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A tetragonal C4N (t-C4N) structure was predicted via CALYPSO code, and the effects of pressure on its structural and mechanical properties were studied. The results show that t-C4N is different from various 2D CxNy compounds with a new type 3D crystal structure, which is similar to diamond. Bulk t-C4N is equipped with excellent elastic properties. When the pressure is increased from 0 GPa to 350 GPa, its bulk modulus B, shear modulus G and Young's modulus E are increased from 426.9 GPa to 1123.1 GPa, 371.4 GPa to 582.9 GPa and 863.7 GPa to 1490.9 GPa, respectively. The anisotropic Bmax, Gmax and Emax are increased from 582.38 GPa to 1751.41 GPa, 478.29 GPa to 1033.97 GPa and 1281.26 GPa to 2490.14 GPa, respectively. When the pressure is 0 GPa, the hardness calculated by Chen's and Tian's models are 51.15 GPa and 51.81 GPa, respectively. Its ideal tensile strength in [111] orientation is the smallest (63.46 GPa), which indicates that the (111) planes allow easy cleavage. The smallest ideal shear strength (67.98 GPa) can be obtained in the (111)[1 0] orientation, which suggests its theoretical hardness is about 67.98 GPa. Due to its excellent mechanical properties, t-C4N can be used as an industrial superhard material.

Cellulose, as a component of green plants, becomes attractive for fabricating biocompatible flexible functional devices but plagued by hydrophilic properties which make it easily break down in water by poor mechanical stability. Here we report a class of SiO2-nanoparticle-decorated bacteria-cellulose meta-skin with a superior stability in water, excellent machining property, ultrathin thickness, and bacteria repairing capacity. We further develop the methodology of meta-skin kirigami that can generate intricate patterns of ~10 μm precision. Benefited from the ultrasound insulation of the surface Cassie-Baxter states, we utilize the meta-skin kirigami to design and fabricate ultrathin (~ 20 μm) and super-light (< 20 mg) chip-scale devices, such as nonlocal holographic meta-lens and the 3D imaging meta-lens, realizing complicated acoustic holograms and high-resolution 3D ultrasound imaging in the far field. The cellulose-based meta-skin kirigami opens the way for exploiting flexible and bio-degradable soft metamaterial devices with functionality customization and key applications in advanced biomedical engineering technologies.

3D microstructured biomaterials are favorable in tissue engineering due to their superior guidance to cellular activities. Herein, we developed a 3D microstructured bacterial cellulose (BC) with arranged fibers by controlling Acetobacter xylinum through an electric field (EF) application. The real-time video analysis showed that EF directed the migration of A. xylinum and increased its migration speed with the increased EF. The bacteria quickly changed direction with high motility in response to the switch on/off of the EF. In the long-term EF stimulation (ES), bacterial cells were oriented along the direction of EF while bacteria simultaneously produced nanocellulose, resulting in three-dimensional (3D) networks with aligned fibers. Moreover, the prepared 5 mA-BC hydrogels presented the ordered 3D microstructure with significantly higher fiber alignment and diameter than the NO EF-BC hydrogels. The in vitro biological evaluation demonstrated that the 5 mA-BC hydrogels were biocompatible whereon NIH3T3 cells proliferated along the direction of fiber alignment. These findings demonstrate that ES provides a promising strategy for the natural fabrication of aligned 3D microstructured BC to guide cellular activities for tissue engineering.

Deterioration in the environmental ecosystems through the depletion of nonrenewable resources and the burden of deleterious contaminants is considered a global concern. To this end, great interest has been shown in the use of renewable and environmentally-friendly reactive materials dually to promote environmental sustainability and cope with harmful contaminants. Among the different available options, the use of nanocellulose (NC) as an environmentally benign and renewable natural nanomaterial is an attractive candidate for environmental remediation owing to its miraculous physicochemical characteristics. This review discusses the intrinsic properties and the structural aspects of different types of NC, including cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), and bacterial cellulose (BC) or bacterial nanocellulose (BNC). Also, the different modification strategies involving the functionalization or hybridization of NC by using different functional and reactive materials aimed at wastewater remediation have been elaborated. The modified or hybridized NC has been explored for its applications in the removal or degradation of aquatic contaminants through adsorption, filtration, coagulation, catalysis, photocatalysis, and pollutant sensing. This review highlights the role of NC in the modified composites and describes the underlying mechanisms involved in the removal of contaminants. The life-cycle assessment (LCA) of NC is discussed to unveil the hidden risks associated with its production to the final disposal. Moreover, the contribution of NC in the promotion of waste management at different stages has been described in the form of the five-Rs strategy. In summary, this review provides rational insights to develop NC-based environmentally-friendly reactive materials for the removal and degradation of hazardous aquatic contaminants.

