Crosslinking-induced patterning of MOFs by direct photo- and electron-beam lithography.

Metal-organic frameworks (MOFs) with diverse chemistry, structures, and properties have emerged as appealing materials for miniaturized solid-state devices. The incorporation of MOF films in these devices, such as the integrated microelectronics and nanophotonics, requires robust patterning methods. However, existing MOF patterning methods suffer from some combinations of limited material adaptability, compromised patterning resolution and scalability, and degraded properties. Here we report a universal, crosslinking-induced patterning approach for various MOFs, termed as CLIP-MOF. Via resist-free, direct photo- and electron-beam (e-beam) lithography, the ligand crosslinking chemistry leads to drastically reduced solubility of colloidal MOFs, permitting selective removal of unexposed MOF films with developer solvents. This enables scalable, micro-/nanoscale (≈70 nm resolution), and multimaterial patterning of MOFs on large-area, rigid or flexible substrates. Patterned MOF films preserve their crystallinity, porosity, and other properties tailored for targeted applications, such as diffractive gas sensors and electrochromic pixels. The combined features of CLIP-MOF create more possibilities in the system-level integration of MOFs in various electronic, photonic, and biomedical devices.

Modelling tomato pericarp microstructure as force control reference for harvesting robot.

BACKGROUND: The harvest of fruit can be significantly advanced with the thriving development of intelligent and automated robot technologies. Nevertheless, the picking success rate of tomato fruit still requires improvement as some fruits are unexpectedly damaged inside, which is imperceptible by machine vision. Herein, a modelling method based on modified Voronoi algorithm is proposed to reconstruct the cellular structure of tomato pericarp. RESULTS: Based on the reconstructed micro-model, the compression physical behaviour of the pericarp cells is simulated to observe internal local stress and potential damage. It is revealed that the simulation result for pericarps of tomatoes with different ripeness is highly consistent to the experimental tests, which has well validated the feasibility of this modelling and simulation method. CONCLUSION: A Voronoi-based modelling method is proposed for micro-reconstruction of tomato pericarp, and the corresponding compression simulation results agree well with the experimental tests. Such result can be utilized as reference to improve the grasping force control for harvesting robot to avoid invisible damage induced by accident overload issue. With the predicting result, superior success rate can be achieved to enhance robot performance. © 2024 Society of Chemical Industry.

3D printing of inorganic nanomaterials by photochemically bonding colloidal nanocrystals.

3D printing of inorganic materials with nanoscale resolution offers a different materials processing pathway to explore devices with emergent functionalities. However, existing technologies typically involve photocurable resins that reduce material purity and degrade properties. We develop a general strategy for laser direct printing of inorganic nanomaterials, as exemplified by more than 10 semiconductors, metal oxides, metals, and their mixtures. Colloidal nanocrystals are used as building blocks and photochemically bonded through their native ligands. Without resins, this bonding process produces arbitrary three-dimensional (3D) structures with a large inorganic mass fraction (~90%) and high mechanical strength. The printed materials preserve the intrinsic properties of constituent nanocrystals and create structure-dictated functionalities, such as the broadband chiroptical responses with an anisotropic factor of ~0.24 for semiconducting cadmium chalcogenide nanohelical arrays.

An effective DLP 3D printing strategy of high strength and toughness cellulose hydrogel towards strain sensing.

Photocurable 3D printing technology has outperformed extrusion-based 3D printing technology in material adaptability, resolution, and printing rate, yet is still limited by the insecure preparation and selection of photoinitiators and thus less reported. In this work, we developed a printable hydrogel that can effectively facilitate various solid or hollow structures and even lattice structures. The chemical and physical dual-crosslinking strategy combined with cellulose nanofibers (CNF) significantly improved the strength and toughness of photocurable 3D printed hydrogels. In this study, the tensile breaking strength, Young's modulus, and toughness of poly(acrylamide-co-acrylic acid)D/cellulose nanofiber (PAM-co-PAA)D/CNF hydrogels were 375 %, 203 % and 544 % higher than those of the traditional single chemical crosslinked (PAM-co-PAA)S hydrogels, respectively. Notably, its outstanding compressive elasticity enabled it to recover under 90 % strain compression (about 4.12 MPa). Resultantly, the proposed hydrogel can be utilized as a flexible strain sensor to monitor the motions of human movements, such as the bending of fingers, wrists, and arms, and even the vibration of a speaking throat. The output of electrical signals can still be collected through strain even under the condition of energy shortage. In addition, photocurable 3D printing technology can provide customized services for hydrogel-based e-skin, such as hydrogel-based bracelets, fingerstall, and finger joint sleeves.

