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Generating and manipulating magnetic skyrmions at ultrafast time scales is essential for future skyrmion-based racetrack memory and logic gate applications. Using the atomistic spin dynamics simulations, we demonstrate the nucleation of ultra-small field-free magnetic skyrmions in amorphous GdFeCo at picosecond time scales by femtosecond laser heating. The ultrafast nature of laser heating and subsequent cooling from a high-temperature state is crucial for forming magnetic skyrmion. The magnon localization and magnon coalescence are the key driving mechanisms responsible for stabilizing the magnetic skyrmions at zero-field conditions. The polarization and, hence, the topological charge can be switched by exploiting the all-optical switching observed in GdFeCo. The skyrmion sizes and numbers can be controlled by varying pulse width and fluence of incident laser pulses. Applying an external magnetic field provides an additional degree of freedom to tune the skyrmion radius during the ultrafast optical creation of magnetic skyrmions. Our results provide a detailed understanding of the ultrafast creation of magnetic skyrmions using femtosecond laser pulses, a vital step in advancing next-generation skyrmion-based memory technologies. [ABSTRACT FROM AUTHOR]

Glass-ceramic is widely used in aerospace, bionics, optics and other fields with low expansion and high strength and low dielectric loss, but its hardness and brittleness as well as its high strength have been classified as a kind of difficult-to-process materials. In this paper, free-form machining of glass-ceramic is performed by combining a pulsed laser with fast tool servo (FTS) technology to utilize laser-induced irradiation effects. During pulsed laser synchronously enhanced servo-turning (s-LAST), the material removal process as well as the selection range of operating temperatures were first determined by means of finite elements. The cutting forces on hard and brittle glass-ceramic materials during laser-assisted manufacturing (LAM) were predicted by developing an analytical force model that takes into account the thermal manufacturing damage caused by laser irradiation, using the discretisation method as well as the shear and ploughing effects associated with laser heating. The s-LAST experiments were performed on a selected ultra-low expansion glass-ceramic (Zerodur), and both the modelling and experimental results were validated, with laser irradiation leading to a 12 % reduction in cutting force, and an average principal cutting force of 3.124 N was recorded. [ABSTRACT FROM AUTHOR]

In non-destructive testing for metallic materials, 'Flying-spot' thermography allows the detection of cracks thanks to the scanning of samples by a local laser heat source observed in the infrared spectrum. However, distinguishing a crack from other surface structures such as air ducts or non-planar shapes on the material surface can be challenging in an automation perspective. To address this, we propose to use deep learning techniques, which can exploit contextual information but require a significant amount of labelled data. This study presents a training method based on curriculum learning and recent denoising diffusion models to generate synthetic images. The protocol progressively increases the complexity of training images, using successively simulated data from a multi-physics finite-element software, synthetically generated data with diffusion process, and finally real data. Several detection scores are measured for various machine learning and deep learning architectures, demonstrating the benefits of the proposed approach for regular application cases and degraded experimental conditions, consisting of limited thermal enlightenment recordings. [ABSTRACT FROM AUTHOR]

Surface science instruments require excellent vacuum to ensure surface cleanliness; they also require control of sample temperature, both to clean the surface of contaminants and to control reaction rates at the surface, for example, for molecular beam epitaxy and studies of heterogeneous catalysis. Standard approaches to sample heating within high vacuum chambers involve passing current through filaments of refractory metals, which then heat the sample by convective, radiative, or electron bombardment induced heat transfer. Such hot filament methods lead to outgassing of molecules from neighboring materials that are inadvertently heated; they also produce electrons and ions that may interfere with other aspects of the surface science experiment. Hot filaments may even disintegrate when used in the presence of gases introduced to induce surface reactions on the sample. Optical heating using lasers can deliver energy directly to the sample, ensuring that only the sample is heated and surroundings within the vacuum chamber are not, while simultaneously eliminating the need for hot filaments. Despite this advantage, optical heating is not commonly employed—such methods are considered complex, expensive, and unreliable. More fundamentally, surface scientists are often interested in metallic samples, whose reflectivity may limit the efficiency of laser heating. In this paper, we describe a simple and inexpensive sample heater based on a commercial diode laser, whose heating efficiency is enhanced by a concave aluminum mirror placed behind the sample. The geometry of the reflector and sample ensures that a stable optical cavity is produced. Using only 26 W of laser power directed to the sample with a fiber optic, a 1-cm diameter × 2-mm thick Pt sample could be heated to 1400 K within 1 min. Excellent programmable temperature control and long-term temperature stability are also demonstrated. Sample heating to 900 °C was performed with negligible increase in chamber pressure. The entire setup comprises components costing less than typical electron bombardment heaters. [ABSTRACT FROM AUTHOR]

This study introduces an innovative photo-thermoacoustic-diffusion model to explore wave propagation in a hydro-poroelastic semiconductor medium under laser excitation. The model combines photothermal transport principles with mass diffusion and poroelasticity, capturing the interconnected effects of thermal, chemical, and carrier diffusion processes induced by laser heating. Analytical solutions for the primary physical fields within the medium are obtained using the normal mode analysis method. By incorporating the distinctive properties of hydro-semiconductors, such as fluid-saturated pore interactions, the model is particularly suited for studying porous semiconductor materials. The interaction of photo-induced thermal and mechanical waves with diffusion processes is analyzed under specific boundary conditions. Graphical representations of numerical results highlight the influence of critical parameters, showcasing the model's effectiveness in advancing material understanding and optimization, with potential applications in optoelectronics, photothermal therapy, and semiconductor device design. [ABSTRACT FROM AUTHOR]