Microneedles (MNs) have attracted the interest of researchers. Polymeric MNs offer tremendous promise as drug delivery vehicles for bio-applications because of their high loading capacity, strong patient adherence, excellent biodegradability and biocompatibility, low toxicity, and extremely cheap cost. Incorporating enhanced-property nanomaterials into polymeric MNs matrix increases their features such as better mechanical strength, sustained drug delivery, lower toxicity, and higher therapeutic effects, therefore considerably increasing their biomedical application. This paper discusses polymeric MN fabrication techniques and the present status of polymeric MNs as a delivery method for enhanced drug delivery in cancer therapeutic applications. Furthermore, the opportunities and challenges of polymeric MNs for improved drug delivery in cancer therapy are highlighted.

Chronic wounds are associated with infectious microbial complex communities called biofilms. The management of chronic wound infection is limited by the complexity of selecting an appropriate antimicrobial dressing with antibiofilm activity due to antimicrobial resistance in biofilms. Herein, the in situ developed bacterial cellulose/poly(vinyl alcohol) (BC-PVA) composite is ex situ modified with genipin-crosslinked silk sericin (SS) and azithromycin (AZM) (SSga). The composite is evaluated as a wound dressing material for preventing the development, dispersion, and/or eradication of microbial biofilm. Fourier transform infrared spectroscopy confirms the intermolecular interactions between the components of BC-PVA@SSga scaffolds. The addition of PVA during BC production significantly increases the porosity from 53.5% ± 2.3% to 83.5% ± 2.9%, the pore size from 2.3 ± 1.9 to 16.8 ± 4.5 µm, the fiber diameter from 35.5 ± 10 to 120 ± 27.4 nm, and improves the thermal stability and flexibility. Studies using bacteria and fungi indicate high inhibition and disruption of biofilms upon AZM addition. In vitro biocompatibility analysis confirms the nontoxic nature of BC-PVA@SSga toward HaCaT and NIH3T3 cells, whereas the addition of SS enhances cell proliferation. The developed BC-PVA@SSga accelerates wound healing in the infected mouse model, thus can be a promising wound dressing biomaterial.

Glycolic acid (GA), as an anti-aging skincare ingredient, plays a pivotal role in anti-aging treatment. However, its benefits could be overshadowed due to its side effects including skin burning and irritation when overused. Bacterial cellulose (BC) is a highly pure form of cellulose, biosynthesized in the form of a swollen membrane by several kinds of bacteria that was demonstrated to modulate the release of model drugs owing to its porous and 3D fibrous network structure, and glycerol (GL), as a plasticizer, could enhance the controlled drug delivery. Herein, we report a topical controlled drug delivery system based on BC membrane, GA and GL for controlling sustainable release of GA to reduce its side effects on the skin, while maintaining its prolonged and maximum therapeutic effect. The results showed that the incorporation of GL increased the malleability and flexibility of BC/GA/GL membrane, as compared with BC/GA membrane. In addition, the GL enhanced the control of the GA delivery, as evidenced by a higher swelling capacity and thereby a slower release of the GA from BC/GA/GL membrane. More importantly, in vitro study indicated that both BC/GA and BC/GA/GL membranes could effectively stimulate endogenous collagen synthesis in NIH3T3 cells owing to the release of GA, and that BC/GA/GL membrane is more conducive to a long-term cell adhesion, spreading, and proliferation of NIH3T3 and HaCaT cells due to its lower and sustainable release of GA than BC/GA membrane. This study suggests the BC/GL/GA composite membrane holds great promise as an appealing platform to control the release of GA to greatly promote renewal of skin cells for effective anti-aging treatment.