Epitaxial CsPbBr3 /CdS Janus Nanocrystal Heterostructures for Efficient Charge Separation.

Epitaxial heterostructures of colloidal lead halide perovskite nanocrystals (NCs) with other semiconductors, especially the technologically important metal chalcogenides, can offer an unprecedented level of control in wavefunction design and exciton/charge carrier engineering. These NC heterostructures are ideal material platforms for efficient optoelectronics and other applications. Existing methods, however, can only yield heterostructures with random connections and distributions of the two components. The lack of epitaxial relation and uniform geometry hinders the structure-function correlation and impedes the electronic coupling at the heterointerface. This work reports the synthesis of uniform, epitaxially grown CsPbBr3 /CdS Janus NC heterostructures with ultrafast charge separation across the electronically coupled interface. Each Janus NC contains a CdS domain that grows exclusively on a single {220} facet of CsPbBr3 NCs. Varying reaction parameters allows for precise control in the sizes of each domain and readily modulates the optical properties of Janus NCs. Transient absorption measurements and modeling results reveal a type II band alignment, where photoexcited electrons rapidly transfer (within ≈9 picoseconds) from CsPbBr3 to CdS. The promoted charge separation and extraction in epitaxial Janus NCs leads to photoconductors with drastically improved (approximately three orders of magnitude) responsivity and detectivity, which is promising for ultrasensitive photodetection.

A General Approach to Stabilize Nanocrystal Superlattices by Covalently Bonded Ligands.

Self-assembled inorganic nanocrystal (NC) superlattices are powerful material platforms with diverse structures and emergent functionalities. However, their applications suffer from the low structural stability against solvents and other stimuli, due to the weak interparticle interactions. Existing strategies to stabilize NC superlattices typically require the design and incorporation of special ligands prior to self-assembly and are only applicable to superlattices of certain NCs, ligands, and structures. Here we report a general method to stabilize superlattices of various NC compositions and structures via strong, covalently bonded ligands. The core is the use of light-triggered, nitrene-based cross-linkers that do not interfere the self-assembly process while nonspecifically and effectively bonding the native ligands of NCs. The stabilized 2D and 3D superlattices of metal, semiconductor, and magnetic NCs retain their structures when being exposed to solvents of different polarities (from toluene to water) and show high thermal stability and mechanical rigidity. This can further stabilize binary NC superlattices, beyond those achievable in previous methods. Stabilized superlattices show robust and reproducible functionalities, for instance, when serving as reusable substrates for surface enhanced Raman spectroscopy. These results create more possibilities in exploiting the impressive library of NC superlattices in a broad scope of applications.

Tuning the Poisson's ratio of poly(ethylene glycol) diacrylate/cellulose nanofibril aerogel scaffold precisely for cultivation of bone marrow mesenchymal stem cell.

