Liquid Eutectic Gallium Indium Research Articles

An Antiferroelectric‐Coated Metal Foam Infiltrated with Liquid Metal as a Dielectric Capacitor

Nickel metal foams serve as both a substrate and bottom electrode for a dielectric capacitor using atomic‐layer deposition (ALD) and a eutectic gallium–indium (EGaIn) liquid metal (LQM) counter electrode. The conformal dielectric has a composition of 6.25% Al–HfO2 in the antiferroelectric phase, confirmed with polarization versus electric field measurements. Liquid EGaIn is pressure‐infiltrated within the coated foams to form the dielectric capacitor. Capacitances up to 4 μF are realized. Calorimetry of the infiltrated capacitor shows a 60 J g−1 latent heat upon melting a frozen EGaIn electrode, suggesting that the phase change can alleviate thermal deviations from pulsed power capacitor operation. Infiltrated capacitors are also shown to survive bending and freeze–thaw cycles. The metal foam–ALD dielectric–LQM capacitor shows a combined set of thermal and electrical properties not available in other classes of capacitors.

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.

Stretchable Electrodes Based on Over-Layered Liquid Metal Networks.

Liquid metals are attractive materials for stretchable electronics owing to their high electrical conductivity and near-zero Young's modulus. However, the high surface tension of liquid metals makes it difficult to form films. A novel stretchable film is proposed based on an over-layered liquid-metal network. An intentionally oxidized interfacial layer helps to construct uninterrupted indium and gallium nanoclusters and produces additional electrical pathways between the two metal networks under mechanical deformation. The films exhibit gigantic negative piezoresistivity (G-NPR), which decreased the resistance up to 85% during the first 50% stretching. This G-NPR property is due to the rupture of the metal oxides, which allows the formation of liquid eutectic gallium-indium (EGaIn) and the connection of the over-layered networks to build new electrical paths. The electrodes exhibiting G-NPR are complementarily combined with conventional electrodes to amplify their performance or achieve some unique operations.

Liquid metal embrittlement and deformation induced martensite: The case of 316 L austenitic steel LME by liquid eutectic gallium-indium

The liquid metal embrittlement sensitivity of a low nickel 316 L austenitic steel has been studied with eutectic gallium indium alloy. The embrittlement case is firmly established with this steel and studied by X-Ray fractography and EBSD. Brittle to ductile recoveries were observed via a dedicated parametric study (varying cross-head speed and temperature). The return to ductility with temperature is strongly correlated with a significant reduction in plastically induced α’ phase change suggesting it is a requirement for LME. This implies a strategy focused on limiting deformation induced martensite to design LME resistant austenitic steels at low temperature.

Dependence of the effective surface tension of liquid phase eutectic gallium indium on wrinkles of the surface oxide

We investigated the effective surface tension of liquid eutectic gallium indium (EGaIn) with oxide skin. Our visualization of the EGaIn interface during extension and compression indicated the compression causes the wrinkles on the oxide skin, which is then partially smoothed out by extension. We found that the creation of the interface was the combined result of tearing of the oxide skin and the unfolding of oxide wrinkles. Our experiments revealed that the effective surface tension depends on oxide wrinkle, and the value is 0.7 N/m in the absence of wrinkles, but can be as small as ∼0.5 N/m in the presence of surface wrinkles.

New Approach for Large-Area Thermoelectric Junctions with a Liquid Eutectic Gallium-Indium Electrode.

A challenge in organic thermoelectrics is to relate thermoelectric performance of devices to the chemical and electronic structures of organic components inside them on a molecular scale. To this end, a reliable and reproducible platform relevant to molecular-level thermoelectric measurements is essentially needed. This paper shows a new, efficient approach for thermoelectric characterization of a large area of molecular monolayers using liquid eutectic gallium-indium (EGaIn). A cone-shaped EGaIn microelectrode permits access to noninvasive, reversible top-contact formation onto organic surfaces in ambient conditions, high yields of working devices (up to 97%), and thus statistically sufficient thermoelectric data sets (∼6000 data per sample in a few hours). We here estimated thermopowers of EGaIn (3.4 ± 0.1 μV/K) and the Ga2O3 layer (3.4 ± 0.2 μV/K) on the EGaIn conical tip and successfully validated our platform with widely studied molecules, oligophenylenethiolates. Our approach will open the door to thermoelectric large-area molecular junctions.

