In this paper,higher order modes(HOMs) and loss factor of a new type of 500-MHz superconducting cavity is studied,by simulating its broadband HOMs damping at different positions of the ferrite HOM-absorber and differe...In this paper,higher order modes(HOMs) and loss factor of a new type of 500-MHz superconducting cavity is studied,by simulating its broadband HOMs damping at different positions of the ferrite HOM-absorber and different lengths of the ferrite.The results show that the impedance and Q value of the HOMs in transverse and longitudinal modes could be greatly reduced.The HOM longitudinal impedance could be damped to meet the requirement of SSRF beam instability threshold.The calculated loss factor of the new SC cavity was compared with cavities at SSRF.It was estimated that the HOM absorber could absorb a total power of 3.16 kW at 4-mm beam bunch length.展开更多
In the superconducting RF module, the dissipation power of the niobium cavity is an important parameter. In the Superconducting radio frequency (SRF) module's acceptance test at Shanghai Synchrotron Radiation Faci...In the superconducting RF module, the dissipation power of the niobium cavity is an important parameter. In the Superconducting radio frequency (SRF) module's acceptance test at Shanghai Synchrotron Radiation Facility (SSRF), the Venturi tube is used to measure the quality factor of SRF cavity at 4.2 K. During the test, the venturi tube is be calibrated by increasing heat load with internal heater. In this paper, the horizontal test principle and venturi effect are briefly introduced. The authors find out a correct way to calibrate the venturi tubes, the calibration results are presented here. From the calibration results, one can deduce the static loss of each module, the source of static loss is also analyzed.展开更多
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 fluctu...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 ap- pendages. This article is dedicated to present a summarization and systematic interpretation on brain cooling strategies devel- oped in animals by classifying and comparatively analyzing each typical biological brain cooling mechanism from the per- spective 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.展开更多
Surface preparation is an important processing in production procedures of superconducting niobium cavities,deciding whether the performance of the niobium cavities can meet the specifications. A series of surface pre...Surface preparation is an important processing in production procedures of superconducting niobium cavities,deciding whether the performance of the niobium cavities can meet the specifications. A series of surface preparation methods and relevant apparatuses have been constructed at Shanghai Institute of Applied Physics(SINAP) and the standard procedures of cavity processing were established and successfully applied to different types of cavities. With standard surface preparation procedures on the 500 MHz 5-cell niobium cavity, the cavity accelerating voltage at T = 4.2 K reached 7.5 MV while its quality factor was still higher than 1 × 109.The accelerating gradient of the IMP-HWR010 cavity reached 4.9 MV/m with the quality factor of better than3 × 108 at 4.2 K.展开更多
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 offi ce printer. The fi rstever prototype of a liquid-metal printer...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 offi ce printer. The fi rstever 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 li ght-emitting diode(LED) displays. This liquid-metal printer is an automatic, easyto-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 cuttingedge 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.展开更多
Reusable electronics have received widespread attention and are urgently needed. Here, nanocellulosebased liquid metal(NC-LM) printed circuit has been fabricated by the evaporation-induced transfer printing technology...Reusable electronics have received widespread attention and are urgently needed. Here, nanocellulosebased liquid metal(NC-LM) printed circuit has been fabricated by the evaporation-induced transfer printing technology. In this way, the liquid metal pattern is embedded into the nanocellulose membrane, which is beneficial for the stability of the circuit during use. Besides, the NC-LM circuit is ultrathin with just tens of microns. In particular, the finished product is environmentally friendly because it can be completely dissolved by water, and both the liquid metal ink and the nanocellulose membrane can be easily recollected and reused, thereby reducing waste and pollution to the environment. Several examples of flexible circuits have been designed to evaluate their performance. The mechanism of evaporation-induced transfer printing technology involves the deposition, aggregation, and coverage tightly of the nanosized cellulose fibrils as the water evaporated. This study provides an economical and environmentally friendly way for the fabrication of renewable flexible electronics.展开更多
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...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 de- vice that integrated hybrid coolants, radiator and annular channel together for chip thermal management. Particularly, the elec- trically 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 effective- ly maintain the temperature of a hotpot （3.15 W/cm2） below 55℃ with an extremely small power consumption rate （0.8 W）. Sev- eral 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.展开更多
Surface tension plays a core role in dominating various surface and interface phenomena. For liquid metals with high melting temperature, a profound understanding of the behaviors of surface tension is crucial in indu...Surface tension plays a core role in dominating various surface and interface phenomena. For liquid metals with high melting temperature, a profound understanding of the behaviors of surface tension is crucial in industrial processes such as casting, welding, and solidification, etc. Recently, the room temperature liquid metal （RTLM） mainly composed of gallium-based alloys has caused widespread concerns due to its increasingly realized unique virtues. The surface properties of such materials are rather vital in nearly all applications involved from chip cooling, thermal energy harvesting, hydrogen generation, shape changeable soft machines, printed electronics to 3D fabrication, etc. owing to its pretty large surface tension of approximately 700 mN/m. In order to promote the research of surface tension of RTLM, this paper is dedicated to present an overview on the roles and mechanisms of surface tension of liquid metal and summarize the latest progresses on the understanding of the basic knowledge, theories, influencing factors and experimental measure- ment methods clarified so far. As a practical technique to regulate the surface tension of RTLM, the fimdamental principles and applications of electrowetting are also interpreted. Moreover, the unique phenomena of RTLM surface tension issues such as surface tension driven self- actuation, modified wettability on various substrates and the functions of oxides are discussed to give an insight into the acting mechanism of surface tension. Furthermore, future directions worthy of pursuing are pointed out.展开更多