Tissue engineering (TE) scaffolds with appropriate Poisson's ratio (PR) are suitable for mimicking the environment of native tissues on which cells could survive and thrive better. Herein, cellular structured scaffolds are made by a new composite poly(ethylene glycol) diacrylate/cellulose nanofibril aerogel, with prototypes of the hexagonal, reentrant, and semireentrant models. Scaffolds with different geometry parameters (l, t, α) are designed and simulated by COMSOL to enable precise regulation of their PR. Then, nine groups of scaffolds with different PRs ranging from -0.5 to 0.85 are designed by adjusting geometry parameters and fabricated by using stereolithography and freeze-drying techniques. Subsequently, bone marrow mesenchymal stem cells (BMSc) are cultured on these scaffolds for 21 days, during which CCK8 assay, fluorescence microscope observation, and real-time polymerase chain reaction experiments are performed to characterize the proliferation and differentiation of BMSc. The results reflect that the scaffolds with different PR can provide various stress environments for cells, and the scaffold with zero PR is the most suitable for BMSc differentiating into chondrocytes during early culture experiments. This study suggests that tuning PR precisely is an attractive and effective strategy to provide a cells-suitable environment for scaffold fabrication for TE.

Direct Patterning of Colloidal Nanocrystals via Thermally Activated Ligand Chemistry.

Precise patterning with microscale lateral resolution and widely tunable heights is critical for integrating colloidal nanocrystals into advanced optoelectronic and photonic platforms. However, patterning nanocrystal layers with thickness above 100 nm remains challenging for both conventional and emerging direct photopatterning methods, due to limited light penetration depths, complex mechanical and chemical incompatibilities, and others. Here, we introduce a direct patterning method based on a thermal mechanism, namely, the thermally activated ligand chemistry (or TALC) of nanocrystals. The ligand cross-linking or decomposition reactions readily occur under local thermal stimuli triggered by near-infrared lasers, affording high-resolution and nondestructive patterning of various nanocrystals under mild conditions. Patterned quantum dots fully preserve their structural and photoluminescent quantum yields. The thermal nature allows for TALC to pattern over 10 µm thick nanocrystal layers in a single step, far beyond those achievable in other direct patterning techniques, and also supports the concept of 2.5D patterning. The thermal chemistry-mediated TALC creates more possibilities in integrating nanocrystal layers in uniform arrays or complex hierarchical formats for advanced capabilities in light emission, conversion, and modulation.

Nanocellulose/PEGDA Aerogels with Tunable Poisson's Ratio Fabricated by Stereolithography for Mouse Bone Marrow Mesenchymal Stem Cell Culture.

In this study, nanocellulose aerogels with a tunable Poisson's ratio were fabricated. Tissue engineering scaffolds with a tunable Poisson's ratio may be better able to simulate the mechanical behavior of natural tissues. A mixture of cellulose nanofibers (CNFs) and polyethylene glycol diacrylate (PEGDA) was used as the raw material to prepare CNF/PEGDA aerogels with a multiscale pore structure through a combination of stereolithography (SLA) and freeze-drying. The aerogels were fabricated with a regular macropore network structure and a random and homogeneous distribution of micropores. The macropore structure of the scaffolds could be customized through SLA, which resulted in scaffolds that exhibited one of three different mechanical behaviors: positive Poisson's ratio (PPR), negative Poisson's ratio (NPR) or zero Poisson's ratio (ZPR). Then, the hydrogel scaffolds were transformed into aerogel scaffolds through the freeze-drying method, which endowed the scaffolds with homogeneously distributed micropores. The material ratio and exposure were adjusted to obtain scaffolds with a clear pore structure. Then, the CNF/PEGDA scaffolds with different Poisson's ratios were subjected to mechanical tests, and their chondrogenic induction characteristics were determined. The NPR scaffold not only provided a good environment for cell growth but also affected mouse bone marrow mesenchymal stem cell (mBMSC) proliferation and chondrogenic induction. Thus, we provide a feasible scheme for the preparation of three-dimensional scaffolds with a multiscale pore structure and tunable Poisson's ratio, which contributes to cartilage repair in tissue engineering.

A new PEGDA/CNF aerogel-wet hydrogel scaffold fabricated by a two-step method.

