A liquid metal enabled corrosion sculpture technique for quickly fabricating complex patterns on aluminum substrate is proposed and experimentally demonstrated. According to the conceptual investigation, it is clarified that the width and the depth of a printed track are dominated by sculpture time and working temperature. The printed size can reach small values of 38 μm through controlling the sculpture time for 60 s. As the sculpture time was increased from 5 to 25 min at 20°C, the depth of the fabricated pattern was improved from 13.3 to 25.6 μm. The sculptured depth of the pattern would increase from 13.3 to 106.9 μm when the sculpture time was fixed at 5 min and the temperature was raised from 20 to 60°C. To investigate the sculpture behavior in detail, the phases and microstructure of sculpture surface were quantitatively measured via a group of microscope imaging system with fundamental mechanisms interpreted. The present liquid metal sculpture method on aluminum substrate adds a new valuable soft tool for current metal engraving technology family.

•A facile strategy of electrical uni-directional de-icing surface is presented.•The superhydrophobic surface is composed of liquid metal (Ga90In10) and ZnO nano-petals.•Uni-directional de-icing on the surface was successfully realized in 6 seconds caused by thermal gradient.•After rushing water impact test, the surface shows an outstanding mechanical and superhydrophobic durability.A novel superhydrophobic electro-conductive coating with liquid metal (Ga90In10) and ZnO nano-petals is fabricated by integrating the methods of spraying, crystal growth and low surface energy modification. The results indicate that the paper-based surface could be superhydrophobic in cold environment and successfully realize uni-directional ice driving with the help of thermal gradient. We anticipate that the combination of excellent superhydrophobic performance of the composite structure with inherent conductive advantage of liquid metal will find a vast application prospect.The water droplet is uni-directionally driven off the surface with the help of the temperature gradient.Download high-res image (88KB)Download full-size image

The Marangoni flow of room temperature liquid metal has recently attracted significant attention in developing advanced flexible drivers. However, most of its induction methods are limited to an external electric field. This study disclosed a new Marangoni flow phenomenon of liquid gallium induced by the gallium–copper galvanic corrosion couple. To better understand this effect, the flow field distribution of liquid gallium was modeled and quantitatively calculated. Then, the intrinsic mechanism of this flow phenomenon was interpreted, during which natural convection and temperature gradient were both excluded and the galvanic corrosion couple was identified as the main reason. In addition, this conclusion was further confirmed by combining the experimental measurement of liquid gallium surface potential and the thermocapillary effect. Moreover, the temperature condition was found to be an indirect factor to the Marangoni flow. This finding broadens the classical understanding of liquid metal surface flow, which also suggests a new way for the application of soft machines.

In this research, a zinc oxide micro-/nano-structured hollow sphere (MNHS) with a large specific surface area is applied as energy storage material to encapsulate poly(vinyl chloride) solution and control the fuel release. The sustained release effect of MNHS not only makes the motion more controllable, but enhances the motion time and distance.

Recent studies have disclosed that liquid metal (Ga–In alloy) can be applied to activate aluminum in electrolytes to generate hydrogen at room temperature. To present a close to reality experimental demonstration of this method and to realize a continuous reaction between an Al plate and seawater, the liquid metal GaIn10 alloy is adopted to directly erode the surface of the Al plate. Then the eroded Al plate is immersed into NaCl solution (simulated seawater) to produce hydrogen. The results indicate that the existence of gallium can accelerate the average H2 production rate. In addition, the average hydrogen generation rate increased from 3 × 10−5 L s−1 to 4.5 × 10−4 L s−1 as the temperature rose from 20 °C to 80 °C when the corrosion area of the Al plates was 1 × 10−4 m2. However, the H2 production first increased and then decreased with the increase of NaCl concentration. The average hydrogen generation effectiveness is 0.71 L g−1 in the aluminum–water reaction in 5% NaCl solution at 20 °C within 20 min. Over the experimental process, the capability of producing hydrogen has a linear relationship with the corrosion area on the surface of the Al plates corroded by the liquid metal. This work suggests good prospects in the future practice of large-scale hydrogen generation using Al and seawater as reaction sources.

