Thermally Conductive Elastomer Composites with High Toughness, Softness, and Resilience Enabled by Regulating Interfacial Structure and Dynamics.

The emerging applications of thermally conductive elastomer composites in modern electronic devices for heat dissipation require them to maintain both high toughness and resilience under thermomechanical stresses. However, such a combination of thermal conductivity and desired mechanical characteristics is extremely challenging to achieve in elastomer composites. Here this long-standing mismatch is resolved via regulating interfacial structure and dynamics response. This regulation is realized both by tuning the molecular weight of the dangling chains in the polymer networks and by silane grafting of the fillers, thereby creating a broad dynamic-gradient interfacial region comprising of entanglements. These entanglements can provide the slipping topological constraint that allows for tension equalization between and along the chains, while also tightening into rigid knots to prevent chain disentanglement upon stretching. Combined with ultrahigh loading of aluminum-fillers (90 wt%), this design provides a low Young's modulus (350.0 kPa), high fracture toughness (831.5 J m-2), excellent resilience (79%) and enhanced thermal conductivity (3.20 W m-1 k-1). This work presents a generalizable preparation strategy toward engineering soft, tough, and resilient high-filled elastomer composites, suitable for complex environments, such as automotive electronics, and wearable devices.

Brush Swelling and Attachment Strength of Barnacle Adhesion Protein on Zwitterionic Polymer Films as a Function of Macromolecular Structure.

The exceptional hydration of sulfobetaine polymer brushes and their resistance toward nonspecific protein absorption allows for the construction of thin films with excellent antibiofouling properties. In this work, swollen sulfobetaine brushes, prepared by surface-initiated atom transfer radical polymerization of two monomers, differentiated by the nature of the polymerizable group, are studied and compared by a liquid-cell atomic force microscopy technique and spectroscopic ellipsometry. Colloidal AFM-based force spectroscopy is employed to estimate brush grafting density and characterize nanomechanical properties in salt water. When the ionic strength-induced swelling behaviors of the two systems are compared, the differences observed on the antipolyelectrolyte response can be correlated with the stiffness variation on brush compression, likely to be promoted by solvation differences. The higher solvation of amide groups is proposed to be responsible for the lower adhesion force of the barnacle cyprid's temporary adhesive proteins. The adhesion results provide further insights into the antibiofouling activity against barnacle cyprid settlement attributed to polysulfobetaine brushes.

New Insights into Planar Defects in Layered α-MoO3 Crystals.

The observation of regular ( h0 l) planar defects in α-MoO3 crystals can be traced back to over 60 years ago. Two mechanisms have been proposed to interpret the formation of the planar defects. One is related to the diffusion of oxygen vacancies because of thermal-driven release of oxygen atoms in vacuum and the consequent crystallographic shear of α-MoO3. The other is associated with redox reactions of moisture and/or hydrocarbons that give rise to H xMoO3 precipitates. Here, we report that regularly spaced (302) planar defects can be introduced into α-MoO3 belt crystals by heating in liquid sulfur at 300 °C. These defects are undetectable by both atomic force microscopy and scanning electron microscopy at the crystal surface. Raman scattering enhancement and weakening have been observed for different phonon modes of α-MoO3 at the (302) planar defects as probed from the (010) surface. Their comparisons with the Raman scattering enhancements at the edges and the argon-plasma-induced Raman spectral evolutions of the as-grown α-MoO3 belt crystals provide new insights into the planar defects with regard to their formation and characteristics.

Highly Efficient Supramolecular Aggregation-Induced Emission-Active Pseudorotaxane Luminogen for Functional Bioimaging.

