Liquid Metal Research Articles

Phase Behavior and Atomic Dynamics in Rb x Na1-x : Insights from Machine Learning Interatomic Potentials based on Ab Initio Molecular Dynamics

Abstract Liquid alkali metal alloys have garnered significant attention because of their potential applications in coolant systems and batteries, driven by the need for environmental conservation and technological development. However, research on these complex systems is limited, necessitating a deeper understanding to ensure their safe and effective utilization. This study presents a comprehensive investigation of the factors that determine the phase diagram of Rb x Na1-x . By reproducing the experimental results using the thermodynamic integration method and machine learning interatomic potentials based on ab initio molecular dynamics simulations, we uncovered the delicate balance between the energy and entropy contributions that influence the phase stability of these liquid metal alloys. Further analysis of the liquid phase revealed the crucial roles of volume and atomic mass. Additionally, the coordination numbers of the atoms revealed distinct clustering behaviors, where Na atoms tended to avoid proximity to other Na atoms, whereas Rb atoms exhibited a strong tendency to cluster together. Moreover, the diffusion dynamics further illustrated the asymmetry in the behavior of Rb and Na, with Rb showing increased diffusion at higher concentrations and Na exhibiting higher diffusion at lower concentrations. These findings offer significant insights into the phase stability and the dynamic and structural properties of these complex liquid metal alloys.

The Next Generation of Recyclable Epoxy-anhydride Networks Combining Metallic Ionic Liquid (MIL) and Epoxidized IL-Based Monomers

The Next Generation of Recyclable Epoxy-anhydride Networks Combining Metallic Ionic Liquid (MIL) and Epoxidized IL-Based Monomers

Spontaneous Phase Transition Charge of Liquid Metals Induced NH3 Decomposition To Achieve GaN Nanomaterials at Room Temperature

Spontaneous Phase Transition Charge of Liquid Metals Induced NH₃ Decomposition To Achieve GaN Nanomaterials at Room Temperature

Flexible Bridged Thermoelectric Device with an Optimized Heatsink for Personal Thermal Management.

A wearable thermoelectric cooler (TEC) for personal thermal management exhibits significant growth in numerous applications in personal thermal comfort and saving the energy consumed by space cooling. Most TECs provide a large cooling performance with the assistance of rigid heatsinks and electrodes, limiting wearability and practical implementation. Here, we design and propose a flexible bridged personal TEC with a high thermal management heatsink and spray-printed liquid metal electrodes. The system combines a bendable heatsink, a thermally insulative TE layer, and a bottom thermally conductive layer. Especially, the flexible heatsink composed of metal foam, phase change material, and fin structure greatly enhances the thermal conduction, storage, and diffusion capacities. Our TEC exhibits the desired comfortability and obtains an ideal temperature drop of 3 °C on human skin. Also, it could work as a self-generator providing 45 mV with a ΔT of 5 °C, which improves the generation efficiency by more than 3 times due to the stable temperature difference between the two sides. This work provides an effective way to develop wearable TEC devices and paves the way for achieving practical, personalized cooling applications.

Bioinspired Ultra‐Stretchable and Highly Sensitive Structural Color Electronic Skins

AbstractOrganisms possess remarkably adaptive ability to complex environments. For example, chameleons can alter their skin color to adapt to varying environments, which has inspired significant advances in bioinspired soft electronic skins (E‐skins), and their wide applications in wearable sensors, intelligent robots, and health monitoring. However, current bioinspired E‐skins face challenges in ultra‐stretchability, high sensitivity, and long‐term stability owing to the intrinsic limitations associated with their mismatched interface between soft matrix and hard conductive fillers, hindering their practical applications. Here, it is reported that bioinspired structural color electronic skins (SC E‐skins) that consist of liquid metal particles (LMPs), periodical ordered colloidal crystal arrays, and ultra‐stretchable hydrogel, imparting synergistic and durable electrical–optical sensing capabilities. Such SC E‐skins demonstrate outstanding performances including superior flexibility (elongation at break > 1100%), high sensitivity (gauge factor = 3.26), fast synergetic electric–optical response time (≈100 ms), outstanding durability (over 1500 cycles), and high accuracy (R2 > 99.5%). These bioinspired SC E‐skins with excellent capability of converting mechanical signals into synergetic electrical–optical outputs hold great promise for smart wearable devices, affording a new horizon in developing advanced health monitoring technologies.