The experimental and theoretical study of photovoltage formation in perovskite solar cells under pulsed laser excitation at 0.53 μm wavelength is presented. Two types of solar cells were fabricated on the base of cesium-containing triple cation perovskite films: (1) Csx(FA0.83MA0.17)(1−x)Pb(I0.83Br0.17)3 and (2) Csx(FA0.83MA0.17)(1−x)Pb0.8Sn0.2(I0.83Br0.17)3. It is found that photovoltage across the solar cells consists of two components, U = Uph + Uf. The first one, Uph, is the traditional photovoltage arising due to laser radiation-induced electron-hole pair generation. The second one, Uf, is the fast component following the laser pulse and has a polarity opposite to that of Uph. It is shown that the fast photovoltage component results from the laser radiation-caused heating of free carriers. The transient photovoltage measurements show that the values of the fast component Uf are nearly the same in both types of perovskite solar cells. The magnitude of the traditional photovoltage of mixed Pb-Sn perovskite solar cells is lower than that of Pb-based cells. [ABSTRACT FROM AUTHOR]

The boron carbide coatings deposited on tungsten using three methods have been tested by pulsed heating, which is expected on the first wall and in the divertor zone of the ITER tokamak. The deposition methods chosen were detonation spraying, atmospheric plasma spraying, and electron beam synthesis. The experiments revealed that the best resistance to pulsed heating is demonstrated by coatings applied using detonation and atmospheric plasma spraying methods. [ABSTRACT FROM AUTHOR]

The synergic effects of time dependence and thermodynamic driving on the metastable phase separation of liquid Fe50Cu50 hypoperitectic alloy were explored with three kinds of experimental methods including differential scanning calorimetry (DSC), laser heating, and drop tube. The calculated incubation time indicated that the secondary Cu-rich liquid phase kept the priority to nucleate when alloy undercooling exceeded 28 K. The cooling rates in three kinds of experiments covered six orders of magnitude from 3×10–1 to 6×105 K/s, and resulted in wide range of phase separation time and globule migration velocity. The extent of phase separation was determined by the globule migration distance in the phase separation time. Under 0.33 and 0.83 K/s slow cooling rates in DSC experiments, liquid phase separation was dominated by Stokes motion, and extended phase separation time led to more complete macrosegregation. At a higher cooling rate of 1500 K/s in laser heating experiment, the enhanced Marangoni migration resulted in distinctive macrosegregation in short phase separation time. Once liquid phase separation occurred under microgravity state in drop tube experiment, the phase separation time was the crucial factor dominating microstructure evolution. Core–shell macrosegregation formed in medium size alloy droplets with sufficient phase separation time, while dispersed structure appeared in small droplets with reduced phase separation time. Peritectic structure arose again due to the extremely short phase separation time in tiny alloy droplets. [ABSTRACT FROM AUTHOR]

This study investigates the dynamics of thermal plumes interacting with the liquid–air interface in straight-chain alcohols and their mixtures using a photothermal imaging technique based on thermal lensing. This method enables the indirect measurement of temperature gradients via changes in refractive index caused by localized laser heating. Employing a collimated laser beam, the results show the formation and evolution of cylindrical heated zones and their interactions with the liquid–air interface. The study reveals that, while some alcohols exhibit stable surface behaviors, others demonstrate complex dynamical behaviors, including strong stable steady-state oscillations. The findings contribute to understanding fluid dynamics in molecular liquids near their liquid–air interfaces. [ABSTRACT FROM AUTHOR]

The temperature coefficient of resistivity (θ T) of carbon-based materials is a critical property that directly determines their electrical response upon thermal impulses. It could have metal- (positive) or semiconductor-like (negative) behavior, depending on the combined temperature dependence of electron density and electron scattering. Its distribution in space is very difficult to measure and is rarely studied. Here, for the first time, we report that carbon-based micro/nanoscale structures have a strong non-uniform spatial distribution of θ T. This distribution is probed by measuring the transient electro-thermal response of the material under extremely localized step laser heating and scanning, which magnifies the local θ T effect in the measured transient voltage evolution. For carbon microfibers (CMFs), after electrical current annealing, θ T varies from negative to positive from the sample end to the center with a magnitude change of >130% over <1 mm. This θ T sign change is confirmed by directly testing smaller segments from different regions of an annealed CMF. For micro-thick carbon nanotube bundles, θ T is found to have a relative change of >125% within a length of ∼2 mm, uncovering strong metallic to semiconductive behavior change in space. Our θ T scanning technique can be readily extended to nm-thick samples with μm scanning resolution to explore the distribution of θ T and provide a deep insight into the local electron conduction. [ABSTRACT FROM AUTHOR]

The most interesting, but insufficiently known results obtained by the author in modeling laser-induced hyperthermia of human tumors are discussed. It is important that the traditional equation for the local bio-heat transfer does not work in superficial layers of the body. It is shown also that the classical Arrhenius law is not applicable to living tissues because of the tissue regeneration due to oxygen supplied by the arterial blood. The latter is one of the main reasons of the suggested strategy of laser heating of tumors in the therapeutic window of semitransparency when the tumor asphyxiation is considered as one of important weapons against the cancer. The other advantages of this advanced strategy of a soft thermal treatment (in few of sessions), which is painless for patients, are discussed as well. Some features of modeling various heat transfer modes are also considered. The best choice between the simplest differential models for the radiative transfer calculations is dependent of the particular problem statement. The known finite-difference or finite element algorithms can be preferable in solving transient heat transfer problems. As a rule, it depends on the shape of the computational region. It is expected that this paper will help the colleagues to overcome some typical weaknesses of computational modeling of infrared photothermal treatment of superficial tumors. [ABSTRACT FROM AUTHOR]

AbstractThis paper aims to investigate the transient thermo-viscoelastic memory-dependent responses of the temperature-dependent laminated polymethyl methacrylate (PMAA) composites with imperfect interfaces, of which the bounding surface subjected to non-Gauss laser heating loads, are investigated based on integral-type non-Fourier thermo-viscoelasticity model with memory-dependent derivative (MDD). The Laplace transformation is used to solve the multi-physics differential governing equations. The influences of the viscoelastic material constants ratios, temperature-dependent parameters, laser parameters, memory-dependent parameters and kernel functions on the responses are elucidated to offer guidelines to thermal control and mechanical strength evaluation for the laminated PMMA composites. [ABSTRACT FROM AUTHOR]