The direct tracking of cells using fluorescent dyes is a constant challenge in cell therapy due to aggregation-induced quenching (ACQ) effect and biocompatibility issues. Here, we demonstrate the development of a biocompatible and highly efficient aggregation-induced emission (AIE)-active pseudorotaxane luminogen based on tetraphenylethene conjugated poly(ethylene glycol) (TPE-PEG2) (guest) and α-cyclodextrin (α-CD) (host). It is capable of showing significant fluorescent emission enhancement at the 400-600 nm range when excited at 388 nm, without increasing the concentration of AIE compound. The fluorescent intensity of TPE-PEG2 solution was effectively enhanced by 4-12 times with gradual addition of 1-4 mM of α-CD. 2D NOSEY 1H NMR revealed clear correlation spots between the characteristic peaks of α-CD and PEG, indicating the interaction between protons of ethylene glycol and cyclodextrin, and the structures are mainly based on threaded α-CD. The host-guest complex exhibits boosted fluorescent emission because the PEG side chains are confined in "nano-cavities" (host), thus, applying additional restriction on intermolecular rotation of TPE segments. In vitro cell experiments demonstrated the potential of AIE-active pseudorotaxane polymer as a biocompatible bioimaging probe.

Engineered, Robust Polyelectrolyte Multilayers by Precise Control of Surface Potential for Designer Protein, Cell, and Bacteria Adsorption.

Cross-linked layer-by-layer (LbL) assemblies with a precisely tuned surface ζ-potential were fabricated to control the adsorption of proteins, mammalian cells, and bacteria for different biomedical applications. Two weak polyions including a synthesized polyanion and polyethylenimine were assembled under controlled conditions and cross-linked to prepare three robust LbL films as model surfaces with similar roughness and water affinity but displaying negative, zero, and positive net charges at the physiological pH (7.4). These surfaces were tested for their abilities to adsorb proteins, including bovine serum albumin (BSA) and lysozyme (LYZ). In the adsorption tests, the LbL films bind more proteins with opposite charges but less of those with like charges, indicating that electrostatic interactions play a major role in protein adsorption. However, LYZ showed higher nonspecific adsorption than BSA, because of the specific behavior of LYZ molecules, such as stacked multilayer formation during adsorption. To exclude such stacking effects from experiments, protein molecules were covalently immobilized on AFM colloidal probes to measure the adhesion forces against the model surfaces utilizing direct protein molecule-surface contacts. The results confirmed the dominating role of electrostatic forces in protein adhesion. In fibroblast cell and bacteria adhesion tests, similar trends (high adhesion on positively charged surfaces, but much lower on neutral and negatively charged surfaces) were observed because the fibroblast cell and bacterial surfaces studied possess negative potentials. The cross-linked LbL films with improved stability and engineered surface charge described in this study provide an excellent platform to control the behavior of different charged objects and can be utilized in practical biomedical applications.

Silencing of Long Non-Coding RNA MALAT1 Promotes Apoptosis of Glioma Cells.

The metastasis-associated lung adenocarcinoma transcription 1 (MALAT1) is a highly conserved long non-coding RNA (lncRNA) gene. However, little is known about the pathological role of lncRNA MALAT1 in glioma. In the present study, we explored the expression level of lncRNA MALAT1 in primary glioma tissues as well as in U87 and U251 glioma cell lines. Using qRT-PCR, we found that the expression of lncRNA MALAT1 was significantly increased in glioma tissues compared with that of paracancerous tissues. Meanwhile, the expression of MALAT1 was highly expressed in U98 and U251 cells. In order to explore the function of MALAT1, the expression of MALAT1 was greatly reduced in U87 and U251 cells transfected with siRNA specifically targeting MALAT1. Consequently, cell viability of U87 and U251 cells were drastically decreased after the knockdown of MALAT1. Concomitantly, the apoptosis rate of the two cell lines was dramatically increased. Furthermore, the expression levels of some tumor markers were reduced after the knockdown of MALAT1, such as CCND1 and MYC. In summary, the current study indicated a promoting role of MALAT1 in the development of glioma cell.

Multilayers of fluorinated amphiphilic polyions for marine fouling prevention.

