Table of contents

In the last two decades, it has become evident that the mechanical properties of the microenvironment of biological cells are as important as traditional biochemical cues for the control of cellular behavior and fate. The field of cell and matrix mechanics is quickly growing and so is the development of the experimental approaches used to study active and passive mechanical properties of cells and their surroundings. Within this topical review we will provide a brief overview, on the one hand, over how cellular mechanics can be probed physically, how different geometries allow access to different cellular properties, and, on the other hand, how forces are generated in cells and transmitted to the extracellular environment. We will describe the following experimental techniques: atomic force microscopy, traction force microscopy, magnetic tweezers, optical stretcher and optical tweezers pointing out both their advantages and limitations. Finally, we give an outlook on the future of the physical probing of cells.

Control over carbon dioxide (CO₂) release is extremely important to decrease its hazardous effects on the environment such as global warming, ocean acidification, etc. For CO₂ capture and storage at industrial point sources, nanoporous materials offer an energetically viable and economically feasible approach compared to chemisorption in amines. There is a growing need to design and synthesize new nanoporous materials with enhanced capability for carbon capture. Computational materials chemistry offers tools to screen and design cost-effective materials for CO₂ separation and storage, and it is less time consuming compared to trial and error experimental synthesis. It also provides a guide to synthesize new materials with better properties for real world applications. In this review, we briefly highlight the various carbon capture technologies and the need of computational materials design for carbon capture. This review discusses the commonly used computational chemistry-based simulation methods for structural characterization and prediction of thermodynamic properties of adsorbed gases in porous materials. Finally, simulation studies reported on various potential porous materials, such as zeolites, porous carbon, metal organic frameworks (MOFs) and covalent organic frameworks (COFs), for CO₂ capture are discussed.

How cells establish and maintain a well-defined size is a fundamental question of cell biology. Here we investigated to what extent the microtubule cytoskeleton can set a predefined cell size, independent of an enclosing cell membrane. We used electropulse-induced cell fusion to form giant multinuclear cells of the social amoeba Dictyostelium discoideum. Based on dual-color confocal imaging of cells that expressed fluorescent markers for the cell nucleus and the microtubules, we determined the subcellular distributions of nuclei and centrosomes in the giant cells. Our two- and three-dimensional imaging results showed that the positions of nuclei in giant cells do not fall onto a regular lattice. However, a comparison with model predictions for random positioning showed that the subcellular arrangement of nuclei maintains a low but still detectable degree of ordering. This can be explained by the steric requirements of the microtubule cytoskeleton, as confirmed by the effect of a microtubule degrading drug.

Multi layer capacitors (MLCs) are considered the most promising refrigerant elements for the design and development of electrocaloric cooling devices. Recently, the heat transfer of these MLCs has been considered. However, the heat exchange with the surrounding environment has been poorly addressed. In this work, we measure by infrared thermography the temperature change versus time in four different heat exchange configurations. Depending on the configurations, Newtonian and non-Newtonian regimes with their corresponding Biot number are determined, providing useful thermal characteristics. Indeed, in the case of large area thermal pad contacts, heat transfer coefficients up to 3400 W · m⁻² · K⁻¹ were obtained, showing that the standard (non-optimised) MLCs already reach the needs for designing efficient prototypes. We also determined the ideal Brayton cooling power in case of thick wires contact that varied between 3.4 mW and 9.8 mW for operating frequencies varying from 0.25 Hz to 1 Hz. While only heat conduction was considered here, our work provides some design rules for improving heat exchanges in future devices.

