Gallium-indium Alloy Research Articles

An enhanced heat transfer method based on the electrocapillary effect of gallium-based liquid metal.

As electronic products become smaller and more powerful, there is an increasing need for effective heat dissipation. An effective heat exchange method is necessary for the equipment to function reliably in a compact space. To tackle the limitations of current microfluidic cooling technology, including difficulty in manufacturing, maintenance, and cost reduction, a heat exchange method with a simple system is proposed in this work. This method is based on the electrocapillary effect, using eutectic gallium-indium alloy droplets with high thermal conductivity, surface tension, and controllability as the basic unit. An electric field is applied to generate unevenly distributed charges in the electric double layer on the droplet surface, thereby creating a surface tension gradient that can drive the surrounding solution to flow. Simultaneously, the oscillation of the droplet can also intensify the disturbance of the solution. The violent disturbance of the solution causes the heat transfer mode to change from conduction to convective heat transfer and greatly reduces the thermal resistance, resulting in a substantial increase in heat flux. For this heat transfer method, the temperature distribution and flow characteristics of the solution in low-frequency oscillating and direct-current-biased alternating current electric fields are studied, and the effect of voltage, frequency, and the number of droplets on heat transfer enhancement is clarified. Compared with conduction without internal disturbance, the heat flux can be increased by up to 110% based on the combined effect of two droplets. This work provides a solution for enhancing the heat transfer of microfluidics.

Bubble Printing of Liquid Metal Colloidal Particles for Conductive Patterns.

Bubble printing is a patterning method in which particles are accumulated by the convection of bubbles generated by laser focusing. It is attracting attention as a method that enables the high-speed, high-precision patterning of various micro/nanoparticles. Although the bubble printing method is used for metallic particles and organic particles, most reports have focused on the patterning of solid particles and not on the patterning of liquid particles. In this study, liquid metal wiring patterns were fabricated using a bubble printing method in which eutectic gallium‒indium alloy (EGaIn) colloidal particles (≈diameter 0.7 µm) were fixed on a glass substrate by generating microbubbles through heat generation by focusing a femtosecond laser beam on the EGaIn colloidal particles. The wiring was then made conductive by replacing gallium oxide, which served as a resistance layer on the surface of the EGaIn colloidal particles, with silver via galvanic replacement. Fine continuous lines of liquid metal colloids with a line width of 3.4 µm were drawn by reducing the laser power. Liquid metal wiring with a conductivity of ≈1.5 × 105 S/m was formed on a glass substrate. It was confirmed that the conductivity remained consistent even when the glass substrate was bent to a curvature of 0.02 m-1.

Deterministic Fabrication of Liquid Metal Nanopatterns for Nanophotonics Applications

AbstractGallium‐based liquid metals (LMs) are widely used for stretchable and reconfigurable electronics thanks to their fluidic nature and excellent conductivity. These LMs possess attractive optical properties for photonics applications as well. However, due to the high surface tension of the LMs, it is challenging to form LM nanostructures with arbitrary shapes using conventional nanofabrication techniques. As a result, LM‐based nanophotonics has not been extensively explored. Here, a simple yet effective technique is demonstrated to deterministically fabricate LM nanopatterns with high yield over a large area. This technique demonstrates for the first time the capability to fabricate LM nanophotonic structures of various precisely defined shapes and sizes using two different LMs, that is, liquid gallium and liquid eutectic gallium–indium alloy. High‐density arrays of LM nanopatterns with critical feature sizes down to ≈100 nm and inter‐pattern spacings down to ≈100 nm are achieved, corresponding to the highest resolution of any LM fabrication technique developed to date. Additionally, the LM nanopatterns demonstrate excellent long‐term stability under ambient conditions. This work paves the way toward further development of a wide range of LM nanophotonics technologies and applications.

The coalescence and oscillation of eutectic gallium indium alloy droplets

Gallium-based liquid metal droplets have excellent deformation performance, and their oscillation has huge potential in oscillator and organ-on-chip research. At present, the oscillation of gallium-based liquid metal droplets controlled by external energy (such as the application of electric fields and chemical reactions) has been thoroughly studied, while there are vacancies in the study of the oscillation due to coalescence of droplets without external energy input. A numerical simulation study on the oscillation process after the coalescence of two and three eutectic gallium indium alloy droplets is conducted. The degree of deformation of the droplet is described by the dimensionless length change in the symmetry axis direction of the line connecting the centers of the initial droplets in the top view, that is, in the y direction. The oscillation curve of the droplet is obtained by the fitting method. The results show that the oscillation of coalesced droplets has obvious periodicity and damping attenuation characteristics, and increasing the number of droplets or reducing the droplet radius will increase the damping coefficient. Furthermore, the ratio of droplet sizes and their initial distribution have an impact on the variations in kinetic energy of the three droplets in the y direction, thereby influencing the deformation of the droplets. This research enriches the theory of gallium-based liquid metal droplet deformation and plays a significant role in guiding the application of droplet oscillation in the fields of micromixers and measuring the physical parameters of solutions.

