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Surface tension of liquid metal: role, mechanism and application

Xi ZHAO, Shuo XU, Jing LIU

《能源前沿（英文）》 2017年 第11卷 第4期   页码 535-567 doi: 10.1007/s11708-017-0463-9

摘要： 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 measurement methods clarified so far. As a practical technique to regulate the surface tension of RTLM, the fundamental 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.

关键词： surface tension     liquid metal     soft machine     printed electronics     electrowetting     self-actuation    

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Preparation and performance of soft actuator based on IPMC with silver electrodes

Qi CHEN, Ke XIONG, Kan BIAN, Ning JIN, Bangfeng WANG,

《机械工程前沿（英文）》 2009年 第4卷 第4期   页码 436-440 doi: 10.1007/s11465-009-0054-5

摘要： The surface electrodes of traditional ionic polymer-metal composites (IPMC) are made of platinum. To reduce the production cost, nonprecious metals such as silver is proposed. A new approach of electroless silver plating based on chemical deposition method is adopted, getting two types of IPMCs, Pt-Ag IPMC, and Ag-Ag IPMC. The microscopic analysis, driving abilities tests, and their surface-electrode resistance analysis show that Ag and Pt particles penetrate inside Nafion membrane with gradient distribution throughout the membrane. The maximum electro-active bending deformation angles of the specimens, which are obtained under the same specimen dimension and constrains, are about 60° for Pt-Pt IPMC and Pt-Ag IPMC and 90° for the Ag-Ag IPMC, respectively, corresponding to the driving voltage of 3 V, 4 V, and 1.5 V. The surface-electrode resistance of Ag-Ag IPMC is the lowest and the most stable, which shows that the proposed approach is valid. The experiments show that the IPMC technology based on the silver electrode is feasible.

关键词： ionic polymer-metal composites (IPMC)     Nafion     intelligent material     soft actuators     electroless silver plating    

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Perspective on gallium-based room temperature liquid metal batteries

《能源前沿（英文）》 2022年 第16卷 第1期   页码 23-48 doi: 10.1007/s11708-022-0815-y

摘要： Recent years have witnessed a rapid development of deformable devices and epidermal electronics that are in urgent request for flexible batteries. The intrinsically soft and ductile conductive electrode materials can offer pivotal hints in extending the lifespan of devices under frequent deformation. Featuring inherent liquidity, metallicity, and biocompatibility, Ga-based room-temperature liquid metals (GBRTLMs) are potential candidates to fulfill the requirement of soft batteries. Herein, to illustrate the glamour of liquid components, high-temperature liquid metal batteries (HTLMBs) are briefly summarized from the aspects of principle, application, advantages, and drawbacks. Then, Ga-based liquid metals as main working electrodes in primary and secondary batteries are reviewed in terms of battery configurations, working mechanisms, and functions. Next, Ga-based liquid metals as auxiliary working electrodes in lithium and nonlithium batteries are also discussed, which work as functional self-healing additives to alleviate the degradation and enhance the durability and capacity of the battery system. After that, Ga-based liquid metals as interconnecting electrodes in multi-scenarios including photovoltaics solar cells, generators, and supercapacitors (SCs) are interpreted, respectively. The summary and perspective of Ga-based liquid metals as diverse battery materials are also focused on. Finally, it was suggested that tremendous endeavors are yet to be made in exploring the innovative battery chemistry, inherent reaction mechanism, and multifunctional integration of Ga-based liquid metal battery systems in the coming future.

关键词： liquid metals     soft electrodes     flexible batteries     deformable energy supply devices     epidermal electronics    

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Application of MoS in the space environment: a review

《机械工程前沿（英文）》 2023年 第18卷 第3期 doi: 10.1007/s11465-023-0755-1

摘要： A considerable portion of space mechanism failures are related to space tribological problems. Cold welding in high vacuum; surface erosion and collision damage caused by various radiations, high temperature oxidation under atomic oxygen (AO) bombardment; and thermal stress caused by temperature alternation all alter the physical, chemical, and friction properties of materials. In particular, the space vibration caused by alternating temperatures and microgravity environments can alter the motion of the contact body, further affecting its friction properties. Improving the friction properties of contact surfaces in the space environment is an important way to extend the service life of spacecraft. Traditional lubricants can no longer meet the lubrication requirements of the space environment. This study describes the characteristics of the space environment and the applications of solid lubricants. The friction properties of MoS2, a solid lubricant widely used in space, are discussed. The synergistic lubrication of MoS2 with surface textures or metals is presented. Advances in research on the friction properties of collision sliding contacts in the space environment are reviewed. The combination of MoS2 and soft metals with surface textures is introduced to reduce the effects of vibration environments on the friction properties of moving parts in space mechanisms. Finally, the challenges and future research interests of MoS2 films in space tribology are presented.