•PCM heat sink against ultra-high thermal shock is developed and optimized.•Figure of merit of PCM is used to guide the thermal design.•The proposed heat sink can cope with 102 W/cm2 (1 s) thermal shock.•Guidance for optimization and evaluation of the heat sink are provided.In this paper, the low melting point metal phase change material (PCM) heat sink for coping with ultra-high thermal shock (102 W/cm2) is developed and optimized theoretically and numerically. Gallium is selected as the best PCM candidate from the point of view of thermal performance based on an approximate theoretical analysis, and gallium based PCM heat sink with internal copper fin is configured. Different fin structures, namely plate fin, crossed fin and pin fin are investigated and compared; the effects of fin number, fin width and base thickness are parametrically studied; the influence of the structural material is briefly discussed. For arbitrarily given heating condition, the optimal geometric configuration of the heat sink is suggested and corresponding thermal performance is provided. The proposed low melting point metal PCM heat sink can cope with very large thermal shock like 100 W/cm2 (1 s) with maximum device temperature of 46 °C, under the ambient temperature of 25 °C, which is extremely difficult to deal with otherwise by conventional PCMs. The conclusions drawn in this paper can serve as valuable reference for thermal design and analysis of PCM heat sink against ultra-high thermal shock.

In this paper, low melting point metal (LMPM), eutectic alloy Bi31.6In48.8Sn19.6 (E-BiInSn), was adopted as phase change material for potential thermal management applications. First, E-BiInSn was prepared and its main thermophysical properties were characterized. Then, transient thermal performances of E-BiInSn based heat sinks with internal crossed fins were tested, in comparison with that of organic PCM (octadecanol) which has close melting point. Three types of heat sink structures which have different number of internal fins were studied. Three heating conditions were applied, namely 80 W (2.2 W/cm2), 200 W (5.6 W/cm2) and 320 W (8.9 W/cm2). For all of the cases, E-BiInSn exhibited much superior thermal performance than that of octadecanol. Furthermore, cyclic test of the E-BiInSn heat sink was carried out, which showed good repeatability and stability, and without supercooling. Finally, a simplified 3D conjugate numerical model was developed to simulate the melting process of LMPM heat sink, which showed good agreement with the experimental results. This simplified model would be much useful in practical thermal design and optimization of LMPM heat sink, for that it would significantly save the computational time consumption.

•General optimization process for micro/mini-channel heat sink is developed.•Various analytical correlations are compared with numerical results.•Appropriate correlations and optimal geometrical parameters are recommended.•Liquid metal based mini-channel heat sink is optimized which shows excellent performance.This paper is dedicated to present a comprehensive comparison and discussion on the flow and thermal modeling of micro/mini-channel heat sink for better understanding and further sophistication of this technology. A general optimization process for the flow and thermal performance of micro/mini-channel heat sink is developed, for water cooling and liquid metal cooling both in micro scale and millimeter scale together. Numerical calculation is adopted in the optimization process and serves as baseline for the comparison of different correlations, while 1D thermal resistance model is used for thermal analysis. Appropriate correlations are recommended and optimal parameter selections and suggestions are provided for practical design. Liquid metal cooling and water cooling are compared in mini-channel heat sink, the former exhibits much superior flow and thermal performance. For water cooling, 1D model works well. While for liquid metal cooling, significant deviation exists between the model and the numerical results, and more experimental and analytical works are needed for the thermal design of this kind of coolant.

•Metal substrate would enhance hydrogen generation of Al-fed liquid phase Ga–In alloy in electrolyte.•Different hydrogen evolution modes and performances on varied substrates were clarified.•Metal substrate promote escape of Al grains from the Al-liquid metal amalgam and thus accelerate hydrogen production rate.•Rough metal substrate surface would promote hydrogen production rate.Hydrogen is a kind of promising clean energy with huge potential values for human being. Developing a convenient real-time and on-demand hydrogen production and utilization method is critical for its wide practices. Liquid metal was recently found to be able to easily activate aluminum in aqueous solution to continuously and quickly generate hydrogen at room temperature, and thus provides a straightforward hydrogen production way. To further improve this technology, we are dedicated here to investigate the effects of the container substrate on such hydrogen generation process. An interesting phenomenon was found that metal substrate material would evidently enhance the hydrogen generation rate. For conceptual illustration purpose, comparative experiments were conducted to demonstrate the different hydrogen evolution modes between the present method and former approach, and the enhancement mechanism lying behind was revealed. In addition, the influence of the surface roughness of the substrate on the hydrogen production performance was also clarified. The present finding would help motivate an improved extremely simple, straightforward and low cost way for the liquid metal assisted aluminum hydrogen production.