Sequential layer-by-layer (LbL) deposition of polyelectrolytes followed by chemical cross-linking was investigated as a method to fabricate functional amphiphilic surfaces for marine biofouling prevention applications. A novel polyanion, grafted with amphiphilic perfluoroalkyl polyethylene glycol (fPEG) side chains, was synthesized and subsequently used to introduce amphiphilic character to the LbL film. The structure of the polyanion was confirmed by FTIR and NMR. Amphiphilicity of the film assembly was demonstrated by both water and hexadecane static contact angles. XPS studies of the cross-linked and annealed amphiphilic LbL films revealed the increased concentration of fPEG content at the film interface. In antifouling assays, the amphiphilic LbL films effectively prevented the adhesion of the marine bacterium Pseudomonas (NCIMB 2021).

Design and Fabrication of Annular-Array Ultrasound Transducer Based (K, Na) NbO3 Lead-Free 1-3 Piezoelectric Composite.

This article reports the design, fabrication, and performance of an annular-array ultrasound transducer using (K, Na)NbO3 (KNN)-based lead-free 1-3 piezoelectric composite. The 1-3 piezoelectric composite based on lead-free 0.965(K0.45Na0.55)(Nb0.96Sb0.04)O3-0.035 Bi0.5Na0.5Zr0.85Hf0.15O3 (KNNS-BNZH) was first prepared with the dice-and-fill method. Different from previous reported studies, by patterning annular electrodes on this kind of 1-3 composite, a five-element annular-array transducer in diameter of 6 mm was designed and successfully fabricated and its working center frequency was increased from 5 MHz to around 15 MHz. Meanwhile, a -6 dB bandwidth of 50% was achieved for each annular-array element via a pulse-echo response measurement. Moreover, the obtained annular-array transducer exhibits low crosstalk (<-40 dB) and a high electromechanical coupling coefficient of around 0.7. The application of ultrasonic imaging was further demonstrated to show its excellent performance. Both theoretical analysis and experimental results show that the obtained annular-array transducer presented in this work has a competitive capability for ultrasonic application.

Biomechanics of Macrophages on Disordered Surface Nanotopography.

Macrophages are involved in every stage of the innate/inflammatory immune responses in the body tissues, including the resolution of the reaction, and they do so in close collaboration with the extracellular matrix (ECM). Simplified substrates with nanotopographical features attempt to mimic the structural properties of the ECM to clarify the functional features of the interaction of the ECM with macrophages. We still have a limited understanding of the macrophage behavior upon interaction with disordered nanotopography, especially with features smaller than 10 nm. Here, we combine atomic force microscopy (AFM), finite element modeling (FEM), and quantitative biochemical approaches in order to understand the mechanotransduction from the nanostructured surface into cellular responses. AFM experiments show a decrease of macrophage stiffness, measured with the Young's modulus, as a biomechanical response to a nanostructured (ns-) ZrOx surface. FEM experiments suggest that ZrOx surfaces with increasing roughness represent weaker mechanical boundary conditions. The mechanical cues from the substrate are transduced into the cell through the formation of integrin-regulated focal adhesions and cytoskeletal reorganization, which, in turn, modulate cell biomechanics by downregulating cell stiffness. Surface nanotopography and consequent biomechanical response impact the overall behavior of macrophages by increasing movement and phagocytic ability without significantly influencing their inflammatory behavior. Our study suggests a strong potential of surface nanotopography for the regulation of macrophage functions, which implies a prospective application relative to coating technology for biomedical devices.

Soft, Tough, Antifatigue Fracture Elastomer Composites with Low Thermal Resistance through Synergistic Crack Pinning and Interfacial Slippage.