Demineralized cancellous bone scaffolds as reinforcement for degradable magnesium biocomposite

AbstractThis study investigates demineralized bone matrix (DBM) combined with magnesium (Mg) to create degradable composite materials. Two types of DBM were utilized: carbon-coated (H.A.) and non-carbon-coated (HA-HT). An advanced liquid metal infiltration method prevented the structural collapse of the scaffold due to capillary forces. Both composites exhibited an interphase layer primarily composed of MgO, differing in thickness by 50%, attributed to the reaction between H.A. and Mg. The Mg/H.A. composite demonstrated a compressive yield strength 1.7 times higher than Mg/HA-HT, resembling Mg’s mechanical behavior but with a lower metal phase fraction than other composites. Compared to pure Mg, the composites generated less hydrogen (45–54 ml cm−2), reducing the corrosion rate (~ 0.1181 mm year−1) under simulated conditions (90 ml cm−2 and 4.2 mm year−1 for Mg). A localized phenomenon was identified mainly at the interphase of both composites but specifically in the Mg/H.A., where the scaffold structure was kept over extended exposure periods. These materials hold promise for temporary bone fixation applications. Graphical abstract

Material efficiency at the component level: how much metal can we do without?

Global production of steel and aluminium is a major driver of greenhouse gas emissions. Various processes might allow continued primary production of the two metals, but all depend on emissions-free electricity or carbon storage, and global capacity of these two key resources will be below demand for decades to come. As a result, zero-emissions steel and aluminium will mainly come from recycling, but supply will be lower than demand. This motivates demand reduction, and for the first time, this article estimates the inefficiency in current metal use by component type. The results demonstrate that around 80% of steel and 90% of aluminium liquid metal produced today may be unnecessary. Around 40% of liquid steel and 60% of liquid aluminium are never used in final components as they are removed along the supply chain of manufacturing. Of the metal that enters final service, approximately one-third could be saved by avoiding component over-specification. A further third could be saved, where the properties of metal are not used to their limits. These results point to specific opportunities for innovation in design and manufacturing technology, of which the highest priority is to re-think the use of sheet metal in construction.This article is part of the discussion meeting issue 'Sustainable metals: science and systems'.

Inelastic scattering effects on the inhomogeneous transverse conductivity of liquid metals and plasmas

Abstract On the basis of the quantum Wigner density operator formalism for multicomponent charged particle systems, the wavenumber (k)- and frequency (ω)- dependent transverse conductivity σ^T (k,ω) of simple liquid metals is presented for homogeneous (k = 0) and inhomogeneous (k≠0) electric fields separately. The theory takes into account correlated density fluctuations of electrons and ions, with their mutual inelastic scattering being described by the ionic dynamic structure factors. Since homogeneous and inhomogeneous fields perturb the diagonal and off-diagonal elements of the density matrix, respectively, the corresponding transport equations exhibit a dissimilarity in their collision terms. In both cases, approximate solutions to the transport equations yield a conductivity of generalized Drude form characterized by the k- and ω-dependent complex relaxation time. It is shown that the k→0 limit of the inhomogeneous conductivity, σ^T (k→0,ω), coincides with the homogeneous one in classical ion regime such that βℏω_i≪1, where β is the inverse temperature and ω_i is a characteristic frequency of ionic density fluctuation; this condition may be satisfied for metals well above melting. At lower temperatures, it is suggested that the (homogeneous) DC conductivity σ(0) can exceed the (inhomogeneous) optical conductivity extrapolated to zero frequency, σ^T (k→0,0). This trend is qualitatively consistent with earlier observations for liquid polyvalent metals.