High internal phase emulsions gel ink for direct-ink-writing 3D printing of liquid metal

3D printing of liquid metal remains a big challenge due to its low viscosity and large surface tension. In this study, we use Carbopol hydrogel and liquid gallium-indium alloy to prepare a liquid metal high internal phase emulsion gel ink, which can be used for direct-ink-writing 3D printing. The high volume fraction (up to 82.5%) of the liquid metal dispersed phase gives the ink excellent elastic properties, while the Carbopol hydrogel, as the continuous phase, provides lubrication for the liquid metal droplets, ensuring smooth flow of the ink during shear extrusion. These enable high-resolution and shape-stable 3D printing of three-dimensional structures. Moreover, the liquid metal droplets exhibit an electrocapillary phenomenon in the Carbopol hydrogel, which allows for demulsification by an electric field and enables electrical connectivity between droplets. We have also achieved the printing of ink on flexible, non-planar structures, and demonstrated the potential for alternating printing with various materials.

Electrochemical platform for detecting Escherichia coli bacteria using machine learning methods

We present an electrochemical platform designed to reduce time of Escherichia coli bacteria detection from 24 to 48-h to 30 min. The presented approach is based on a system which includes gallium-indium (eGaIn) alloy to provide conductivity and a hydrogel system to preserve bacteria and their metabolic species during the analysis. The work is dedicated to accurate and fast detection of Escherichia coli bacteria in different environments with the supply of machine learning methods. Electrochemical data obtained during the analysis is processed via multilayer perceptron model to identify i.e. predict bacterial concentration in the samples. The performed approach provides the effectiveness of bacteria identification in the range of 102–109 colony forming units per ml with the average accuracy of 97%. The proposed bioelectrochemical system combined with machine learning model is prospective for food analysis, agriculture, biomedicine.

Liquid-metal-based three-dimensional microelectrode arrays integrated with implantable ultrathin retinal prosthesis for vision restoration

Electronic retinal prostheses for stimulating retinal neurons are promising for vision restoration. However, the rigid electrodes of conventional retinal implants can inflict damage on the soft retina tissue. They also have limited selectivity due to their poor proximity to target cells in the degenerative retina. Here we present a soft artificial retina (thickness, 10 μm) where flexible ultrathin photosensitive transistors are integrated with three-dimensional stimulation electrodes of eutectic gallium–indium alloy. Platinum nanoclusters locally coated only on the tip of these three-dimensional liquid-metal electrodes show advantages in reducing the impedance of the stimulation electrodes. These microelectrodes can enhance the proximity to the target retinal ganglion cells and provide effective charge injections (72.84 mC cm−2) to elicit neural responses in the retina. Their low Young’s modulus (234 kPa), owing to their liquid form, can minimize damage to the retina. Furthermore, we used an unsupervised machine learning approach to effectively identify the evoked spikes to grade neural activities within the retinal ganglion cells. Results from in vivo experiments on a retinal degeneration mouse model reveal that the spatiotemporal distribution of neural responses on their retina can be mapped under selective localized illumination areas of light, suggesting the restoration of their vision.

Clean and efficient recovery of gallium–indium alloy from gallium-based liquid metal waste using a two-stage vacuum distillation method

Gallium (Ga) and indium (In) are rare metals widely used in the high-tech industry. Gallium-based liquid metal (G-LM) waste is produced during the preparation of liquid metal and related products. G-LM waste is a potential source of gallium and indium. In this study, the saturated vapor pressure, separation coefficient, and gas–liquid equilibrium phase diagram were determined using the simplified molecular interaction volume model. A two-stage vacuum distillation method was used to recover Ga–In alloy from G-LM waste. First, low-temperature vacuum distillation was used to recover 98.23 % of Zn under optimal conditions (1–5 Pa; 773 K; 60 min). Then, the Ga–In alloy was recovered through high-temperature vacuum distillation. Under the optimal conditions (1–5 Pa; 1523 K; 120 min), the recovery rates of gallium and indium were 85.14 and 95.23 %, and the content of Ga–In alloy in the product was 99.46 %. Compared with the traditional hydrometallurgical process for recovering gallium and indium, this process generates no exhaust gas or waste. In addition, this new method is simple, efficient, clean, and pollution-free. Overall, this new method for recovering Ga–In alloy provides a new avenue for comprehensively utilizing G-LM waste.