Liquid metal printing is emerging as an important tool for making wearable electronics. However, very limited academic efforts were made to fulfill such an increasing need. This paper is dedicated to present relativel...Liquid metal printing is emerging as an important tool for making wearable electronics. However, very limited academic efforts were made to fulfill such an increasing need. This paper is dedicated to present relatively complete theoretical and experimental characterizations for liquid metal spraying printing towards developing wearable electronic textile. The practical conditions of liquid metal droplets in the spraying printing process such as the jet velocity, the size distribution of droplets and their evenness degree, the morphology of droplets and their unrolling areas after impacting the substrate are quantified. The dominating factors, including the oxidation of liquid metal and the pressure force on cloth substrate during the impacting process, which ensure liquid metal firmly adhere to the cloth, are clarified. Further, various clothes are comparatively investigated to test their capabilities in printing liquid metal conductors, where the resistance difference can be over thousand-fold. In addition to interpreting the basic mechanisms and performances of the spraying printing, two programmable flexible circuits with specifically designed functions such as blinking LED lighting and wireless infrared temperature measurement via current manufacture technology were also demonstrated and evaluated for their washable ability. With the realization of wearable modules via liquid metal printing technology, it can be expected that flexible functional devices on cloth fabricated quickly and directly would witness more broad applications in the coming time.展开更多
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 microfiuidics, etc. Particularly, the mo...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 microfiuidics, 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.展开更多
Recent breakthrough in eutectic gallium-indium alloy has revealed its great potential in modern electronic engineering. Here, we established a general method towards super-fast fabrication of flexible electronics via ...Recent breakthrough in eutectic gallium-indium alloy has revealed its great potential in modern electronic engineering. Here, we established a general method towards super-fast fabrication of flexible electronics via semi-liquid metal and adhesion-selection enabled rolling and transfer (SMART) printing on various substrates. Based on the semiliquid metal and its adhesion-difference on specifically designed target materials, we demonstrated that the rolling and transfer printing method could serve to rapidly manufacture a wide variety of complicated patterns with high resolution and large size. The process is much faster than most of the currently existing electronic fabrication strategies including liquid metal printing ever developed, and the cost either in time or consumption rate is rather low. As illustrated, a series of functional flexible and stretchable electronics such as multiple layer and large area circuits were fabricated to show their superior merit in combination with electrical conductivity and deformability. In addition, it was also demonstrated that the electronics fabricated in this way exhibited good repeatablity. A most noteworthy advantage is that all the fabrication processes could be highly automatic in the sense that user-friendly machines can thus be developed. This method paves a practical way for super-fast soft electronics manufacture and is expected to play an important role in the coming industry and consumer electronics.展开更多
The hydrodynamic characteristics of hybrid fluid made of liquid metal/aqueous solution are elementary in the design and operation of conductive flow in a variety of newly emerging areas such as chip cooling, soft robo...The hydrodynamic characteristics of hybrid fluid made of liquid metal/aqueous solution are elementary in the design and operation of conductive flow in a variety of newly emerging areas such as chip cooling, soft robot, and biomedical practices. chemical properties, such as In terms of physical and density, thermal conductivity and electrical conductivity, their huge differences between the two fluidic phases remain a big challenge for analyzing the hybrid flow behaviors. Besides, the liquid metal immersed in the solution can move and deform when administrated with non-contact electromagnetic force, or even induced by redox reaction, which is entirely different from the cases of conventional contact force. Owing to its remarkable capability in flow and deformation, liquid metal immersed in the solution is apt to deform on an extremely large scale, resulting in marked changes on its boundary and interface. However, the working mechanisms of the movement and deformation of liquid metal lack appropriate models to describe such scientific issues via a set of well-established unified equations. To promote investigations in this important area, the present paper is dedicated to summarizing this unconventional hydrodynamics from experiment, theory, and simulation. Typical experimental phenomena and basic working mechanisms are illustrated, followed by the movement and deformation theories to explain these phenomena. Several representative simulation methods are then proposed to tackle the governing functions of the electrohydrodynamics. Finally, prospects and challenges are raised, offering an insight into the new physics of the hybrid fluid under applied fields.展开更多
