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To obtain the optimum performance of thermoelectric materials, engineering their characteristics, such as crystal structures and phases, is critical. Liquid metal-based processes are great methods for controlling and tuning such properties. In this study, indium (In), of different concentrations, is introduced into bismuth (Bi) via a liquid metal-based process to tailor the crystallization arrangements and investigate the thermoelectric properties of the Bi–In systems. These systems were prepared by a liquid metal-based melting and solidification process. Thermoelectric properties, including the Seebeck coefficient, thermal conductivity, and resistivity, were analyzed using in-house built apparatus units. The sample with 2% indium concentration showed the highest Seebeck coefficient and electrical resistivity. Thermal conductivity was observed to decrease with increasing indium concentration up to 5%, followed by a reverse trend above this concentration. Dominated by the thermal conductivity effect, the sample with 5% indium concentration showed the highest average value for the figure of merit (zT) for the Bi–In systems. The zT value of this sample was nearly twice than that of the pristine bismuth. According to our analyses, this increase could be attributed to the crystal modalities of the formed BiIn crystals with optimum crystallite dimensions and distributions, along with the emergence of specific diffraction peaks, in the pool of bismuth. This study provides a facile and low-cost liquid metal-based pathway for designing thermoelectric materials by tuning their crystal structures and orientations using liquid metal-enabled processes. [ABSTRACT FROM AUTHOR]

Gallium (Ga) is a low melting point metal in the liquid state in the biological environment which presents a unique combination of fluidity, softness, and metallic electrical and thermal properties. In this work, liquid Ga is proposed as a biocompatible electrode material for cell culture by electro-stimulation since the cytotoxicity of Ga is generally considered low and some Ga compounds have been reported to exhibit anti-bacterial and anti-inflammatory activities. Complementarily, polydopamine (PDA) was coated on liquid Ga to increase the attachment capability of cells on the liquid Ga electrode and provide enhanced biocompatibility. The liquid Ga layer could be readily painted at room temperature on a solid inert substrate, followed by the formation of a nanoscale PDA coating layer resulting in a conformable and biocompatible composite electrode. The PDA layer was shown to coordinate with Ga3+, which is sourced from liquid Ga, providing electrical conductivity in the cell culture medium. The PDA–Ga3+ composite acted as a conductive substrate for advanced electro-stimulation for cell culture methods of representative animal fibroblasts. The cell proliferation was observed to increase by ∼143% as compared to a standard glass coverslip at a low potential of 0.1 V of direct coupling stimulation. This novel PDA–Ga3+ composite has potential applications in cell culture and regenerative medicine. [ABSTRACT FROM AUTHOR]

With growing research interest in liquid metals, such as Ga and Ga-based alloys, understanding their behaviours at reduced dimensions is becoming of more fundamental significance, especially for exploiting their properties in a variety of applications. Mechanical sonication is a common technique used for micronising bulk liquid metals into smaller sized particles. One distinct characteristic of Ga and Ga-based liquid metal alloy particles, micronised via sonication, is the formation of native oxygen species such as GaOOH and Ga2O3. However, the nitridation of these particles has not been reported. In this work, we demonstrate a room temperature nitridation process during the micronisation of eutectic Ga–In alloy (EGaIn). Characterisations reveal that the sonication in the N-containing precursors of PVP and N2 results in the formation of GaN within the GaOOH crystallites that separate themselves from the bulk of EGaIn during sonication. As a model example of the applicability of such particles, low-detection-limit biosensing by photoluminescence of the obtained particles is demonstrated. The work shows a room temperature pathway for the creation of GaN that can be further investigated, expanded upon, and implemented for different future applications. [ABSTRACT FROM AUTHOR]

Mitigation of the health hazards and environmental pollution caused by Pb is necessary. However, piezoelectric Pb containing compounds, such as PZT, are still widely used in many industries and health sectors. One approach to reduce the hazards and contamination caused by Pb is to decrease the amount of this element in the devices by size reduction. In this regard, the possibility of using ultra-thin piezoelectric PbO films should be investigated. However, to date, the development of such two-dimensional (2D) PbO films, in large lateral dimensions, has faced certain challenges. Here a liquid metal-based 2D printing technique is employed to produce unit-cell thick PbO sheets by harvesting the interfacial oxide layer of liquid Pb. The resulting PbO monolayer, with lateral dimensions of hundreds of microns, exhibits an orthorhombic crystal phase with a wide direct band gap of 3.3 eV, larger than that of its bulk counterpart. In addition, remarkable vertical piezoelectric coefficients of ∼30 pm V−1 were obtained in unit-cell thick PbO through both measurements and density functional theory calculations. The PbO monolayers can be employed as an environmentally friendly alternative to PZT, in many commercial applications, due to the low content of Pb. [ABSTRACT FROM AUTHOR]

