Room Temperature Liquid Metal Research Articles

Tough and temperature-resistant mask-based separator realized by K-β”-Al2O3 protective layer for stabilizing NaK liquid metal batteries

The development of low-cost, high-temperature-resistant separators is crucial for optimizing the reaction interface and improving the safety performance of liquid NaK metal batteries. This paper presents a novel separator with a solid electrolyte layer, Mask@40 %β-Al2O3, primarily composed of K-β”-Al2O3 known for its exceptional ionic conductivity and high-temperature resistance. Specifically designed for room-temperature liquid NaK metal batteries, the Mask@40 %β-Al2O3 separator effectively transforms the unstable liquid–liquid interface between liquid NaK metal electrodes and traditional organic electrolytes into a stable solid–liquid interface. This transformation prevents short-circuiting caused by area collapse under high-temperature conditions. Moreover, the Bare Mask component can adsorb a conventional organic electrolyte to construct a stable solid–liquid interface on the cathode side, thereby reducing the typically observed high interfacial resistance associated with conventional solid electrolytes. The cost-effective nature and simple preparation process of the Mask@40 %β-Al2O3 separator address cost concerns while presenting an encouraging new direction for applying room-temperature liquid NaK metal batteries in extreme conditions.

Oxidation-Induced Oxide Shell Rupture and Phase Separation in Eutectic Gallium-Indium Nanoparticles.

Eutectic gallium-indium (EGaIn), a room-temperature liquid metal, has garnered significant attention for its applications in soft electronics, multifunctional materials, energy engineering and drug delivery. A key factor influencing these diverse applications is the spontaneous formation of a native passivating oxide shell that not only encapsulates the liquid metal but also alters the properties from the bulk counterpart. Using environmental scanning transmission electron microscopy, we report in situ observations of the oxidation of EGaIn nanoparticles by ambient air under high-energy electron beam irradiation. Our findings demonstrate that uneven oxide shell growth, driven by inward diffusion of adsorbed O species, creates unbalanced stresses. This compels the liquid metal to deform toward regions with slower oxide growth, resulting in shell rupture and allowing the liquid metal core to flow out. This process initiates top-down self-similar replication of the core-shell liquid metal nanoparticles, causing larger particles to break down into smaller particles. Additionally, internal oxidation triggers phase separation within the liquid core, ultimately leading to the pulverization of the liquid metal into finer solid particles rich in indium. These mechanistic insights into the oxidation behavior of the liquid metal hold practical implications for leveraging this process to reconfigure EGaIn nanoparticles for various applications.

Liquid metal manifold microchannel heat sink for ultra-high heat flux cooling

Advanced heat dissipation technology is crucial for chip operation and performance utilization. Room temperature liquid metal convection cooling technology has demonstrated its efficacy as a viable approach for addressing high heat flux heat dissipation. However, the smaller specific heat capacity of liquid metal leads to a large temperature rise, hindering the advancement of its cooling technology. To address this, a liquid metal manifold channel structure is proposed to convert the continuous long-range flow into a segmented short-range flow. The good matching between liquid metal and manifold structures is adequately demonstrated through a comparison with alternative coolant and channel structure. The simulation results demonstrate the effectiveness of liquid metal manifold channel cooling in dealing with a heat flux of 1000 W/cm2, ensuring that the maximum temperature of the chip remains below 351.7 K. Moreover, the convective heat transfer coefficient even reaches 106 W/(m2·K), which is ten times larger than that of water conventional microchannel heat sink. Orthogonal experiments analyzed the impact of structural parameters on dissipation performance, including the height of the microchannel, ratio of manifold length to fin length, length of fin in manifold, width of channel, and ratio of fin with to channel width. The height of the microchannel has been identified as the most critical factor. This manifold structure mitigates the inherent limitation of liquid metal's lower specific heat capacity, enabling efficient thermal management for electronic devices under ultra-high heat flux conditions.