The scaffold is one of the most important components in tissue engineering. There are a lot of natural or synthetic materials applied for the fabrication of scaffolds. Among them, cellulose nanofibril (CNF) is an important natural polymer with characteristics of superior biocompatibility, notable nanostructure effect and excellent hydrophilia, which make it qualified for serving as a raw material of scaffolds. In this paper, polyethylene glycol diacrylate (PEGDA) was mixed with CNF at different content ratios, which were 0%, 0.35%, 0.7%, 1.05% and 1.4% (m/v). Furthermore, the visible light photoinitiator (eosin Y + TEA + NVP) was first added to this mixture solution to form a new kind of bio-resin. A two-step method including stereolithography and freeze-drying is put forward to fabricate a new aerogel-wet hydrogel scaffold. Scaffolds were fabricated by using a self-built stereolithography platform and the mechanical properties, printability and biocompatibility of the hydrogel scaffolds were investigated thoroughly. The original hydrogel scaffold was fabricated through stereolithography, where CNFs were applied to regulate the mechanical properties of the hydrogel and the printability of the bio-resin. After the freeze-drying process, the original hydrogel was transformed into the aerogel-wet hydrogel whose compressive modulus is reduced by 20%. Furthermore, the surface structure of the hydrogel scaffold is modified to provide a better environment for adhesion and growth of BMSc.

Reconstruction of plant microstructure using distance weighted tessellation algorithm optimized by virtual segmentation.

The accurate reconstruction model of plant microstructure is important for obtaining the mechanical properties of plant tissues. In this paper, a virtual segmentation technique is proposed to optimize Delaunay triangulation. Based on the optimized Delaunay triangulation, an Optimized Distance Weighted Tessellation (ODWT) algorithm is developed. Two different structures, namely carrot and retting maize vascular bundles, were reconstructed via the ODWT algorithm. The accuracy of ODWT is evaluated statistically by comparing with Centroid-based Voronoi Tessellation (CVT) and Area Weighted Tessellation (AWT). The results show that ODWT has distinct advantages over CVT and AWT. It is worth mentioning that ODWT has better performance than CVT when there exists large diversity in adjacent cell area. It is found that CVT and AWT fail to reconstruct cells with elongated and concave shapes, while ODWT shows excellent feasibility and reliability. Furthermore, ODWT is capable of establishing finite tissue boundary, which CVT and AWT have failed to realize. The purpose of this work is to develop an algorithm with higher accuracy to implement the preprocessing for further numerical study of plants properties. The comparison results of the simulated values of the longitudinal tensile modulus with the experimental value show that ODWT algorithm can improve the prediction accuracy of multi-scale models on mechanical properties.

Nanocellulose/PEGDA aerogel scaffolds with tunable modulus prepared by stereolithography for three-dimensional cell culture.

Three-dimensional (3D) porous scaffolds made of biopolymers have attracted significant attention in tissue engineering applications. In this study, cellulose-nanofibers/polyethylene glycol diacrylate (CNFs/PEGDA) mixture, a novelty 3D material, was prepared by physical mixing the CNFs with a waterborne photopolymerizable acrylic resin (PEGDA). Then the CNFs/PEGDA mixture was used to fabricate 3D cytocompatibility CNFs/PEGDA hydrogel scaffold by stereolithograph（SLA）process. The CNFs/PEGDA hydrogels were shaped by SLA, and then the aerogel scaffolds were prepared by the freeze-drying of hydrogels. The results showed that the CNFs/PEGDA mixtures with different CNFs contents are all transparent, homogeneous and with obvious shear-thinning property. The SLA fabricated CNFs/PEGDA aerogel scaffolds possess high and tunable compressive modulus and high porosity of approximately 90%. It is found that CNFs in the composite scaffolds played a significant role in structural shape integrity, porous structure and mechanical strength. In addition, the NIH 3T3 cells tightly adhere on the CNFs/PEGDA materials and spread on the scaffolds with good differentiation and viability. These results have revealed a superior method to prepare tissue engineering scaffolds which possesses suitable mechanical strength and biocompatibility for 3D cell cultivation.

Patrinia scabiosaefolia Inhibits Growth of 5-FU-Resistant Colorectal Carcinoma Cells via Induction of Apoptosis and Suppression of AKT Pathway.