The development of various nanomaterials production technologies has led to the possibility of producing nanoparticles (NPs) and nanostructures, which can find a wide range of applications, from the fabrication of microelectronic devices to the improvement of material properties and the treatment of cancer. The unique characteristics of nanoparticles are primarily due to their small size, which makes size control important in their preparation. Modification of nanoparticles by laser irradiation and obtaining desired nanoparticle properties is a promising approach because of its ease of implementation. The purpose of this review is to analyze the works devoted to the study of laser-induced heating and melting of nanoparticles, to collect information and evaluate the results of using this method for functionalization and modification of metallic nanoparticles, and to discuss promising directions for the use of this technique. [ABSTRACT FROM AUTHOR]

This study investigates the spheroidization of titanium Ti-6Al-4V powder particles using numerical models developed in Abaqus and OpenFOAM. Spherical particles are crucial in powder-based additive manufacturing due to their superior flowability, packing density, and mechanical properties, enhancing printing precision and the quality of final products. While conventional techniques such as gas atomization and plasma spheroidization have been extensively researched, the potential of laser spheroidization remains underexplored. To address this gap, detailed numerical analyses of laser spheroidization were conducted, modeling heat transfer from the laser to powder particles using a transient uncoupled heat transfer method with latent heat considerations, while particle deformation was simulated with a phase-fraction-based interface-capturing approach integrated with Navier-Stokes equations. The results, validated against analytical models, indicate that particles within the 20–80 μm range experience optimal spheroidization within a 0.005-second residence time under laser heating, with particles smaller than 30 μm reaching evaporation temperatures of 5,000°C, while larger particles reshape without evaporating under a typical heat flux of 94 MW/m2 (1.8 kW laser power). This study demonstrates that laser spheroidization of Ti-6Al-4V powder can potentially increase powder yield by 10%, offering higher power density and shorter melting times compared to plasma spheroidization, thus presenting a more efficient alternative for achieving spherical particles of specific sizes. [ABSTRACT FROM AUTHOR]

Laser-assisted turning (LAT) involves locally heating a rotating workpiece using a focused laser beam before the removal of material. A key aspect in optimising productivity with laser-assisted turning is understanding the thermal relationship between laser heating, the improved material removal rate, and machinability. Consequently, in this paper, a thermal heating and laser-assisted turning finite element model and experiments were conducted to assess the machinability of an Al/SiC p MMC workpiece, considering the circumferential location of the laser beam from the cutting point. The results confirm that laser power and cutting velocity influence the temperature profile from the laser spot to the tool point and the heat-affected depth. Positioning the cutting tool closer to the laser spot effectively reduces the Von Mises stress during cutting at higher cutting temperatures. At the same time, the experiment indicates an increased risk of directly heating the tool, which can affect the integrity of the cutting tool. The work further reveals that at specified cutting velocities, lower specific cutting energy improves the tool condition and surface quality of the machined parts. Based on a range of material removal rates and laser-specific energy density, a new criterion for optimal laser-tool circumferential distance was determined. Establishing this distance can act as a guide for the laser-assisted turning of Al/SiC p metal matrix composites and potentially other materials. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is the formation and growth of nanoscale intermetallic compounds (IMCs) when laser is used as a heat source to form solder joints. Design/methodology/approach: This study investigates the Sn/Cu and Sn-0.1AlN/Cu structure using laser soldering under different laser power: (200, 225 and 250 W) and heating time: (2, 3 and 4 s). Findings: The results show clearly that the formation of nano-Cu6Sn5 films is feasible in the laser heating (200 W and 2 s) with Sn/Cu and Sn-0.1AlN/Cu system. The nano-Cu6Sn5 films with thickness of 500 nm and grains with 700 nm are generally parallel to the Cu surface with Sn-0.1AlN. Both IMC films thickness of Sn/Cu and Sn-0.1AlN/Cu solder joints gradually increased from 524.2 to 2025.8 nm as the laser heating time and the laser power extended. Nevertheless, doping AlN nanoparticles can slow down the growth rate of Cu6Sn5 films in Sn solder joints due to its adsorption. Originality/value: The formation of nano-Cu6Sn5 films using laser heating can provide a new method for nanofilm development to realize the metallurgical interconnection in electronic packaging. [ABSTRACT FROM AUTHOR]

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Smooth metal microspheres with uniform sizes are ideal for constructing particle-arrayed anisotropic conductive films (ACF), but synthesis is hindered by challenges in controlling anisotropic metal growth. Here, we present a positioned transient-emulsion self-assembly and laser-irradiation strategy to fabricate pure gold microsphere arrays with smooth surfaces and uniform sizes. The fabrication involves assembling gold nanoparticles into uniform colloidosomes within a pre-designed microhole array, followed by rapid transformation into well-defined microspheres through laser heating. The gold nanoparticles melt and merge in a layer-by-layer manner due to the finite skin depth of the laser, leading to a localized photothermal effect. This strategy circumvents anisotropic growth, enables tunable control of microsphere size and positioning, and is compatible with conventional lithography. Importantly, these pure gold microspheres exhibit stable conductivity under deep compression, offering promising applications in soldering micro-sized chips onto integrated circuits. The authors present a simple and rapid way for fabricating gold microsphere arrays through a laser-irradiated ripening strategy. These gold microspheres are suitable for reliable high-resolution bonding applications due to their stable conductivity. [ABSTRACT FROM AUTHOR]