One of the major challenges in the development of soft electronics is to devise scalable and automated strategies for the microfabrication of deformable and flexible electronic components and sensors. Liquid metals have demonstrated unique characteristics suitable for such applications. To date, conductive patterning using liquid metals has mainly focused on writing or injection of liquid metals into prefabricated channels, requiring multiple complicated procedures and reliance on specific inks formulae. Here a new strategy has been introduced for direct patterning of liquid metal particles onto substrates via UV photolithography. A variety of different tracks, patterns and sensors, on both rigid and flexible substrates, are demonstrated using a dispersion of eutectic alloy of gallium and indium in photoresist, to present the extent of capability of the introduced method. The method provides simple, effective, high-resolution and precision patterning of liquid metals for the emerging fields of soft electronics and sensors. [ABSTRACT FROM AUTHOR]

The argument of phase coexistence in the lead-free piezoelectric perovskite K0.5Na0.5NbO3 (KNN) has led to significant discrepancies in the interpretation of its exact crystalline structure in the literature. In this work, the structural details of hydrothermally prepared KNN nanofibres and microcubes were investigated by a combination of high resolution transmission electron microscopy (TEM), solid-state 23Na and 93Nb nuclear magnetic resonance (NMR) spectroscopy and two-dimensional 23Na 3QMAS NMR. Although powder X-ray diffraction yielded an average orthorhombic structure for both morphologies, high resolution TEM revealed mixed phases of orthorhombic (O) and monoclinic (M) symmetry with a growth direction of [001] and [110], respectively, in individual KNN nanofibres. Consistent with the TEM analysis, solid-state 23Na NMR indicated a distribution of multiple Na sites in the KNN nanofibers, which were not observed in the KNN microcubes. This study provided microscopic evidence of phase coexistence in KNN nanofibers and suggested that a two-phase concomitant state might be highly dependent on the size and morphologies of the KNN nanostructures. [ABSTRACT FROM AUTHOR]

Liquid metal interfaces with their unique chemistry can provide an extraordinary tool to synthesise materials with controlled characteristics at room temperature. Here, the templated synthesis of cupric oxide (CuO) onto a gallium based liquid metal (galinstan) surface is explored. The interaction between galinstan and copper sulphate solution yields initial interfacial CuO sheets and then secondary dendritic nanostructures are grown from the sheets. It is shown that the pH of the aqueous environment plays a critical role in tuning the synthesis of substoichiometric CuxO to CuO. For enhancing the interfacial area and establishing heterojunctions, the liquid metal is processed into a suspension of micro and nano droplets by sonication and the example of using the synthesised nano structures for enhanced photocatalysis is demonstrated for the catalysis of a model dye. This study presents a facile approach for synthesising highly functional systems based on liquid metals, and it can be extended to explore other metal oxide–liquid metal composites. [ABSTRACT FROM AUTHOR]

Gallic acid, a natural phenolic compound, efficiently establishes surface complexes with liquid gallium leading to the formation of an aqueous gallium dispersion via sonication. The surface functionalised gallium particles thus obtained were easily impregnated into paper membranes that could be turned from insulating to conductive by pressure induced deformation of the embedded particles. [ABSTRACT FROM AUTHOR]

Exploring the concept of liquid processing and solidification of low melting point alloys can provide new routes for the creation of functional micro and nanoparticles. Here we show that it is possible to produce particles of Field's metal (an alloy of bismuth 32.5 wt%, tin 16.5 wt% and indium 51 wt%) in a one-step mechanical agitation (ultrasonication) procedure. The synthesis takes place just above 62 °C, the melting point of Field's metal, and results in the formation of low-dimensional particles after solidification. It is demonstrated that the sonication process produces nearly spherical core–shell metal–metal oxide heterostructures. Classic alloy-related defects, in the forms of grain boundaries and edge locations, emerge after the solidification. We show that by the incorporation of Ag, either using direct alloying or an Ag salt precursor during the sonication process, this metal appears in the core of the metal–metal oxide heterostructures. Interestingly, the modification of particles with Ag gives specific selectivity for the degradation of two typical azo dyes. The one-step low-temperature synthesis and solidification procedure, presented in this work, can be readily extended for designing catalysts or other functional materials with desired specificity and selectivity. [ABSTRACT FROM AUTHOR]

Liquid metals can offer extraordinary properties for application in the field of sensors, yet their potential has not been fully realised. In this work, we present a heterostructure mix of eutectic alloy of gallium and two dimensional (2D) flakes of tungsten oxides (WO3) for gas sensing. We show that the eutectic alloy of EGaIn, made of gallium and indium, can be co-sonicated with acid bath synthesised 2D WO3 for chemisorption sensing of H2 gas molecules. We demonstrate that this co-sonication results in extra trap bands within the bandgap of WO3 to enhance the gas sensing properties. Another interesting observation was the effect on reducing the size of the sonicated EGaIn droplets in the presence of 2D WO3 flakes, which is likely due to the increase of shear force during the sonication. Mixes using different ratios of WO3 and EGaIn were synthesised. The optimum gas sensing operation in terms of response factor was seen in the 70% WO3–30% EGaIn mix. This work provides a viable pathway towards a new platform where liquid metals can be used for sensing applications and they offer advantages to augment the capabilities of sensors. [ABSTRACT FROM AUTHOR]