Self-actuation phenomena of liquid metal spheres in NaOH solution, including spreading, oscillating and stretching, induced by graphite alone were demonstrated for the first time. A liquid metal sphere could spontaneously spread on the surface of the graphite once immersed in the NaOH solution. The surface tension gradient on the sphere induced by the graphite/liquid metal galvanic cell was responsible for this deformation. When a liquid metal sphere was leaned against the side of a piece of graphite, it could oscillate periodically. As the sphere contacted the graphite, it rapidly collapsed, while the curvature radius of the sphere at the contact point decreased. Also, as the capillary force imposed on the sphere was larger than the friction force, the sphere recovered its original spherical shape. The surface tension of the liquid metal sphere acted as the restoring force of the oscillatory movement. Further, a phenomenon of resonance could be observed when two spheres were laid respectively on the top and the side of the graphite. The vibration of the top sphere was induced by the vibration of the side sphere. This finding provides a novel enhancement for the fabrication of future liquid metal beating heart systems and graphite/liquid metal-based batteries or machines.

•Liquid phase aluminum alloy was proposed and fabricated to develop simple hydrogen source.•Dynamic hydrogen generation phenomenon of Al-fed liquid phase GaIn alloy in electrolyte was disclosed.•Hydrogen was generated mainly at interface between liquid alloy and Petri dish.•Liquid alloy is very different with solid alloy in hydrogen generation behavior.•Liquid metal assisted dynamic hydrogen generation mechanisms were revealed.Reaction between aluminum and water offers a simple way for hydrogen generation. However, the passive oxide film subsequently formed on Al would become a major obstacle for its continuous reaction. Gallium was proved to be an effective way to remove the passive oxide film through penetrating into Al granules, which fosters the reaction between Al and water. However, fabrications of Al–Ga alloy so far are generally highly time and energy consuming. Here, unlike the existing strategies of using solid state Al-rich alloys for the reaction system, the liquid phase alloy was introduced and prepared to develop an extremely simple source for hydrogen generation where the mass percentage of Al can be less than 1%. Such conceptual innovation would help maintain the alloy in liquid state which thus allows for rather convenient operation. To probe into the methodology, the dynamic hydrogen generation phenomenon of such Al-fed liquid phase GaIn alloy inside NaOH electrolyte was disclosed. According to the experimental observations, the hydrogen was generated mainly at the interface between the liquid metal and the Petri dish rather than the liquid metal-electrolyte interface. Homogenous hydrogen generation only takes place at the liquid–solid interface while heterogeneous hydrogen generation from the moving accumulated Al granules happens on all surfaces. The present finding is expected to open a new way towards low cost and straightforward hydrogen generation. It would also help better understand the mechanisms lying behind as well as the dynamic traveling behaviors of the aluminum powered gallium alloy machine.

Heat dissipation of electronic devices keeps as a tough issue for decades. As the most classical coolant in a convective heat transfer process, water has been widely adopted which however inherits with limited thermal conductivity and relies heavily on mechanical pump. As an alternative, the room temperature liquid metal was increasingly emerging as an important coolant to realize much stronger enhanced heat transfer. However, its thermal capacity is somewhat lower than that of water, which may restrict the overall cooling performance. In addition, the high cost by taking too much amount of liquid metal into the device also turns out to be a big concern for practical purpose. Here, through combining the individual merits from both the liquid metal with high conductivity and water with large heat capacity, we proposed and demonstrated a new conceptual cooling device that integrated hybrid coolants, radiator and annular channel together for chip thermal management. Particularly, the electrically induced actuation effect of liquid metal was introduced as the only flow driving strategy, which significantly simplified the whole system design. This enables the liquid metal sphere and its surrounding aqueous solution to be quickly accelerated to a large speed under only a very low electric voltage. Further experiments demonstrated that the cooling device could effectively maintain the temperature of a hotpot (3.15 W/cm2) below 55ºC with an extremely small power consumption rate (0.8 W). Several situations to simulate the practical working of the device were experimentally explored and a theoretical thermal resistance model was established to evaluate its heat transfer performance. The present work suggests an important way to make highly compact chip cooling device, which can be flexibly extended into a wide variety of engineering areas.

A composite liquid metal marble made of metal droplet coated with water film was proposed and its impact dynamics phenomenon was disclosed. After encapsulating the liquid metal into water droplets, the fabricated liquid marble successfully avoided being oxygenized by the metal fluid and thus significantly improved its many physical capabilities such as surface tension modification and shape control. The striking behaviors of the composite liquid metal marbles on a substrate at room temperature were experimentally investigated in a high speed imaging way. It was disclosed that such marbles could disintegrate, merge, and even rebound when impacting the substrate, unlike the existing dynamic fluidic behaviors of liquid marble or metal droplet. The mechanisms lying behind these features were preliminarily interpreted. This fundamental finding raised profound multiphase fluid mechanics for understanding the complex liquid composite which was also critical for a variety of practical applications such as liquid metal jet cooling, inkjet printed electronics, 3D printing or metal particle fabrication etc.

