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).

High performance liquid metal thermal interface materials.

Conventional thermal interface materials (TIMs) as widely used in thermal management area is inherently limited by their relatively low thermal conductivity. From an alternative, the newly emerging liquid metal based thermal interface materials (LM-TIMs) open a rather promising way, which can pronouncedly improve the thermal contact resistance and offers tremendous opportunities for making powerful thermal management materials. The LM-TIMs thus prepared exhibits superior thermal conductivity over many conventional TIMs which guarantees its significant application prospect. And the nanoparticles mediated or tuned liquid metal further enable ever conductive LM-TIMs which suggests the ultimate goal of thermal management. In this review, a systematic interpretation on the basic features of LM-TIMs was presented. Representative exploration and progress on LM-TIMs were summarized. Typical approaches toward nanotechnology enhanced high performance LM-TIMs were illustrated. The perspect of this new generation thermal management material were outlined. Some involved challenges were raised. This work is expected to provide a guide line for future research in this field.

The Design and Manufacturing Process of an Electrolyte-Free Liquid Metal Frequency-Reconfigurable Antenna.

This communication provides an integrated process route of smelting gallium-based liquid metal (GBLM) in a high vacuum, and injecting GBLM into the antenna channel in high-pressure protective gas, which avoids the oxidation of GBLM during smelting and filling. Then, a frequency-reconfigurable antenna, utilizing the thermal expansion characteristic of GBLM, is proposed. To drive GBLM into an air-proof space, the thermal expansion characteristics of GBLM are required. The dimensions of the radiating element of the liquid metal antenna can be adjusted at different temperatures, resulting in the reconfigurability of the operating frequency. To validate the proposed concept, an L-band antenna prototype was fabricated and measured. Experimental results demonstrate that the GBLM in the antenna was well filled, and the GBLM was not oxidized. Due to the GBLM being in an air-proof channel, the designed liquid metal antenna without electrolytes could be used in an air environment for a long time. The antenna is able to achieve an effective bandwidth of over 1.25-2.00 GHz between 25 °C and 100 °C. The maximum radiation efficiency and gain in the tunable range are 94% and 2.9 dBi, respectively. The designed antenna also provides a new approach to the fabrication of a temperature sensor that detects temperature in some situations that are challenging for conventional temperature sensing technology.

A Handy Flexible Micro-Thermocouple Using Low-Melting-Point Metal Alloys.

A handy, flexible micro-thermocouple using low-melting-point metal alloys is proposed in this paper. The thermocouple has the advantages of simple fabrication and convenient integration. Bismuth/gallium-based mixed alloys are used as thermocouple materials. To precisely inject the metal alloys to the location of the sensing area, a micro-polydimethylsiloxane post is designed within the sensing area to prevent outflow of the metal alloy to another thermocouple pole during the metal-alloy injection. Experimental results showed that the Seebeck coefficient of this thermocouple reached -10.54 µV/K, which was much higher than the previously reported 0.1 µV/K. The thermocouple was also be bent at 90° more than 200 times without any damage when the mass ratio of the bismuth-based alloy was <60% in the metal-alloy mixture. This technology mitigated the difficulty of depositing traditional thin⁻film thermocouples on soft substrates. Therefore, the thermocouple demonstrated its potential for use in microfluidic chips, which are usually flexible devices.

Stretchable Pressure Sensor with Leakage-Free Liquid-Metal Electrodes.

Nowadays, with the development of wearable devices, stretchable pressure sensors have been widely adopted in all kinds of areas. Most of the sensors aim to detect small pressure, such as fingertip tactile sensing, but only a few are focused on high-pressure sensing, such as foot pressure sensing during men's walking. In this work, a liquid metal-based stretchable sensor for large-pressure measurement is investigated. This sensor is fully stretchable because it is made of soft materials. However, when the soft sensor is subjected to high pressure, the liquid metal easily leaks from microchannels because it maintains the liquid state at room temperature. We therefore propose to fabricate liquid metal-based leakage-free electrodes to handle the liquid-metal leak. Parametric studies are conducted to compare this sensor with liquid-metal-only electrodes and leakage-free electrodes. The leakage-free electrodes increase the measurement ranges from 0.18, 0.18, and 0.15 MPa to 0.44 MPa, with higher linearity and precision. The improvement in the liquid-metal electrode enables the sensors to work stably within 0.44 MPa pressure and 20% strain. In addition, we integrate two capacitors, namely, a working capacitor and a reference capacitor, into one sensor to reduce the influence of parasitic capacitance brought about by external interference. This stretchable capacitive sensor capable of working under a wide range of pressure with good repeatability, sensitivity, and linearity, exhibits great potential use for wearable electronics. Finally, the method for fabricating leakage-free electrodes shows great value for hyperelastic electronics manufacturing and micromachine technology.