Soft elastomer composites are promising functional materials for engineer interfaces, where the miniaturized electronic devices have triggered increasing demand for effective heat dissipation, high fracture energy, and antifatigue fracture. However, such a combination of these properties can be rarely met in the same elastomer composites simultaneously. Here a strategy is presented to fabricate a soft, extreme fracture tough (3316 J m-2) and antifatigue fracture (1052.56 J m⁻2) polydimethylsiloxane/aluminum elastomer composite. These outstanding properties are achieved by optimizing the dangling chains and spherical aluminum fillers, resulting in the combined effects of crack pinning and interfacial slippage. The dangling chains that lengthen the polymer chains between cross-linked points pin the cracks and the rigid fillers obstruct the cracks, enhancing the energy per unit area needed for fatigue failure. The dangling chains also promote polymer/filler interfacial slippage, enabling effective deflection and blunting of an advancing crack tip, thus enhancing mechanical energy dissipation. Moreover, the elastomer composite exhibits low thermal resistance (≈0.12 K cm2 W-1), due to the formation of a thermally conductive network. These remarkable characteristics render this elastomer composite promising for application as a thermal interface material in electronic devices.

Generating Airy surface acoustic waves with dislocated interdigital transducers.

We propose an innovative design for interdigital transducers (IDTs), enabling phase modulation of surface acoustic waves (SAWs) with a dislocated electrode structure. By designing the size and arrangement of these dislocated IDTs, a novel type of Airy SAWs can be generated, exhibiting self-accelerating, self-bending, and self-healing characteristics. The acceleration of the generated Airy SAW is 0.081 cm-1. Furthermore, particles and bubbles can be precisely manipulated using the generated Airy SAW. The proposed dislocated IDTs could be used for generation of many other types of SAWs, hence holding great promise for applications including SAW shaping, particle manipulation/sorting, and acoustic sensing/detection.

Structural heterogeneity of the ion and lipid channel TMEM16F.

Transmembrane protein 16 F (TMEM16F) is a Ca2+-activated homodimer which functions as an ion channel and a phospholipid scramblase. Despite the availability of several TMEM16F cryogenic electron microscopy (cryo-EM) structures, the mechanism of activation and substrate translocation remains controversial, possibly due to restrictions in the accessible protein conformational space. In this study, we use atomic force microscopy under physiological conditions to reveal a range of structurally and mechanically diverse TMEM16F assemblies, characterized by variable inter-subunit dimerization interfaces and protomer orientations, which have escaped prior cryo-EM studies. Furthermore, we find that Ca2+-induced activation is associated to stepwise changes in the pore region that affect the mechanical properties of transmembrane helices TM3, TM4 and TM6. Our direct observation of membrane remodelling in response to Ca2+ binding along with additional electrophysiological analysis, relate this structural multiplicity of TMEM16F to lipid and ion permeation processes. These results thus demonstrate how conformational heterogeneity of TMEM16F directly contributes to its diverse physiological functions.

Study on the Adsorption Behavior of Polymeric Dispersants to S-ZnF Particles during Grinding Process.

Three sodium polyacrylate copolymers PD0x (Poly acrylic acid-co-sodium 4-vinylbenzenesulfonate or PD01; Poly acrylic acid-co-sodium 4-vinylbenzenesulfonate-co-hydroxyethyl methacrylate or PD02 and Poly methyl methacrylate-co-acrylic acid-co-sodium 4-vinylbenzenesulfonate-co-hydroxyethyl methacrylate or PD03) were synthesized as water-based dispersants for grinding red-brown pigment ZnFe1.2Cr0.8O4 particles prepared by the solid phase method (S-ZnF). The particle size distribution, viscosity of suspensions, and adsorption capacity of dispersants were explored by laser particle size analysis, viscometer, and thermogravimetry (TG), respectively. The application of 2 wt.% dispersant PD02 in the S-ZnF suspension ground for 90 min can deliver a finer product with the narrower particle size distribution. The added dispersant PD02 in the grinding process of the S-ZnF particles exhibits a suitable viscosity of the suspension and generates more hydrogen bonds on the S-ZnF particle surface. The sulfonic acid groups (SO3-) and carboxylic acid groups (-COO-) in the dispersant PD02 can also provide a strong charge density, which is favorable for the dispersion and grinding of the S-ZnF particles in the suspensions. Furthermore, the adsorption behavior of polymeric dispersant PD02 adsorbed on the S-ZnF particles surface was simulated and analyzed by adsorption thermodynamic models and adsorption kinetic models. It is indicated that the adsorption thermodynamic behavior of dispersant PD02 adsorbed on the S-ZnF particles surface follows the Langmuir model, and the adsorption process is endothermic and a random process with increased confusion during the grinding process. In addition, the adsorption kinetics of dispersant PD02 adsorbed on the S-ZnF particles surface are more in line with the pseudo-first-order kinetic models. Therefore, the adsorption process of dispersant PD02 on the S-ZnF particles surface can be considered as a single-surface adsorption process.