As a class of newly emerging functional material, Gallium based liquid metals have attracted increasing attentions in many fields, such as chip cooling, printed electronics and microfluidics, etc. Particularly, the motion control of liquid metal droplet has been recently tried for its importance in microelectromechanical system (MEMS), microfluidics and potential use in micro-machine or reconfigurable soft robot. This paper is dedicated to explore the motion behavior of liquid metal droplet under AC electric field. The quickly induced oscillation phenomena of liquid metal droplet and surrounding electrolyte solution were observed and the major factors to influence such behaviors are theoretically interpreted and experimentally investigated, including the size of the liquid metal droplet, electrode voltage, electrolyte solution concentration and AC signal frequency etc. Moreover, some typical features to distinguish AC filed actuation with DC field are observed, such as intensive fluid waving induced by the resonance stimulation, and the efficient inhibition of solution electrolysis. Finally, two important applications of adopting AC induced surface oscillation of liquid metal droplet to develop solution mixer as well as fluidic pump were demonstrated which successfully avoid gas generation inside electrolyte environment. The bulk oscillation effects of liquid metal as clarified here could be very useful in a variety of areas such as solution disturbance and mixing, and fluid oscillator or pump etc.

In this paper, a pressured liquid metal screen printing method for rapidly manufacturing electronically conductive patterns is proposed and experimentally demonstrated. The atomized liquid metal microdroplets are pushed through the mesh openings to wet the target substrate under the airflow force. As the screen is removed away from the substrate, a liquid metal pattern is formed. The width and the thickness of the printed track can reach small values of 233.7 μm and 94.5 μm, respectively, with the surface root mean square roughness of the printed plane at 1.27 μm. With such a printing method, various kinds of complex electronic patterns such as functional circuits, general art drawings etc. can be fabricated in a short time on flexible or rigid substrates with different surface roughnesses. Durability and bending tests are performed to investigate the reliability and mechanical stability of the printed line resistors. In order to illustrate the screen printing of functional electronics, a liquid metal radio frequency identification antenna tag is fabricated with the reflection coefficient measured. Future applications of the liquid metal screen printing technique can be envisaged in flexible printed circuit board manufacturing, paper-based electronics, metal tags, the art of metal calligraphy & painting and so on.

We disclosed the interiorly driven macroscopic Brownian motion behavior of self-powered liquid metal motors. Such tiny motors in millimeter scale move randomly at a velocity magnitude of centimeters per second in aqueous alkaline solution, well resembling the classical Brownian motion. However, unlike the existing phenomena, where the particle motions were caused by collisions from the surrounding molecules, the current random liquid metal motions are internally enabled and self-powered, along with the colliding among neighboring motors, the substrate and the surrounding electrolyte molecules. Through uniformly dissolving only 1 % (mass percentage) Al into GaIn10, many tiny motors can be quickly fabricated and activated to take the Brownian-like random motions. Further, we introduced an experimental approach of using optical image contrast, which works just like the Wilson cloud chamber, to distinctively indicate the motor trajectory resulted from the generated hydrogen gas stream. A series of unusual complicated multi-phase fluid mechanics phenomena were observed. It was also identified that the main driving factor of the motors comes from the H2 bubbles generated at the bottom of these tiny motors, which is different from the large size self-fueled liquid metal machine. Several typical mechanisms for such unconventional Brownian-like motion phenomena were preliminarily interpreted.本文揭示了液态金属马达在碱性水溶液中类布朗运动的机制:固-液界面接触产氢。实验将微量铝箔(质量分数1%)融入GaIn10中,以注射方式产生大量自主运动型微小马达。采用高速摄像仪记录,并基于图像处理量化进行分析。结果表明液态金属马达呈现高速(约4 cm/s)无序的运动模式,我们将其命名为宏观布朗运动。不同于经典布朗现象,宏观布朗运动系由液态金属合金产氢反应、液态金属马达间及其与溶液和基底的多重相互作用所致。此外,通过搭建类似于威尔逊云室的光学平台可以清晰显示液态金属马达产生的氢气轨迹,并证实驱动马达的主要因素来自氢气泡,这与大尺寸液态金属机器主要受表面张力驱动的机制不同。