Liquid metal bath as conformable soft electrodes for target tissue ablation in radio-frequency ablation therapy.

BACKGROUND: Radio-frequency ablation has been an important physical method for tumor hyperthermia therapy. The conventional rigid electrode boards are often uncomfortable and inconvenient for performing surgery on irregular tumors, especially for those tumors near the joints, such as ankles, knee-joints or other facets like finger joints. MATERIAL AND METHODS: We proposed and demonstrated a highly conformable tumor ablation strategy through introducing liquid metal bath as conformable soft electrodes. Different heights of liquid metal bath electrodes were adopted to perform radio-frequency ablation on targeted tissues. Temperature and ablation area were measured to compare the ablation effect with plate metal electrodes. RESULTS: The recorded temperature around the ablation electrode was almost twice as high as that with the plate electrode and the effective ablated area was 2-3 fold larger in all the mimicking situations of bone tumors, span-shaped or round-shaped tumors. Another unique feature of the liquid metal electrode therapy is that the incidence of heat injury was reduced, which is a severe accident that can occur during the treatment of irregular tumors with plate metal boards. CONCLUSIONS: The present method suggests a new way of using soft liquid metal bath electrodes for targeted minimally invasive tumor ablation in future clinical practice.

Bismuth-based liquid metals: advances, applications, and prospects.

Bismuth-based liquid metals (LMs) are a large group of alloys with melting points slightly above room temperature. They are associated with fewer encapsulation constraints than room temperature LMs such as mercury, sodium-potassium alloys, and gallium-based alloys and are more likely to remain stable in the natural environment. In addition, their low melting point properties enable them to soften and melt via easy control. Bismuth-based alloys can also be modified with metal-based, carbon-based, and ceramic-based micro/nano particles as well as polymeric materials to create a series of novel composites owing to their outstanding functions. Based on these considerations, this review provides a comprehensive overview of bismuth-based LMs. The categories of bismuth and bismuth-based LMs are first briefly introduced to better systematize the physical and chemical properties of bismuth-based LMs. Based on these properties, bismuth-based LMs have been prepared using various methods, and this review briefly categorizes these preparation methods based on their finished forms (lumps, powders, and films). In addition, this review details the research progress of bismuth-based LMs in the fields of printed electronics, 3D printing, thermal management, biomedicine, chemical engineering, and deformable robotics. Finally, the challenges and future opportunities of bismuth-based LMs in the development process are discussed and visualized from different perspectives.

Preparation of eGaIn NDs/TPU Composites for X-ray Radiation Shielding Based on Electrostatic Spinning Technology.

Thermoplastic polyurethane (TPU) composites with eutectic gallium (Ga) and indium (In) (eGaIn) fillings of 0 wt%-75 wt% were prepared using the electrostatic spinning method. Field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy were used to characterize the eGaIn NDs/TPU composites. To evaluate their X-ray shielding properties, Phy-X/PSD and WinXCom were employed to calculate the mass attenuation coefficients, linear attenuation coefficients, half-value layers, tenth value layers, mean free paths, and adequate atomic numbers of the eGaIn NDs/TPU composites. The SEM results indicated that the eGaIn nanodroplets were evenly distributed throughout the TPU fibers, and the flowable eGaIn was well-suited for interfacial compatibility with the TPU. A comparison of the eGaIn NDs/TPU composites with different content levels showed that the composite with 75 wt% eGaIn had the highest µm at all the evaluated energies, indicating a superior ability to attenuate X-rays. This non-toxic, lightweight, and flexible composite is a potential material for shielding against medical diagnostic X-rays.

Liquid-Metal Molecular Scissors.

Molecules are the smallest units of matter that can exist independently, relatively stable, maintaining their physical and chemical activities. The key factors that dominate the structures and properties of molecules include atomic species, alignment commands, and chemical bonds. Herein, we reported a generalized effect in which liquid metals can directly cut off oxygen-containing groups in molecular matter at room temperature, allowing the remaining groups to recombine to form functional materials. Thus, we propose basic liquid-metal scissors for molecular directional clipping and functional transformations. As a proof of concept, we demonstrate the capabilities of liquid-metal scissors and reveal that the gallium on the surface of liquid metals directly extracts oxygen atoms from H2O or CH3OH molecules to form oxides. After clipping, the remaining hydrogen atoms from the H2O molecules recombine to form H2, while the remaining fragments of CH3OH produce H2, carbon materials, and carboxylates. This finding refreshes our basic understanding of chemistry and should lead to the development of straightforward molecular weaving techniques, which can help to overcome the limitations of molecular substances with single purposes. It also opens a universal route for realizing future innovations in molecular chemical engineering, life sciences, energy and environment research, and biomedicine.