The developmental switch to sporulation in Physarum polycephalum is a phytochrome-mediated far-red light-induced cell fate decision that synchronously encompasses the entire multinucleate plasmodial cell and is associated with extensive reprogramming of the transcriptome. By repeatedly taking samples of single cells after delivery of a light stimulus pulse, we analysed differential gene expression in two mutant strains and in a heterokaryon of the two strains all of which display a different propensity for making the cell fate decision. Multidimensional scaling of the gene expression data revealed individually different single cell trajectories eventually leading to sporulation. Characterization of the trajectories as walks through states of gene expression discretized by hierarchical clustering allowed the reconstruction of Petri nets that model and predict the observed behavior. Structural analyses of the Petri nets indicated stimulus- and genotype-dependence of both, single cell trajectories and of the quasipotential landscape through which these trajectories are taken. The Petri net-based approach to the analysis and decomposition of complex cellular responses and of complex mutant phenotypes may provide a scaffold for the data-driven reconstruction of causal molecular mechanisms that shape the topology of the quasipotential landscape.

Metasurface, composed of subwavelength antennas, allows us to obtain arbitrary permittivity and permeability in electromagnetic (EM) waveband. It can be used to control the polarization, frequency, amplitude, and phase of the EM wave. Conventional terahertz (THz) components, such as high-impedance silicon lens, polyethylene lens, and quartz wave plate, rely on the phase accumulation along the wave propagation to reshape the THz wavefront. The metasurface employs the localized surface plasmon resonance to modulate the wavefront. Compared with conventional THz components, metasurface has the advantages of being ultrathin, ultralight, and low cost. In recent years, a large number of THz devices based on metasurface have been proposed. We review in broad outline the metasurface devices in the THz region and describe the progress of static and tunable THz field-modulated metasurfaces in detail. Finally, we discuss current challenges and opportunities in this rapidly developing research field.

The magnetic, structural and thermomagnetic properties of the MM'X material system of MnNiGe are evaluated with respect to their utilization in magnetocaloric refrigeration. The effects of separate and simultaneous substitution of Fe for Mn and Si on the Ge site are analysed in detail to highlight the benefits of the isostructural alloying method. A large range of compounds with precisely tunable structural and magnetic properties and the tuning of the phase transition by chemical pressure are compared to the effect of hydrostatic pressure on the martensitic transition.

We obtained very large isothermal entropy changes $\Delta S_{\rm iso}$ of up to $-37.8$ J ${\rm kg}^{-1}$${\rm K}^{-1}$ based on magnetic measurements for (Mn,Fe)NiGe in moderate fields of 2 T. The enhanced magnetocaloric properties for transitions around room temperature are demonstrated for samples with reduced Ge, a resource critical element. An adiabatic temperature change of 1.3 K in a magnetic field change of 1.93 T is observed upon direct measurement for a sample with Fe and Si substitution. However, the high volume change of 2.8% results in an embrittlement of large particles into several smaller fragments and leads to a sensitivity of the magnetocaloric properties towards sample shape and size. On the other hand, this large volume change enables to induce the phase transition with a large shift of the transition temperature by application of hydrostatic pressure (72 K ${\rm GPa}^{-1}$). Thus, the effect of 1.88 GPa is equivalent to a substitution of 10% Fe for Mn and can act as an additional stimulus to induce the phase transition and support the low magnetic field dependence of the phase transition temperature for multicaloric applications.

The paper focuses on the study of transformation of silicon crystal into silicon carbide crystal via substitution reaction with carbon monoxide gas. As an example, the Si(1 0 0) surface is considered. The cross section of the potential energy surface of the first stage of transformation along the reaction pathway is calculated by the method of nudged elastic bands. It is found that in addition to intermediate states associated with adsorption of CO and SiO molecules on the surface, there is also an intermediate state in which all the atoms are strongly bonded to each other. This intermediate state significantly reduces the activation barrier of transformation down to 2.6 eV. The single imaginary frequencies corresponding to the two transition states of this transformation are calculated, one of which is reactant-like, whereas the other is product-like. By methods of quantum chemistry of solids, the second stage of this transformation is described, namely, the transformation of precarbide silicon into silicon carbide. Energy reduction per one cell is calculated for this 'collapse' process, and bond breaking energy is also found. Hence, it is concluded that the smallest size of the collapsing islet is 30 nm. It is shown that the chemical bonds of the initial silicon crystal are coordinately replaced by the bonds between Si and C in silicon carbide, which leads to a high quality of epitaxy and a low concentration of misfit dislocations.

