethered grasping robot, weightlifting robot, and climbing robot capable of climbing a vertical pole. Such actuators consisting entirely of biodegradable materials will offer a sustainable future for untethered soft robots.

Dual Protective Porous Ti3 C2 Tx MXene/Polyimide Composite Film for Thermal Insulation and Electromagnetic Interference Shielding.

The thriving 5G communication technology leads to the high demand for EMI shielding materials and thermal management materials. Particularly, portable thermal-sensitive electronic devices have more stringent requirements for thermal insulation performances. In most cases, ultrathin EMI shielding materials integrated with ultralow thermal conductivity are not easy to be achieved. To overcome this obstacle, dual protective porous composite films based on Ti3 C2 Tx MXene and polyimide are fabricated by sacrificing polymethyl methacrylate (PMMA) templates. By optimizing the contact thermal resistance and Kapitza resistance, the composite film presents superior thermal insulation performances with a thermal conductivity of 0.0136 W m-1 K-1 . Moreover, the hybrid porous film maintains superior EMI shielding effectiveness of 63.0 dB and high SSE/t of 31651.2 dB cm2 g-1 . Nevertheless, the excellent active and passive heating ability based on Joule heating and photothermal conversion makes the composite film an ideal portable material for thermal management. This work sheds light on designing thermal management materials and EMI shielding materials for cutting-edge electronic devices.

Achieving fast interfacial solar vapor generation and aqueous acid purification using Ti3C2Tx MXene/PANI non-woven fabrics.

Acid rain is a worldwide problem because of the emission of acidic gases into the atmosphere, leading to the acidification of first-order streams and aggravation of fresh water shortage. Therefore, it is of great importance to develop an environmentally friendly method for removing acid from water. Herein, an advanced technology that can achieve aqueous acid purification using solar energy is realized with Ti3C2Tx MXene/polyaniline (PANI) hybrid non-woven fabrics (MPs) through interfacial solar vapor generation, with PANI acting as an acid absorber through the doping process. Benefiting from the porous structure and crumpled micro-surface of MPs, a high evaporation rate of 2.65 kg m-2 h-1 with an efficiency of 93.7% can be achieved under one-sun illumination. Moreover, MPs present an even higher evaporation rate of 2.83 kg m-2 h-1 in high concentration aqueous acid and can generate clean water with a pH higher than 6.5. More importantly, thanks to the unique reversible doping process of PANI, when used as an aqueous acid purifier, MPs show good stability and reusability after dedoping. Our work sheds light on an efficient strategy for dealing with aqueous acid and acid rain.

Deletion of Arrb2 Down-regulates Autophagy in the Mouse Hippocampus via Akt-mTOR Pathway Activation.

The cytoplasmic multifunctional adaptor protein ß-arrestin 2 (Arrb2) is involved in the occurrence of various nervous system diseases, such as Alzheimer's disease and Parkinson's disease. Previous laboratory studies have shown that the expression and function of the Arrb2 gene was increased in valproic acid-induced autistic mice models. However, few reports have examined the possible role of Arrb2 in the pathogenesis of autism spectrum disorder. Therefore, Arrb2-deficient (Arrb2-/-) mice were further studied to uncover the physiological function of Arrb2 in the nervous system. In this study, we found that Arrb2-/- mice had normal behavioral characteristics compared with wild-type mice. The autophagy marker protein LC3B was decreased in the hippocampus of Arrb2-/- mice compared to wild-type mice. Western blot analysis revealed that deletion of Arrb2 caused hyperactivation of Akt-mTOR signaling in the hippocampus. In addition, abnormal mitochondrial dysfunction was observed in Arrb2-/- hippocampal neurons, which was characterized by a reduction in mitochondrial membrane potential and adenosine triphosphate production and an increase in reactive oxygen species levels. Therefore, this study elucidates the interaction between Arrb2 and the Akt-mTOR signaling pathway and provides insights into the role of Arrb2 in hippocampal neuron autophagy.

Genetic mutation of TRPV2 induces anxiety by decreasing GABA-B R2 expression in hippocampus.