With pretty high surface tension, the room temperature liquid metal may inherit with unexpected behaviors that conventional fluids could not own. Here, we disclosed the coalescence and ejection phenomena of liquid metal droplets via high-speed camera. It was experimentally found that, when gently contacting (rather than colliding) two metal droplets with identical size together in NaOH solution, oscillating coalescence would happen which runs just like a spring after the interface ruptures and forms capillary waves. For two metal droplets with evidently different diameters, the coalescence induces rather unusual ejection phenomena. The large droplet would swallow part of the small one and then eject another much smaller droplet. Such phenomenon provides a direct evidence for the existence of electrical double layer on metal droplets. The dynamics fluid impacting behaviors were quantified through processing images from the recorded movies, and the basic differences between the liquid metal droplets and that of water droplets were clarified. Theoretical mechanisms related to the events were preliminarily interpreted. The present finding refreshes the basic understanding of the liquid metal droplets, which also suggests potential values of applying such fundamental effects to characterize viscosity, surface tension, electrical double layer of the metal fluids and droplet formations.室温液态金属因低黏、超高表面张力(约为水的10倍)及高密度等属性, 蕴藏着新奇的物理景象有待认识. 本文发现了一种金属液滴的相互作用机制: 震荡性融合与接触弹射现象. 实验借助注射泵生成金属液滴, 并采用高速摄像仪记录液滴间的接触融合过程. 基于图像处理的量化结果表明: 金属液滴由于具有较小Oh数, 表面张力在双液滴的接触性震荡融合过程中起主导作用; 金属液滴表面的毛细波传播速度随其半径增大而减小; 造成金属液滴出现接触弹射现象的动力学机制部分来源于表面张力波和双电层效应. 这一基础认识丰富了液滴流体动力学的范畴, 同时也为金属液滴的生成、操控乃至流体特性的刻画提供了理论依据.

Conventional 3D metal printings are generally time-consuming as well as lacking of high performance printable inks. From an alternative way, here we proposed the method of liquid phase 3D printing for quickly making conductive metal objects. Through introducing metal alloys whose melting point is slightly above room temperature as printing inks, several representative structures spanning from one, two and three dimension to more complex patterns were demonstrated to be quickly fabricated. Compared with the air-cooling in a conventional 3D printing, the liquid-phase-manufacturing offers a much higher cooling rate and thus significantly improves the speed in fabricating the target metal objects. This unique strategy also efficiently prevents the liquid metal inks from air oxidation, which is hard to avoid otherwise in an ordinary 3D printing. The key physical factors (such as properties of the cooling fluid, air pressure within the syringe barrel and needle diameter, types and properties of the printing ink) and several interesting intermediate fluids interaction phenomena between liquid metal and conventional cooling fluids such as water or ethanol, which evidently affecting the printing quality, were disclosed. In addition, a basic route to make future liquid phase 3D printer incorporated with both syringe pump and needle arrays was also suggested. The liquid phase 3D printing, which owns potential values not available in a conventional method, opens an efficient way for quickly making conductive metal objects in the coming time.

The currently available 3D printing still cannot simultaneously deal with the metal and nonmetal inks together due to their huge difference in the melting points and poor compatible printability between each other. Here through introducing the low melting point alloy Bi35In48.6Sn16Zn0.4 and silicone rubber as functional inks, we proposed a compatible hybrid 3D printing method for manufacturing the desired device, the supporting substrate and the allied package structure together. The principle of pneumatic-typed 3D printing of multiple inks was described and typical physical properties of the ink Bi35In48.6Sn16Zn0.4 were measured. Several key factors dominating the printing quality such as the temperature of the printing head, the air pressure exerted upon the liquid metal ink in the syringe, the moving velocity and the height of the printing head etc. were clarified. A general way of directly printing out 3D structured electronic devices consisting of both metal and nonmetal materials was demonstrated. Such hybrid objects were patterned and formed up layer by layer with Bi35In48.6Sn16Zn0.4 alloy and silicone rubber which would become solidified after standing for a period of time under room temperature. To illustrate the compatible printability of these printing inks, a three-layer tricolor LED stereo circuit with controlled lighting capability was further manufactured and evaluated. The present study opens an important hybrid 3D printing way for directly manufacturing functional and structural end devices in an easy and low cost way.