The fabrication of high‐performance microbial fuel cells requires the evaluation of the activity of electrochemically active bacteria. However, this is challenging because of the time‐consuming nature of biofilm formation and the invasive nature of labeling. To address this issue, we developed a fast, label‐free, single‐cell Raman spectroscopic method. This method involves investigating the “pure” linear Stark effect of endogenous CO in the silent region of biological samples, which allows for probing the intrinsic electric field in the outer‐membrane cytochromes of live bacterial cells. We found that reduced outer‐membrane cytochromes can generate an additional intrinsic electric field equivalent to an applied potential of +0.29 V. We also found that the higher the electrical activity of the cell, the larger the generated electric field. This was also reflected in the output current of the constructed microbial fuel cells. Raman spectroscopy was employed to facilitate the assessment of electrochemical activity at the single‐cell level in highly‐diluted bacterial samples. After analysis, inactive bacteria were ablated by laser heating, and 20 active cells were cultured for further testing. The rapid and high‐throughput probing of the intrinsic electric field offers a promising platform for high‐efficiency screening of electrochemically active bacterial cells for bioenergetic and photosynthetic research. [ABSTRACT FROM AUTHOR]

Recent progress has seen multiple Ta2O5 polymorphs generated by different synthesis techniques. However, discrepancies arise when these polymorphs are produced in widely varying thermodynamic conditions and characterized using different techniques. This work aimed to characterize and compare Ta2O5 particles formed at high and low temperatures using nanosecond pulsed laser ablation (PLA) and continuous wave (CW) laser heating of a local area of tantalum in either air or an 18O2 atmosphere. Scanning electron microscopy (SEM) and Raman spectroscopy of the micrometer-sized particles generated by PLA were consistent with either a localized amorphous Ta2O5 phase or a similar, but not identical, crystalline β-Ta2O5 phase. The Raman spectrum of the material formed at the point of CW laser impingement was in good agreement with the previously established ceramic "H-Ta2O5" phase. TEM and electron diffraction analysis of these particles indicated the phase structure matched an oxygen-vacated superstructure of monoclinic H-Ta2O5. Further from the point of laser impingement, CW heating produced particles with a Raman spectrum that matched β-Ta2O5. We confirmed that the high-temperature ceramic phase characterized in previous work by Raman spectroscopy was the same monoclinic phase characterized in different work by TEM and could be produced by direct laser heating of metal in air. [ABSTRACT FROM AUTHOR]

Ultrafast manipulation of the Néel vector in metallic antiferromagnets most commonly occurs by generation of spin-orbit (SOT) or spin-transfer (STT) torques. Here, we predict another possibility for antiferromagnetic domain switching by using novel laser optical torques (LOTs). We present results of atomistic spin dynamics simulations from the application of LOTs for all-optical switching of the Néel vector in the antiferromagnet Mn2Au. The driving mechanism takes advantage of the sizeable exchange enhancement, characteristic of antiferromagnetic dynamics, allowing for picosecond 90 and 180-degree precessional toggle switching of the Néel vector with laser fluences on the order of mJ/cm2. A special symmetry of these novel torques greatly minimises the over-shooting effect common to precessional spin switching by SOT and STT methods. We demonstrate the opportunity for LOTs to produce deterministic, non-toggle switching of single antiferromagnetic domains. Lastly, we show that even with sizeable ultrafast heating by laser in metallic systems, there exist a large interval of laser parameters where the LOT-assisted toggle and preferential switchings in magnetic grains have probabilities close to one. The proposed protocol could be used on its own for all-optical control of antiferromagnets for computing or memory storage, or in combination with other switching methods to lower energy barriers and/or to prevent over-shooting of the Néel vector. [ABSTRACT FROM AUTHOR]

"MightyLev," a new multi-emitter ultrasonic acoustic levitation device capable of extremely stable levitation of materials of density up to at least 11.3 g cm−3, is described. The exceptional stability of medium- to high-density samples levitated in MightyLev makes the device highly suitable for chemical and structural analysis using micro-focused spectroscopic and x-ray scattering techniques. In combination with mid-infrared laser heating, MightyLev is capable of levitating metallic and oxide materials during high-temperature cycling and melting above 1500 K. Instabilities in particle confinement during heating were investigated by directly visualizing the acoustic field using schlieren imaging. The results reveal jets of hot-air directed along the anti-nodes of the acoustic field. The reaction force on the sample from the jet, coupled with the restoring force of the acoustic trap, generates a parametric lateral oscillation of the sample. This result provides valuable insight for future optimization and wider application of acoustic levitation for high-temperature containerless material processing. [ABSTRACT FROM AUTHOR]

This study explores the modeling, design, simulation, and testing of a new composite material designed for high-strength and high-temperature resistance in in-space optical mining, examining its properties at both the polymer and atomic/molecular levels. At the polymer level, the investigation includes mechanical and thermal performance analyses using COMSOL Multiphysics 6.1, employing layerwise theory, equivalent single layer (ESL) theory, and a multiple-model approach for mechanical modeling, alongside virtual thermal experiments simulating laser heating. Experimentally, porous Polyaniline (PANI) films are fabricated via electrochemical polymerization, with variations in voltage and deposition time, to study their morphology, optical performance, and electrochemical behavior. At the atomic and molecular levels, this study involves modeling the composite material, composed of Nomex, Kevlar, and Spirooxazine-Doped PANI, and simulating its behavior. The significance of this work lies in developing a novel composite material for in-space optical mining, integrating it into optical mining systems, and introducing innovative thermal management solutions, which contribute to future space exploration by improving resource efficiency and sustainability, while also enhancing the understanding of PANI film properties for in-space applications. [ABSTRACT FROM AUTHOR]

Currently, there is limited research on the in situ forming process of thermoplastic prepreg tape winding, and the unclear impact of process parameters on mechanical properties during manufacturing is becoming increasingly prominent. The study aimed to investigate the influence of process parameters on the mechanical properties of thermoplastic composite materials (CFRP) using laser-assisted CF/PPS winding forming technology. The melting point and decomposition temperature of CF/PPS materials were determined using DSC and TGA instruments, and based on the operating parameters of the laser-assisted winding equipment, the process parameter range for this fabrication technology was designed. A numerical model for the temperature of laser-heated CF/PPS prepreg was established, and based on the filament winding process setup, the heating temperature and tensile strength were simulated and tested. The effects of process parameters on the heating temperature of the prepreg and the tensile strength of NOL rings were then analyzed. The non-dominated sorting genetic algorithm (NSGA-II) was employed to globally optimize the process parameters, aiming to maximize winding rate and tensile strength. The results indicated that core mold temperature, winding rate, laser power, and their interactions significantly affected mechanical properties. The optimal settings were 90 °C, 418.6 mm/s, and 525 W, achieving a maximum tensile strength of 2571.51 MPa. This study provides valuable insights into enhancing the forming efficiency of CF/PPS-reinforced high-performance engineering thermoplastic composites. [ABSTRACT FROM AUTHOR]