There is currently a growing demand for developing efficient techniques for cooling integrated electronic devices with ever increasing heat generation power. To better tackle the high-density heat dissipation difficul...There is currently a growing demand for developing efficient techniques for cooling integrated electronic devices with ever increasing heat generation power. To better tackle the high-density heat dissipation difficulty within the limited space, this paper is dedicated to clarify the heat transfer behaviors of the liquid metal flowing in mini-channel exchangers with different geometric configurations. A series of comparative experiments using liquid metal alloy Ga68%In20%Sn12% as coolant were conducted under prescribed mass flow rates in three kinds of heat exchangers with varied geometric sizes. Meanwhile, numerical simulations for the heat exchangers under the same working conditions were also performed which well interpreted the experimental measurements. The simulated heat sources were all cooled down by these three heat dissipation apparatuses and the exchanger with the smallest channel width was found to have the largest mean heat transfer coefficient at all conditions due to its much larger heat transfer area. Further, the present work has also developed a correlation equation for characterizing the Nusselt number depending on Peclet number, which is applicable to the low Peclet number case with constant heat flux in the hydrodynamically developed and thermally developing region in the rectangular channel. This study is expected to provide valuable reference for designing future liquid metal based mini-channel heat exchanger.展开更多
A third harmonic superconducting niobium cavity has been proposed for installation in the Shanghai Synchrotron Radiation Facility （SSRF） storage ring to improve the Touschek lifetime. In order to investigate the fea...A third harmonic superconducting niobium cavity has been proposed for installation in the Shanghai Synchrotron Radiation Facility （SSRF） storage ring to improve the Touschek lifetime. In order to investigate the feasibility of the superconducting cavity fabrication indigenously and the possibility to master the fabrica tion techniques, cavities were fabricated from copper and niobium sheets by deep drawing and electron-beam welding, and a series of measurements, such as resonant frequency, shape dimensions and wall thickness, were carried out during this process. After analysis of various problems existing in the fabrication process, technique improvements were proposed, and finally the precise shape as designed and resonant frequency within 1.2 MHz were achieved for the new completed cavities. In addition, full annealing was finally proved to be a good cure for niobium sheets＇ tearing up during deep drawing. By fabricating niobium cavities successfully, some problems to the next step were cleared. This paper introduces the process of cavity fabrication and its technique improvements towards forming, and the initial vertical test result of niobium cavity is also presented.展开更多
Conventional rigid electronics are usually unconformable with soft skins and tend to fail in accurate physiological monitoring and precise treatment. Electronic skins(e-Skins) made by conductive and stretchable materi...Conventional rigid electronics are usually unconformable with soft skins and tend to fail in accurate physiological monitoring and precise treatment. Electronic skins(e-Skins) made by conductive and stretchable materials offer mechanical compliance for fabricating flexible and conformable wearables. Compared to common organic or inorganic conductive materials, gallium-based liquid metals alone own superior conductivity and compliance. Here, we demonstrate a highly conductive and stretchable electronic skin with liquid metal circuits(LMCs) embedded in silicone rubber film, which are functionalized for physiological signals monitoring. Through the designs of serpentine structure, LMCs maintained good electrical conductivity and functionality under over 100% strain. Also, a wearable electrocardiogram(ECG) recording device was fabricated and tested. The device was able to acquire steady signals during real-time measurement of physical activities. The proposed liquid metal e-Skin can be further extended to conformable bio-integrated healthcare devices and intelligent health monitoring networks.展开更多
With the rapid development of deep space exploration and commercial flight, a series of tough scientific and technological challenges were raised, which urgently require ever advanced technologies to tackle with. Rece...With the rapid development of deep space exploration and commercial flight, a series of tough scientific and technological challenges were raised, which urgently require ever advanced technologies to tackle with. Recently, liquid metals, as a kind of newly emerging functional material, are attracting various attention and many breakthroughs have been made on earth. Such a scientific trend also suggests promising approaches for solving those extreme challenges in space environment. To fulfill the increasing needs thus involved, this article is dedicated to systematically introducing liquid metal material and its related disciplines into space science and technology. Firstly, existing application of liquid metal cooling for space nuclear power was summarized. Then, some potential space practices were tentatively put forward, such as liquid metal thermal interface medium,liquid metal phase change material, liquid metal convection cooling, metal alloy thermal storage, liquid metal electromagnetic shielding and liquid metal electronic printing. Fundamental as well as practical issues that would differ with earth were interpreted. Finally, potential liquid metal space experiments were proposed to investigate the liquid metal hydrodynamic characteristic, wettability and phase change mechanism in space physical environment. Overall, liquid metal enabled space science and technology investigation will not only help efficiently solve the current and future space technological problems, but also aid to stimulate the advancement of liquid metal space material science.展开更多
Liquid metal(LM)is a type of metal or alloy that has a low melting point near room temperature and exhibits the properties of both liquids and metals.Such unconventional materials have been gaining increasing attentio...Liquid metal(LM)is a type of metal or alloy that has a low melting point near room temperature and exhibits the properties of both liquids and metals.Such unconventional materials have been gaining increasing attention within the scientific and industrial communities.Recently,fiber-shaped LM and its composites have especially attracted diverse interest owing to their unique merits,such as excellent conductivity,intrinsic stretchability,facile phase transition,and the ability to be woven or knitted into smart fabrics.This review is dedicated to summarizing different aspects of LM-based fibers,such as their material components,fabrication and design strategies,and remarkable applications by way of their representative properties.Typical fabrication approaches,such as 3D printing of pure LM wire,coating the LM shell on the surface of the fiber,injecting a LM core into hollow fibers,and spinning of LM and polymer hybrids have been comparatively illustrated.Moreover,emerging applications that primarily utilize LM fibers have been demonstrated.Finally,future directions and opportunities in the field are discussed.This categorization of LM fibers is expected to facilitate further investigation and practice in the coming society.展开更多