•A systematic review on the newly emerging nano liquid metal was presented.•Unique features of nano liquid metal over conventional nano fluid were outlined.•Innovative ways to enhance functions of the nano liquid metal were suggested.•Fundamental and technical challenges raised by nano liquid metal were summarized.•Perspective applications of the nano liquid metal in energy area were envisioned.Conventional nanofluid used in energy area is inherently limited by the relatively low thermal conductivity of the base fluids. As an alternative, the recently proposed nano liquid metal opens a new way for making ever powerful energy material. The liquid composite thus prepared exhibits superior thermal and electrical properties over conventional fluid which guarantees its significant functional potentials in energy management, conversion and storage. In this article, a systematic interpretation on the basic features of the nano liquid metal was presented. Perspective applications of this newly emerging energy material were outlined. Some involved fundamental issues and technical challenges were raised. This work is expected to provide a startup guide line for future research in the area.Graphical abstract

In this study, a novel cooling strategy through ventilating ambient air to the front surface of the hot chips of the high power light-emitting diodes (LEDs) was proposed to tackle the ever tough issues facing the conventional thermal management approaches. Preliminary thermal resistance analysis, numerical simulation and conceptual experiments were carried out to evaluate the cooling performance thus enabled. In the system analysis, a thermal network model was established to characterize the thermal resistance of an ordinary high power LED light and that of the newly proposed light module. Through ventilating the high speed ambient airflow directly onto the chip surface, the thermal resistance of the whole light could be evidently reduced and additional pathway was thus opened for releasing heat from the chips. Further, three-dimensional finite volume simulations were adopted to investigate the temperature distribution of the new light. It was found that even without heat sink or active cooling at the back part of the LED light, the new method via cooling the front part still works well. Lastly, a conceptual experiment was performed, which again demonstrated that cooling the LED at its front surface suggests an effective way to maintain the safe running of LED light within an allowable temperature scale just as cooling the light at the back part. The present method initiates a new way for future thermal management of high power LEDs.

With explosive applications of many advanced mobile electronic devices, a pervasive energy system with long term sustainability becomes increasingly important. Among the many efforts ever tried, human power is rather unique due to its independence of weather or geographical conditions and is therefore becoming a research focus. This paper is dedicated to demonstrate the possibility and feasibility of harvesting thermal energy from human body by sandwiching a thermoelectric generator (TEG) between human shoe bottom and ground, aiming to power a portable electronic device. Through the conceptual experiments conducted on adults, a maximum 3.99mW steady state power output at a ground temperature with 273 K is obtained, which is sufficient enough to drive a lot of microelectronic devices. Also, parametric simulations are performed to systematically clarify the factors influencing the TEG working performance. To further reveal the mechanism of this power generation modality, analytical solutions to the coupled temperature distributions for human foot and TEG module are obtained and the correlation between TEG characteristics and the output power are studied. It was demonstrated that, the TEG working as a wearable power resource by utilizing thermal energy of human foot shows enormous potential and practical values either under normal or extreme conditions.

A new conceptual modality for nano-cryosurgical ablation of tumors is proposed in this article. The main strategy is to apply MgO nanoparticles (NPs), which are nontoxic, biodegradable, and have few side-effects on the human body, to mediate the freezing procedure effectively. Detailed investigation via animal experiments and nucleation analysis demonstrated that delivery of MgO NPs into the target tissues would significantly improve the cryosurgical outcome. The formation of an iceball during the freezing process is accelerated and enlarged due to the excellent thermal properties of MgO NPs. In addition this method could promote the generation of ice nuclei and thus enhance cryoinjury to the target cells. Therefore, combining the biodegradability and nontoxicity of MgO NPs with their relatively lightweight properties, excellent thermal properties would help develop a high-performance cryosurgery. These findings may lead to methods for safe and targeted nano-cryosurgery and possibly break through the barriers facing current clinical treatments of cancer.From the Clinical EditorCryosurgery is a promising evolving modality to address malignancies. The work presented in this paper may add a novel concept to the field of nanomedicine by demonstrating that MgO nanoparticles enable more efficient ice-ball formation and cryoinjury in the target tissue.This article proposed a new conceptual modality for ablating tumors, the biodegradable MgO nanoparticles mediated cryosurgery. Experiments via infrared thermograph, histopathology section, differential scanning calorimetry, and nucleation theory all demonstrate that introduction of MgO nanoparticles into the target tissue significantly improves its freezing capability, which would lead to a highly promising “green” therapy on tumors.