A model of a thermoelectric generator is proposed, in which composite materials obtained by sintering diamond nanoparticles are used as the main component. To increase the useful conversion of heat into electric current, it is proposed to use the effect of electron drag by ballistic phonons. To reduce the ineffective heat spread, it is proposed to use the effect of thermal resistance of the boundaries between the graphite-like and diamond-like phases of the composite.

An experimental confirmation of the existence of an optimal volume ratio between graphite-like and diamond-like phases of the composite is predicted and obtained.

The highest achieved value of thermoelectric coefficient in the actual structure is 80 µV K⁻¹ (which means 20 times increase compared to that of composites not of the optimal structure), with a thermal conductivity of 50 W m⁻¹ K⁻¹. These results were obtained with constant electrical conductivity. The combined influence of these two effects in case of the ideal composite structure should result in an increase of the thermoelectric efficiency parameter by three orders of magnitude.

We investigate the acousto-electric transport induced by surface acoustic waves (SAWs) in epitaxial graphene (EG) coated by a MgO/ZnO film. The deposition of a thin MgO layer protects the EG during the sputtering of a piezoelectric ZnO film for the efficient generation of SAWs. We demonstrate by Raman and electric measurements that the coating does not harm the EG structural and electronic properties. We report the generation of two SAW modes with frequencies around 2 GHz. For both modes, we measure acousto-electric currents in EG devices placed in the SAW propagation path. The currents increase linearly with the SAW power, reaching values up to almost two orders of magnitude higher than in previous reports for acousto-electric transport in EG on SiC. Our results agree with the predictions from the classical relaxation model of the interaction between SAWs and a two dimensional electron gas.

The discovery of magnetism-driven ferroelectricity has recently given new hope for multiferroic devices, but very low magnetic ordering temperature as well as negligibly small electric polarization in these systems are still a challenge. Here, we report a new collinear magnetic multiferroic, ${\rm Nd}_{2}$${\rm CoMnO}_{6}$ (${{T_{\rm C}} \sim 150}$ K) with a spontaneous electric polarization, ${P_{\rm S}}\simeq 1.3 ~\mu$C ${\rm cm}^{-2}$, much higher than the other known magnetic multiferroics. The high polarization value has been associated to the intrinsic $\uparrow\uparrow\downarrow\downarrow$ spin ordering-driven broken symmetry and the high degree of antisite disorder present in the system, which are confirmed through dc magnetization measurements.

Controlling discrete fluid droplets using magnetic fields on a hydrophobic surface offers new opportunities in microfluidics. Manipulation of two pure magnetic ionic liquids (MILs) [Emim][FeCl₄] and [Bmim][FeCl₄] was investigated on a hydrophobic surface under the influence of an external magnetic field. The effects of increasing and decreasing magnetic field strength on the shape of the MIL droplets were first studied at three different temperatures. Both MILs showed good robustness to temperature variations. Moreover, the hysteresis phenomena of height and contact line diameter were observed for both MIL droplets with different volumes. Next, the movement of the MIL droplets under the actuation of a horizontal moving magnet was investigated. It was found that the maximum attainable speed increased linearly with the droplet volume, and it was up to 22 mm s⁻¹ for a 10 µl [Emim][FeCl₄] droplet when the surface magnetic field strength was 400 mT. Finally, a electrostatic energy harvester using conductive MIL droplets rolling across a charged electret film was studied. An average output power of 78 nW was obtained with a 20 µl droplet. The manipulation of individual real pure MIL droplets without adding or dispersing magnetic particles was persistent and neither evaporation nor phase separation took place.