Despite recent advancements, artificial muscles have not yet been able to strike the right balance between exceptional mechanical properties and dexterous actuation abilities that are found in biological systems. Here, we present an artificial magnetic muscle that exhibits multiple remarkable mechanical properties and demonstrates comprehensive actuating performance, surpassing those of biological muscles. This artificial muscle utilizes a composite configuration, integrating a phase-change polymer and ferromagnetic particles, enabling active control over mechanical properties and complex actuating motions through remote laser heating and magnetic field manipulation. Consequently, the magnetic composite muscle can dynamically adjust its stiffness as needed, achieving a switching ratio exceeding 2.7 × 10³. This remarkable adaptability facilitates substantial load-bearing capacity, with specific load capacities of up to 1000 and 3690 for tensile and compressive stresses, respectively. Moreover, it demonstrates reversible extension, contraction, bending, and twisting, with stretchability exceeding 800%. We leverage these distinctive attributes to showcase the versatility of this composite muscle as a soft continuum robotic manipulator. It adeptly executes various programmable responses and performs complex tasks while minimizing mechanical vibrations. Furthermore, we demonstrate that this composite muscle excels across multiple mechanical and actuation aspects compared to existing actuators. Artificial muscles often struggle to match the performance of biological systems. Here, the authors report an artificial magnetic muscle that shows remarkable mechanical and actuating capabilities, comparable to natural muscles. [ABSTRACT FROM AUTHOR]

The article discusses the evidence of superconductivity in electrical resistance measurements of hydrides under high pressure. It highlights the importance of considering different probe orientations to eliminate artifacts and assess sample homogeneity. The study demonstrates the vanishing resistance in hydrogen-rich compounds across all probe orientations, supporting the emergence of superconductivity in these materials. The authors advocate for a comprehensive methodology in investigating superconductivity to enhance the reliability and reproducibility of findings. [Extracted from the article]

Ultrashort pulse laser processed sulfur hyperdoped black silicon represents a promising silicon-based material for infrared optoelectronic applications due to its high sub-bandgap optical absorptance. Non-thermal melting and resolidification processes associated with such laser processing, however, result in amorphous and polycrystalline phases which may be detrimental for this purpose. Furthermore, the sulfur impurities are electrically inactive, impeding the formation of a rectifying junction. This work demonstrates an ultrafast laser heating process based on heat accumulation with laser pulses of 10 ps pulse duration at high repetition rates of 41 MHz and peak fluences between 33% and 66% of the ablation threshold as a method to (i) recrystallize the material and (ii) electrically activate the sulfur dopants while (iii) maintaining the sub-bandgap absorption. Furthermore, laser heating recovers the optical activity of sulfur states that have been previously deactivated by thermal annealing. The demonstrated process can have versatile applications in material functionalization due to its highly localized heat input accompanied by high cooling rates. [ABSTRACT FROM AUTHOR]

Fused filament fabrication (FFF) has become the preferred method for 3D printing of thermoplastic polymer parts due to its cost-effectiveness in comparison with powder- or resin-based 3D printing methods in both machines and materials. It also holds the potential to replace injection molding for small batch production, due to significantly reduced tooling costs, lead time, and the ability to create complex structures. However, the mechanical strength of polymer parts fabricated using this method is significantly lower than those produced using injection molding; this issue is worse in printed polymer composites due to undesirable rheological behaviors of infills during the filament extrusion process. This study investigates the use of an in-process orbiting laser pre-deposition heating technique aimed to enhance the mechanical strength of carbon fiber–reinforced filament in FFF. In this work, the mechanical strength, strain, and fracture behavior are investigated. This innovative technology increases tensile strength from 17.4 to 34.9 MPa at 0.45 W laser power and increases strain from 0.028 to 0.084. Moreover, the laser-treated samples exhibit marked differences in fracture surface characteristics when compared to control samples. The adoption of this approach can provide a solution to the main barrier to the adoption of FFF 3D for engineering and industrial applications. [ABSTRACT FROM AUTHOR]

The continuous development and application of laser technology, and the increasing energy and power of laser output have promoted the development of various types of laser optical systems. The optical components based on quartz materials are key components of high-power laser systems, and their quality directly affects the load capacity of the system. Due to the photothermal effect when the laser interacts with the quartz material and generates extremely high temperatures in a short period of time, it is impossible to experimentally solve the phenomena and physical mechanisms under extreme conditions. Therefore, it is very important to select a suitable method to investigate the thermal effect of intense laser interaction with quartz materials and explain the related physical mechanism. In this study, a three-dimensional quarter-symmetric laser heating quartz material geometry model by using nonlinear transient finite element method was established, and its transient temperature field distribution of the quartz material after being heated by a 1,064 nm continuous laser was investigated. In addition, the influence of different laser parameters (laser spot radius, heat flux and irradiation time), material parameters (material thickness, material absorption rate of laser) on the thermal effect of heating quartz material were also studied. When the laser heat flux is 20 W/cm2, the diameter of the laser spot is 10 cm, the irradiation time is 600 s and the thickness is 4 cm, the temperature after laser heating can reach 940.18°C, which is far lower than the melting point. In addition, the temperature maximum probes were set at the overall model, spot edge and rear surface respectively, and their temperature rise curves with time were obtained. It is also found that there is a significant hysteresis period for the rear surface temperature change of the quartz material compared with the overall temperature change due to heat conduction. Finally, the method proposed can also be applied to the laser heating of other non-transparent materials. [ABSTRACT FROM AUTHOR]