Liquid Metal-Based Flexible Bioelectrodes for Management of In-Stent-Restenosis: Potential Application.

Although vascular stents have been widely used in clinical practice, there is still a risk of in-stent restenosis after their implantation. Combining conventional vascular stents with liquid metal-based electrodes with impedance detection, irreversible electroporation, and blood pressure detection provides a new direction to completely solve the restenosis problem. Compared with conventional rigid electrodes, liquid metal-based electrodes combine high conductivity and stretchability, and are more compliant with the implantation process of vascular stents and remain in the vasculature for a long period of time. This perspective reviews the types and development of conventional vascular stents and proposes a novel stent that integrates liquid metal-based electrodes on conventional vascular stents. This vascular stent has three major functions of prediction, detection and treatment, and is expected to be a new generation of cardiovascular implant with intelligent sensing and real-time monitoring.

Pressure Driven Rapid Reconfigurable Liquid Metal Patterning.

This paper proposes a method for pressure driven rapid reconfigurable liquid metal patterning. A sandwich structure of "pattern-film-cavity" is designed to complete this function. Both sides of the highly elastic polymer film are bonded with two PDMS slabs. One PDMS slab has microchannels patterned on the surface. The other PDMS slab has a large cavity on its surface for liquid metal storage. These two PDMS slabs are bonded together, face to face, with the polymer film in the middle. In order to control the distribution of the liquid metal in the microfluidic chip, the elastic film will deform under the high pressure of the working medium in the microchannels and then extrude the liquid metal into different patterns in the cavity. This paper studies the factors of liquid metal patterning in detail, including external control conditions, such as the type and pressure of the working medium and the critical dimensions of the chip structure. Moreover, both a single-pattern and a double-pattern chip are fabricated in this paper, which can form or reconfigure the liquid metal pattern within 800 ms. Based on the above methods, reconfigurable antennas of two frequencies are designed and fabricated. Meanwhile, their performance is simulated and tested by simulation and vector network tests. The operating frequencies of the two antennas are respectively significantly switching between 4.66 GHz and 9.97 GHz.

Liquid Metal-Based Electrode Array for Neural Signal Recording.

Neural electrodes are core devices for research in neuroscience, neurological diseases, and neural-machine interfacing. They build a bridge between the cerebral nervous system and electronic devices. Most of the neural electrodes in use are based on rigid materials that differ significantly from biological neural tissue in flexibility and tensile properties. In this study, a liquid-metal (LM) -based 20-channel neural electrode array with a platinum metal (Pt) encapsulation material was developed by microfabrication technology. The in vitro experiments demonstrated that the electrode has stable electrical properties and excellent mechanical properties such as flexibility and bending, which allows the electrode to form conformal contact with the skull. The in vivo experiments also recorded electroencephalographic signals using the LM-based electrode from a rat under low-flow or deep anesthesia, including the auditory-evoked potentials triggered by sound stimulation. The auditory-activated cortical area was analyzed using source localization technique. These results indicate that this 20-channel LM-based neural electrode array satisfies the demands of brain signal acquisition and provides high-quality-electroencephalogram (EEG) signals that support source localization analysis.

Phase change composites of octadecane and gallium with expanded graphite as a carrier.

Phase change materials (PCMs) have attracted more and more attention in the field of energy and thermal management due to the characteristic of exchanging heat with small temperature change. In order to obtain perfect PCMs, previous researchers usually prepared various phase change composites (PCCs), but there is still a gap toward the goal. Perhaps the development of PCMs with adjustable properties in a wide range to meet different needs is a feasible option. Given that the properties of organic PCMs and metal PCMs are highly complementary, using expanded graphite (EG) as a mediator, a stable PCC of octadecane and gallium that are difficult to directly mix, was successfully prepared. Octadecane and gallium are stored in the microstructures of EG, and the microstructures of EG play the role of storing nucleation embryos, and the suppression of supercooling can reach more than 86.82%. The test results showed that the properties of the PCC are indeed a balance between octadecane and gallium, and can be adjusted in a wide range. The PCC also has good structural and chemical stability, which can effectively avoid the corrosion risk caused by gallium leakage. The PCC samples containing equal amounts of gallium and paraffin were selected for thermal management performance tests. The results indicated that the PCC has application potential in related fields, and can provide a reference for the development of other PCCs.