关键词： MoS2     soft metal     space environment     surface texture     synergistic effect     vibration    

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Development of soft kernel durum wheat

Craig F. MORRIS

《农业科学与工程前沿（英文）》 2019年 第6卷 第3期   页码 273-278 doi: 10.15302/J-FASE-2019259

摘要：

Kernel texture (grain hardness) is a fundamental and determining factor related to wheat ( spp.) milling, baking and flour utilization. There are three kernel texture classes in wheat: soft and hard hexaploid ( ), and very hard durum ( subsp. ). The genetic basis for these three classes lies with the Puroindoline genes. Phenotypically, the easiest means of quantifying kernel texture is with the Single Kernel Characterization System (SKCS), although other means are valid and can provide fundamental material properties. Typical SKCS values for soft wheat would be around 25 and for durum wheat≥80. Soft kernel durum wheat was created via homeologous recombination using the mutation, which facilitated the transfer of ca. 28 Mbp of 5DS that replaced ca. 21 Mbp of 5BS. The 5DS translocation contained a complete and intact locus and both puroindoline genes. Expression of the puroindoline genes in durum grain resulted in kernel texture and flour milling characteristics nearly identical to that of soft wheat, with high yields of break and straight-grade flours, which had small particle size and low starch damage. Dough water absorption was markedly reduced compared to durum flour and semolina. Dough was essentially unchanged and reflected the inherent gluten properties of the durum background. Pasta quality was essentially equal-to-or-better than pasta made from semolina. Agronomically, soft durum germplasm showed good potential with moderate grain yield and resistance to a number of fungal pathogens and insects. Future breeding efforts will no doubt further improve the quality and competitiveness of soft durum cultivars.

关键词： soft durum wheat     grain hardness     puroindolines     milling     baking     pasta     noodles    

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液态金属科技与工业的崛起：进展与机遇

刘静

《中国工程科学》 2020年 第22卷 第5期   页码 93-103 doi: 10.15302/J-SSCAE-2020.05.016

摘要：

常温液态金属及其衍生材料是近年来异军突起的新兴功能物质，该领域取得了一系列突破性发现，催生出诸多全新的材料创制与应用，被视为人类利用金属的第二次革命。本文扼要介绍了液态金属物质科学领域涌现出的若干典型进展、基础问题与工业应用范例，剖析现象背后的科学规律，具体包括：芯片冷却与能源利用、印刷电子学与增材制造（3D打印）、生物材料学、柔性智能机器学。在此基础上，论述了提出“液态金属谷”的时代背景、发展液态金属新工业体系的基本途径，阐述了推进液态金属材料基因工程研究并构建相应数据库的重要意义。液态金属作为兼具基础探索与实际应用价值的重大科学、技术与工业前沿，发展前景广阔；相应研究有望促进人类物质文明进步、优化社会生产和生活方式，也将深刻影响中国乃至世界寻求新一代变革性科技与工业的进程。

关键词： 液态金属     新材料     颠覆性技术     新工业     先进冷却     印刷电子     生物医学材料     柔性机器人    

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Al-NaOH复合液态金属——一种具有热和气动特性且快速响应的水触发材料 Article

袁博, 孙旭阳, 刘静

《工程（英文）》 2020年 第6卷 第12期   页码 1454-1462 doi: 10.1016/j.eng.2019.08.020

摘要：

水触发材料因其操作简单、驱动柔和、成本低廉、环境友好等诸多优点受到越来越多的关注。但是，大多数此类材料通常具有较长的反应时间，并且需要严格的保存条件，这限制了它们在实践中的适应性。本研究提出并证明了一种基于Al-NaOH复合共晶镓-铟（eGaIn）合金的新型水触发材料，该材料具有快速响应性和可变形性。一旦加入水，制成的材料将在短短几秒钟内随着气体的产生而升温40 ℃，这表明它具有用作热驱动器和气动驱动器的巨大潜力。此外，研究还测试了新材料的可重复使用性和降解能力。并据此设计了双层结构的智能绷带，其内部填充了Al-NaOH复合eGaIn，而BiInSn则作为外部支撑材料。实验显示，厚度为2 mm的片状结构经过冷却处理后能够支撑1.8 kg的重物，这比常用的玻璃纤维高分子绷带的承重能力要好得多。同时，研究还使用Al-NaOH复合eGaIn制作了水触发球形机器人的原型，该原型在特定的外部刺激下实现了滚动和弹跳行为。这些发现表明，当前材料在开发未来的可穿戴设备、软驱动器和软机器人方面具有潜在价值。