Sulfur-rich MoS3 cathode for high-performance room-temperature liquid and solid-state lithium metal batteries

Sulfur-based compounds have been considered one of the most attractive cathode materials for next-generation batteries owing to their high energy density and environmental benignity. Among them, metal sulfides like MoS2 show high conductivity as well as intrinsic catalytic activity, however, the sulfur content and specific capacity are relatively low. In this article, we proposed a sulfur-rich amorphous molybdenum trisulfide‑carbon nanotubes (MoS3-CNT) cathode via in situ deposition. Benefiting from the enhanced electrical conductivity and enriched abundant reactive sites, the cathode exhibits impressive performance when assembled as liquid and solid-state lithium metal batteries at room temperature. In liquid lithium metal batteries, optimized MoS3-CNT20% cathode exhibits an impressive high specific capacity of 900.7 mAh/g in the first cycle, while the cycling stability is poor (35.4% after 50 cycles) owing to severe shuttle effect. When fabricated with polymer solid-state electrolyte, the cycling stability could be significantly improved to 85.7% after 50 cycles with an initial capacity of 314.2 mAh/g. This study provides a rational strategy for developing high-performance metal sulfide cathodes thus helping sustainable development.

A system for fluid pumping by liquid metal multi-droplets.

The transportation and control of microfluidics have an important influence on the fields of biology, chemistry, and medicine. Pump systems based on the electrocapillary effect and room-temperature liquid metal droplets have attracted extensive attention. Flow rate is an important parameter that reflects the delivery performance of the pump systems. In the systems of previous studies, cylindrical structures are mostly used to constrain the droplet. The analysis and quantitative description of the influence of voltage frequency, alternating voltage, direct current voltage bias, and solution concentration on the flow rate are not yet comprehensive. Furthermore, the systems are driven by only one droplet, which limits the increase in flow rate. Therefore, a pump with a cuboid structure is designed and the droplet is bound by pillars, and the flow rate of the pump is increased by more than 200% compared with the cylindrical pump. For this structure, the mechanism of various factors on the flow rate is analyzed. To further enhance the flow rate, a pump system with multi-droplets is proposed. Moreover, the expression of flow velocity of the solution on the surface of each droplet and the relationship between the flow rate, alternating voltage, and the number of droplets are deduced. Finally, the potential of applying the multi-droplet cuboid pump system in drug delivery and analytical chemistry is demonstrated. Additionally, the core of the pump, the droplet area, is modularized, which breaks the overall structural limitations of the liquid metal pump and provides ideas for pump design.

Towards High Efficiency and Rapid Production of Room-Temperature Liquid Metal Wires Compatible with Electronic Prototyping Connectors.

We present in this work new methodologies to produce, refine, and interconnect room-temperature liquid-metal-core thermoplastic elastomer wires that have extreme extendibility (>500%), low production time and cost at scale, and may be integrated into commonly used electrical prototyping connectors like a Japan Solderless Terminal (JST) or Dupont connectors. Rather than focus on the development of a specific device, the aim of this work is to demonstrate strategies and processes necessary to achieve scalable production of liquid-metal-enabled electronics and address several key challenges that have been present in liquid metal systems, including leak-free operation, minimal gallium corrosion of other electrode materials, low liquid metal consumption, and high production rates. The ultimate goal is to create liquid-metal-enabled rapid prototyping technologies, similar to what can be achieved with Arduino projects, where modification and switching of components can be performed in seconds, which enables faster iterations of designs. Our process is focused primarily on fibre-based liquid metal wires contained within thermoplastic elastomers. These fibre form factors can easily be integrated with wearable sensors and actuators as they can be sewn or woven into fabrics, or cast within soft robotic components.

Alkali-Ion Batteries by Carbon Encapsulation of Liquid Metal Anode.