The current highly integrated electronics and energy systems are raising a growing demand for more sophisticated thermal management in harsh environments such as in space or some other cryogenic environment. Recently,...The current highly integrated electronics and energy systems are raising a growing demand for more sophisticated thermal management in harsh environments such as in space or some other cryogenic environment. Recently, it was found that room temperature liquid metals （RTLM） such as gallium or its alloys could significantly reduce the electronics temperature compared with the conventional coolant, like water, oil or more organic fluid. However, most of the works were focused on RTLM which may subject to freeze under low temperature. So far, a systematic interpretation on the preparation and thermal properties of liquid metals under low temperature （here defined as lower than O^C） has not yet been available and related applications in cryogenic field have been scarce. In this paper, to promote the research along this important direction and to overcome the deficiency of RTLM, a comprehensive evaluation was proposed on the concept of liquid metal with a low melting point below zero centigrade, such as mercury, alkali metal and more additional alloy candidates. With many unique virtues, such liquid metal coolants are expected to open a new technical frontier for heat transfer enhancement, especially in low temperature engineering. Some innovative ways for making low melting temperature liquid metal were outlined to provide a clear theoretical guideline and perform further experiments to discover new materials. Further, a few promising applied situations where low melting temperature liquid metals could play irreplaceableroles were detailed. Finally, some main factors for optimization of low temperature coolant were summarized. Overall, with their evident merits to meet various critical requirements in modem advanced energy and power industries, liquid metals with a low melting temperature below zero centigrade are expected to be the next- generation high-performance heat transfer medium in thermal managements, especially in harsh environment in space.展开更多
Achieving the directional and long-range droplet transport on solid surfaces is widely preferred for many practical applications but has proven to be challenging.Particularly,directionality and transport distance of d...Achieving the directional and long-range droplet transport on solid surfaces is widely preferred for many practical applications but has proven to be challenging.Particularly,directionality and transport distance of droplets on hydrophobic surfaces are mutually exclusive.Here,we report that drain fly,a ubiquitous insect maintaining nonwetting property even in very high humidity,develops a unique ballistic droplet transport mechanism to meet these demanding challenges.The drain fly serves as a flexible rectifier to allow for a directional and long-range propagation as well as self-removal of a droplet,thus suppressing unwanted liquid flooding.Further investigation reveals that this phenomenon is owing to the synergistic conjunction of multiscale roughness,structural periodicity,and flexibility,which rectifies the random and localized droplet nucleation(nanoscale and microscale)into a directed and global migration(millimeter-scale).The mechanism we have identified opens up a new approach toward the design of artificial rectifiers for broad applications.展开更多
CONSPECTUS:Conventional robots can accomplish defined tasks but often encounter troubles when handling irregular objects under unstructured environments.Soft robots,with supercompliance,large transformation,and high e...CONSPECTUS:Conventional robots can accomplish defined tasks but often encounter troubles when handling irregular objects under unstructured environments.Soft robots,with supercompliance,large transformation,and high environmental adaptability,hold big promise for delicate manipulations such as grasping soft objects or delivering precious biomedical samples.Even a step further,if soft robots are endowed with the extraordinary behaviors to freely transform among different morphologies and constructions just like those already existing in literature and science fiction films,more fantastic challenges can be tackled.Representing one of the most potential robotic soft materials,liquid metals have been given sufficient expectations on realizing the transformable machines that might fundamentally reform modern daily life.Accordingly,inspiring discoveries on controllable transformations of the liquid metal have been obtained surprisingly and tremendous efforts have been made over the past decade,indicating a significant step toward such a formidable dream.It is clear that the discovery of liquid metal-based largescaled transformation with several hundred-fold fast change on the surface area opens a brand new direction of manufacturing future transformable machines.Even unusual findings on a self-fueled liquid metal with biological life-like behavior to freely explore the unknown space that solves the energy supply issue also came into being,holding big promise for making bionic transformable robots.This Account aims to systematically sort out the developmental history of liquid metal transformable machines with special focus on the fundamental scientific discoveries,the underlying mechanisms,and the potential applied scenarios based on liquid metal enabled solid−liquid hybrids.The fantastic properties and unique transformation capabilities of liquid metals have built the basis for a new era of designing soft robotics and we believe that liquid metal transformable machines are evolving into new forms of soft robots.展开更多
文摘In this paper,higher order modes(HOMs) and loss factor of a new type of 500-MHz superconducting cavity is studied,by simulating its broadband HOMs damping at different positions of the ferrite HOM-absorber and different lengths of the ferrite.The results show that the impedance and Q value of the HOMs in transverse and longitudinal modes could be greatly reduced.The HOM longitudinal impedance could be damped to meet the requirement of SSRF beam instability threshold.The calculated loss factor of the new SC cavity was compared with cavities at SSRF.It was estimated that the HOM absorber could absorb a total power of 3.16 kW at 4-mm beam bunch length.