Thermal spin injection is a unique and fascinating method for generating spin current. If magnetization can be controlled by thermal spin injection, various advantages will be provided in spintronic devices, through its wireless controllability. However, the generation efficiency of thermal spin injection is believed to be lower than that of electrical spin injection. Here, we explore a suitable ferromagnetic metal for an efficient thermal spin injection, via systematic experiments based on diffusive spin transport under temperature gradients. Since a ferromagnetic metal with strong spin splitting is expected to have a large spin-dependent Seebeck coefficient, a lateral spin valve based on CoFe electrodes has been fabricated. However, the superior thermal spin injection property has not been observed, because the CoFe electrode retained its crystalline signature—where s-like electrons dominate the transport property in the ferromagnet. To suppress the crystalline signature, we adopt a CoFeAl electrode, in which the Al impurity significantly reduces the contribution from s-like electrons. Highly efficient thermal spin injection has been demonstrated using this CoFeAl electrode. Further optimization for thermal spin injection has been demonstrated by adjusting the Co and Fe composition.

The occurrence of both interlayer exchange coupling and perpendicular magnetic anisotropy is evidenced in Pt/Co/Ir/Co/Pt magnetron sputtered structures. We point out the effect of lattice strains on stabilizing the perpendicular magnetic anisotropy. The surface magnetic anisotropy constant is around 1.76 erg cm⁻² and around 1.5 erg cm⁻² for the Co layers, depending on their positioning within the stack. We demonstrate a relatively high interlayer exchange constant of  −2.5 erg cm⁻² at the first antiferromagnetic coupling maximum corresponding to an exchange field larger than 12 kOe. The interlayer exchange coupling shows remarkable annealing endurance being preserved for annealing temperatures up to 400 °C.

The influence of Co-doping in off-stoichiometric Ni–Mn–Ga and Ni–Mn–Ga–Co thin films on the magnetic coupling of the atoms is investigated with x-ray magnetic circular dichroism in both the martensitic as well as austenitic phase, respectively. Additionally, first principles calculations were performed to compare the experimentally obtained absorption spectra with theoretical predictions. Calculated exchange constants and density of states for the different atomic sites underline the large influence of chemical and magnetic order on the magnetocaloric properties of the material.

Using first-principles calculations, we report on charge injection induced switching between ferromagnetic (FM) and antiferromagnetic (AFM) in a 2H-${\rm MoS}_{2}$ monolayer. ${\rm MoS}_{2}$ monolayers doped with different transition metals (TM)—Fe and Mn—initially demonstrate FM and AFM magnetic ground state, respectively. Once the injected charge approaches $1.0$ e/unit, the systems respectively tend to AFM and FM states, due to the modulation effect of the exchange splitting of spins via injected charge. The interesting switch between FM and AFM can be explained by the competition between FM double-exchange and AFM super-exchange interaction. In contrast, the ${\rm MoS}_{2}$/${\rm WS}_{2}$ heterojunction, because of the direct bonding between dopant TM atoms, remains in the AFM state even under charge injection. These findings point toward the possible development of spintronic switch devices using charge injection in TM doped ${\rm MoS}_{2}$ materials, which could be pivotal to information storage and spintronic applications.

Based on the concept of green environmental protection, we hope to find a substitute for lead perovskites to reduce the pollution and achieve high photoelectric conversion efficiency. In this paper, the structural, electronic and optical properties of γ-RbGeX₃ (X  =  Cl, Br and I) hybrid perovskites are investigated by density functional theory (DFT) calculations. The result shows that the γ-RbGeI₃ has direct band gap of 1.38 eV and exhibits strong optical absorption in the visible light spectrum. However, the electron effective mass in the z direction is larger, which restricts the carrier mobility in the (0 0 1) direction. The blemish can be overcome by applying the  −2% strain in the z direction, which causes the mutation of electron effective mass from 1.35 to 0.09 with little influence on the value of the band gap and the hole effective mass. These above findings also offer a new view to explore the inorganic perovskite for solar cell absorbers.