Transient receptor potential vanillic acid 2 (TRPV2) are well recognized for their contributions to neuronal development, cardiac function, immunity and cancer. However, the precise roles for this thermo TRPchannels in neurological disorder remain unknown. In this study, we employed the CRISPR/Cas9 system to generate genetic mutations of TRPV2. Genetic mutation of TRPV2 resulted in autistic-like phenotypes in mice accompanied with the disordered electrical signals recorded by multi-channels in vivo. To determine possible molecular mechanisms, western blotting was further used to assess the possible involvement of several autism-related proteins. The significantly decreased expression of the R2 subunit of the GABA-B receptor in the hippocampus was observed. Together, our findings suggest that genetic mutation of TRPV2 induces autism-like behavior, results in decreased expression of the R2 subunit of the GABA-B receptor.

ß-arrestin2 mediates the hippocampal dopaminergic system in autistic mouse through the ERK signaling pathway.

Autism is a complex neurodevelopmental disease that may be caused by genetic and environmental factors, that are incompletely understood. Overactivation of dopaminergic receptors can lead to autistic-like behavior. ß-arrestin2 (Arrb2) is a scaffolding protein of the arrestin family, which function as cytosolic multifunctional adapter proteins that activate cell signal transduction and mediate the signal termination and endocytosis of G-protein-coupled receptors (GPCRs) complexes. In this study, we established an Arrb2 knockout (Arrb2-/-) mouse to explore the biological function of Arrb2 in autistic-like behavior caused by abnormality in the dopaminergic system. We found that Arrb2-/- mice did not exhibit the autistic-like behavior normally induced by SKF38393, an agonist of the dopamine receptor 1 (D1R). Compared with wild-type (WT) untreated mice, the SKF38393-treated WT mice and Arrb2-/- mice, with or without SKF38393 treatment, showed abnormalities on electroencephalography (EEG) and increased stimulation of the phosphorylated form of extracellular signal-regulated kinase (p-ERK) via the PKA/Rap1/B-Raf/MEK pathway. These results demonstrated that Arrb2 regulated the dopaminergic system through the ERK signaling pathway in the occurrence and development of autism, and that targeted deletion of Arrb2 impeded the development of autistic-like behavior.

An ultra-broad-range pressure sensor based on a gradient stiffness design.

The question of how to make artificial intelligence robots perceive the power of "light as a feather" and "heavy as a mountain" at the same time has always been a goal that people are striving to achieve. However, pressure sensors, the key components of electronic equipment, are often unable to incorporate high sensitivity and wide range performance. Here, we proposed a "gradient stiffness design" strategy to prepare a kind of carbon nanotube sponge with a stiffness difference of up to 254 times between different layers, but still maintaining an integral conductive network without delamination. This gradient stiffness structure sponge shows prominent sensing properties with ultra-broad range (from 0.0022 MPa to 5.47 MPa) and high sensitivity. The low stiffness layer can detect low stress (0.0022 MPa) with high sensitivity of 0.765 MPa-1, and the high stiffness layer can greatly extend the sensing range to an unprecedentedly high value (5.47 MPa). It can concisely detect various motions with different stress, from slight clamping of fragile fries by the robot fingers to heavily stomping motions by a 90 kg person. Moreover, a series of human movements from small-scale to large-scale can be also monitored, revealing the great potential of this gradient stiffness structure in future sensing research.

Flame-retardant MXene/polyimide film with outstanding thermal and mechanical properties based on the secondary orientation strategy.

With the development of multifunction and miniaturization in modern electronics, polymeric films with strong mechanical performance and high thermal conductivity are urgently needed. Two-dimensional transition metal carbides and nitrides (MXenes) have attracted extensive attention due to their tunable surface chemistry, layered structure and charming properties. However, there are few studies on using MXenes as fillers to enhance polymer properties. In this paper, we fabricate a three-dimensional foam by the freeze-drying method to enhance the interfacial interaction between adjacent MXene sheets and polyimide (PI) macromolecules, and then a composite film with a dense and well-ordered layer-by-layer structure is produced by the hot-pressing process. Based on the secondary orientation strategy, the resultant MXene/PI film exhibits an enhanced thermal conductivity of 5.12 ± 0.37 W m-1 K-1 and tensile strength of 102 ± 3 MPa. Moreover, the composite film has good flexibility and flame retardancy owing to the synergistic effect of MXene sheets and PI chains. Hence, the MXene/PI composite film with the properties of flexibility, flame-retardancy, high mechanical strength and efficient heat transmission is expected to be used as the next thermal management material in a variety of applications.