Inhibition of barnacle cyprid settlement using low frequency and intensity ultrasound.

Low frequency, low intensity ultrasound was demonstrated as an effective inhibitor of barnacle cyprid settlement. When the same substratum vibration amplitude (10.05 nm) and acoustic pressure (5 kPa) were applied, ultrasound at a frequency of 23 kHz significantly reduced cyprid settlement. The mechanism appeared to differ from the ultrasonic cavitation induced inhibition previously reported as no increased mortality was observed, and no change in the exploratory behaviour of cyprids was observed when they were exposed to this continuous ultrasonic irradiation regime. The application of ultrasound treatment in an intermittent mode of '5 min on and 20 min off' at 20-25 kHz and at the low intensity of 5 kPa produced the same effect as the continuous application of 23 kHz. This energy efficient approach to the use of low frequency, low intensity ultrasound may present a promising and efficient strategy regarding irradiation treatment for antifouling applications.

Identification of serum miR-378 and miR-575 as diagnostic indicators and predicting surgical prognosis in human epilepsy.

Background: Epilepsy (EP) is a common neurological disorder which is characterized by excessive abnormal synchronization of neuronal discharges in the brain due to chronic recurrent seizures of multiple etiologies. Variety of microRNAs have been associated with the occurrence and development of EP. This study aimed to determine the aberrant expression of miR-378 and miR-575 in EP patients to validate their potential to distinguish EP from healthy patients. Methods: RT-qPCR was used to determine the expressions of miR-378 and miR-575 from serum specimens of 106 EP and 103 control individuals. Clinical indicators between EP patients and controls were assessed. Based on surgical outcome, EP patients were further divided into Engel I-IV EP. The potentials of miR-378 and miR-575 in discriminating EP from healthy participants and predicting surgical prognosis were calculated by receiver operating characteristic (ROC) analysis. Results: We found the miR-378 and miR-575 were significantly declined (P<0.001) in Engel I-II and III-IV EP patients with no difference in clinical parameters compared. Moreover, miR-378 and miR-575 displayed high sensitivity, specificity, and accuracy in distinguishing EP patients and predicting surgical outcomes. Moreover, after surgical treatment, miR-378 and miR-575 levels were increased compared with those at admission, suggesting their potentials in treatment response. Conclusions: miR-378 and miR-575 could be utilized as novel and non-invasive serum biomarkers in discriminating EP from healthy controls and predicting surgical outcome, shedding new insights on epileptogenesis and EP treatment.

Retraction: Metal-free [2+2+1] cycloaddition polymerization of alkynes, nitriles, and oxygen atoms to functional polyoxazoles.

[This retracts the article DOI: 10.1039/D0RA04249H.].

Correction: Metal-free [2+2+1] cycloaddition polymerization of alkynes, nitriles, and oxygen atoms to functional polyoxazoles.

[This corrects the article DOI: 10.1039/D0RA04249H.].

Automatic Quantification of Subsurface Defects by Analyzing Laser Ultrasonic Signals Using Convolutional Neural Networks and Wavelet Transform.