Gallium-based metallic liquids, exhibiting high theoretical capacity, are considered a promising anode material for room-temperature liquid metal alkali-ion batteries. However, electrochemical performances, especially the cyclic stability, of the liquid metal anode for alkali-ion batteries are strongly limited because of the volume expansion and unstable solid electrolyte interphase film of liquid metal. Here, the bottleneck problem is resolved by designing carbon encapsulation on gallium-indium liquid metal nanoparticles (EGaIn@C LMNPs). A superior cycling stability (644mAhg-1 after 800 cycles at 1.0Ag-1 ) is demonstrated for lithium-ion batteries, and excellent cycle stability (87mAhg-1 after 2500 cycles at 1.0Ag-1 ) is achieved for sodium-ion batteries by carbon encapsulation of the liquid metal anode. Morphological and phase changes of EGaIn@C LMNPs during the electrochemical reaction process are revealed by in situ transmission electron microscopy measurements in real-time. The origin for the excellent performance is uncovered, that is the EGaIn@C core-shell structure effectively suppresses the non-uniform volume expansion of LMNPs from ≈160% to 127%, improves the electrical conductivity of the LMNPs, and exhibits superior electrochemical kinetics and a self-healing phenomenon. This work paves the way for the applications of room-temperature liquid metal anodes for high-performance alkali-ion batteries.

Amorphous TiO2 shells: an Essential Elastic Buffer Layer for High-Performance Self-Healing Eutectic GaSn Nano-Droplet Room-Temperature Liquid Metal Battery.

Gallium-based alloy liquid metal batteries currently face limitations such as volume expansion, unstable solid electrolyte interface (SEI) film and substantial capacity decay. In this study, amorphous titanium dioxide is used to coat eutectic GaSn nanodroplets (eGaSn NDs) to construct the core-shell structure of eGaSn@TiO2 nanodroplets (eGaSn@TiO2 NDs). The amorphous TiO2 shell (~6.5 nm) formed a stable SEI film, alleviated the volume expansion, and provided electron/ion transport channels to achieve excellent cycling performance and high specific capacity. The resulting eGaSn@TiO2 NDs exhibited high capacities of 580, 540, 515, 485, 456 and 426 mAh g-1 at 0.1, 0.2, 0.5, 1, 2 and 5 C, respectively. No significant decay was observed after more than 500 cycles with a capacity of 455 mAh g-1 at 1 C. In situ X-ray diffraction (in situ XRD) was used to explore the lithiation mechanism of the eGaSn negative electrode during discharge. This study elucidates the design of advanced liquid alloy-based negative electrode materials for high-performance liquid metal batteries (LMBs).

Beneath the Skin: Nanostructure in the Sub‐Oxide Region of Liquid Metal Nanodroplets

AbstractLiquid metals (LMs) are emerging as unique fluids for a variety of applications, but their nanoscale solvation properties remain largely understudied. In this work, a combination of atomic force microscopy (AFM) and molecular dynamics (MD) simulations are used to investigate the structure of the interface between the bulk room temperature liquid metal (RTLM) and the LM oxide in nanodroplet systems of gallium, EGaIn (75.5% gallium, 24.5% indium), and Galinstan (68.5% gallium, 21.5% indium, 10% tin). Field's metal (51% indium, 32.5% bismuth, 16.5% tin) is also investigated, which melts at ≈62 °C, as a contrast to the other systems. AFM measurements reveal distinct sub‐oxide nanostructured layering in all three RTLM systems, and Field's metal above the melting point, to differing degrees. EGaIn and Galinstan show multiple penetration events between 20 and 30 nm, with smaller, less complex events in Ga. MD simulations suggest that this layering is a result of the near‐surface ordering of LM atoms beneath the oxide layer. Importantly, the atoms in this region do not behave as solids but are more ordered than in a pure disordered liquid system. The surface nanostructure elucidated here significantly expands the understanding of LM systems and their behavior at interfaces.

Preparation and electrochemical performance study of a self-healing electrode composite material with WSe2/liquid metal Galinstan for lithium-ion batteries

In this work, a room temperature liquid metal alloy (Galinstan) and tungsten diselenide (WSe2) composite anode (LMx@WSe2) were synthesized utilizing a one-step hydrothermal method. Through a comprehensive characterization process, including XRD, SEM, HRTEM, Raman spectroscopy, XPS, and BET, the structural and morphological properties of the synthesized composites were extensively explored. The liquid metal alloy was observed to combine effectively with WSe2 via electrostatic adsorption, coordination, and additional bonding methods. Furthermore, it displayed high fluidity, deformability, and chemical stability. Consequently, the alloy promoted the repair of cracked surface areas in the electrode material and reduced internal oxidation-reduction reactions, leading to improved electrochemical performance during repeated lithium-ion insertion and extraction cycles. After 500 cycles at a current density of 1 A g−1, this composite electrode retained a capacity of 224.5 mAh g−1. Impressively, at a low temperature of − 10 °C, it maintained a capacity of 290 mAh g−1 after 50 cycles at a current density of 0.2 A g−1. Our research may open avenues for addressing mechanical difficulties experienced in flexible electronic devices and self-healing electronic circuits exposed to chemical reaction processes.