Spray-on electronic tattoos with MXene and liquid metal nanocomposites

Electronic tattoos present appealing forms of wearable devices operated directly on the skin. Although two-dimensional transition metal carbides (MXenes) are promising material choices, their films are susceptible to fracturing when subjected to tensile deformations. This study presents electronic tattoos comprising MXenes and liquid metal microcapsules fabricated by spray deposition onto the skin. The resulting nanocomposite has a low sheet resistance of approximately 2.2 Ω/sq. and can be repetitively deformed to 50 % strain. The enhanced deformability is attributed to the release of liquid metal from the microcapsules upon stretching, facilitating the repair of cracks in the nanocomposite layer. In addition, the nanocomposite conforms to the skin, sticks well, and moves with the body. It is also resistant to friction and sweat, making it suitable for various applications. A bifunctional electronic tattoo has been further developed, showcasing its capability to acquire biopotential signals and deliver electrical stimulation. Our study effectively improves the deformability of MXene-based nanocomposites for electronic tattoos, achieving seamless device integration in the body.

Experimental study on flow boiling and circumferential non-uniform heat transfer characteristics in helically-coiled tube under coupled heat transfer conditions

Helically-coiled tube steam generator has been widely used in nuclear reactor, energy power, petrochemical and other systems. In the liquid metal reactor, the liquid metal on the primary side of the helically-coiled tube steam generator exchanges heat with the water on the secondary side. Due to the coupled heat transfer between liquid metal and water, the distribution of the wall temperature or heat transfer coefficient of helically-coiled tube are significant different in the circumferential direction of the tube cross-section. An experimental system of helically-coiled tube steam generator was set up in this paper. The non-uniform heat transfer characteristics of secondary side fluid of helically-coiled tube steam generator were studied under the coupled heat transfer conditions between the heat transfer of primary side and secondary sides fluid. It was found that the wall temperature or heat transfer coefficient in the circumferential direction of tube cross-section were significantly different, the maximum and minimum wall temperature appeared on the inside and bottom of the tube cross-section, respectively, the maximum and minimum heat transfer coefficient appeared on the outside and top of the tube cross-section, respectively. The effect of secondary side refrigerant pressure, secondary side refrigerant supercooling degree, mass flux of secondary side refrigerant, primary side heating water temperature and mass flux of primary side heating water on the maximum wall temperature, minimum wall temperature, maximum heat transfer coefficient, minimum heat transfer coefficient were obtained. Beside, The local and overall non-uniformity of the wall temperature and heat transfer coefficient in the circumferential direction of tube cross-section were obtained and the influence of each parameter on the local and overall non-uniformity were revealed, respectively. Finally, it was concluded that the non-uniformity of heat transfer coefficient in the circumferential direction of tube cross-section under coupled heat transfer conditions was more obvious than that under constant heat flux conditions. And the the overall non-uniformity of heat transfer coefficient (δh) obtained in our experimental were larger than the δh of Chang et al. [33], Zheng et al. [38], Kong et al. [34], Yao et al. [36] and Niu et al. [37] by 130.67%, 48.10%, 289.48%, 151.28% and 271.67%, respectively.

Stretchable liquid metal grid/metallized polyurethane composites with switchable electromagnetic interference shielding and efficient infrared stealth performance

Intelligent electromagnetic interference (EMI) shielding materials with tunable electromagnetic shielding properties becomes a significant and urgent concern for information society. Hence, a switchable and low-reflectivity EMI shielding composite is fabricated by electroless nickel plating on the surface of polyurethane nonwoven fabric (Ni@TPU), and followed by combining with liquid metal (LM) grid. The synergistic combination of Ni@TPU and LM grid effectively facilitates the rational construction of hierarchical impedance matching. Meanwhile, it promotes destructive interference between electromagnetic waves reflected from Ni@TPU and the LM grid. As a result, an excellent low-reflectivity EMI shielding performance can be achieved. More importantly, the switchable EMI shielding performance can be easily realized by repeatedly stretching Ni@TPU/LM. In addition, the fluffy nonwoven fabric and LM grid with low infrared emissivity endow it with an outstanding infrared stealth performance. Such excellent low-reflectivity EMI shielding switch performance incorporated with flexible infrared stealth makes it possible to become smart EMI shielding material with a great promise to be employed in the application scenario of window in camouflage container.