The interface properties of CeAlO3 (110)/NbC (111) were calculated by the first-principles and the refinement of CeAlO3 on NbC in hypereutectic Fe–Cr–C–Nb hardfacing alloy was demonstrated by experiments. The calculation results show that the mismatch of CeAlO3 (110)/NbC (111) is 7.2%, which indicates that the interface between CeAlO3 (110) and NbC (111) is a semi-coherent interface. Then, 11 layer CeAlO-terminated CeAlO3 (110) surface was selected to build interface with NbC (111) surface, whose surface energy is 0.380 eV/A2. Because of the instability of O-terminated CeAlO3 (110) surface, its surface energy cannot achieve convergence. 6 kinds of interfaces between CeAlO3 (110)/NbC (111) were constructed, in which, interface-3 is the most stable with strong ionic and covalent bonds. Theoretically, CeAlO3 can act as the heterogeneous nucleation site for NbC. The experimental results show that the (Cr, Fe)7C3, NbC and γ-Fe phases exist in hypereutectic Fe–Cr–C–Nb–CeAlO3 hardfacing alloys. When CeAlO3 was added into the alloy, NbC can be refined.

Superhydrophobic surfaces repel water and other liquids such as tissue fluid, blood, urine, and pus, which can open up a new avenue for the development of biomedical devices and has led to promising advances across diverse fields, including plasma separator devices, blood-repellent sensors, vascular stents, and heart valves. Here, the fabrication of superhydrophobic liquid-solid contact triboelectric nanogenerators (TENGs) and their biomedical applications as droplet sensors are reported. Triboelectrification energy can be captured and released when droplets are colliding or slipping on the superhydrophobic layer. The developed superhydrophobic TENG possesses multiple advantages in terms of simple fabrication, bendability, self-cleaning, self-adhesiveness, high sensitivity, and repellency to not only water but also a variety of solutions, including blood with a contact angle of 158.6°. As a self-powered sensor, the developed prototypes of a drainage bottle droplet sensor and a smart intravenous injection monitor based on the superhydrophobic liquid-solid contact TENG can monitor the clinical drainage operation and intravenous infusion in real time, respectively. These prototypes suggest the potential merit of this superhydrophobic liquid-solid contact TENG in clinical application, paving the way for accurately monitoring clinical drainage operations and intravenous injection or blood transfusion in the future.

Additive manufacturing of composites offers a potential for a new level of control over a material’s structure at the microscale. The focus of this work is a 2-hydroxyethyl methacrylate (HEMA)–based gelation system with orderly distributed carbon nanotubes (CNTs). CNTs undergo shear-induced alignment during printing process, and retain their orientation after the polymerisation of HEMA monomers, thereby, forming a nanocomposite with anisotropic mechanical and electrical properties. It is characterised with an intensive programme of mechanical tests including quasistatic uniaxial stretching, and dynamic cyclic loadings, as well as its four-terminal sensing of conductive characteristics. A coupling effect of mechanical and electrical properties is also studied. The experimental findings are discussed in detail and demonstrate that the orientation of CNTs affects both the mechanical and electrical conductive properties of the nanocomposites in terms of its ultimate strength, resistivity, and a piezoresistive coefficient. Understanding of anisotropic electromechanical properties of printed PHEMA-CNT hydrogel nanocomposite will ultimately underpin the development of smart soft materials for diverse applications, such as biomimetic nucleus pulposus or flexible electronics.