A U-Shaped Dual-Frequency-Reconfigurable Monopole Antenna Based on Liquid Metal.

This study presents a U-shaped dual-frequency-reconfigurable liquid-metal monopole antenna. Eutectic Gallium-Indium (EGaIn) was used as a conductive fluid and filled in the two branches of the U-shaped glass tube. A precision syringe pump was connected to one of the branches of the U-shaped tube by a silicone tube to drive EGaIn, forming a height difference between the two liquid levels. When the height of liquid metal in the two branches met the initial condition of L1 = L2 = 10 mm, and L1 increased from 10 mm to 18 mm, the two branches obtained two working bandwidths of 2.27-4.98 GHz and 2.71-8.58 GHz, respectively. The maximum peak gain was 4.00 dBi. The initial amount of EGaIn also affected the available operating bandwidth. When the liquid metal was perfused according to the initial condition: L1 = L2 = 12 mm, and L1 was adjusted within the range of 12-20 mm, the two branches had the corresponding working bandwidths of 2.18-4.32 GHz and 2.57-9.09 GHz, and the measured maximum peak gain was 3.72 dBi. The simulation and measurement data corresponded well. A series of dual-frequency-reconfigurable antennas can be obtained by changing the initial amount of EGaIn. This series of antennas may have broad application prospects in fields such as base stations and navigation.

A handy reversible bonding technology and its application on fabrication of an on-chip liquid metal micro-thermocouple.

We report a novel reversible bonding technique for liquid metal (LM) microelectrode fabrication in this study. This technique greatly simplifies the process of LM micro-electrode fabrication and can be used to achieve the rapid fabrication of LM blind-end electrodes. Three kinds of treatments, including heat treatment, plasma treatment and heat/plasma treatment, were tested for bonding strength. The experimental results showed that the heat/plasma treatment has the strongest bonding strength. All the three treatments can be completely released by simple water treatment. This handy fabrication method can help to integrate micro-liquid metal electrodes vertically in a microchannel. At the end of this work, this fabrication method was used to integrate liquid metal thermocouples in a microchannel, which greatly shortened the fabrication time and lowered the cost compared with traditional deposition or sputtering methods.

Self-Assembled Copper Film-Enabled Liquid Metal Core-Shell Composite.

Liquid metal (LM) droplets covered with functional materials, especially metallic, often make breakthroughs in performance and functionality. In this study, self-assembly was used to synthesize copper films on the surface of LM. Herein, using CuO nanoparticles as the monomers, driven by the electrostatic interaction between CuO and eutectic gallium-indium (EGaIn) in the alkaline environment, EGaIn@Cu is realized by taking advantage of the reducing property of the EGaIn-alkaline interface. The copper film is smooth and dense, and under its protection, a layer of gallium oxide remains on the reaction interface between copper and LM, which enabled EGaIn@Cu to possess the volt-ampere curves similar to the Schottky mode, showing that the proposed mechanism has the potential to be used in the bottom-up synthesis of the semiconductor junction. Owing to the support of the copper film, the stiffness coefficient of the LM droplet can be increased by 56.9%. Coupled with the melting latent heat of 55.46 J/g and the natural high density of metal, EGaIn@Cu is also a potential phase change capsule. In addition, a method based on stream jetting and self-breaking up mechanisms of LM to batch-produce sub-millimeter capsules was also introduced. The above structural and functional characteristics demonstrate the value of this work in related fields.

A Gravity-Triggered Liquid Metal Patch Antenna with Reconfigurable Frequency.

In this paper, a gravity-triggered liquid metal microstrip patch antenna with reconfigurable frequency is proposed with experimental verification. In this work, the substrate of the antenna is quickly obtained through three-dimensional (3D) printing technology. Non-toxic EGaIn alloy is filled into the resin substrate as a radiation patch, and the NaOH solution is used to remove the oxide film of EGaIn. In this configuration, the liquid metal inside the antenna can be flexibly flowed and deformed with different rotation angles due to the gravity to realize different working states. To validate the conception, the reflection coefficients and radiation patterns of the prototyped antenna are then measured, from which it can be observed that the measured results closely follow the simulations. The antenna can obtain a wide operating bandwidth of 3.69-4.95 GHz, which coverage over a range of frequencies suitable for various channels of the 5th generation (5G) mobile networks. The principle of gravitational driving can be applied to the design of reconfigurable antennas for other types of liquid metals.