Liquid Metal Patterning and Unique Properties for Next-Generation Soft Electronics.

Room-temperature liquid metal (LM)-based electronics is expected to bring advancements in future soft electronics owing to its conductivity, conformability, stretchability, and biocompatibility. However, various difficulties arise when patterning LM because of its rheological features such as fluidity and surface tension. Numerous attempts are made to overcome these difficulties, resulting in various LM-patterning methods. An appropriate choice of patterning method based on comprehensive understanding is necessary to fully utilize the unique properties. Therefore, the authors aim to provide thorough knowledge about patterning methods and unique properties for LM-based future soft electronics. First, essential considerations for LM-patterning are investigated. Then, LM-patterning methods-serial-patterning, parallel-patterning, intermetallic bond-assisted patterning, and molding/microfluidic injection-are categorized and investigated. Finally, perspectives on LM-based soft electronics with unique properties are provided. They include outstanding features of LM such as conformability, biocompatibility, permeability, restorability, and recyclability. Also, they include perspectives on future LM-based soft electronics in various areas such as radio frequency electronics, soft robots, and heterogeneous catalyst. LM-based soft devices are expected to permeate the daily lives if patterning methods and the aforementioned features are analyzed and utilized.

Compositional Design of Surface Oxides in Gallium–Indium Alloys

Room-temperature liquid metal alloys encompass a highly versatile family of materials possessing a unique set of chemical, electronic, biological, and mechanical properties. The surface oxide of liquid metals has a direct influence on these properties and is often composed of one of the major alloy components (i.e., gallium or indium). However, this is not a foregone conclusion, as the identity of the surface oxide can be altered by the addition of minority elements into the liquid metal. Through judicious choice of a minority alloying metal, the composition of the oxide and therefore the resulting molten alloy’s properties are significantly modified. We demonstrate this by adding a small amount (∼5%) of several thermodynamically favorable alloying elements (X = Zn, Mg, Al) to eutectic gallium indium (EGaIn), resulting in a new class of alloys with designed surface oxide compositions that we term XGaIn. Using both STEM-EDS and XPS, XGaIn alloys are shown to form oxide layers enriched in the lowest-redox element as expected based on the thermodynamics of the alloy system. This approach is shown to be generalizable across both Ga and non-Ga-based liquid metal alloy compositions. XGaIn alloys with added Zn and Mg are shown to have strong antimicrobial activity, which has exciting implications for the development of flexible electronic medical devices and sensors.

A yolk-shell eGaSn@Void@SiO2 nanodroplet design for high-performance cathodes in room temperature liquid metal batteries

Gallium-based liquid alloys that exhibit high capacity and self-healing properties have been demonstrated to be promising cathodes for room temperature liquid metal batteries (RTLMBs). However, the electrochemical performances of these alloys are poor due to severe volume expansion and an unstable solid electrolyte interface layer during the lithiation process. Here, a sol-gel strategy was performed to construct yolk-shell structure nanodroplets (eGaSn@Void@SiO2) that contain sufficient void space by amorphous silicon oxide, which generated a liquid metal electrode with a high performance. The amorphous SiO2 shells not only play an important role in building stable SEI films, providing efficient electron/ion conduction channels and preventing agglomeration of active substances, but exhibit good elastic behavior during charging/discharging. Due to the appropriate voids in the yolk-shell structure, the eGaSn nanodroplets can expand freely without breaking or disrupting the electrode structure; thus, the resulting eGaSn@Void@SiO2 NDs exhibited high capacities of 538, 454, and 338 mA h g−1 at current rates of 0.2, 1 and 5 C, respectively. No obvious decay was observed with more than 500 cycles and a capacity of 377 mA h g−1 at 2 C. Interestingly, the density functional theory (DFT) calculations revealed that the effective chemisorption between the discharge products and SiO2 provides sufficient electrical contact sites with a significant drop in electrochemical impedance during cycling. The causes of the superior electrodes performance were investigated in depth using in situ X-ray diffraction and theoretical calculations. Our rational design may shed unprecedented light on the development of liquid alloy-based cathodes for high-performance RTLMBs.