基金Supported by Shanghai Synchrotron Radiation Facility
文摘In the superconducting RF module, the dissipation power of the niobium cavity is an important parameter. In the Superconducting radio frequency (SRF) module's acceptance test at Shanghai Synchrotron Radiation Facility (SSRF), the Venturi tube is used to measure the quality factor of SRF cavity at 4.2 K. During the test, the venturi tube is be calibrated by increasing heat load with internal heater. In this paper, the horizontal test principle and venturi effect are briefly introduced. The authors find out a correct way to calibrate the venturi tubes, the calibration results are presented here. From the calibration results, one can deduce the static loss of each module, the source of static loss is also analyzed.
文摘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 ap- pendages. This article is dedicated to present a summarization and systematic interpretation on brain cooling strategies devel- oped in animals by classifying and comparatively analyzing each typical biological brain cooling mechanism from the per- spective 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.
基金Supported by the National Natural Science Foundation of China(No.11205233)
文摘Surface preparation is an important processing in production procedures of superconducting niobium cavities,deciding whether the performance of the niobium cavities can meet the specifications. A series of surface preparation methods and relevant apparatuses have been constructed at Shanghai Institute of Applied Physics(SINAP) and the standard procedures of cavity processing were established and successfully applied to different types of cavities. With standard surface preparation procedures on the 500 MHz 5-cell niobium cavity, the cavity accelerating voltage at T = 4.2 K reached 7.5 MV while its quality factor was still higher than 1 × 109.The accelerating gradient of the IMP-HWR010 cavity reached 4.9 MV/m with the quality factor of better than3 × 108 at 4.2 K.
基金supported by the Research Funding of the Chinese Academy of Sciences (KGZD-EW-T04-4)
文摘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 offi ce printer. The fi rstever 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 li ght-emitting diode(LED) displays. This liquid-metal printer is an automatic, easyto-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 cuttingedge 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.
基金financially supported by the National Natural Science Foundation of China(No.51605472)the Beijing Municipal Science&Technology Commission research fund(No.Z171100000417004)。
文摘Reusable electronics have received widespread attention and are urgently needed. Here, nanocellulosebased liquid metal(NC-LM) printed circuit has been fabricated by the evaporation-induced transfer printing technology. In this way, the liquid metal pattern is embedded into the nanocellulose membrane, which is beneficial for the stability of the circuit during use. Besides, the NC-LM circuit is ultrathin with just tens of microns. In particular, the finished product is environmentally friendly because it can be completely dissolved by water, and both the liquid metal ink and the nanocellulose membrane can be easily recollected and reused, thereby reducing waste and pollution to the environment. Several examples of flexible circuits have been designed to evaluate their performance. The mechanism of evaporation-induced transfer printing technology involves the deposition, aggregation, and coverage tightly of the nanosized cellulose fibrils as the water evaporated. This study provides an economical and environmentally friendly way for the fabrication of renewable flexible electronics.
基金supported by the Research Funding from the Technical Institute of Physics and ChemistryChinese Academy of Sciences
文摘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 de- vice that integrated hybrid coolants, radiator and annular channel together for chip thermal management. Particularly, the elec- trically 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 effective- ly maintain the temperature of a hotpot （3.15 W/cm2） below 55℃ with an extremely small power consumption rate （0.8 W）. Sev- eral 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.
文摘Surface tension plays a core role in dominating various surface and interface phenomena. For liquid metals with high melting temperature, a profound understanding of the behaviors of surface tension is crucial in industrial processes such as casting, welding, and solidification, etc. Recently, the room temperature liquid metal （RTLM） mainly composed of gallium-based alloys has caused widespread concerns due to its increasingly realized unique virtues. The surface properties of such materials are rather vital in nearly all applications involved from chip cooling, thermal energy harvesting, hydrogen generation, shape changeable soft machines, printed electronics to 3D fabrication, etc. owing to its pretty large surface tension of approximately 700 mN/m. In order to promote the research of surface tension of RTLM, this paper is dedicated to present an overview on the roles and mechanisms of surface tension of liquid metal and summarize the latest progresses on the understanding of the basic knowledge, theories, influencing factors and experimental measure- ment methods clarified so far. As a practical technique to regulate the surface tension of RTLM, the fimdamental principles and applications of electrowetting are also interpreted. Moreover, the unique phenomena of RTLM surface tension issues such as surface tension driven self- actuation, modified wettability on various substrates and the functions of oxides are discussed to give an insight into the acting mechanism of surface tension. Furthermore, future directions worthy of pursuing are pointed out.