The thermo-mechanical coupled behavior of biological tissues excited by a transient heating has been studied in this paper, in which the temperature-dependent physical properties are considered. A non-linear bio-thermo-mechanical coupled model with variable physical parameters has been proposed firstly in the context of the generalized theory with the dual-phase relaxation mechanism. An effective procedure constructed on an explicit finite difference scheme is then implemented to solve this non-linear model numerically. On this basis the thermo-mechanical coupled response and relative thermal damage within a skin tissue irradiated by a pulse laser has been explored. The temporal and spatial distributions of each physical field resulting from various cases have been obtained and illustrated. The results stated that the thermo-mechanical interaction induced by a laser heating would be inhibited by temperature-dependent physical parameters and this inhibition is more significant on the tissue displacement and normal stresses than tissue temperature. The thermal damage is also inhibited when the temperature dependence is considered and the time that healthy tissues can be tolerated would be a larger extension for its accumulative effect with tissue temperature. [ABSTRACT FROM AUTHOR]

The present study assumes that the material properties of the fin vary by a force rule in the axial direction, with the exception of the thermal relaxation coefficient, which is assumed to be constant. The temperature distribution in the longitudinal fin with homogeneous cross-section exposed to the laser heat source is numerically investigated. This is because these constraints lead to a linear differential equation with partial solutions that cannot be analytically resolved using conventional methods, except for a few elementary order functions. Consequently, a linear or nonlinear system of equations as a function of time is obtained by transforming a differential equation attained with one or more independent factors using the highly efficient, potent, and practical semianalytical method known as the Chebyshev pseudospectral method. Temperature distributions in the fin are then examined in terms of different homogeneity factors and timevarying heat source capacity. Furthermore, the numerical solutions’ convergence is emphasised, and the results are confirmed using homogeneous solutions from the literature. [ABSTRACT FROM AUTHOR]

This work reveals the rules of using figures of merit on selecting efficient plasmonic nanoheaters. Here, a size dependence of plasmonic nanoparticle optical heating was disclosed. The continuous laser heating of gold nanospheres is evaluated exploring a theoretical approach and thermal lens spectroscopy, which allowed identifying micro-degree temperature changes of laser heated colloidal gold nanospheres of varying sizes. Our findings indicate that the temperature of photoheating colloidal particles rises according to the Joule number values. The optimal gold nanospheres diameter for efficient colloidal laser heating was identified to be 50 nm. Moreover, we demonstrated that long-time domain measurements of colloidal sample enable the identification of single-particle intermediate steady-state temperature. Considering a single particle, nanospheres with diameter larger than 80 nm exhibit superior heating performance than smaller particles, revealing that the optimal particle size for single-particle optical heating applications is different from the optimal particle size for collective heating of nanoparticles. Our results pave the way for the rational use of plasmonic nanoheaters in photothermal applications. [ABSTRACT FROM AUTHOR]

This study employs neutron diffraction to investigate the relationship between residual stress and coating thickness in cold sprayed 304L austenitic stainless steel. Results show that shot peening predominantly impacts the residual stress profile, leading to substantial in-plane compressive force. The impact of laser heating, a widely used method to alter cold spray's microstructural properties, on the coating's residual stress is also analyzed. The findings indicate that the maximum compressive residual stress in the in-plane component is mainly independent of coating thickness, which suggests that the material properties determine the maximum residual stress. The cold sprayed deposits possessed compressive, nearly biaxial strain and stresses. After laser heating, these stresses were replaced by tensile residual stresses. Two analytical models, the Tsui and Clyne and the Boruah models, for predicting residual stresses are also evaluated, and both models provide reasonable fits to the experimental data. At this point, the deviations between the experimental results and the models are principally caused by the inability of the current models to address plastic deformation and relaxation, and the residual stresses generated by thermal gradients. [ABSTRACT FROM AUTHOR]

Laser therapy has been widely used to treat port-wine stains (PWS) and other cutaneous vascular lesions via selective photothermolysis. Animal models are a valuable tool for investigating thermal responses beneath the skin. However, in previous animal experiments, such as the dorsal skin chamber model, one side of the skin was removed, resulting in the loss of mechanical support for the target blood vessel. In this study, the optical clearing technique was applied to the dorsal skin, allowing direct observation of real thermal responses within the tissue without removing the covering skin. The target blood vessels were irradiated with a pulsed 1064 nm Nd: YAG laser. The corresponding thermal responses were recorded using a CCD camera. Additionally, variations in skin reflectance spectra were measured before and after laser irradiation. Due to the optical clearing and reflectance spectra measurement, vessel responses such as contraction, reperfusion, and full occlusion were correlated with specific variation patterns in reflectance spectral signals. [ABSTRACT FROM AUTHOR]

Hyperdoped germanium (Ge) has demonstrated increased sub-bandgap absorption, offering potential applications in the short-wavelength-infrared spectrum (1.0–3.0 μm). This study employs ion implantation to introduce a high concentration of selenium (Se) into Ge and investigates the effects of post-implantation annealing techniques on the recovery of implantation damage and alterations in optical properties. We identify optimal conditions for two distinct annealing techniques: rapid thermal annealing (RTA) at a temperature of 650 °C and ultrafast laser heating (ULH) at a fluence of 6 mJ/cm2. The optimized ULH process outperforms the RTA method in preserving high doping profiles and achieving a fourfold increase in sub-bandgap absorption. However, RTA leads to regrowth of single crystalline Ge, while ULH most likely leads to polycrystalline Ge. The study offers valuable insights into the hyperdoping processes in Ge for the development of advanced optoelectronic devices. [ABSTRACT FROM AUTHOR]