A review of hyperthermia combined with radiotherapy/chemotherapy on malignant tumors.

Therapeutic hyperthermia is a procedure that involves heating tissues to a higher temperature level, typically ranging from 41 degrees C to 45 degrees C. Its combination with radiotherapy and/or chemotherapy has been performed for many years, with remarkable success in treating advanced and recurrent cancers. The current hyperthermia strategies generally include local, regional, and whole-body hyperthermia, which can be implemented by many heating methods, such as microwave, radiofrequency, laser, and ultrasound. There are several hyperthermic treatment modalities in conjunction with radiotherapy/chemotherapy. Numerous studies have attempted to explain the mechanisms of thermosensitization from radiation and chemotherapy; however, a generalized standard for determining an optimal hyperthermia modality combined with radiotherapy/chemotherapy has not been established, so more research is needed. Fortunately, phase II/III clinical trials have demonstrated that hyperthermia combination therapy is beneficial for local tumor control and survival in patients with high-risk tumors of different types. The aim of this article is to present a comprehensive review of the latest advances in tumor hyperthermia combined with radiotherapy and/ or chemotherapy. We specifically focus on synergistic cellular and molecular mechanisms, thermal dose, treatment sequence, monitoring and imaging, and clinical outcomes of the combination therapy. The role of nanoparticles in sensitization during radio-/chemotherapy is also evaluated. Finally, research challenges and future trends in the related areas are presented.

Nano-cryosurgery: advances and challenges.

In clinics, the minimally invasive freezing therapy, commonly known as cryosurgery, has been increasingly used for the controlled destruction of tumor tissue. However, there are still many bottlenecks to impede the success of a cryosurgery. One of the most critical factors has been that insufficient or inappropriate freezing will not completely destroy the target tumor tissues, which as a result may lead to tumor regenesis and thus failure of treatment. In addition, the surrounding healthy tissues may suffer from serious freeze injury due to unavoidable release of a large amount of cold from the freezing probe. To resolve these challenges, we recently proposed a new strategy, termed as nano-cryosurgery, to improve freezing efficiency of the conventional cryosurgical procedure. The basic principle of this protocol is to deliver functional suspension of nanoparticles with favorable physical and/or chemical properties into the target tissues, which then serve as adjuvant or drug carrier either to maximize the freezing heat transfer process, regulate freezing scale, modify ice-ball formation orientation or prevent the surrounding healthy tissues from being frozen. In addition, introduction of nanoparticles during cryosurgery could also help better image the edge of a tumor as well as the margin of the iceball. The new therapy raised many critical fundamental as well as practical issues for solving. This review is dedicated to present a comprehensive review on multiscale fundamental phase change heat transfer issues thus involved. Attentions would span from micro-scale heat transfer in cellular scale to tissue level. Some related thermal physical effects of nanoparticles on the freezing process such as ice nucleation enhancement, water transport during freezing of a single cell will be discussed. Cryosurgical thermal management of using nanoparticles to modify thermal properties of the tissue-particle components, regulate the growth orientation and strength of an ice ball, enable a conformal tumor destruction in tissues with or without large blood vessels, etc. will be illustrated. Meanwhile, the fundamental issue for the transport of nanoparticle and its assisted drug delivery will be summarized. Theoretical modeling as well as experimental approaches for studying the micro/nano-scale heat transfer throughout the tissue or cell domain during nano-cryosurgery will be suggested. Some potential applications and possible challenges when nanotechnology meets cryosurgery will be outlined. The nano-cryosurgery is expected to help expand the boundary of the emerging frontier of nano-biomedical engineering.

[Deeply cooled far-infrared thermal imaging strategy for early tumor diagnostics].

This paper is dedicated to evaluate the thermal behavior of skin surface embedded with tumor tissue through construction of three-dimensional heat transfer model of the human body. It was found that the far-infrared imaging equipment could not yet get the accurate results for diagnosis of tumors developed in early stage or located deeply in the human body, because of limited resolution and accuracy in the current system. Conceptual experiments with a thermal imaging system under various cooling levels were performed to confirm this issue. A dual cooling cavity was proposed to realize ultra-low-temperature so as to improve the cooling of the current infrared equipment and thereby to enhance its image precision and accuracy. This study is expected to be of significant reference value for realizing an early diagnosis of cancers through medical image.