OBJECTIVE: To investigate the effects of ethanol extract of Patrinia scabiosaefolia (EEPS) on chemo-resistance of colorectal cancer cells (CRC) and explore the possible molecular mechanisms. METHODS: 5-fluorouracil (5-FU)-resistant human colorectal carcinoma cell line (HCT-8/5-FU) and its parental cells HCT-8 were treated with EEPS (0, 0.25, 0.50, 1 or 2 mg/mL), or 5-FU (0, 100, 200, 400, 800 or 1600 µmol/L). The 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay was performed to evaluate the cell viability. Cell density was observed by phase-contrast microscope, cell counting and colony formation assay were used to determine the cell proliferation of HCT-8/5-FU cells treated with 0, 0.5, 1 or 2 mg/mL EEPS. Cell apoptosis was determined by Hoechst staining. Western-blot was performed to detect the phosphorylation of AKT as well as the protein expression level of B-cell CLL/lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax). RESULTS: Compared with HCT-8 cells, MTT assay results indicated that HCT-8/5-FU cells were resistant to 5-FU treatment (P<0.05), and sensitive to EEPS treatment (P>0.05). Moreover, compared with untreated HCT-8/5-FU cells, 1 and 2 mg/mL of EEPS treatment significantly reduced cell density, cell number, inhibited cell survival (P<0.05), and induced apoptosis in HCT-8/5-FU cells. Furthermore, 1 and 2 mg/mL of EEPS significantly decreased the phosphorylation level of p-AKT and Bcl-2 protein expression, and increased the expression of Bax protein (P<0.05). CONCLUSION: EEPS is a promising therapeutic agent that may overcome chemo-resistance in cancer cells, likely through suppression of the AKT pathway and promotion of cancer cell apoptosis.

Effect of multiscale structural parameters on the mechanical properties of rice stems.

The objective of this study was to investigate the relation between the structural parameters and the mechanical properties of rice stem at different scales. Tensile modulus and bending properties of different kinds of rice stems were measured through tensile and three-point bending tests. The morphology and microstructures of rice stems at different scales are detected by the scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). It is found that the microfibril angle (MFA) and the volume fraction of the supporting materials dominate the tensile modulus of rice stem. Whereas, the bending properties of rice stem are more sensitive to the structural parameters of the matrix materials. Moreover, compared to the number or volume fraction of small/large vascular bundle, the volume fraction of the mechanical tissue layer in skin exerts a greater influence on the tensile modulus of the rice stem.

Qingxuan Jiangya Decoction Mitigates Renal Interstitial Fibrosis in Spontaneously Hypertensive Rats by Regulating Transforming Growth Factor-ß1/Smad Signaling Pathway.

Qingxuan Jiangya Decoction (QXJYD) is a traditional Chinese medicine commonly used in the clinical treatment of hypertension. Earlier studies had shown that QXJYD could inhibit the elevation of blood pressure in spontaneously hypertensive rats (SHRs) and prevent remodeling of arterial vessels. This study examines the therapeutic efficacy of QXJYD against elevated blood pressure using the SHR model, as well as the mechanisms behind its antihypertensive activity and protection against renal fibrosis. The results showed that QXJYD significantly attenuated the increase in blood pressure in SHRs and mitigated the development of renal interstitial fibrosis. In addition, QXJYD also robustly decreased the excess accumulation of extracellular matrix and attenuated the elevated expression of MMPs. The antihypertensive effects and renal protection of QXJYD were determined to be strongly associated with inhibition of TGF-ß1/Smad signaling pathway.

Water transport in leaf vein systems and the flow velocity measurement with a new method.