Therapeutic hypothermia has been the most effective therapy to treat serious cardiovascular and cerebrovascular diseases. Among them, intravascular cooling is identified as a most efficient approach to induce brain hypothermia. However until now, some key parameters and temperature management method for intravascular cooling are still not well addressed because of the complexity of human thermoregulation mechanism. Aiming at predicting temperature variation of tissues and organs in a more accurate way during therapeutic hypothermia, this study is dedicated to integrate the blood flow model in the circle of Willis together with the compartmental model for characterizing the heat and blood transport throughout the whole human body. According to the theoretical evaluation, the new model could well simulate the temperature response of the whole human body especially the brain under various cooling. Effects of different intervention site and cooling power to the hypothermia performance are discussed, which shows that carotid artery intervention is a more suitable therapeutic hypothermia method in comparison with femoral artery or femoral vein intervention. These results could help design controlling software for intravascular therapeutic hypothermia device in the near future.

Employing thermoelectric generators (TEGs) to gather heat dissipating from the human body through the skin surface is a promising way to supply electronic power to wearable and pocket electronics. The uniqueness of this method lies in its direct utilization of the temperature difference between the environment and the human body, and complete elimination of power maintenance problems. However, most of the previous investigations on thermal energy harvesters are confined to the TEG and electronic system themselves because of the low quality of human energy. We evaluate the energy generation capacity of a wearable TEG subject to various conditions based on biological heat transfer theory. Through numerical simulation and corresponding parametric studies, we find that the temperature distribution in the thermopiles affects the criterion of the voltage output, suggesting that the temperature difference in a single point can be adopted as the criterion for uniform temperature distribution. However, the criterion has to be shifted to the sum of temperature difference on each thermocouple when the temperature distribution is inconsistent. In addition, the performance of the thermal energy harvester can be easily influenced by environmental conditions, as well as the physiological state and physical characteristics of the human body. To further validate the calculation results for the wearable TEG, a series of conceptual experiments are performed on a number of typical cases. The numerical simulation provides a good overview of the electricity generation capability of the TEG, which may prove useful in the design of future thermal energy harvesters.

The recent decades have witnessed a remarkable advancement of very large scale integrated circuits (VLSI) and electronic equipments in micro-electronic industry. Meanwhile, the ever increasing power density of microdevices leads to the tough issue that thermal management becomes rather hard to solve. Conventional water cooling is widely used, but the convective coefficient is not high enough. Liquid metal owns much higher convective coefficient and has been identified as an effective coolant recently, but the high cost greatly precludes its large scale utilization. In this paper, a hybrid liquid metal–water cooling system which combines the advantages of both water and liquid metal cooling was proposed and demonstrated. By utilizing a liquid metal “heat spreader” in front of the water cooling module, this system not only owns more excellent cooling capability than that based on water alone, but also has much lower initial cost compared with absolute liquid metal cooling system. A series of experiments under different operation conditions have been performed to evaluate the cooling performance of this hybrid system. The compared results with absolute water cooling and liquid metal cooling system showed that the cooling capability of the new system is competitive with absolute liquid metal cooling, but the initial cost could be much lower. The theoretical thermal resistance model and economic feasibility also have been analyzed and discussed, which shows that the hybrid liquid metal–water cooling system is quite feasible and useful.

This paper is dedicated to present a low cost way for flexibly driving micro flow in a Lab-on-Chip system through utilizing the wetting mechanism. The unique merit of the method lies in its intentional employment of the wettability between liquid and the dry porous structure. The device thus fabricated only constitutes with a piece of dry porous material and a micro tube filled with liquid. When starting driving, connecting the objective liquid to the micro tube with pre-filled liquid at the entrance; then attaching the dry material to the exit end of the micro tube. Due to wettability between the pre-filled liquid and the dry material, the volume of the pre-filled liquid would decrease which subsequently induce a pressure reduction in the micro tube. As a result, the objective liquid will be jammed into the micro tube by the atmospheric pressure. With this working principle, the driving device is provided with several advantages such as being simple, cheap, safe, and clean; it also owns a wide range of applications in micro fluidics analysis. Theoretical interpretation and demonstration experiments were performed to evaluate the working performances of the driving device. Several factors liable to affect the running state of the driving device have been proposed and evaluated. It has been proved that this driving device is highly feasible and can be adopted as a micro pump for disposable Lab-on-Chip.