基金supported by Beijing Municipal Science and Technology Funding(Grant No.Z151100003715002)Key Project Funding of Chinese Academy of Sciences
文摘Liquid metal printing is emerging as an important tool for making wearable electronics. However, very limited academic efforts were made to fulfill such an increasing need. This paper is dedicated to present relatively complete theoretical and experimental characterizations for liquid metal spraying printing towards developing wearable electronic textile. The practical conditions of liquid metal droplets in the spraying printing process such as the jet velocity, the size distribution of droplets and their evenness degree, the morphology of droplets and their unrolling areas after impacting the substrate are quantified. The dominating factors, including the oxidation of liquid metal and the pressure force on cloth substrate during the impacting process, which ensure liquid metal firmly adhere to the cloth, are clarified. Further, various clothes are comparatively investigated to test their capabilities in printing liquid metal conductors, where the resistance difference can be over thousand-fold. In addition to interpreting the basic mechanisms and performances of the spraying printing, two programmable flexible circuits with specifically designed functions such as blinking LED lighting and wireless infrared temperature measurement via current manufacture technology were also demonstrated and evaluated for their washable ability. With the realization of wearable modules via liquid metal printing technology, it can be expected that flexible functional devices on cloth fabricated quickly and directly would witness more broad applications in the coming time.
基金partially supported by the Dean’s Research Funding of the Chinese Academy of Sciences and Beijing Municipal Science and Technology Project(Grant No.Z141100000514005)
文摘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 microfiuidics, 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.
基金partially supported by the National Natural Science Foundation of China Key Project (91748206)Dean’s Research Funding and the Frontier Project of the Chinese Academy of Sciences
文摘Recent breakthrough in eutectic gallium-indium alloy has revealed its great potential in modern electronic engineering. Here, we established a general method towards super-fast fabrication of flexible electronics via semi-liquid metal and adhesion-selection enabled rolling and transfer (SMART) printing on various substrates. Based on the semiliquid metal and its adhesion-difference on specifically designed target materials, we demonstrated that the rolling and transfer printing method could serve to rapidly manufacture a wide variety of complicated patterns with high resolution and large size. The process is much faster than most of the currently existing electronic fabrication strategies including liquid metal printing ever developed, and the cost either in time or consumption rate is rather low. As illustrated, a series of functional flexible and stretchable electronics such as multiple layer and large area circuits were fabricated to show their superior merit in combination with electrical conductivity and deformability. In addition, it was also demonstrated that the electronics fabricated in this way exhibited good repeatablity. A most noteworthy advantage is that all the fabrication processes could be highly automatic in the sense that user-friendly machines can thus be developed. This method paves a practical way for super-fast soft electronics manufacture and is expected to play an important role in the coming industry and consumer electronics.
基金This work was partially supported by the National Natural Science Foundation of China Key Project （Grant No. 91748206）, the Dean＇s Research Funding and the Frontier Project of the Chinese Academy of Sciences, as well as Beijing Municipal Science （Grant No. z151100003715002）.
文摘The hydrodynamic characteristics of hybrid fluid made of liquid metal/aqueous solution are elementary in the design and operation of conductive flow in a variety of newly emerging areas such as chip cooling, soft robot, and biomedical practices. chemical properties, such as In terms of physical and density, thermal conductivity and electrical conductivity, their huge differences between the two fluidic phases remain a big challenge for analyzing the hybrid flow behaviors. Besides, the liquid metal immersed in the solution can move and deform when administrated with non-contact electromagnetic force, or even induced by redox reaction, which is entirely different from the cases of conventional contact force. Owing to its remarkable capability in flow and deformation, liquid metal immersed in the solution is apt to deform on an extremely large scale, resulting in marked changes on its boundary and interface. However, the working mechanisms of the movement and deformation of liquid metal lack appropriate models to describe such scientific issues via a set of well-established unified equations. To promote investigations in this important area, the present paper is dedicated to summarizing this unconventional hydrodynamics from experiment, theory, and simulation. Typical experimental phenomena and basic working mechanisms are illustrated, followed by the movement and deformation theories to explain these phenomena. Several representative simulation methods are then proposed to tackle the governing functions of the electrohydrodynamics. Finally, prospects and challenges are raised, offering an insight into the new physics of the hybrid fluid under applied fields.