In this paper, a novel coding metasurface is proposed to realize polarization-controllable diffusion scattering. The anisotropic Jerusalem-cross unit cell is employed as the basic coding element due to its polarization-dependent phase response. The isotropic random coding sequence is firstly designed to obtain diffusion scattering, and the anisotropic random coding sequence is subsequently realized by adding different periodic coding sequences to the original isotropic one along different directions. For demonstration, we designed and fabricated a flexible polarization-controllable diffusion metasurface (PCDM) with both chessboard diffusion and hedge diffusion under different polarizations. The specular scattering reduction performance of the anisotropic metasurface is better than the isotropic one because the scattered energies are redirected away from the specular reflection direction. For potential applications, the flexible PCDM wrapped around a cylinder structure is investigated and tested for polarization-controllable diffusion scattering. The numerical and experimental results coincide well, indicating anisotropic low scatterings with comparable performances. This paper provides an alternative approach for designing high-performance, flexible, low-scattering platforms.

High n-type doping in germanium is essential for many electronic and optoelectronic applications especially for high performance Ohmic contacts, lasing and mid-infrared plasmonics. We report on the combination of in situ doping and excimer laser annealing to improve the activation of phosphorous in germanium. An activated n-doping concentration of 8.8  ×  10¹⁹ cm⁻³ has been achieved starting from an incorporated phosphorous concentration of 1.1  ×  10²⁰ cm⁻³. Infrared reflectivity data fitted with a multi-layer Drude model indicate good uniformity over a 350 nm thick layer. Photoluminescence demonstrates clear bandgap narrowing and an increased ratio of direct to indirect bandgap emission confirming the high doping densities achieved.

We propose a valve structure composed of zero-index metamaterial to manipulate the electromagnetic wave conveniently and effectively through regulating the phase of reflected waves. Both the structure and characteristics of zero-index metamaterial need not to be changed when manipulating the transmission, which maintains the stability of zero-index metamaterial. Moreover, the good performance of tuning the electromagnetic wave is not limited by the shape and size of our proposed structure. By using our proposed valve structure, we demonstrate the realization of the tunable curved anisotropic ε-near-zero material waveguide with irregular shape, arbitrarily sized isotropic ε-near-zero material waveguide with high transmittance and the curved isotropic impedance matched ε-near-zero material waveguide without polarization limitations.

We investigated the effect of process conditions on the electrochromic (EC) properties of tungsten trioxide (WO₃) films. When WO₃ films deposited using a sol-gel method were thermally treated in air at 150 °C, the majority of tungsten species in the films became W⁶⁺, which is important for the realization of an optically transparent bleached state. On the other hand, annealing in a vacuum required only 60 °C to induce a similar level of W⁶⁺ in the WO₃ films. However, a cracked film morphology was observed at higher temperatures, regardless of whether the films were annealed in air or vacuum. Using the WO₃ films prepared under various conditions, EC devices (ECDs) were fabricated to evaluate EC properties. We concluded that the optimal annealing conditions for WO₃ films for ECDs are 60 °C in vacuum, at which the highest coloration efficiency, largest transmittance difference, and fastest bleaching/coloration dynamics were obtained. These mild fabrication conditions at a low temperature (60 °C) provide the opportunity to utilize flexible electrodes on plastic. Therefore, we successfully demonstrated a flexible WO₃-based ECD.