Validation of a torsional balance for thrust measurements of Hall effect and microwave-based space propulsion systems.

A torsional thrust balance has been designed and validated by Surrey Space Centre and Added Value Solutions UK Ltd. in collaboration with the UK Space Agency. The thrust stand has been tested with two electric propulsion (EP) systems operating with xenon: the Halo thruster and the XJET thruster. The first consists of a low-power (<1 kW) Hall effect-based thruster, whose thrust level is between 3 and 20mN, depending on the power of the system. The second is an electron cyclotron resonance thruster whose operative point is in the 0.3-1.5mN thrust range. The thruster is mounted on a titanium rotating beam, whose movement is measured by an optical fiber displacement sensor. The thrusters' direct current electrical connections are routed through room temperature liquid metal pots and microwave power is transmitted via a wireless transfer system, minimizing friction effects. To reduce thermal issues during long thruster operations, the torsional thrust balance is designed with a water-cooling hub around the flex pivot. Noise from the laboratory environment is lessened by using four vibration-dampening spring systems as thrust balance feet. The tests on the two EP systems have shown accurate and repeatable results, demonstrating that the balance can be used to characterize different EP systems in the μN-mN thrust range.

Wetting behavior of gallium-based room temperature liquid metal (LM) on nanosecond-laser-structured metal surfaces

Gallium-based room-temperature liquid metal (LM) is a promising emerging functional material in e-skin, soft robots and thermal management systems for its fluidity, conductivity and nontoxicity. However, the intricate wettability of the LM with various surfaces impedes its further development. Knowledge on the gallium-based LM wetting properties especially with structured metal surfaces is relatively insufficient. Herein, wetting behavior of eutectic gallium-indium (EGaIn) on various micro-structured metal surfaces processed by nano-second laser ablation method is systematically studied. Increasing surface roughness, synergized with a high oxygen content, significantly strengthens the LM resistance. Micro-patterns composed of small, discontinuous facets exhibit better EGaIn repellence. Relative humidity (RH) is substantiated to influence the LM wetting behavior as well. Metal surfaces with excellent superlyophobicity (the contact angle> 160°, the adhesion force< 10 μN) are obtained. The LM repellence stability and anti-corrosion properties of the optimized treated metal surfaces are proved via the droplet impacting experiment and the corrosion test. These findings improve the understanding of gallium-based LM wetting behavior on structured metal surfaces, and the obtained LM-repellent metal surfaces will reduce undesired adhesion, blockage or LM corrosion during device preparation and long-term applications, which will facilitate its potential use.

Acoustic, Phononic, Brillouin Light Scattering and Faraday Wave-Based Frequency Combs: Physical Foundations and Applications.

Frequency combs (FCs)—spectra containing equidistant coherent peaks—have enabled researchers and engineers to measure the frequencies of complex signals with high precision, thereby revolutionising the areas of sensing, metrology and communications and also benefiting the fundamental science. Although mostly optical FCs have found widespread applications thus far, in general FCs can be generated using waves other than light. Here, we review and summarise recent achievements in the emergent field of acoustic frequency combs (AFCs), including phononic FCs and relevant acousto-optical, Brillouin light scattering and Faraday wave-based techniques that have enabled the development of phonon lasers, quantum computers and advanced vibration sensors. In particular, our discussion is centred around potential applications of AFCs in precision measurements in various physical, chemical and biological systems in conditions where using light, and hence optical FCs, faces technical and fundamental limitations, which is, for example, the case in underwater distance measurements and biomedical imaging applications. This review article will also be of interest to readers seeking a discussion of specific theoretical aspects of different classes of AFCs. To that end, we support the mainstream discussion by the results of our original analysis and numerical simulations that can be used to design the spectra of AFCs generated using oscillations of gas bubbles in liquids, vibrations of liquid drops and plasmonic enhancement of Brillouin light scattering in metal nanostructures. We also discuss the application of non-toxic room-temperature liquid–metal alloys in the field of AFC generation.