The article presents the estimation of temperature and emissivities of niobium and 100c6 steel around their melting points using techniques based on the minimization of the least squares norm or on Bayesian inference. Two models were considered for the spectral emissivity, including a linear variation with respect to the wavelength and independent spectral values. The measured data used for the solution of the parameter estimation problem were radiative fluxes collected from a five-wavelength pyrometer. The experimental apparatus used in this work was designed for the characterization of metal samples with sizes of few millimeters at high temperatures, combining aerodynamic levitation and laser heating. The use of the linear spectral emissivity model provided quite consistent results with the ordinary least squares estimator and with stochastic simulations using the Metropolis-Hastings algorithm. Similarly, the model of independent spectral emissivities resulted in accurate emissivities, but it required an informative prior for temperature, such as the known melting point of the metal sample. Therefore, whatever the inverse method used, a priori supplementary information in terms of emissivities or temperatures are needed due to the temperature-emissivity correlation and the unknow emissivity behavior. [ABSTRACT FROM AUTHOR]

Single-crystal germanium, as an excellent infrared optical material, has been widely applied in X-ray monochromators, night vision systems, and gamma radiation detectors. However, how to obtain high-quality optical lenses on their surfaces still faces challenges due to their hard and brittle properties. To this end, this paper proposes the in situ laser-assisted diamond turning (ILADT) process, which is the combination of a laser heating technique and a single-point diamond turning process. The in situ laser heating technique is employed to enhance the surface quality of the workpiece material, while the single-point diamond turning process is utilized to fabricate optical lenses. Experimental results showed that optical lenses with high surface quality were successfully machined. The profile error is 0.135 μm, indicating the high machining accuracy. The surface roughness Sa of the aspheric lens is 0.909 nm, indicating the high machining quality achieved by the proposed ILADT process. Therefore, this study provides an effective approach for producing high-quality optical lenses on single-crystal germanium surfaces, which holds great promise for future applications in the manufacturing of optical lenses with exceptional quality. [ABSTRACT FROM AUTHOR]

Nanometre- to micrometre-sized solid dust particles play a vital role in star and planet formations. Despite of their importance, however, our understanding of physical and chemical properties of dust particles is still provisional. We have conducted a condensation experiment of the vapour generated from a solid starting material having nearly cosmic proportions in elements. A laser flash heating and subsequent cooling has produced a diverse type of nanoparticles simultaneously. Here we introduce four types of nanoparticles as potential dust particles in space: amorphous silicate nanoparticles (type S); core/mantle nanoparticles with iron or hydrogenized iron core and amorphous silicate mantle (type IS); silicon oxycarbide nanoparticles and hydrogenized silicon oxycarbide nanoparticles (type SiOC); and carbon nanoparticles (type C), all produced in a single heating–cooling event. Type IS and SiOC nanoparticles are new for potential astrophysical dust. The nanoparticles are aggregated to a wide variety of structures: compact, fluffy, and networked. A simultaneous formation of these nanoparticles, which are diverse in chemistry, shape, and structure, prompts a re-evaluation of astrophysical dust particles. [ABSTRACT FROM AUTHOR]

Multilayer core–shell microparticles with a liquid core and a polycomposite light-absorbing shell (microcapsules) are important components of modern bio- and medical technologies. Opening of the microcapsule shell and payload release can be realized by optical radiation. The photophoretic force is due to the radiation-stimulated thermal gradient and arises from the temperature inhomogeneity of the microparticle. Photophoretic forces, as well as radiation pressure forces, are inherently mechanical forces and can cause microcapsules to move during the opening cycle. We numerically simulate the microcapsule photophoretic motion when illuminated by an intense laser pulse. Numerical calculations of the temperature field in a spherical microcapsule are carried out using the finite element method, taking into account the auxiliary nanoparticles, which are randomly distributed around the capsule and serve to enhance the heating of the capsule under short pulse exposure. The spatial distribution of the absorbed optical power as well as the temporal dynamics of microcapsule heating depending of its size are investigated in detail. We show, for the first time to our knowledge, that under the joint action of light pressure and photophoretic forces, the microcapsule can move along the laser incidence direction both forward and backward at the distance of several tens of nanometers depending on the particle size and conditions of optical absorption. [ABSTRACT FROM AUTHOR]

Laser irradiation can induce local modulations of functional material properties, such as a decreased resistivity or a variation in reflectance. Recent studies investigated the laser-induced phase separation of 4 H-SiC into carbon and silicon on top of regrown SiC to customize its electrical conductivity for the application in electronic devices. To understand the physical processes leading to the laser-induced phase separation, time-resolved pump-probe measurements represent a suitable tool. This study advances the state of the art by characterizing the transient reflectance changes in 4 H-SiC upon irradiation by spatially resolved pump-probe reflectometry. Since the laser heating alters the reflectance of the sample, the spatially resolved measurement enables to observe the heat conduction from the irradiated to the non-irradiated areas, which sustains for several milliseconds. Numerical simulations of the temperature evolution reveal a restricted one-dimensional heat conduction into depth due to the broad lateral extent of the irradiated area. The associated sustained increased temperature within the irradiated area most certainly abets the feasibility of the phase separation. These findings offer practical insights for optimizing the applied laser parameters to tailor the material properties via phase separation. [ABSTRACT FROM AUTHOR]

According to experiments, the initial martensitic structure with inherent carbon content is most suitable for high-speed laser hardening during preliminary volumetric heat treatment, releasing a suitable amount and dispersion of carbides during tempering. When choosing a volumetric heat treatment mode, it is necessary to consider that the α→γ transformation during laser heating occurs via a shear mechanism with the hereditary transfer of carbon atoms and alloying elements, as well as defects in the crystal structure, to austenite from the original martensite. High-temperature laser-hardened austenite has a fragmented structure with subgrains 200–300 nm in size. This feature is due to the dynamic polygonization of austenite, which occurs because of the superposition of dynamic thermostrictive effects in the laser processing zones on phase hardening during the α→γ transition. After high-speed cooling, the irradiated zones contain hereditary fine-needle martensite with high-strength properties, a certain amount of textured residual austenite, and a carbide phase. It has been established that the strengthening of irradiated steel, which occurs under conditions of thermal deformation of laser radiation, is associated, among other things, with the formation of nanosized zones at the carbide steel matrix composition interface, which have a dispersed structure and increased hardness (10–12 GPa). Metallophysical and urometric studies showed that the maximum hardness of laser-hardened steels is achieved if dispersed carbides occupy more than 40% of the irradiated area and have dimensions of 0.5–1.5 μm. A reasonable choice of the initial steel structure and laser processing mode enabled obtaining a structural state of surface layers on the working surfaces of products having high and predictable performance properties. [ABSTRACT FROM AUTHOR]