关键词： 液体金属     水触发材料     自热材料     软驱动器    

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Performance of soft-hard-soft (SHS) cement based composite subjected to blast loading with consideration

Jun WU,Xuemei LIU

《结构与土木工程前沿（英文）》 2015年 第9卷 第3期   页码 323-340 doi: 10.1007/s11709-015-0301-2

摘要： This paper presents a combined experimental and numerical study on the damage and performance of a soft-hard-soft (SHS) multi-layer cement based composite subjected to blast loading which can be used for protective structures and infrastructures to resist extreme loadings, and the composite consists of three layers of construction materials including asphalt concrete (AC) on the top, high strength concrete (HSC) in the middle, and engineered cementitious composites (ECC) at the bottom. To better characterize the material properties under dynamic loading, interface properties of the composite were investigated through direct shear test and also used to validate the interface model. Strain rate effects of the asphalt concrete were also studied and both compressive and tensile dynamic increase factor (DIF) curves were improved based on split Hopkinson pressure bar (SHPB) test. A full-scale field blast test investigated the blast behavior of the composite materials. The numerical model was established by taking into account the strain rate effect of all concrete materials. Furthermore, the interface properties were also considered into the model. The numerical simulation using nonlinear finite element software LS-DYNA agrees closely with the experimental data. Both the numerical and field blast test indicated that the SHS composite exhibited high resistance against blast loading.

关键词： high strength concrete (SHS)     engineered cementitious composite     interface     blast test     strain rate effect    

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Design and modeling of a novel soft parallel robot driven by endoskeleton pneumatic artificial muscles

《机械工程前沿（英文）》 2022年 第17卷 第2期 doi: 10.1007/s11465-022-0678-2

摘要： Owing to their inherent great flexibility, good compliance, excellent adaptability, and safe interactivity, soft robots have shown great application potential. The advantages of light weight, high efficiency, non-polluting characteristic, and environmental adaptability provide pneumatic soft robots an important position in the field of soft robots. In this paper, a soft robot with 10 soft modules, comprising three uniformly distributed endoskeleton pneumatic artificial muscles, was developed. The robot can achieve flexible motion in 3D space. A novel kinematic modeling method for variable-curvature soft robots based on the minimum energy method was investigated, which can accurately and efficiently analyze forward and inverse kinematics. Experiments show that the robot can be controlled to move to the desired position based on the proposed model. The prototype and modeling method can provide a new perspective for soft robot design, modeling, and control.

关键词： pneumatic artificial muscles     soft robot     modeling approach     principle of virtual work     external load    

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Analysis of load and adaptability of disc cutters during shield tunneling in soft–hard varied strata

《结构与土木工程前沿（英文）》 2023年 第17卷 第4期   页码 533-545 doi: 10.1007/s11709-023-0946-1

摘要： The disc cutters of shield machines exhibit unsatisfactory adaptability and performance during the soft–hard varied strata tunneling process. To analyze the rotation state, cutting performance, and adaptability of disc cutters during shield tunneling in soft–hard varied strata, the Holmquist Johnson Cook and Federal Highway Administration constitutive models are introduced to numerically simulate the failure process of materials on the excavation face and to calculate the load of disc cutters. Additionally, the parameters of the models are modified based on laboratory disc cutter excavation test results. The results of numerical calculation can reflect the load level and the behavior of the disc cutters during operation. The tangential loads of the disc cutters during the cutting of four typical soft-strata excavation face models are numerically calculated, thus providing reference values for the starting torque of the disc cutters. A greater penetration is suggested for soft-strata tunneling to allow the disc cutters to rotate smoothly and continuously as well as to guarantee a better cutting effect. The disc cutters in the center of the cutterhead should be specified with a lower starting torque to prevent uneven wear, rotation stagnation, cutterhead clogging, and other adverse phenomena.