A Photoactuator Based on Stiffness-Variable Carbon Nanotube Nanocomposite Yarn.

Actuators based on carbon nanotube (CNT) yarn have attracted extensive attention due to their great properties and potential applications such as artificial muscles, sensors, intelligent robots, and so on. However, the CNT yarn actuators with one-dimensional structure were often only used to drive through electrochemical, thermal, or electrical stimulation, which limits the applications of CNT yarn actuators. In addition, the slow response speed, low output stress, uncontrollable driving deformation, and self-recovery without an external stimulus are also great challenges. Here, we propose a photoactuator with large output stress, fast response speed, large and reversible driving deformation, and good reusability based on stiffness-variable CNT nanocomposite yarn (CNT-NCY). Such a CNT-NCY photoactuator can achieve torsional and contractive actuation under irradiation of near-infrared (NIR) light; it is important that the actuation is reversible and controllable. The maximum rotation rate of the CNT-NCY photoactuator during the torsional actuation is about 45 rpm, and the contractive deformation can reach more than 9%. This CNT-NCY photoactuator can create more than 12 MPa output stress, which is 40 times higher than that of the human skeletal muscle. The driving mechanism of this CNT-NCY photoactuator has been analyzed, and its potential application has also been demonstrated.

Active control of graphene-based membrane-type acoustic metamaterials using a low voltage.

Membrane-type acoustic metamaterials for acoustic insulation applications have been attracting ever increasing attention. However, the first anti-resonant frequency of these acoustic metamaterials is fixed once the membrane type is chosen. Here, we propose a novel yet convenient strategy to actively adjust the anti-resonant frequency of the membrane. The poly(vinyl alcohol)/graphene (PVA/GR) nanocomposite membrane is introduced into the acoustic metamaterial, the effective modulus of which is tunable by applying an external electric field. As a result, the first anti-resonant frequency of membrane-type acoustic metamaterials can be actively tuned between 369.2 to 420 Hz, leading to excellent sound attenuation properties. The noise reduction frequency can be actively modulated by DC voltage. Moreover, the change in frequency is consistent with the modulus variation of the PVA/GR nanocomposite membrane when the graphene concentration is varied. In addition, the conductive PVA/GR nanocomposite membrane also exhibits good electromagnetic interference shielding performance in the frequency range of 8-12 GHz. Being actively tunable by an external electric field, this PVA/GR nanocomposite membrane-based acoustic metamaterial is very promising for use in frequency-tunable acoustic insulation applications.

Artificial muscle with reversible and controllable deformation based on stiffness-variable carbon nanotube spring-like nanocomposite yarn.

Carbon nanotube yarn actuators are in great demand for flexible devices or intelligent applications. Artificial muscles based on carbon nanotube yarn have achieved great progress over past decades. However, uncontrollable, small deformations and relatively slow deformation recovery are still great challenges for carbon nanotube yarn artificial muscles. Here we propose an artificial muscle based on a stiffness-variable carbon nanotube spring-like nanocomposite yarn. This nanocomposite yarn can be fabricated as artificial muscles by directly inflating epoxy resin on spring-like carbon nanotube yarn, and it shows a rapid response, and reversible and controllable deformation. The driving mechanism of the nanocomposite yarn artificial muscle is based on the change in the resin modulus controlled by Joule heat. This novel nanocomposite yarn artificial muscle can work at low voltages (≤0.8 V), and the whole reversible driving process is completed within 5 seconds (the deformation recovery process is about 2 seconds). The strain of the nanocomposite yarn artificial muscle is controlled by applied voltages, and the maximum strain can reach more than 12%. The novel nanocomposite yarn artificial muscle can produce output forces more than 20 times higher than human skeletal muscle. This CNT nanocomposite yarn artificial muscle with a spiral structure shows potential applications for actuators, sensors and micro robots.