Currently, various electronic devices make our life more and more safe, healthy, and comfortable, but at the same time, they produce a large amount of nondegradable and nonrecyclable electronic waste that threatens our environment. In this work, we explore an environmentally friendly and flexible mechanical sensor that is biodegradable and recyclable. The sensor consists of a bacterial cellulose (BC) hydrogel as the matrix and imidazolium perchlorate (ImClO

To solve the problems of heavy protection tasks and low operational intelligence in China's apple production, this paper designs a crawler-type agricultural robot dedicated to the apple orchard, which is easy to obtain growth information and plant protection of fruit trees in apple orchards. Based on the working environment of the agricultural robot, the parameter indexes are designed; the motion model of the lifting sprayer is established and the length dimension of the lifting frame is obtained; the parameter requirements of the robot's driving motor are derived based on its force and motion analysis; the control system of the robot is designed using the control flow chart. The simulation results show that the structure and control system of the robot meet the design requirements. The design is also of reference value for the design of other fruit tree protection robots.

In this work, the (Nb,Ti)C reinforced Fe matrix coatings were prepared by gas metal arc welding (GMAW) hardfacing technology. The microstructure, hardness and wear resistance of (Nb,Ti)C reinforced coatings with different Ti contents were investigated by experiments. The interfacial properties of (Nb,Ti)C/α-Fe interfaces were calculated by first principles method based on density functional theory (DFT). The experiment results show that as the Ti content in the coating changes from 0.15 to 0.41 wt%, the average diameter of NbC primary carbide grains decreases from 3.2 μm to 1.7 μm and their amount increase from 0.35 to 0.51 μm−2. The coating with 0.15 wt% Ti performs the lowest wear loss, which is 0.47 g/N ∗ cm2. From the calculated results, the interfacial combination between carbide and matrix are improved after Ti addition. The adhesion work of (Nb,Ti)C/Fe interfaces show the following order: CNb-Fe < NbC-Fe < CTiNb-Fe < CNbTi-Fe < NbTiC-Fe < TiNbC-Fe. In CTiNb-Fe, CNbTi-Fe and CNb-Fe surfaces, weak Fe-M covalent bonds are formed at the interfaces. In NbC-Fe, NbTiC-Fe and TiNbC-Fe surfaces, strong Fe–C and M-C covalent bond can be found at (Nb,Ti)C/α-Fe interfaces, besides, Fe–C ionic bonds are also formed.

With consideration about the different termination conditions of atomic layer, six kinds of YAlO3(001)/TiC(100) coherent interface models were selectively constructed based on the results of lattice mismatch calculation and surface convergence test. The work of adhesion and interfacial energy were calculated by first principles method, which is used to analyze their interface adhesive strength and stability to find out interface structures with excellent property. Charge density difference and electron localization functions were calculated to analyze interfacial atomic bonding characteristics. The YAlO3(001)/TiC(100) interfacial structure with the best grain boundary crack and displacement resistance were predicted by the adhesive sliding simulation and potential barrier calculation of preferable formed interfacial structures. The calculation results show that the lattice mismatch of YAlO3(001)/TiC(100) interfacial structures is very small, about 2.5%, which indicates they have the advantage of forming coherent interfaces. The work of adhesion of O1-Ti interface is the largest (Wad = 5.74 J/m2), which is followed by that of the O1-C interface (Wad = 5.73 J/m2). Their interface structures are similar and interfacial atomic bond type are both mixture of covalent bond (between O atom and C atom) and ionic bond (between O atom and Ti atom). However, the interfacial energy of O1-C is the smallest (γ = 2.16 J/m2), which reveals that the O1-C type YAlO3(001)/TiC(100) interface is the most stable. In addition, the sliding direction static friction force of O1-C model is 1.24 times larger than that of O1-Ti, and most of the O1-C interfacial barrier is larger than that of O1-Ti structure in a sliding period. Therefore, it can be predicted that a YAlO3(001)/TiC(100) interface with excellent combination property will be preferable formed in type of O1-C structure. The densification and mechanical property are expected to be greatly improved in TiC reinforced wear-resistance coating and other functional ceramics after adding YAlO3 additive.

Crystallographic characters of austenite and primary-carbide in hypereutectic Fe-Cr-C alloy were analyzed by EBSD and TEM. Band-structure on primary-carbide/austenite interface was observed by TEM and HRTEM. Observations proved the band-structure to be austenite plastic-deformation zone full of strip nanograins and dislocations, which is caused by thermal-mismatch-stress. The coefficient of thermal expansion anisotropy of austenite caused different deformation phenomena.