The Dielectrophoretic Alignment of Biphasic Metal Fillers for Thermal Interface Materials.

Pad-type thermal interface materials (TIMs) with composite structures are required to exhibit high thermal conductivity while maintaining conformal contact with the heat sink, which is strongly influenced by the type and content of the thermally conductive filler. This study presents that biphasic metal particles can be effectively aligned using the dielectrophoretic chaining (DEP-C) mechanism, thereby enhancing the thermal conductivity of a pad-type TIM. A eutectic gallium-indium (EGaIn) alloy liquid metal and solid copper were used as the filler materials with two different phases. The biphasic metal particle mixture of EGaIn and Cu (EGaIn-Cu) were better aligned by DEP-C than when they presented individually because fusion between the two particles increased the effective size. As expected, the thermal conductivity of the TIM composites increased when DEP-C aligned the filler. Notably, TIMs with both EGaIn-Cu fillers showed the largest increase in thermal conductivity, of up to 64.6%, and the highest thermal conductivity values after DEP-C application compared to TIMs with only the EGaIn or Cu filler. Finally, the heat dissipation performance of the TIM composite on a lit light-emitting diode is shown, where the TIM with DEP-C-aligned fillers exhibits improved performance.

Turing Instability of Liquid-Solid Metal Systems.

The classical Turing morphogenesis often occurs in nonmetallic solution systems due to the sole competition of reaction and diffusion processes. Here, this work conceives that gallium (Ga) based liquid metals (LMs) possess the ability to alloy, diffuse, and react with a range of solid metals (SMs) and thus should display Turing instability leading to a variety of nonequilibrium spatial concentration patterns. This work discloses a general mechanism for obtaining labyrinths, stripes, and spots-like stationary Turing patterns in the LM-SM reaction-diffusion systems (GaX-Y), taking the gallium indium alloy and silver substrate (GaIn-Ag) system as a proof of concept. It is only when Ga atoms diffuse over Y much faster than X while X reacts with Y preferentially, that Turing instability occurs. In such a metallic system, Ga serves as an inhibitor and X as an activator. The dominant factors in tuning the patterning process include temperature and concentration. Intermetallic compounds contained in the Turing patterns and their competitive reactions have also been further clarified. This LM Turing instability mechanism opens many opportunities for constructing microstructure systems utilizing condensed matter to experimentally explore the general morphogenesis process.

Liquid Metal‐Based Perovskite Solar Cells: In Situ Formed Gallium Oxide Interlayer Improves Stability and Efficiency

AbstractIn this study, eutectic gallium–indium alloy (EGaIn) liquid metal is used as the rear electrode for perovskite solar cells (PSCs), where the interfacial properties of the device, particularly the beneficial roles of the surface oxide of the liquid metal, are explored. The findings demonstrate that the native oxide of the EGaIn electrode significantly affects the stability of photovoltaic performance and impedance characteristics including series and shunt resistances. Based on the results, the following hypothesis is formulated: the oxide interlayer serves two crucial functions of a barrier against metal diffusion and a tunnel for enhancing charge extraction and transfer. The results of elemental mapping and trap density calculation support the former function of the hypothesis that the oxide film can effectively prevent metal penetration into the perovskite layer. Furthermore, measurements involving capacitance−voltage and time‐resolved photoluminescence confirm that the oxide film on the liquid metal eliminates the interfacial Schottky barrier, promoting efficient charge extraction and transfer processes. Finally, the investigation is extended to develop flexible PSCs using the EGaIn electrode, which consistently exhibits stable performance during repeated bending cycles. Notably, the EGaIn rear electrode can be readily removed and collected through a straightforward acid treatment, offering a promising avenue for efficient cell recycling.

Enabling High-Performance Pressure and Proximity Dual-Mode Sensing with EGaIn/Ag/ZnO Egg-Shell Ternary Composite Particles.