The combined effect mechanism of electrode materials and Al₂O₃ nanoparticles on the insulating characteristics of transformer oil was investigated. Impulse breakdown tests of pure transformer oil and Al₂O₃ nano-modified transformer oil of varying concentrations with different electrode materials (brass, aluminum and stainless steel) showed that the breakdown voltage of Al₂O₃ nano-modified transformer oil is higher than that of pure transformer oil and there is a there is an optimum concentration for Al₂O₃ nanoparticles when the breakdown voltage reaches the maximum. In addition, the breakdown voltage was highest with the brass electrode, followed by that with stainless steel and then aluminum, irrespective of the concentration of nanoparticles in the transformer oil. This is explained by the charge injection patterns from different electrode materials according to the results of space charge measurements in pure and nano-modified transformer oil using the Kerr electro-optic system. The test results indicate that there are electrode-dependent differences in the charge injection patterns and quantities and then the electric field distortion, which leads to the difference breakdown strength in result. As for the nano-modified transformer oil, due to the Al₂O₃ nanoparticle's ability of shielding space charges of different polarities and the charge injection patterns of different electrodes, these two factors have different effects on the electric field distribution and breakdown process of transformer oil between different electrode materials. This paper provides a feasible approach to exploring the mechanism of the effect of the electrode material and nanoparticles on the breakdown strength of liquid dielectrics and analyzing the breakdown process using the space charge distribution.

The present study investigated the electrical characteristics and radical production efficiency of a coplanar barrier discharge (CBD) device manufactured by Kyocera by multilayer ceramic technology. The device consisted of a number of linear electrodes with electrode and gap widths of 0.75 mm, immersed into a ceramic dielectric barrier. A closed flow-through system necessary for the measurements was prepared by placing a quartz plate at a height of 3 mm from the ceramic barrier. The production of nitrogen radicals was determined from the removal of a trace amount of NO in pure N₂ gas, while the production of oxygen radicals was determined by ozone production in pure O₂ or synthetic air. The production efficiency of N and O radicals and NO oxidation in synthetic air was comparable with the efficiency of a volume barrier discharge device. The power density per unit of surface area of the CBD device was more than two times larger than that of a similar volume barrier discharge setup, which makes the CBD device a compact alternative for gas treatment. The production of ozone and different nitrogen oxides was also evaluated for the open system of the CBD which is usable for surface treatment. The ozone concentration of this system was nearly independent from the input power, while the concentration of nitrogen oxides increased with input power. The open system of the CBD was additionally tested for the treatment of a silicon surface. An increase of applied power decreased the time required to reduce the water contact angle below 10 degrees but also started to have an impact on the surface roughness.

Growth mode of tensile-strained Ge quantum dots on different III–V buffers by molecular beam epitaxy is studied by a combination of reflection high-energy electron diffraction, atomic force microscopy and transmission electron microscopy. The Ge-QDs growth on the InAlAs buffer lattice matched to InP and on InAs buffer on GaSb follows the Volmer–Weber growth mode with round Ge QDs and no Ge wetting layer, while it obeys the Stranski–Krastanov growth mode on GaSb, AlSb and AlGaSb on GaSb substrates, showing rectangular shaped platelets and a clear Ge wetting layer. The discovery of the Volmer–Weber growth mode is essential to avoid forming a wetting layer and the subsequent antiphase-domain defects when capping III–Vs on Ge-QDs, important for potential optoelectronic applications.

Semiconductor armchair MoS₂ nanoribbons can be converted into conductors by edge functionalization of H atoms or OH groups. Those metallic nanoribbons exhibit I–V characteristics of a single half-filled band with strong negative differential resistance (NDR) under a voltage bias less than 1 V. This originates from the spatial separation between electrons in the conduction and valence bands. The NDR becomes spin dependent if the H atoms or OH groups are not uniformly adsorbed on the edge. Furthermore, the spin polarization can be greatly enhanced in heterojunctions of H- and OH-passivated nanoribbons.

We proposed and experimentally demonstrated the generation of high-power 1176 nm Stokes wave by frequency shifting of a 885 nm diode-side-pumped Nd:YAG laser using a YVO₄ crystal in a Z-shaped cavity configuration. Employing the 885 nm diode-side-pumped scheme and the Z-shaped cavity, for the first time to our knowledge, we realized the thermal management effectively, achieving excellent 1176 nm Stokes wave consequently. With an incident pump power of ~190.0 W, a maximum average output power of 16.7 W was obtained at the pulse repetition frequency of 10 kHz. The pulse duration and spectrum linewidth of the Stokes wave at the maximum output power were 20.3 ns and ~0.08 nm, respectively.