In this work, the Micro-properties such as stability, mechanical parameter and bonding structures of (Nb,M)C carbides (M = V, Mo, W and Cr) were calculated. And the misfit and interfacial combination between (Nb,M)C carbides and Fe matrix were investigated by first principles calculation. The precipitation behavior of (Nb,V)C carbides were studied. The element V distribution of the carbide in the coatings were analyzed by experiments. The calculation results show that, in the (Nb,M)C carbides, the lattice constant and formation energy of Nb0.75V0.25C carbide are the smallest, and its hardness and brittleness are the largest. According to bonding analysis, Nb-C covalent bonds are the main factor for its high hardness in Nb0.75V0.25C carbide. The combination between carbide and Fe matrix is improved from the results of misfit and adhesion work. Based on the diagrams of the hardfacing alloys with different V contents, the fraction of MC carbides is increased with increase of V contents, and VC carbide can precipitate when V content is high enough. It indicates that element V can be introduced into NbC carbide from the chemical elements analysis experiments.

Three kinds of hypereutectic Fe–Cr–C hardfacing coatings were designed to research the refinement effect and heterogeneous nucleation mechanism of NbC on nano-Y2O3 in the coatings. The microstructure and elemental maps of Fe–Cr–C–Nb–Y2O3 coating were investigated by field emission scanning electron microscope. The phase structures of the coating and heterogeneous nucleation were researched by transmission electron microscope (TEM). The lattice mismatch between Y2O3 and NbC was computed by Bramfitt’s two-dimensional lattice mismatch theory. The adhesive strength, interface energy and electronic properties of Y2O3(111)/NbC(110) interfaces were calculated by a first-principles method. The bonding characteristics of heterogeneous nucleation interfaces were analyzed by charge density difference, electron localization function and Bader charge population. The experimental results show that the primary M7C3 can be refined by NbC, when Nb additive was added into the Fe–Cr–C coating. When nano-Y2O3 and Nb additive were added into the coating simultaneously, the primary M7C3 can be further refined. The SEM results show that NbC can be effective heterogeneous nucleation substrate of the primary M7C3 and there is a compound containing rare earth (RE) element Y in NbC particle. The TEM results verified the RE compound in NbC particle is Y2O3, and they combine together tightly. The calculation results indicate that the two-dimensional lattice mismatch of Y2O3(111)/NbC(110) interface is 6.8%, which reveals that Y2O3 meets the geometric condition to act as a medium-effective heterogeneous nucleation substrate of NbC. In all interface models, the adhesive strength of O-Bridge model is the largest (Wad = 9.75 J/m2) and its stability is the best (γ = − 0.87 J/m2). The major bond type of O-terminated interfaces is covalent one. Actually, the interfacial energy of O-terminated interface is negative, which reveals that their formation process is a process of energy reduction and structure stabilization. It means Y2O3 and NbC can form stable interface structure. It can be predicted that the heterogeneous nucleation occurs preferably on the O-terminated interfaces. Therefore, Y2O3 can serve as an effective heterogeneous nucleation substrate of NbC to refine it.

The development of nanogenerators that is capable of converting mechanical energy into electricity could enable extraordinary advances in biomedical devices and wearable consumer electronics. Piezoelectric composites have no intricate assemblies, providing a compact and reliable alternative to energy interconversion in biomedical electronics. This work deals with the development of a new class of piezoelectric elastomer composite which is integrated multiple potential functionalities. To fully understand and exploit the unique properties of the composited material, characterisations in terms of general mechanical, dynamic mechanical, and dynamic piezoelectric experimental investigations have been conducted. Three prototypes with individual application have been successfully built up utilising the piezoelectric elastomer composite. The versatility of the composite developed in this work presents its outstanding potential in building self-powered systems or biomedical implanted sensors.