As an exploration to the nature, research about plants' physiological properties have never been suspended. Water transport in leaf vein systems is an essential part of plant growth and development. In this paper, a simple but efficient method combined the fluorescence labeling technology frequently used in bioresearch and the image-processing technology in the computer realm was developed to measure the flow velocity, which was used as a quantitative description to reveal the regulation of water transport in leaf vein systems. Three ordinary species of plants were selected for the experiments and the influence of the experimental conditions, such as the concentration of fluorescein and illumination intensity of LEDs, was investigated. Differences among the flow velocities of different leaf veins of the same leaf as well as the flow velocities of different species were shown in bar charts. The mean measured flow velocities of the midrib and secondary vein of Ficus virens Ait. var. sublanceolata (Miq.) Corner were 4.549m/h and 3.174m/h. As for Plumeria rubra L. cv. Acutifolia and Hamelia patens, that were 0.339m/h and 0.463m/h, 2.609m/h and 2.586m/h, respectively. With the algorithm developed in this paper, the variation of the flow velocity in leaf veins was investigated by setting a constant time interval. Then a verification of the flow velocity measured by the algorithm was performed. Finally, according to the natural conditions of a plant leaf, a simulation about the water transport in leaf vein systems was carried out, which is especially different from the previous research.

A new photoelectric ink based on nanocellulose/CdS quantum dots for screen-printing.

CdS quantum dots with excellent photoelectrical properties embedded in nanocellulose could be exploited for use in photoelectrical ink. In this work, nanocellulose/CdS quantum dot composites were fabricated by controlling the carboxylate content of the nanocellulose and the molar ratio of Cd(2+)/-COOH. New photoelectric inks were prepared based on the composites, in which the CdS quantum dots acted as the pigment and the nanocellulose as the binder. The results of the photocurrent of the composites showed that the photocurrent could be tailored by the carboxylate content and the molar ratio of Cd(2+)/-COOH. And the photocurrent could be as high as 2µA. The surface tension of the photoelectric ink was 27.80±0.03mN/m and its viscosity was 30.3mPas. The photoelectric ink was stable with excellent fluidity and rheology, it could therefore be applied to screen-printing and three-dimensional (3D) printing.

The mechanical influences of the graded distribution in the cross-sectional shape, the stiffness and Poisson׳s ratio of palm branches.

The branching system plays an important role in maintaining the survival of palm trees. Due to the nature of monocots, no additional vascular bundles can be added in the palm tree tissue as it ages. Therefore, the changing of the cross-sectional area in the palm branch creates a graded distribution in the mechanical properties of the tissue. In the present work, this graded distribution in the tissue mechanical properties from sheath to petiole were studied with a multi-scale modeling approach. Then, the entire palm branch was reconstructed and analyzed using finite element methods. The variation of the elastic modulus can lower the level of mechanical stress in the sheath and also allow the branch to have smaller values of pressure on the other branches. Under impact loading, the enhanced frictional dissipation at the surfaces of adjacent branches benefits from the large Poisson׳s ratio of the sheath tissue. These findings can help to link the wind resistance ability of palm trees to their graded materials distribution in the branching system.

The structure-mechanical relationship of palm vascular tissue.

The structure-mechanical relationship of palm sheath is studied with numerical and experimental methods. The cellular structure of the vascular tissue is rebuilt with an image-based reconstruction method and used to create finite element models. The validity of the models is firstly verified with the results from the tensile tests. Then, the cell walls inside each of the specific regions (fiber cap, vessel, xylem, etc.) are randomly removed to obtain virtually imperfect structures. By comparing the magnitudes of performance degradation in the different imperfect structures, the influences of each region on the overall mechanical performances of the vascular tissue are discussed. The longitudinal stiffness and yield strength are sensitive to the defects in the vessel regions. While in the transverse directions (including the radial and tangential directions), the parenchymatous tissue determines the mechanical properties of the vascular tissue. Moreover, the hydraulic, dynamic response and energy absorption behavior of the vascular tissue are numerically explored. The flexibility of natural palm tissue enhances its impact resistance. Under the quasi-static compression, the cell walls connecting the fiber cap and the vessel dissipate more energy. The dominant role of the fiber cap in the plastic energy dissipation under high-speed impact is observed. And the radially-arranged fiber cap also allows the palm tissue to improve its tangential mechanical performances under hydraulic pressure.