Based on fully relativistic first-principles calculations, we studied the topological properties of layered XIn₂P₂ (X $=$ Ca, Sr). Band inversion can be induced by strain without SOC, forming one nodal ring in the $k_z = 0$ plane, which is protected by the coexistence of time reversal and glide mirror symmetries. Including SOC, a substantial band gap is opened along the nodal line and the line-node semimetal would evolve into a topological insulator. These results reveal a category of materials showing quantum phase transition from trivial semiconductors and topologically nontrivial insulators by tuneable elastic strain engineering. Our investigations provide a new perspective about the formation of topological line-node semimetal under stain.

This study presents an investigation on the behavior of adhesive contact between a rigid sphere and an elastic film which is either perfectly bonded (case I) or in frictionless contact (case II) with a rigid substrate. By using linear fracture mechanics, we formulate an convenient semi-analytical approach to develop relations between the applied force, penetration depth and contact radius. Finite element analysis (FEA) is used to verify the relationships. Our results reveal that the interfacial boundary conditions between the film and substrate have distinct effects on the adhesive contact behavior between the sphere and the film. The aim of the present study is to provide an instructive inspiration for controlling adhesion strength of the thin film subject to adhesive contact.

High-aspect-ratio microchannels were fabricated by femtosecond-double-pulse-laser-assisted polarization-selective etching. The etching rate and uniformity of the microchannels were mainly determined by the double-pulse polarization and time delay. We found that when the two sub-pulses had a different polarization (one linear, the other circular), the microchannel etching rate increased by a factor of 10 compared to when both sub-pulses were linearly polarized. The maximum etching rate was obtained when the polarization combination was circular for the first sub-pulse and vertical for the second one. In this case, the etching rate was independent from the time delay. Laser confocal microscopy images showed that when the polarization was circular, the area modified by the laser was larger than when the polarization was linear, explaining the higher etching rate value obtained after irradiation with circularly polarized laser light.

The influence of different Er:YAG laser pulse durations on the shear bond strength (SBS) of bleached dentin was investigated in this study. In total, 176 crowns of extracted human premolars were cut horizontally, embedded and ground to expose the sound dentin. Of these, 132 specimens were bleached with 12% hydrogen peroxide (HP) and divided into three groups, irradiated by an Er:YAG laser with different pulse lengths of 50 µs super short pulse (SSP), 100 µs moderate short pulse (MSP) and 300 µs short pulse (SP), respectively. The energy density of the three groups was the same at about 15.73 J cm⁻² for each. Then, each group was further divided into two subgroups according to whether it had been etched with 37% phosphoric acid or not. The control group (N  =  22) was bleached and etched with acid while the blank group (N  =  22) was just etched with acid. The surface morphology of the dentin was observed using scanning electron microscopy (SEM). The SBS of the composite resin to the conditioned dentin was tested with a universal testing machine. It was found that the SBS of the dentin significantly decreased after bleaching treatment, while it was possible to restore it using Er:YAG laser irradiation. Lasers with various pulse durations led to different surface morphologies but had no effect on the SBS. The SSP laser was more suitable on account of it resulting in less thermal damage, and additional acid etching was not necessary for the irradiated bleached dentin in the clinic because it could not further improve the SBS value.

Carbon dioxide can be converted, by reaction with hydrogen, into fine chemicals and liquid fuels such as methanol and DME. Methane production by the Sabatier reaction opens the way of carbon recycling for a circular economy of carbon resources.

The catalytic process of methanation of carbon dioxide produces two molecules of water as a by-product. A current limitation in the CO₂ methanation is the ageing of catalysts, mainly due to water adsorption during the process. To avoid this adsorption, the process is operated at high temperature (300 °C–400 °C), leading to carbon deposition on the catalyst and its deactivation.