Double network hydrogel confined MXene/Liquid metal by dynamic hydrogen bond for high-performance wearable sensors

Double-network (DN) hydrogels, which integrate long-chain and short-chain molecular structures, exhibit significant potential in wearable sensors due to their exemplary mechanical properties. However, conventional hydrogels often suffer from poor conductivity and low sensitivity. In this study, we develop a novel DN hydrogel (comprising polyacrylamide/sodium alginate) that encapsulates MXene (Ti3C2Tx) and liquid metal (LM). This configuration leverages the conductive properties of two-dimensional MXene and zero-dimensional liquid metal embedded within the DN hydrogel networks. The Ti3C2Tx MXene sheets enhance the binding capacity with LM by serving as a conductive bridge, thereby improving interfacial interactions and reducing hysteresis. The resultant strain sensor, fabricated from this composite DN hydrogel, achieves high sensitivity (gauge factor up to 12.84), a broad detection range (0 %-1500 %), rapid response time (262 ms), and excellent repeatability and stability. We have integrated this strain sensor into wearable flexible devices, such as contact lenses, enabling real-time monitoring of human physiological pressures.

Boosted the thermal conductivity of liquid metal via bridging diamond particles with graphite

Boosted the thermal conductivity of liquid metal via bridging diamond particles with graphite

Selective Growth of Nb-Fe-B Intermetallic Compounds for the Direct Separation of Rare Earths Based on Manipulating Liquation

Since the primary goal of industrialization has changed to carbon neutrality, the importance of rare earths (REs) has increased due to their criticality in green industries. The attainment of sustainable resources via green production processes is necessary due to the increasing need for REs. Liquid metal extraction is regarded as a leading technology for supporting the sustainability of resources based on the selective reactivity between REs and extractants. However, this process requires multiple stages, including pretreatment, extraction and separation, which are considered bottlenecks in industrialization. In this work, reverse selectivity is applied instead of conventional liquid metal extraction (c-LME) for the direct separation of REs in a single stage. Niobium (Nb) is selected because of its thermodynamic properties for enhancing the selectivity of the reactions between the extractant and other elements, excluding REs. The process is thermodynamically designed for liquation systems, and it reflects the interactions between the extractant and magnets. The solidification behavior based on the selective growth of phases without REs is shown with variations in the composition and cooling rate to confirm the kinetics. The composition prevents the formation of RE-Fe intermetallic compounds, and excess Nb is considered a bottleneck for separating REs. In addition, the cooling rate influences the agglomeration of RE as a layer. Because of the manipulation of the liquation, 92.89% of the REs are successfully separated in the form of accumulated layers. This effective process for the direct separation of REs is verified through thermodynamic and experimental assessments. Overall, this investigation can provide new guidelines for the construction of a circular economy after improving the energy efficiency of this system in future research.

Nimble native oxides: Printing circuits from the skin of liquid metal

Nimble native oxides: Printing circuits from the skin of liquid metal

Flow Experiment with Conductive Liquid Metal Using Lorenz Force for Developing High-Performance Electric Casting System

Flow Experiment with Conductive Liquid Metal Using Lorenz Force for Developing High-Performance Electric Casting System

Microstructure and mechanical properties of aluminum alloy laser welded joint assisted by alternating magnetic field