INTERACTION OF ALUMINUM-COBALT AND ALUMINUM-NICKEL ALLOYS ACTIVATED BY LIQUID GALLIUM-INDIUM EUTECTIC WITH TERT-BUTYL CHLORIDE FOR FORMATION OF CATALYTIC METAL - ALUMO-CHLORIDE COMPLEXES

It is known that binary alloys of aluminum and metals of the iron group (cobalt, nickel) after their activation with the liquid eutectic gallium-indium by the removal of “passivating” oxide layers sharply increase the reactivity with respect to organochlorines. Corresponding reactions lead to the formation of metal – alumo - chloride complexes as inorganic products, which are active in many practically important catalytic reactions of liquid-phase conversion of hydrocarbons such as: alkylation, isomerization, oligomerization. This approach which was previously developed by the authors for the polycrystalline aluminum, is of interest in metal-complex catalysis since the formation of catalytic alumo-chloride and/or metal-alumo-chloride complexes can be carried out directly in the reaction medium, i.e. in situ. In this work, the local composition, structure and morphology of surface layers of aluminum-cobalt and aluminum-nickel alloys activated with liquid gallium-indium eutectic were studied using the methods of scanning electron microscopy and X-ray energy-dispersive spectrometry to determine the physicochemical regularities of the dynamics of their interaction with tert-butyl chloride at room temperatures. The formation of metal chloride complexes in the interphase area “activated alloy - tert-butyl chloride” was studied by ATR-FT-IR method in situ. The results obtained indicate that mono- and bi- nuclear alumo-chloride anions stabilized by cobalt and nickel cations are formed during the interaction. It is assumed that the ionic complex pairs formed are the active centers in liquid-phase reactions of hydrocarbons transformation at low temperatures. These structures are responsible for significantly change in the selectivity of catalytic processes compared to aluminum chloride catalyst.
 For citation:
 Arbuzov A.B., Drozdov V.A., Shlyapin D.A., Lavrenov A.V. Interaction of aluminum-cobalt and aluminum-nickel alloys activated by liquid gallium-indium eutectic with tert-butyl chloride for formation of catalytic metal - alumo-chloride complexes. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 9-10. P. 64-69

Self-Regenerating Soft Biophotovoltaic Devices.

This paper describes the fabrication of soft, stretchable biophotovoltaic devices that generate photocurrent from photosystem I (PSI) complexes that are self-assembled onto Au electrodes with a preferred orientation. Charge is collected by the direct injection of electrons into the Au electrode and the transport of holes through a redox couple to liquid eutectic gallium–indium (EGaIn) electrodes that are confined to microfluidic pseudochannels by arrays of posts. The pseudochannels are defined in a single fabrication step that leverages the non-Newtonian rheology of EGaIn. This strategy is extended to the fabrication of reticulated electrodes that are inherently stretchable. A simple shadow evaporation technique is used to increase the surface area of the Au electrodes by a factor of approximately 106 compared to planar electrodes. The power conversion efficiency of the biophotovoltaic devices decreases over time, presumably as the PSI complexes denature and/or detach from the Au electrodes. However, by circulating a solution of active PSI complexes the devices self-regenerate by mass action/self-assembly. These devices leverage simple fabrication techniques to produce complex function and prove that photovoltaic devices comprising PSI can retain the ability to regenerate, one of the most important functions of photosynthetic organisms.

Liquid Metal Corrosion Effects on Conventional Metallic Alloys Exposed to Eutectic Gallium–Indium Alloy Under Various Temperature States

The effects of liquid metal corrosion on the thermophysical properties of three conventional metallic alloys, including T2 copper, 304 stainless steel and anodized 6061 aluminum alloy, in the range of 100–400 °C were comprehensively clarified in this paper. It was experimentally found that the corrosion products on the copper surface existed as the intermetallic compound of CuGa2, and that FeGa3 and Cr3Ga4 were formed on the surface of stainless steel. The heat conductivity of copper plate decreased with the increasing corrosion temperature. The heat conductivity of the corroded copper sample sharply decreased at the beginning stage. When the copper plate was exposed in liquid eutectic gallium–indium over 12 h, the trend of the tested heat conductivity changing curve showed a smooth tendency and reached a steady state finally. The heat conductivity of the corroded copper plate was decided by the corrosion speed with an exponential function of $$ v = a^{t} (0.4 < a < 0.6) $$ . Corrosion phenomena were not found on the surface of the anodized 6061 aluminum alloy according to the experimental results from ambient temperature to 400 °C, which disclosed their suitability as the structural material. The present findings would serve as an important reference for the use of liquid metal cooling in high-power electronic devices and high-temperature systems.