The thermal conductivity of bridgmanite, the primary constituent of the Earth's lower mantle, has been investigated using diamond anvil cells at pressures up to 85 GPa and temperatures up to 3,100 K. We report the results of time‐domain optical laser flash heating and X‐ray Free Electron Laser heating experiments from a variety of bridgmanite samples with different Al and Fe contents. The results demonstrate that Fe or Fe,Al incorporation in bridgmanite reduces thermal conductivity by about 50% in comparison to end‐member MgSiO3 at the pressure‐temperature conditions of Earth's lower mantle. The effect of temperature on the thermal conductivity at 28–60 GPa is moderate, well described as k=k300(300/T)a ${k={k}_{300}(300/T)}^{a}$, where a is 0.2–0.5. The results yield thermal conductivity of 7.5–15 W/(m × K) in the thermal boundary layer of the lowermost mantle composed of Fe,Al‐bearing bridgmanite. Plain Language Summary: Heat transport from the Earth's core and mantle to the surface drives plate tectonics and is crucial for sustaining the magnetic field which shields the surface from the solar wind. To quantify the heat transport process across the core‐mantle boundary layer, it is important to know thermal conductivity of major constituent minerals of the lower mantle in the region. Bridgmanite, which was called silicate perovskite, is the most abundant mineral in the lower mantle. Here we measured thermal conductivity on lab‐grown bridgmanite with different Fe and Al compositions compressed at the tips of two opposing diamonds to reproduce relevant pressures in the mantle. To obtain thermal conductivity, we applied optical and X‐ray Free Electron Lasers combined with optical spectroscopy and X‐ray diffraction to heat and measure time‐dependent temperature distributions of the sample. Our study provides relevant high pressure‐temperature data sets to better constrain the heat flux across the core‐mantle boundary. Key Points: We measured thermal conductivity of Fe,Al‐bearing bridgmanite, the most abundant mineral in the Earth's lower mantle, up to 85 GPa and 3,100 KFinite‐element calculations to temperatures obtained from laser flash and X‐ray Free Electron Laser heating measurements are fitted to evaluate temperature effect on conductivityWe assessed pressure, temperature, composition effects on thermal conductivity of bridgmanite at the thermal boundary layer of the lowermost mantle [ABSTRACT FROM AUTHOR]

A reliable initiation of oblique detonation is critical in oblique detonation engines, especially for oblique detonation engines under extreme conditions such as a high altitude and low Mach number, which may lead to excessive length of the induction zone and even the phenomenon of extinction. In this paper, surface ignition was applied to the initiation of oblique detonation, and a high-temperature region was set on the wedge to simulate the presence of a hot-spot induced by the laser heating. The two-dimensional multi-component Navier–Stokes equations considering a detailed H2 combustion mechanism are solved, and the oblique detonation wave accelerated by a hot-spot is studied. In this paper, hot-spots in the induction zone on the wedge, are introduced to explore the possibility of hot-spot initiation, providing a potential method for initiation control. Results show that these methods can effectively promote the accelerated initiation of the oblique detonation. Furthermore, the hot-spot temperature, size and position are varied to analyze their effects on the initiation position. Increasing the temperature and size of the hot-spot both can accelerate initiation, but from the perspective of energy consumption, a small hot-spot at a high temperature is preferable for accelerating ODW initiation than a large hot-spot at a low temperature. The initiated position of the oblique detonation is sensitive to the position of the hot-spots; if a 2000 K hotspot is at the beginning of the wedge, then the ODW's initiation distance will be reduced to about 30% of that without hotspot acceleration. [ABSTRACT FROM AUTHOR]

Time-domain thermoreflectance (TDTR) is a well-established pump–probe method for measuring thermal conductivity and interface conductance of multilayers. Interpreting signals in a TDTR experiment requires a thermal model. In standard front/front TDTR experiments, both pump and probe beams typically irradiate the surface of a multilayer. As a result, existing thermal models for interpreting thermoreflectance experiments assume that the pump and probe beams both interact with the surface layer. Here, we present a frequency-domain solution to the heat-diffusion equation of a multilayer in response to nonhomogeneous laser heating. This model allows analysis of experiments where the pump and probe beams irradiate opposite sides of a multilayer. We call such a geometry a front/back experiment to differentiate such experiments from standard TDTR experiments. As an example, we consider a 60nm amorphous Si film. We consider how signals differ in a front/front vs front/back geometry and compare thermal model predictions to experimental data. [ABSTRACT FROM AUTHOR]

With the advent of toroidal and double-stage diamond anvil cells (DACs), pressures between 4 and 10 Mbar can be achieved under static compression, however, the ability to explore diverse sample assemblies is limited on these micron-scale anvils. Adapting the toroidal DAC to support larger sample volumes offers expanded capabilities in physics, chemistry, and planetary science: including, characterizing materials in soft pressure media to multi-megabar pressures, synthesizing novel phases, and probing planetary assemblages at the interior pressures and temperatures of super-Earths and sub-Neptunes. Here we have continued the exploration of larger toroidal DAC profiles by iteratively testing various torus and shoulder depths with central culet diameters in the 30–50 µm range. We present a 30 µm culet profile that reached a maximum pressure of 414(1) GPa based on a Pt scale. The 300 K equations of state fit to our P–V data collected on gold and rhenium are compatible with extrapolated hydrostatic equations of state within 1% up to 4 Mbar. This work validates the performance of these large-culet toroidal anvils to > 4 Mbar and provides a promising foundation to develop toroidal DACs for diverse sample loading and laser heating. [ABSTRACT FROM AUTHOR]