The conventional machine learning algorithm for analyzing ultrasonic signals to detect structural defects necessarily identifies and extracts either time- or frequency-domain features manually, which has problems in reliability and effectiveness. This work proposes a novel approach by combining convolutional neural networks (CNNs) and wavelet transform to analyze the laser-generated ultrasonic signals for detecting the width of subsurface defects accurately. The novelty of this work is to convert the laser ultrasonic signals into the scalograms (images) via wavelet transform, which are subsequently utilized as the image input for the pretrained CNN to extract the defect features automatically to quantify the width of defects, avoiding the necessity and inaccuracy induced by artificial feature selection. The experimentally validated numerical model that simulates the interaction of laser-generated ultrasonic waves with subsurface defects is first established, which is further utilized to generate adequate laser ultrasonic signals for training the CNN model. A total number of 3104 data are obtained from simulation and experiments, with 2480 simulated signals for training the CNN model and the remaining 620 simulated data together with 4 experimental signals for verifying the performance of the proposed algorithm. This approach achieves the prediction accuracy of 98.5% on validation set, particularly with the prediction accuracy of 100% for the four experimental data. This work proves the feasibility and reliability of the proposed method for quantifying the width of subsurface defects and can be further expanded as a universal approach to various other defects detection, such as defect locations and shapes.

Feasibility and risk assessment of heavy metals from low-temperature magnetic pyrolysis of municipal solid waste on a pilot scale.

Low-temperature magnetic pyrolysis (LMP) of municipal solid waste (MSW) was conducted in a pilot scale continuous reactor to investigate the distribution and transformation of heavy metals (HMs) in biochar. Environmental safety was evaluated by the risk assessment code (RAC) and the modified potential ecological risk index (MRI). Statistical analyses of HMs revealed that the total concentrations of HMs in biochar was higher than that in MSW and the exchangeable fraction of Cd in biochar under 200 °C and 250 °C were at high risk levels. Temperature increment indicates an increase in regular steps not only migrated more HMs into biochar, but also broke the immobilization of HMs, so resulted in higher environmental risks. The lowest direct toxicity to the environment was obtained by LMP at 200 °C. In light of the residual fraction and the high concentration of HMs in biochar produced in this work, it should be mixed with other uncontaminated plant waste for further application in agriculture. The results of economic assessment reveal that the value of net present value (NPV) and the internal rate of return (IRR) can be positive if high quality bio-products are produced with low operating costs. Optimized design of operation, feedstock and the investment are the key factors to improve the economic feasibility of LMP.

Germacrone alleviates neurological deficits following traumatic brain injury by modulating neuroinflammation and oxidative stress.

BACKGROUND: Germacrone (GM) is a terpenoid compound which is reported to have anti-inflammatory and anti-oxidative effects. However, its role in treating traumatic brain injury (TBI) remains largely unknown. METHODS: Male C57BL/6 mice were divided into the following groups: control group, TBI group [controlled cortical impact (CCI) model], CCI + 5 mg/kg GM group, CCI + 10 mg/kg GM group and CCI + 20 mg/kg GM group. GM was administered via intraperitoneal injection. The neurological functions (including motor coordination, spatial learning and memory abilities) and brain edema were measured. Nissl staining was used to detect the neuronal apoptosis. Colorimetric assays and enzyme linked immunosorbent assay (ELISA) kits were used to determine the expression levels of oxidative stress markers including myeloperoxidase (MPO), malondialdehyde (MDA) and superoxide dismutase (SOD), as well as the expressions of inflammatory markers, including tumor necrosis factor α (TNF-α), interleukin-1ß (IL-1ß) and interleukin-6 (IL-6). Additionally, protein levels of Nrf2 and p-p65 were detected by Western blot assay. RESULTS: GM significantly ameliorated motor dysfunction, spatial learning and memory deficits of the mice induced by TBI and it also reduced neuronal apoptosis and microglial activation in a dose-dependent manner. Besides, GM treatment reduced neuroinflammation and oxidative stress compared to those in the CCI group in a dose-dependent manner. Furthermore, GM up-regulated the expression of antioxidant protein Nrf2 and inhibited the expression of inflammatory response protein p-p65. CONCLUSIONS: GM is a promising drug to improve the functional recovery after TBI via repressing neuroinflammation and oxidative stress.