Liquid eutectic GaIn as an alternative electrode for PTB7:PCBM organic solar cells

Conventional vacuum deposition process of aluminum (Al) is costly, time-consuming and difficult to apply to the large-scale production of organic photovoltaic devices (OPV). This paper reports a vacuum-free fabrication process of poly[[4,8-bis(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thienophenediyl]:[6,6]-phenyl C71 butyric acid methyl ester (PTB7:PCBM) bulk heterojunction organic solar cell with liquid eutectic gallium–indium (EGaIn) electrode as an alternative to the common Al electrode. The insertion of a thin poly(ethylene oxide) (PEO) layer after depositing organic photoactive layer could help prevent the diffusion of liquid EGaIn into the active layer and allow the deposition of the EGaIn electrode. The PEO interfacial layer was formed by spin-coating from a mixed solvent of alcohol and water. Among different alcohol+water (methanol, ethanol, ethylene glycol, n-propanol, isopropanol, and isobutanol) mixed solvent tested, the n-propanol+water mixed solvent showed the greatest enhancement to the performance of OPVs. The improved device performance was attributed to the reactivity of mixed solvent n-propanol+water toward the surface of PTB7:PCBM active layer, which could help optimize surface morphology.

EGaIn Microelectrode for Electrical Characterization of ITO-Based van der Waals Interface and Airborne Molecular Contamination of ITO Surface

This paper describes the electrical characterization of the van der Waals interfaces formed between indium-tin oxide (ITO) and a liquid metal-based microelectrode. We examined the influence of the adventitious contamination of the ITO surface by airborne molecular contaminants on the electrical transport across an ITO-based van der Waals interface. We constructed large-area junctions of the form ITO//Ga2O3/EGaIn, where EGaIn is a liquid eutectic gallium-indium alloy covered with a self-passivating thin oxide film (Ga2O3 of ∼ 0.7 nm), and “//” denotes the van der Waals interface formed between the ITO and EGaIn electrodes. Comparisons of the current density data for junctions formed with ITO surfaces prepared via five different surface cleaning methods—utilizing UV light, ozone and/or organic solvent (ethanol)—indicated that the electrical conductance of the ITO//Ga2O3 van der Waals interface was significantly enhanced (by three orders of magnitude) by UV/ozone surface cleaning, based on comparisons of the median value of the log-current density, and the dispersion of the data was significantly narrowed. The results reported in this work show that the electrical characterization of surfaces using the EGaIn-based microelectrode is an attractive method for investigating the electrical behavior of a conducting surface and the molecular adsorption phenomena on it.

Thermodynamics and separation factor of uranium from lanthanum in liquid eutectic gallium-indium alloy/molten salt system

This work presents the electrochemical study of lanthanum and uranium compounds in fused 3LiCl-2KCl eutectic vs. Cl−/Cl2 reference electrode in the temperature range 723–823K on liquid gallium-indium eutectic alloy. Thermodynamics and the activity coefficients of lanthanum and uranium were studied. The separation factor of uranium from lanthanum on gallium-indium eutectic alloy was determined.

Hyperelastic pressure sensing with a liquid-embedded elastomer

A hyperelastic pressure transducer is fabricated by embedding silicone rubber with microchannels of conductive liquid eutectic gallium–indium. Pressing the surface of the elastomer with pressures in the range of 0–100 kPa will deform the cross-section of underlying channels and change their electric resistance by as much as 50%. Microchannels with dimensions as small as 25 µm are obtained with a maskless, soft lithography process that utilizes direct laser exposure. Change in electrical resistance is measured as a function of the magnitude and area of the surface pressure as well as the cross-sectional geometry, depth and relative lateral position of the embedded channel. These experimentally measured values closely match closed-form theoretical predictions derived from plane strain elasticity and contact mechanics.