Eutectic gallium-indium alloy (EGaIn) is a biocompatible liquid metal, promising for wearable electronics. Through functionalization and formation of composites, EGaIn-based materials have shown potential in multifunctional sensing devices. Here, egg-shell EGaIn/Ag/ZnO ternary composite particles were prepared through an ultrasound-assisted displacement reaction combined with room-temperature hydrolysis. The composite was further constructed as a wearable sensor capable of both pressure and proximity detection. For pressure sensing, due to the decrease in the Young's modulus of the egg-shell structure and the presence of the electrical double layers between Ag and ZnO, which enriched surface charges, the sensor showed excellent sensitivity at low pressures (2.17 KPa-1, <0.4 KPa) and thus the ability to sense body movements. For proximity sensing, the composite sensor was able to detect approaching objects that were up to 20 cm away. By combining and fitting the sensing curves for both the touchless and touching modes, the extracted parameters were used to create fingerprints for different objects, demonstrating the great potential of our sensor in the differentiation and identification of unknown objects for future robotics and artificial intelligence.

Selection of metallic liquid in sub-6 GHz antenna design for 6G networks

The rapid evolution of wireless communication systems toward 6G demands efficient antennas with the features of adaptability and versatility. Liquid antennas have gained significant research interest due to their unique features in realizing small, flexible, transparent, and reconfigurable antennas for promising applications in future wireless systems. In this paper, in order to find a suitable metallic liquid for effective antennas, we design and compare the performance of metallic liquid antennas using Mercury, gallium indium alloy (EGaIn), and Graphene metallic liquid in the sub-6 GHz frequency. The antenna is realized by the metallic liquid in a poly methyl methacrylate microfluidic channel over a liquid crystal polymer substrate at 5.6 GHz frequency. The performance of these metallic liquid antennas is analyzed by their electromagnetic and radiation performance. The Graphene-based metallic liquid antenna shows better electromagnetic performance in comparison to Mercury and EGaIn metallic liquid antennas.

Functionalized EGaIn Electrodes with Tunable Reduced‐Graphene‐Oxide Assembled EGaIn Core–Shell Particles for Soft and Deformable Electrochemical Biosensors

AbstractGallium‐based liquid metal, eutectic gallium–indium alloy (EGaIn), is becoming a leading innovation in soft electronic devices due to its exceptional electronic conductivity and deformability. However, the formation of insulating oxide films on EGaIn surfaces poses a significant impediment to translating electrochemical reactions, thereby limiting its use as an electrochemical biosensor. Here, functionalized EGaIn electrodes with reduced‐graphene‐oxide assembled EGaIn core–shell particles (REGs) for soft and deformable electrochemical biosensors are presented. Exploiting EGaIn's capability as a reducing agent, REGs can undergo further modification with metal nanoparticles through additional galvanic replacement reactions. The REGs and metal‐coated REGs (M‐REGs) provide strong interfacial adhesion with the EGaIn current collector, exhibiting no exfoliation during and after the mechanical deformation. Moreover, RIDE and metal‐decorated RIDE (M‐RIDE) show excellent electrochemical sensing performances by taking advantage of the facile surface tunability of REGs, allowing simultaneous detection of ascorbic acid, dopamine, and uric acid, and enzymatic detection of glucose. The developed RIDE/M‐RIDE paves the way for utilizing EGaIn in the development of soft and deformable electrochemical biosensors.

Solubility of Lanthanum in Liquid Alloys with Gallium and Indium

The solubility of lanthanum in indium and Ga–In alloys containing 21.8, 40 and 70 wt. % In was determined experimentally at temperatures up to 1081 K. The low temperature limit depended on the melting point of the alloy. The solubility was measured using isothermal saturation and high-temperature filtration methods. The phase composition of solid intermetallic compounds formed in the ternary La–Ga–In systems of various compositions was determined by X-ray diffraction. Activity coefficients of lanthanum in the alloys based on gallium, indium and three Ga–In mixtures (21.8, 40 and 70 wt. % In) were calculated. Temperature dependencies of thermodynamically possible separation factors for the uranium/lanthanum couple in “LiCl–KCl–CsCl melt–liquid alloy” systems were derived for various gallium–indium alloys.

Heat of Mixing of the Liquid Silver–Indium and Silver–Gallium–Indium Alloys

Experimental studies of the multicomponent systems are necessary in the development of new materials which can be used in various industries. The literature review showed, that the liquid phase in the silver–gallium–indium system has not been studied yet. In the present work the heat of mixing of the liquid silver–indium and silver–gallium–indium alloys was studied using Calvet type MHTC96 calorimeter. Calorimetric measurements were carried out at the temperatures: 973 K, 1123 K and 1273 K for Ag–In alloys, and at 923 K, 1123 K and 1273 K along two cross-sections XAg/XGa = 1:1 and XGa/XIn = 1:1 for Ag–Ga–In alloys. Next, the Redlich–Kister–Muggianu formalism was applied in the mathematical description of the heat of mixing of the liquid silver–gallium–indium alloys. Experimental results obtained in this work are first, which provided information about the thermodynamic properties of the liquid phase in this ternary system.