The brain is one of the most important organs in a biological body which can only work in a relatively stable temperature range. However, many environmental factors in biosphere would cause cerebral temperature fluctuations. To sustain and regulate the brain temperature, many mechanisms of biological brain cooling have been evolved, including Selective Brain Cooling (SBC), cooling through surface water evaporation, respiration, behavior response and using special anatomical appendages. This article is dedicated to present a summarization and systematic interpretation on brain cooling strategies developed in animals by classifying and comparatively analyzing each typical biological brain cooling mechanism from the perspective of bio-heat transfer. Meanwhile, inspirations from such cooling in nature were proposed for developing advanced bionic engineering technologies especially with two focuses on therapeutic hypothermia and computer chip cooling areas. It is expected that many innovations can be achieved along this way to find out new cooling methodologies for a wide variety of industrial applications which will be highly efficient, energy saving, flexible or even intelligent.

Patients with obesity often suffer pain and risks arising from complications in their pursuit for a trimmer figure. Therefore, an effective and safe treatment for obesity is urgently needed. In this paper, we propose a novel minimally invasive way to treat the target obesity tissues via alternative cooling and heating produced by a microprobe. The validity of the method was evaluated through both numerical simulation and differential scanning calorimetry (DSC) experiments. Theoretical prediction presents the significant effect of typical surgery and assesses the influence of various temperature boundary conditions on the microprobe to obtain the ideal therapeutic effect. An estimation standard was also established on the basis of cryolipolysis and hyperthermia. The DSC test confirms physical and chemical changes in cells during the cooling and heating process. The treatment planning will be varied with operational target, such as longer or shorter treatment time, one or multiple probes, etc. The 3D reconstruction employing MATLAB shows a simulated destruction area. This work is expected to serve as the foundation for identifying a new cure for obesity.Download full-size imageHighlights► Alternative cooling and heating is proposed to treat the target obesity tissues for the first time. ► The performances of one probe and multiple probes are investigated. ► The destroyed area range is estimated through 3-D theoretical simulation. ► The mechanism of destruction is confirmed by DSC tests.

It has long been a dream in the electronics industry to be able to write out electronics directly, as simply as printing a picture onto paper with an office printer. The first-ever prototype of a liquid-metal printer has been invented and demonstrated by our lab, bringing this goal a key step closer. As part of a continuous endeavor, this work is dedicated to significantly extending such technology to the consumer level by making a very practical desktop liquid-metal printer for society in the near future. Through the industrial design and technical optimization of a series of key technical issues such as working reliability, printing resolution, automatic control, human-machine interface design, software, hardware, and integration between software and hardware, a high-quality personal desktop liquid-metal printer that is ready for mass production in industry was fabricated. Its basic features and important technical mechanisms are explained in this paper, along with demonstrations of several possible consumer end-uses for making functional devices such as light-emitting diode (LED) displays. This liquid-metal printer is an automatic, easy-to-use, and low-cost personal electronics manufacturing tool with many possible applications. This paper discusses important roles that the new machine may play for a group of emerging needs. The prospective future of this cutting-edge technology is outlined, along with a comparative interpretation of several historical printing methods. This desktop liquid-metal printer is expected to become a basic electronics manufacturing tool for a wide variety of emerging practices in the academic realm, in industry, and in education as well as for individual end-users in the near future.

•A method to incorporate liquid metals and mechanical structures for functional electronics is presented.•Heating temperature and layer thickness lead to printing elastomer material into mechanical structures with hollow channels.•The circular channel is effective in reducing channel geometry.•The lower flow rates improve the fill effect of liquid metal.With the fabrication freedom and high efficiency introduced by 3D printing, such technology has been explored in the electronic manufacturing processes. In the present work, we reported a developed method for the fabrication of functional electronics with liquid phase electronic circuits. The technique involves printing hollow channels within elastomer structures via fused deposition modeling (FDM), then injecting and encapsulating liquid metal to form electrical traces. The process parameters in printing elastomer objects and the design of hollow channels were investigated via the extrusion experiments. The influence of flow rates on liquid metal injection was also studied under pressure injection. Based on these discussions and validations, the relationships between process parameters and the printing structures were demonstrated, and the flexible substrate with hollow channels was successfully printed by optimization of the process parameters. Moreover, a probe signal circuit has been fabricated to demonstrate the ability of injecting and packaging liquid metal into 3D printed structures for functional electronics.Download high-res image (123KB)Download full-size image

In this research, a zinc oxide micro-/nano-structured hollow sphere (MNHS) with a large specific surface area is applied as energy storage material to encapsulate poly(vinyl chloride) solution and control the fuel release. The sustained release effect of MNHS not only makes the motion more controllable, but enhances the motion time and distance.