To overcome this problem, a methanation plasma-catalytic process has been developed, which achieves high CO₂ conversion rate (80%), and a selectivity close to 100%, working from room temperature to 150 °C, instead of 300 °C–400 °C for the thermal catalytic process.

The main characteristics of this process are high-voltage pulses of few nanoseconds duration, activating the adsorption of CO₂ in bent configuration and the polarization of the catalyst. The key step in this process is the desorption of water from the polarized catalyst.

The high CO₂ conversion at low temperature could be explained by the creation of a plasma inside the nanopores of the catalyst.

Mechanical information processing and control has attracted great attention in recent years. A challenging pursuit is to achieve broad functioning frequency ranges, especially at low-frequency domain. Here, we propose a design of mechanical logic switches based on DNA-inspired chiral acoustic metamaterials, which are capable of having ultrabroad band gaps at low-frequency domain. Logic operations can be easily performed by applying constraints at different locations and the functioning frequency ranges are able to be low, broad and tunable. This work may have an impact on the development of mechanical information processing, programmable materials, stress wave manipulation, as well as the isolation of noise and harmful vibration.

Textured VO₂(0 1 1) microcrystals are grown in the monoclinic, M1 phase which undergoes a reversible first order semiconductor to metal transition (SMT) accompanied by a structural phase transition to rutile tetragonal, R phase. Around the phase transition, VO₂ also experiences noticeable change in its optical and electrical properties. A change in color of the VO₂ micro crystals from white to cyan around the transition temperature is observed, which is further understood by absorption of red light using temperature dependent ultraviolet–visible spectroscopic analysis and photoluminescence studies. The absorption of light in the red region is explained by the optical transition between Hubbard states, confirming the electronic correlation as the driving force for SMT in VO₂. The thermochromism in VO₂ has been studied for smart window applications so far in the IR region, which supports the opening of the band gap in semiconducting phase; whereas there is hardly any report in the management of visible light. The filtering of blue light along with reflection of infrared above the semiconductor to metal transition temperature make VO₂ applicable as advanced smart windows for overall heat management of a closure.

Surface charge accumulation can incur changes in electric field distribution, involved in the electron propagation process, and result in a significant decrease in the surface flashover voltage. The existing 2D surface charge measurement fails to meet the actual needs in real engineering applications that usually adopt the 45° conical frustum insulators. The present research developed a novel 3D measurement platform to capture surface charge distribution on solid insulation under nanosecond pulse in a vacuum. The results indicate that all surface charges are positive under a positive pulse and negative under a negative pulse. Surface charges tend to accumulate more near the upper electrode. Surface charge density increases significantly with the increase in pulse counts and amplitudes. Accumulation of surface charge results in a certain decrease of flashover voltage. Taking consideration of the secondary electron emission for the surface charge accumulation, four materials were obtained to demonstrate the effects on surface charge. Combining the effect incurred by secondary electron emission and the weighty action taken by surface charge accumulation on the flashover phenomena, the discharge mechanism along the insulator surface under nanosecond pulse voltage was proposed.

An innovative multiphase AC arc (MPA) system was developed on the basis of a diode-rectification technique to improve electrode erosion characteristics. Conventionally, electrode erosion in AC arc is severer than that in DC arc. This originated from the fact that the required properties for the cathode and anode are different, although an AC electrode works as the cathode and the anode periodically. To solve this problem, a separation of AC electrodes into pairs of thoriated tungsten cathode and copper anode by diode-rectification was attempted. A diode-rectified multiphase AC arc (DRMPA) system was then successfully established, resulting in a drastic improvement of the erosion characteristics. The electrode erosion rate in the DRMPA was less than one-third of that in the conventional MPA without the diode rectification. In order to clarify its erosion mechanism, electrode phenomena during discharge were visualized by a high-speed camera system with appropriate band-pass filters. Fluctuation characteristics of the electrode temperature in the DRMPA were revealed.