文摘There is currently a growing demand for developing efficient techniques for cooling integrated electronic devices with ever increasing heat generation power. To better tackle the high-density heat dissipation difficulty within the limited space, this paper is dedicated to clarify the heat transfer behaviors of the liquid metal flowing in mini-channel exchangers with different geometric configurations. A series of comparative experiments using liquid metal alloy Ga68%In20%Sn12% as coolant were conducted under prescribed mass flow rates in three kinds of heat exchangers with varied geometric sizes. Meanwhile, numerical simulations for the heat exchangers under the same working conditions were also performed which well interpreted the experimental measurements. The simulated heat sources were all cooled down by these three heat dissipation apparatuses and the exchanger with the smallest channel width was found to have the largest mean heat transfer coefficient at all conditions due to its much larger heat transfer area. Further, the present work has also developed a correlation equation for characterizing the Nusselt number depending on Peclet number, which is applicable to the low Peclet number case with constant heat flux in the hydrodynamically developed and thermally developing region in the rectangular channel. This study is expected to provide valuable reference for designing future liquid metal based mini-channel heat exchanger.
基金Supported by Science and Technology Commission of Shanghai Municipality (026505027, 036505011)
文摘A third harmonic superconducting niobium cavity has been proposed for installation in the Shanghai Synchrotron Radiation Facility （SSRF） storage ring to improve the Touschek lifetime. In order to investigate the feasibility of the superconducting cavity fabrication indigenously and the possibility to master the fabrica tion techniques, cavities were fabricated from copper and niobium sheets by deep drawing and electron-beam welding, and a series of measurements, such as resonant frequency, shape dimensions and wall thickness, were carried out during this process. After analysis of various problems existing in the fabrication process, technique improvements were proposed, and finally the precise shape as designed and resonant frequency within 1.2 MHz were achieved for the new completed cavities. In addition, full annealing was finally proved to be a good cure for niobium sheets＇ tearing up during deep drawing. By fabricating niobium cavities successfully, some problems to the next step were cleared. This paper introduces the process of cavity fabrication and its technique improvements towards forming, and the initial vertical test result of niobium cavity is also presented.
基金supported by the National Natural Science Foundation of China(Grant No.91748206)Funding of Higher Education AgencyFrontier Funding of Chinese Academy of Sciences
文摘Conventional rigid electronics are usually unconformable with soft skins and tend to fail in accurate physiological monitoring and precise treatment. Electronic skins(e-Skins) made by conductive and stretchable materials offer mechanical compliance for fabricating flexible and conformable wearables. Compared to common organic or inorganic conductive materials, gallium-based liquid metals alone own superior conductivity and compliance. Here, we demonstrate a highly conductive and stretchable electronic skin with liquid metal circuits(LMCs) embedded in silicone rubber film, which are functionalized for physiological signals monitoring. Through the designs of serpentine structure, LMCs maintained good electrical conductivity and functionality under over 100% strain. Also, a wearable electrocardiogram(ECG) recording device was fabricated and tested. The device was able to acquire steady signals during real-time measurement of physical activities. The proposed liquid metal e-Skin can be further extended to conformable bio-integrated healthcare devices and intelligent health monitoring networks.
基金supported by the Key Project of the National Natural Science Foundation of China (Grant No. 91748206)the Frontier Project of the Chinese Academy of Sciences and Dean’s Research Funding。
文摘With the rapid development of deep space exploration and commercial flight, a series of tough scientific and technological challenges were raised, which urgently require ever advanced technologies to tackle with. Recently, liquid metals, as a kind of newly emerging functional material, are attracting various attention and many breakthroughs have been made on earth. Such a scientific trend also suggests promising approaches for solving those extreme challenges in space environment. To fulfill the increasing needs thus involved, this article is dedicated to systematically introducing liquid metal material and its related disciplines into space science and technology. Firstly, existing application of liquid metal cooling for space nuclear power was summarized. Then, some potential space practices were tentatively put forward, such as liquid metal thermal interface medium,liquid metal phase change material, liquid metal convection cooling, metal alloy thermal storage, liquid metal electromagnetic shielding and liquid metal electronic printing. Fundamental as well as practical issues that would differ with earth were interpreted. Finally, potential liquid metal space experiments were proposed to investigate the liquid metal hydrodynamic characteristic, wettability and phase change mechanism in space physical environment. Overall, liquid metal enabled space science and technology investigation will not only help efficiently solve the current and future space technological problems, but also aid to stimulate the advancement of liquid metal space material science.
基金supported by the National Nature Science Foundation of China under Key Project#91748206Shuimu Tsinghua Scholarship and China Postdoctoral Science Foundation:2021M691707.
文摘Liquid metal(LM)is a type of metal or alloy that has a low melting point near room temperature and exhibits the properties of both liquids and metals.Such unconventional materials have been gaining increasing attention within the scientific and industrial communities.Recently,fiber-shaped LM and its composites have especially attracted diverse interest owing to their unique merits,such as excellent conductivity,intrinsic stretchability,facile phase transition,and the ability to be woven or knitted into smart fabrics.This review is dedicated to summarizing different aspects of LM-based fibers,such as their material components,fabrication and design strategies,and remarkable applications by way of their representative properties.Typical fabrication approaches,such as 3D printing of pure LM wire,coating the LM shell on the surface of the fiber,injecting a LM core into hollow fibers,and spinning of LM and polymer hybrids have been comparatively illustrated.Moreover,emerging applications that primarily utilize LM fibers have been demonstrated.Finally,future directions and opportunities in the field are discussed.This categorization of LM fibers is expected to facilitate further investigation and practice in the coming society.