Magnetic field-assisted laser welding is an effective method to improve the quality of laser-welded joints. In this study, laser welding was conducted on a 2 mm thick sheet of 6061-T6 aluminum alloy, with the assistance of an alternating magnetic field oriented perpendicular to the surface of the sheet. The effects of the alternating magnetic field on the macrostructure, molten pool flow, porosity, grain morphology, and microhardness of the weld seam were analyzed. The results indicate that applying the alternating magnetic field results in more uniform and finer fish scale patterns on the upper surface of the weld. The porosity of the weld is significantly reduced. The Lorentz force generated by the alternating magnetic field suppresses liquid metal flow from the center to the edges of the molten pool, thereby hindering the heat flow and transfer within the pool. This concentration of heat in the lower part of the molten pool increases the size of equiaxed grains at the weld center and promotes the formation of more branches in the columnar grains near the fusion line. Some columnar grains in the columnar grain zone transform into equiaxed grains. Moreover, the microhardness distribution of the weld becomes more uniform, and the hardness in the heat-affected zone increases. Tensile tests revealed that all samples fractured within the weld seam, with the tensile strength of the welded joints increasing by 12.7%. The fracture mode transitions from a mixed ductile-brittle fracture to a purely ductile fracture.

Facile Formation of Metallic Surface with Microroughness via Spray-Coating of Copper Nanoparticles for Enhanced Liquid Metal Wetting

This paper presents a simple, fast, and cost-effective method for creating metallic microstructured surfaces by spray-coating a dispersion of copper nanoparticles (CuNPs) onto polymethyl methacrylate (PMMA) substrates, enabling the imbibition-induced wetting of liquid metal. The formation of these microstructured patterns is crucial for the spontaneous wetting of gallium-based liquid metals. Traditional techniques for producing such microstructures often involve complex and costly lithography and vacuum deposition methods. In contrast, this study demonstrates that liquid metal wetting can occur with metal microstructures formed through a straightforward spray-coating process. To immobilize the CuNPs on the polymer substrate, an organic solvent that dissolves the polymer surface was employed as the dispersion medium. The effects of various spray-coating parameters, including distance and time, on the uniformity and immobilization of CuNP films were systematically investigated. Under optimal conditions (120 s of spray time and 10 cm spray distance), CuNPs dispersed in dichloromethane (DCM) yielded uniform and stable microstructured surfaces. The spontaneous wetting of gallium-based liquid metal was observed on the fabricated CuNP film. Additionally, liquid metal selectively wet the CuNP patterns formed by stencil techniques, establishing electrical connections between electrodes. These findings underscore the potential of spray-coating for fabricating metallic surfaces to drive the formation of liquid metal patterns in flexible electronics applications.

Evaluation of Thermal and Mechanical Properties of Bi-In-Sn/WO3 Composites for Efficient Heat Dissipation

Phase change materials (PCMs) offer promising solutions for efficient thermal management in electronic devices, energy storage systems, and renewable energy applications due to their capacity to store and release significant thermal energy during phase transitions. This study investigates the thermal and physical properties of Bi-In-Sn/WO3 composites, specifically for their use as phase change thermal interface materials (PCM-TIMs). The Bi-In-Sn/WO3 composite was synthesized through mechanochemical grinding, which enabled the uniform dispersion of WO3 particles within the Bi-In-Sn alloy matrix. The addition of WO3 particles markedly improved the composite’s thermal conductivity and transformed its physical form into a putty-like consistency, addressing leakage issues typically associated with pure Bi-In-Sn alloys. Microstructural analyses demonstrated the existence of a continuous interface between the liquid metal and WO3 phases, with no gaps, ensuring structural stability. Thermal performance tests demonstrated that the Bi-In-Sn/WO3 composite achieved improved thermal conductivity, and reduced volumetric latent heat, and there was a slight increase in thermal contact resistance with higher WO3 content. These findings highlight the potential of Bi-In-Sn/WO3 composites for utilization as advanced PCM-TIMs, offering enhanced heat dissipation, stability, and physical integrity for high-performance electronic and energy systems.

Electrochemical Formation of Pb Microwires with Tunable Morphology on Liquid Metal Electrodes

Electrochemical Formation of Pb Microwires with Tunable Morphology on Liquid Metal Electrodes