Simulations of optical properties of gallium alloy nanorods based on aspect ratio and shell thickness

Liquid plasmonics in contemporary research heavily relies on gallium-based alloy nanoparticles (NPs). The focus of this study is to explore the plasmonic properties of rod-shaped gallium alloy nanoparticles. The primary aim is to examine how variations in Ag shell thickness and aspect ratio affect the optical properties based on localized surface plasmon resonance (LSPR). The outcomes of this study will provide invaluable insights into improving the performance of plasmonic nanostructures. Notably, the focus is solely on analyzing the impact of size and material on the plasmon resonance of gallium-based alloy (GaAg), distinguishing it from the more widely known eutectic gallium-indium (EGaIn) alloy and Galinstan. To investigate the influence of varying aspect ratios and noble metal shell thickness under three different light polarization conditions, the boundary element method (BEM) was utilized. MATLAB-based simulations were employed to generate near-field and far-field plots of the extinction profiles of these nanorods. A large amount of tuning of the extinction spectra observed in the visible domain (380–780 nm) of the electromagnetic spectrum can be achieved with the size variation parameters. The gallium alloy (GaAg) examined in this study exhibits superior plasmonic properties and can be effectively utilized in soft electronic components, plasmonic energy storage devices, and as an alternative to the widely promoted GaIn alloy.

3D Printing of Liquid‐Metal‐in‐Ceramic Metamaterials for High‐Efficient Microwave Absorption

AbstractThis work reports a gallium indium alloy (EGaIn)‐doped SiBOC ceramic that possesses a unique liquid‐metal‐in‐ceramic feature. The low‐viscosity liquid nature of gallium‐based liquid metals (Ga‐LMs) and the reactive core‐shell structure provide possibilities for phase engineering inside polymer‐derived ceramics. As a demonstration, EGaIn nanoparticles (NPs) are directly mixed with a UV‐curable ceramic precursor (UV‐PBS) to obtain a resin suitable for digital light processing 3D‐printing. After pyrolysis at 800–1200 °C, SiBOC ceramics with uniformly distributed EGaIn NP domains (Si(GaIn)BOC) are obtained. EGaIn plays a key role in promoting carbonization and preventing crack formation during the polymer‐to‐ceramic process, resulting in an increase in both ceramic yield and mechanical strength. EGaIn NPs are also found to have a core‐shell structure (EGaIn@(GaxIn1‐x)2O3@SiBOC) inside the SiBOC matrix, which significantly enhances the dielectric properties and improves the interfacial polarization. As a result, an excellent electromagnetic wave absorption performance is achieved across the C, X, and Ku bands, respectively. Through rational design, a novel metastructure design based on the Schwarz P minimal surface is proposed, which exhibits an ultrawide effective absorption band extending up to 11.36 GHz (within C‐Ku bands).

Local Order in Liquid Gallium-Indium Alloys.

Liquid metals such as eutectic Ga-In alloys have low melting points and low toxicity and are used in catalysis and micro-robotics. This study investigates the local atomic structure of liquid gallium-indium alloys by a combination of density measurements, diffraction data, and Monte-Carlo simulation via the empirical potential structure refinement approach. A high-Q shoulder observed in liquid Ga is related to structural rearrangements in the second coordination shell. Structure analysis found coordination environments close to a random distribution for eutectic Ga-In alloy, while electronic effects appear to dominate the mixing enthalpy.

On mechanism of hydrogen generation at oxidation of activated aluminum in aqueous solutions

To clarify the mechanism of hydrogen generation upon aluminum oxidation by water, the behavior of the mechanical alloys {Al+20%Bi} and {Al+7%Ga+3%In} in various salt solutions has been studied. Analysis of the reaction rate and the overall hydrogen yield in the studied systems allows us to suggest that, unlike the oxidation of magnesium-based materials, the hydrogen generation by activated aluminum is not mainly controlled by electrochemical processes. Additives of activating metals, bismuth and gallium-indium alloys, primarily act as surfactants, making an unoxidized intergranular surface accessible to water according to the Rebinder effect.