The lattice misfit of the different CeO2/TiC planes was calculated by Bramfitt two-dimensional lattice misfit degree theory. Then, the interface relation of CeO2(100)/TiC(111) was calculated by first principles, and the possibility of CeO2 as the heterogeneous nucleus of TiC was analyzed as well. Hypereutectic Fe-Cr-C-Ti-CeO2 hardfacing alloy was prepared in this paper, and its microstructure was observed by Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). The calculated results show that the lattice misfit between CeO2 (100) and TiC (111) is 6.09%, which indicates that it is moderately effective for the CeO2 as the TiC heterogeneous nucleus. Four interfaces exist between CeO2 and TiC, which are Ce-C, Ce-Ti, O-C, and O-Ti ones. The interface adhesive works of Ce-C and Ce-Ti interfaces are small, and their interface energies are large, which indicates that they are extremely unstable and easy to decompose. However, the interface adhesive works of O-C and O-Ti interfaces are large, and their interface energies are small, which indicates that the two interfaces are thermodynamic stable. In addition, The O-C interface consists of covalent and metallic bonds, meanwhile the O-Ti interface consists of covalent, ionic and metallic bonds. Therefore, CeO2 can be as the heterogeneous nucleus of TiC. The experimental results show that CeO2 exists in TiC, which proves that CeO2 can be as the heterogeneous nucleus of TiC, then refines TiC.

The lattice misfits of different CeO2/NbC interfaces were calculated by Bramfitt two-dimensional lattice misfit degree theory. The interface relationship of CeO2(100)/NbC(111) was calculated by first principles, and the possibility of CeO2 as the heterogeneous nucleus of NbC was analyzed as well. In this paper, hypereutectic Fe-Cr-C hardfacing coating was prepared with NbC and CeO2 addtion to observe its microstructure by Transmission Electron Microscope (TEM) and optical microscope (OM). The calculated results show that the lattice misfit of CeO2(100)/NbC(111) is the smallest (7.85%), which indicates that it is moderately effective for the CeO2 as the heterogeneous nucleus of NbC. Four interfaces were constructed between CeO2 and NbC, which are Ce-C, Ce-Nb, O-C, and O-Nb ones. The adhesive works of Ce-C and Ce-Nb interfaces are small, which are negative. And their interface energies are large, which indicates that they are extremely unstable and easy to decompose. The adhesive work of O-Nb interface is the largest, which is positive. Its interface energy is the smallest, so that O-Nb interface is thermodynamically stable. O-C interface is less stable than O-Nb interface. In addition, O-C and O-Nb interfaces contains covalent, metallic and ionic bonds. The experimental results proves that CeO2 can be as the heterogeneous nucleus of NbC, then refines NbC.

The characteristics of YAlO3/NbC heterogeneous nucleation interface are strongly associated with the interfacial structure, electronic construction and properties. The lattice mismatch between low index crystal faces of YAlO3 and NbC was calculated by using the Bramfitt two-dimensional lattice mismatch theory. The work of adhesion, interfacial energy and electronic structure of the YAlO3(001)/NbC(100) interface structures were calculated by the first principles method. The charge density difference, electron localization function and crystal orbits overlap population were adopted to analyze the charge transfer and bond characteristics. The microstructure of surfacing alloy was observed by transmission electron microscopy (TEM). The results show that, the two-dimensional lattice mismatch of YAlO3(001)- NbC(100) interface is 5.4%, which testifies that YAlO3 can meet the lattice structure condition of being an effective heterogeneous nucleus of NbC. In all interface structures, the work of adhesion of C-O2 model is the largest (Wad ¼ 6.558 J/m2) and the interfacial energy of C-Y model is the smallest (g ¼ 0.54 J/m2). It can be confirmed that the C-Y interface structure is the most stable one, whose interfacial energy is the smallest. The chemical bonds between interface atoms of all models are major covalent bonds and few metal bonds. The calculation results indicate that YAlO3(001) slab and NbC(100) slab can form a stable interface structure. The TEM results verify that the rare earth compound in NbC particle is YAlO3. In addition, NbC growth encircling YAlO3 and they are combined tightly. Therefore, YAlO3 can act as the effective heterogeneous nucleus of NbC and refine it.