Electromagnetic and acoustic double-shielding graphene-based metastructures.

Nowadays, acoustic and electromagnetic pollution problems are becoming increasingly serious. Thus, electromagnetic interference (EMI) shielding materials and high acoustic insulation materials are urgently needed. EMI shielding materials and high acoustic insulation materials or structures have been rapidly developed. However, electromagnetic yet acoustic shielding (double-shielding) structures have not been reported so far. Herein, we propose a novel metastructure based on a graphene paper and artificial honeycomb, which exhibits not only excellent electromagnetic interference shielding property but also robust acoustic shielding efficiency. The EMI shielding effectiveness of the metastructure is up to 74 dB in a broad range from 2.6 to 26.5 GHz. The acoustic shielding effectiveness reaches 25 dB from 200 to 1500 Hz. It is worth noting that the effectiveness of acoustic shielding reaches up to 40 dB at very low frequency of 200 Hz. A typical double-shielding application demo was assembled to prove the attenuation performance against electromagnetic waves and sound. Our unique metastructure is very promising for protecting from electromagnetic and acoustic pollution.

Lightweight, mechanically flexible and thermally superinsulating rGO/polyimide nanocomposite foam with an anisotropic microstructure.

We report that lightweight, anisotropic, mechanically flexible, and high performance thermally insulating materials are fabricated by the assembly of graphene oxide (GO) and polyimide (PI). With an appropriate ratio between GO and PI building blocks, the rGO/PI thermally insulating material exhibits hierarchically aligned microstructures with high porosity. These microstructures endow the rGO/PI nanocomposite with low mass density and super-insulating property (extremely low thermal conductivity of 0.012 W m-1 K-1 in the radial direction). Meanwhile, the introduction of PI enhances the mechanical strength and thermal stability of rGO foam. Our rGO/PI nanocomposites as super-insulating foams with a low thermal conductivity are highly attractive for potential thermal insulation applications in aerospace, wearable devices, and energy-efficient buildings.

Superflexible Interconnected Graphene Network Nanocomposites for High-Performance Electromagnetic Interference Shielding.

Graphene-enhanced polymer matrix nanocomposites are attracting ever increasing attention in the electromagnetic (EM) interference (EMI) shielding field because of their improved electrical property. Normally, the graphene is introduced into the matrix by chemical functionalization strategy. Unfortunately, the electrical conductivity of the nanocomposite is weak because the graphene nanosheets are not interconnected. As a result, the electromagnetic interference shielding effectiveness of the nanocomposite is not as excellent as expected. Interconnected graphene network shows very good electrical conduction property, thus demonstrates excellent electromagnetic interference shielding effectiveness. However, its brittleness greatly limits its real application. Here, we propose to directly infiltrate flexible poly(dimethylsiloxane) (PDMS) into interconnected reduced graphene network and form nanocomposite. The nanocomposite is superflexible, light weight, enhanced mechanical and improved electrical conductive. The nanocomposite is so superflexible that it could be tied as spring-like sucker. Only 1.07 wt % graphene significantly increases the tensile strengths by 64% as compared to neat PDMS. When the graphene weight percent is 3.07 wt %, the nanocomposite has the more excellent electrical conductivity up to 103 S/m, thus more outstanding EMI shielding effectiveness of around 54 dB in the X-band are achieved, which means that 99.999% EM has been shielded by this nanocomposite. Bluetooth communication testing with and without our nanocomposite confirms that our flexible nanocomposite has very excellent shielding effect. This flexible nanocomposite is very promising in the application of wearable devices, as electromagnetic interference shielding shelter.

Superlight, Mechanically Flexible, Thermally Superinsulating, and Antifrosting Anisotropic Nanocomposite Foam Based on Hierarchical Graphene Oxide Assembly.