Core-shell GaSn@rGO nanoparticles as high-performance cathodes for room-temperature liquid metal batteries

Gallium-based liquid metals with high specific capacity and good self-healing properties are promising cathode materials for room-temperature liquid metal batteries (LMBs). Most liquid metal cathode materials, however, face critical challenges, including the large volume expansion, unstable solid electrolyte interface (SEI) layer, and serious capacity decay. Here, a facile coating strategy is shown to prepare GaSn nanoparticles encapsulated by reduced graphene oxide (rGO) with core–shell structures that exhibit high structural integrity and excellent electrochemical performance. The pleated rGO shell (≈6 nm) offers superior buffering properties and a stable SEI layer during charging and discharging processes, achieving excellent cycling stability. In situ X-ray diffraction patterns reveal that this novel GaSn@rGO NP electrode is based on an alloying/dealloying lithium storage mechanism. This study demonstrates that the rationally designed cathode material offers an unprecedented opportunity for room-temperature LMBs with high rate capability and cycling stability.

High-Performance Liquid Metal/Polyborosiloxane Elastomer toward Thermally Conductive Applications.

With the combination of high flexibility and thermal property, thermally conductive elastomers have played an important role in daily life. However, traditional thermally conductive elastomers display limited stretchability and toughness, seriously restricting their further development in practical applications. Herein, a high-performance composite is fabricated by dispersing room-temperature liquid metal microdroplets (LM) into a polyborosiloxane elastomer (PBSE). Due to the unique solid-liquid coupling mechanism, the LM can deform with the PBSE matrix, achieving higher fracture strain (401%) and fracture toughness (2164 J/m2). Meanwhile, the existence of LM microdroplets improves the thermal conductivity of the composite. Interestingly, the LM/PBSE also exhibits remarkable anti-impact, adhesion capacities under complex loading environments. As a novel stretchable elastomer with enhanced mechanical and thermal behavior, the LM/PBSE shows good application prospects in the fields of thermal camouflages, stretchable heat-dissipation matrixes, and multifunctional shells for electronic devices.

Nitrate-to-Ammonia Conversion at an InSn-Enriched Liquid-Metal Electrode.

The renewable energy driven electrochemical conversion of nitrates to ammonia is emerging as a viable route for the creation of this hydrogen carrier. However, the creation of highly efficient electrocatalysts that show prolonged stability is an ongoing challenge. Here we show that room temperature liquid metal Galinstan can be used as an efficient and stable electrocatalyst for nitrate conversion to ammonia achieving rates of up to 2335 μg h−1 cm−2 with a Faradaic efficiency of 100 %. Density functional theory (DFT) calculations and experimental observation indicated the activity is due to InSn alloy enrichment within the liquid metal that occurs during the electrocatalytic reaction. This high selectivity for NH3 is also due to additional suppression of the competing hydrogen evolution reaction at the identified In3Sn active site. This work adds to the increasing applicability of liquid metals based on Ga for clean energy technologies.

Nitrate‐to‐Ammonia Conversion at an InSn‐Enriched Liquid‐Metal Electrode

AbstractThe renewable energy driven electrochemical conversion of nitrates to ammonia is emerging as a viable route for the creation of this hydrogen carrier. However, the creation of highly efficient electrocatalysts that show prolonged stability is an ongoing challenge. Here we show that room temperature liquid metal Galinstan can be used as an efficient and stable electrocatalyst for nitrate conversion to ammonia achieving rates of up to 2335 μg h−1 cm−2 with a Faradaic efficiency of 100 %. Density functional theory (DFT) calculations and experimental observation indicated the activity is due to InSn alloy enrichment within the liquid metal that occurs during the electrocatalytic reaction. This high selectivity for NH3 is also due to additional suppression of the competing hydrogen evolution reaction at the identified In3Sn active site. This work adds to the increasing applicability of liquid metals based on Ga for clean energy technologies.