To achieve long-term patent small-diameter (6 mm) vascular implants, biomimetic vascular grafts have gained much attention in promoting in situ blood vessel regeneration. In this study, hierarchical-structured bacterial cellulose/potato starch (BC/PS) composites were biosynthesized by the addition of swollen PS. Investigations on the physicochemical properties of BC/PS composites showed that the properties could be improved and tailored by the addition of swollen PS. The composites displayed a morphology, water content, thermal properties, mechanical properties, and biocompatibility appropriate for vascular tissue engineering. Most importantly, the BC/PS grafts, with a dense inner surface and a circumferential macroporous outer layer, possessed 75% patency and promoted rapid blood vessel regeneration in in vivo assessment on rabbits, with complete endothelium monolayer, organized smooth muscle cells, rich new capillaries, and deposited extracellular matrix. Collectively, these findings demonstrate that hierarchical-structured BC/PS tubes hold great promise as artificial small-diameter vascular grafts.

With the development of the aerospace industry, the requirement for mechanical parts, which are serviced under extreme conditions such as high temperature, is more and more severe. Amorphous carbon (a-C) films are widely used in the aviation field as a protective coating because of their excellent antiwear and friction-reduction properties. However, a-C films are vulnerable to failure in a high-temperature environment, and a series of complex changes in the friction process make it a challenge to put forward the friction mechanism. Here, the sliding friction behaviors of amorphous carbon (a-C) films at different simulated temperatures (STs) (300-1300 K) were analyzed by molecular dynamics. The density, average coordination number, and local residual stress as well as the hybridization of sp, sp2, and sp3 of a-C films were analyzed to reveal the high-temperature sliding friction mechanism of a-C films. The results show that the friction coefficient (μ) of a-C films increased with increase in ST. Meanwhile, the friction mechanisms of a-C films are different at an ST lower than 800 K and higher than 1100 K. Compared with those before sliding, the local residual stress of all a-C films is relaxed, which causes transformation of sp3 into sp2. Moreover, when ST is lower than 800 K, the μ increased with increase in sp3%. When ST is higher than 1100 K, the stability of a-C films is broken, which results in the rapid increase in μ.

Traditional wound dressings mainly participate in the passive healing processes and are rarely engaged in active wound healing by stimulating skin cell behaviors. Electrical stimulation (ES) has been known to regulate skin cell behaviors. Herein, a series of multifunctional hydrogels based on regenerated bacterial cellulose (rBC) and MXene (Ti

Fabrication of hydrogel composites embedded with aligned 1D nanoparticles has shown substantial growth over the past 5 years. Direct ink printing technology (DIW) has been used in this work to create the alignment of the 1D nanoparticles due to the shear gradient of the pseudoplastic precursor (2-hydroxyethyl methacrylate (HEMA) with thickening agents). Orderly distributed 1D particles constructing anisotropic nanostructures endow the hydrogel composite with unique mechanical, electric, or electromechanical coupling properties. Quasi-static uniaxial tensile test, electric resistivity, and piezoresistivity measurements have been conducted for investigating the mechanical, electric, and electromechanical coupling properties of the hydrogel composites, respectively. Based on the experimental results, it can be speculated that the developed printing process is able to fabricate hydrogel composites with programmable anisotropic mechanical, electric, and electromechanical properties. The products pumped out from this work have the potential of being substrates for soft devices and may have a great impact on the fields of flexible bioelectronics.

Micro-crimped fibers have been widely used in the field of tissue repair to mimic the natural tissue structure and mechanical properties. However, the electrospun nanofibrous membrane is a kind of dense structure, which cannot meet the requirements of mechanical properties and permeability. In this study, we prepared nanofibrous scaffold with controllable porosity and crimpness by sacrificing fiber components and releasing residual stress. The results show that the crimpness of the fiber is positively related to the porosity, and with the increase of porosity, the fiber crimpness increases greatly. Meanwhile, the scaffold modulus was reduced by 86% and the elongation at break doubled, which is similar to natural blood vessels. Moreover, it is found that the porous micro-crimped fiber scaffold promotes the adhesion and diffusion of endothelial cells, and facilitates the rapid endothelialization of the scaffold, which has a great potential for practical application.