Lightweight, high-performance, thermally insulating, and antifrosting porous materials are in increasing demand to improve energy efficiency in many fields, such as aerospace and wearable devices. However, traditional thermally insulating materials (porous ceramics, polymer-based sponges) could not simultaneously meet these demands. Here, we propose a hierarchical assembly strategy for producing nanocomposite foams with lightweight, mechanically flexible, superinsulating, and antifrosting properties. The nanocomposite foams consist of a highly anisotropic reduced graphene oxide/polyimide (abbreviated as rGO/PI) network and hollow graphene oxide microspheres. The hierarchical nanocomposite foams are ultralight (density of 9.2 mg·cm-3) and exhibit ultralow thermal conductivity of 9 mW·m-1·K-1, which is about a third that of traditional polymer-based insulating materials. Meanwhile, the nanocomposite foams show excellent icephobic performance. Our results show that hierarchical nanocomposite foams have promising applications in aerospace, wearable devices, refrigerators, and liquid nitrogen/oxygen transportation.

Electrically and thermally conductive underwater acoustically absorptive graphene/rubber nanocomposites for multifunctional applications.

Graphene is ideal filler in nanocomposites due to its unique mechanical, electrical and thermal properties. However, it is challenging to uniformly distribute the large fraction of graphene fillers into a polymer matrix because graphene is not easily functionalized. We report a novel method to introduce a large fraction of graphene into a styrene-butadiene rubber (SBR) matrix. The obtained graphene/rubber nanocomposites were mechanically enhanced, acoustically absorptive under water, and electrically and thermally conductive. The Young's modulus of the nanocomposites was enhanced by over 30 times over that for rubber. The electrical conductivity of nanocomposites was ≤219 S m-1 with 15% volume fraction of graphene content, and exhibited remarkable electromagnetic shielding efficiency of 45 dB at 8-12 GHz. The thermal conductivity of the nanocomposites was ≤2.922 W m-1 k-1, which was superior to the values of thermally conductive silicone rubber thermal interface materials. Moreover, the nanocomposites exhibited excellent underwater sound absorption (average absorption coefficient >0.8 at 6-30 kHz). Notably, the absorption performance of graphene/SBR nanocomposites increased with increasing water pressure. These multifunctional graphene/SBR nanocomposites have promising applications in electronics, thermal management and marine engineering.

Stiff, Thermally Stable and Highly Anisotropic Wood-Derived Carbon Composite Monoliths for Electromagnetic Interference Shielding.

Electromagnetic interference (EMI) shielding materials for electronic devices in aviation and aerospace not only need lightweight and high shielding effectiveness, but also should withstand harsh environments. Traditional EMI shielding materials often show heavy weight, poor thermal stability, short lifetime, poor tolerance to chemicals, and are hard-to-manufacture. Searching for high-efficiency EMI shielding materials overcoming the above weaknesses is still a great challenge. Herein, inspired by the unique structure of natural wood, lightweight and highly anisotropic wood-derived carbon composite EMI shielding materials have been prepared which possess not only high EMI shielding performance and mechanical stable characteristics, but also possess thermally stable properties, outperforming those metals, conductive polymers, and their composites. The newly developed low-cost materials are promising for specific applications in aerospace electronic devices, especially regarding extreme temperatures.

Shape-memory polymer nanocomposites with a 3D conductive network for bidirectional actuation and locomotion application.

Electrical stimulation of shape-memory polymers (SMPs) has many advantages over thermal methods; creating an efficient conductive path through the bulk polymers is essential for developing high performance electroactive systems. Here, we show that a three-dimensional (3D) porous carbon nanotube sponge can serve as a built-in integral conductive network to provide internal, homogeneous, in situ Joule heating for shape-memory polymers, thus significantly improving the mechanical and thermal behavior of SMPs. As a result, the 3D nanocomposites show a fast response and produce large exerting forces (with a maximum flexural stress of 14.6 MPa) during shape recovery. We further studied the construction of a double-layer composite structure for bidirectional actuation, in which the shape change is dominated by the temperature-dependent exerting force from the top and bottom layer, alternately. An inchworm-type robot is demonstrated whose locomotion is realized by such bidirectional shape memory. Our large stroke shape-memory nanocomposites have promising applications in many areas including artificial muscles and bionic robots.