文摘The current highly integrated electronics and energy systems are raising a growing demand for more sophisticated thermal management in harsh environments such as in space or some other cryogenic environment. Recently, it was found that room temperature liquid metals （RTLM） such as gallium or its alloys could significantly reduce the electronics temperature compared with the conventional coolant, like water, oil or more organic fluid. However, most of the works were focused on RTLM which may subject to freeze under low temperature. So far, a systematic interpretation on the preparation and thermal properties of liquid metals under low temperature （here defined as lower than O^C） has not yet been available and related applications in cryogenic field have been scarce. In this paper, to promote the research along this important direction and to overcome the deficiency of RTLM, a comprehensive evaluation was proposed on the concept of liquid metal with a low melting point below zero centigrade, such as mercury, alkali metal and more additional alloy candidates. With many unique virtues, such liquid metal coolants are expected to open a new technical frontier for heat transfer enhancement, especially in low temperature engineering. Some innovative ways for making low melting temperature liquid metal were outlined to provide a clear theoretical guideline and perform further experiments to discover new materials. Further, a few promising applied situations where low melting temperature liquid metals could play irreplaceableroles were detailed. Finally, some main factors for optimization of low temperature coolant were summarized. Overall, with their evident merits to meet various critical requirements in modem advanced energy and power industries, liquid metals with a low melting temperature below zero centigrade are expected to be the next- generation high-performance heat transfer medium in thermal managements, especially in harsh environment in space.
基金This work is partially supported by the Research Grants Council of the Hong Kong Special Administrative Region(Nos.11213915 and 11218417)the Innovation and Technology Fund(No.9440248)+1 种基金the National Natural Science Foundation of China(No.21805294)the Shenzhen Science and Technology Innovation Council(Nos.JCYJ20170413141208098 and JCYJ20170818103206501).
文摘Achieving the directional and long-range droplet transport on solid surfaces is widely preferred for many practical applications but has proven to be challenging.Particularly,directionality and transport distance of droplets on hydrophobic surfaces are mutually exclusive.Here,we report that drain fly,a ubiquitous insect maintaining nonwetting property even in very high humidity,develops a unique ballistic droplet transport mechanism to meet these demanding challenges.The drain fly serves as a flexible rectifier to allow for a directional and long-range propagation as well as self-removal of a droplet,thus suppressing unwanted liquid flooding.Further investigation reveals that this phenomenon is owing to the synergistic conjunction of multiscale roughness,structural periodicity,and flexibility,which rectifies the random and localized droplet nucleation(nanoscale and microscale)into a directed and global migration(millimeter-scale).The mechanism we have identified opens up a new approach toward the design of artificial rectifiers for broad applications.
基金This work was supported by the National Nature Science Foundation of China under Key Project(51890893,52106066,81701850,and 91748206)Shuimu Tsinghua Scholarship,China Postdoctoral Science Foundation(2021M691707)the Fundamental Research Funds for the Central Universities(YWF-21-BJ-J-1170).
文摘CONSPECTUS:Conventional robots can accomplish defined tasks but often encounter troubles when handling irregular objects under unstructured environments.Soft robots,with supercompliance,large transformation,and high environmental adaptability,hold big promise for delicate manipulations such as grasping soft objects or delivering precious biomedical samples.Even a step further,if soft robots are endowed with the extraordinary behaviors to freely transform among different morphologies and constructions just like those already existing in literature and science fiction films,more fantastic challenges can be tackled.Representing one of the most potential robotic soft materials,liquid metals have been given sufficient expectations on realizing the transformable machines that might fundamentally reform modern daily life.Accordingly,inspiring discoveries on controllable transformations of the liquid metal have been obtained surprisingly and tremendous efforts have been made over the past decade,indicating a significant step toward such a formidable dream.It is clear that the discovery of liquid metal-based largescaled transformation with several hundred-fold fast change on the surface area opens a brand new direction of manufacturing future transformable machines.Even unusual findings on a self-fueled liquid metal with biological life-like behavior to freely explore the unknown space that solves the energy supply issue also came into being,holding big promise for making bionic transformable robots.This Account aims to systematically sort out the developmental history of liquid metal transformable machines with special focus on the fundamental scientific discoveries,the underlying mechanisms,and the potential applied scenarios based on liquid metal enabled solid−liquid hybrids.The fantastic properties and unique transformation capabilities of liquid metals have built the basis for a new era of designing soft robotics and we believe that liquid metal transformable machines are evolving into new forms of soft robots.