Diamond-like carbon (DLC) is one of the most studied and promising coating materials, but many of the bonding mechanisms involved in interfaces between transition layer and DLC coating are not fully understood. Here, the effect of Cr doping in DLC coating on the adhesion strength of DLC/CrN interface was investigated by using first principles method. The thermodynamic stability of Cr C interface is higher and the bonding strength is larger than that of N C one. Meanwhile, the adhesion work of Cr doped interface is larger that of clean interface. In addition, the segregation heat is positive value when small amounts of Cr atoms are introduced into the interface, which indicates Cr atoms are easy to segregate towards the interface. The differential charge density and bader charge indicate that for the doped interface Cr-CCr(1), the transfer of electrons between the interfaces is inhibited by doping Cr atoms. For the doped interface N-CCr(1), the doping Cr atoms makes the first layer of N atoms and the second layer of Cr atoms on the CrN surface participate in charge transfer. Therefore, the calculation results can provide a good theoretical basis for improving the performance of DLC and broadening its application field.

In this paper, the lattice misfits between Ti and TiN interfaces were calculated by the Bramfitt two-dimensional lattice misfit theory. The adhesive work (Wad), interfacial energy (γ), electronic property and bonding characteristic of Ti(0 0 0 1)/TiN(1 1 1) interface were also investigated by first-principles calculation. The results show that, the lattice misfit of Ti(0 0 0 1)/TiN(1 1 1) interface is only 2.46%, which indicates that Ti(0 0 0 1) and TiN(1 1 1) faces can make good lattice matching. Based on three atomic stacking modes (OT-, SL- and TL-sites) and two terminations of TiN(1 1 1) face, six kinds of Ti(0 0 0 1)/TiN(1 1 1) interface models were established. The interfacial bonding strength and stability of the Ti(0 0 0 1)/TiN(1 1 1) N-terminated (Ti/N) interface models are all larger than those of Ti(0 0 0 1)/TiN(1 1 1) Ti-terminated (Ti/Ti) ones. Wad of the N-TL interface (Ti structure contacting with N-terminated structure of TiN with TL site) is the largest (7.97 J/m2), while the relaxed interfacial separation (d0) is the smallest (1.181 Å) and the γ is the smallest (−3.86 J/m2), which indicates that the bonding strength and stability of the N-TL interface are the largest in all interface models. Additionally, the interface bonds of Ti/Ti interface models are weak, and their interfacial strength and stability are relatively weak. The bonding strengths of the three interface models of Ti/N interfaces are larger than that of the Ti/Ti interfaces, which forms a strong polar covalent bond and a metallic one.

The adhesive work, interfacial energy, charge density, charge density difference and layer-projected density of states (DOS) of h-WC(0001)/γ-Fe (111) interfaces were calculated by the first principles method. The structural stability of the interfaces was researched by the adhesive work and interfacial energy of h-WC(0001)/γ-Fe (111) interfaces. The interfacial electronic structures were analyzed by charge density and charge density difference, and the interface bonding characteristics were revealed by Mulliken charges and layer-projected DOS of the interface models. The results show that the work of adhesion for C-terminated HCP stacking interface structure is the largest (Wad = 3.44 J/m2), which indicates that the reversible work used to separate the C-HCP interface into two free surfaces is the largest in all interfaces. When Δμc changes from −0.37 eV to 0 eV, the interfacial energy of C-terminated HCP stacking interface structure is in the range of 1.186–1.588 J/m2, while that of W-terminated HCP stacking interface structure is in the range of 1.142–1.541 J/m2. When −0.165 eV Δμc 0 eV, the interfacial energy of C-terminated HCP stacking interface is smaller than that of W-terminated one, which indicates the C-terminated HCP stacking interface is more stable. When −0.37 eV Δμc -0.165 eV, W-terminated HCP stacking interface turns to be more stable than C-terminated one. The total charge density of C-terminated HCP stacking interface is much larger than that of W-terminated one, and the degree of ionization of C-terminated HCP interface is also higher. The bonding of C-terminated HCP stacking interface is a mixture of covalent bond, ionic bond and metallic one, while that of W-terminated HCP stacking interface is a mixture of covalent bond and metallic one.