关键词： shield tunneling     disc cutter load     laboratory excavation test     numerical calculation     soft–hard varied strata    

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Risk stratification system for skin and soft tissue infections after allogeneic hematopoietic stem cell

《医学前沿（英文）》 2022年 第16卷 第6期   页码 957-968 doi: 10.1007/s11684-021-0910-1

摘要： Skin and soft tissue infections (SSTIs) refer to infections involving the skin, subcutaneous tissue, fascia, and muscle. In transplant populations with hematological malignancies, an immunocompromised status and the routine use of immunosuppressants increase the risk of SSTIs greatly. However, to date, the profiles and clinical outcomes of SSTIs in hematopoietic stem cell transplantation (HSCT) patients remain unclear. This study included 228 patients (3.67%) who developed SSTIs within 180 days after allogeneic HSCT from January 2004 to December 2019 in Peking University People’s Hospital. The overall annual survival rate was 71.5%. We compared the differences between survivors and non-survivors a year after transplant and found that primary platelet graft failure (PPGF), comorbidities of acute kidney injury (AKI), and hospital-acquired pneumonia (HAP) were independent risk factors for death in the study population. A PPGF–AKI–HAP risk stratification system was established with a mortality risk score of 1×PPGF+1×AKI+1×HAP. The areas under the curves of internal and external validation were 0.833 (95% CI 0.760–0.906) and 0.826 (95% CI 0.715–0.937), respectively. The calibration plot revealed the high consistency of the estimated risks, and decision curve analysis showed considerable net benefits for patients.

关键词： skin and soft tissue infections     hematopoietic stem cell transplantation     risk stratification system     mortality    

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Design and experiment of a novel pneumatic soft arm based on a deployable origami exoskeleton

《机械工程前沿（英文）》 2023年 第18卷 第4期 doi: 10.1007/s11465-023-0770-2

摘要： Soft arms have shown great application potential because of their flexibility and compliance in unstructured environments. However, soft arms made from soft materials exhibit limited cargo-loading capacity, which restricts their ability to manipulate objects. In this research, a novel soft arm was developed by coupling a rigid origami exoskeleton with soft airbags. The joint module of the soft arm was composed of a deployable origami exoskeleton and three soft airbags. The motion and load performance of the soft arm of the eight-joint module was tested. The developed soft arm withstood at least 5 kg of load during extension, contraction, and bending motions; exhibited bistable characteristics in both fully contracted and fully extended states; and achieved a bending angle of more than 240° and a contraction ratio of more than 300%. In addition, the high extension, contraction, bending, and torsional stiffnesses of the soft arm were experimentally demonstrated. A kinematic-based trajectory planning of the soft arm was performed to evaluate its error in repetitive motion. This work will provide new design ideas and methods for flexible manipulation applications of soft arms.

关键词： pneumatic soft arm     soft airbag     deployable origami exoskeleton     bistable characteristics     cargo-loading capacity    

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Crack evolution of soft–hard composite layered rock-like specimens with two fissures under uniaxial compression

《结构与土木工程前沿（英文）》 2021年 第15卷 第6期   页码 1372-1389 doi: 10.1007/s11709-021-0772-2

摘要： Acoustic emission and digital image correlation were used to study the spatiotemporal evolution characteristics of crack extension of soft and hard composite laminated rock masses (SHCLRM) containing double fissures under uniaxial compression. The effects of different rock combination methods and prefabricated fissures with different orientations on mechanical properties and crack coalescence patterns were analyzed. The characteristics of the acoustic emission source location distribution, and frequency changes of the crack evolution process were also investigated. The test results show that the damage mode of SHCLRM is related to the combination mode of rock layers and the orientation of fractures. Hard layers predominantly produce tensile cracks; soft layers produce shear cracks. The first crack always sprouts at the tip or middle of prefabricated fractures in hard layers. The acoustic emission signal of SHCLRM with double fractures has clear stage characteristics, and the state of crack development can be inferred from this signal to provide early warning for rock fracture instability. This study can provide a reference for the assessment of the fracture development status between adjacent roadways in SHCLRM in underground mines, as well as in roadway layout and support.

关键词： soft−hard composite layered rock mass     double cracks     crack evolution     acoustic emission     digital image correlation    

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Seismic responses of subway station with different distributions of soft soil in Tianjin

Dejian YANG,Meiling DUAN

《结构与土木工程前沿（英文）》 2014年 第8卷 第2期   页码 187-193 doi: 10.1007/s11709-014-0252-z

摘要： In connection with the practical project of Kunming Road station of Tianjin subway Line 3, the paper established a two-dimensional finite element model with visco-elastic boundary by using ANSYS and analyzed seismic responses of subway station with different distribution of soft soil. The nonlinear dynamic properties of soft soils are modeled by the KINH. And obtain the response rules about displacement and internal force on subway station in the general field soil and five different distributions of soft soil. Provide reference for improving the seismic performance of subway stations in Tianjin soft soil.

关键词： distribution of soft soil     soft soil in Tianjin     seismic response     ANSYS    

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Numerical investigation of the ultimate lateral resistance of piles in soft clay

Konstantinos P. TZIVAKOS,Michael J. KAVVADAS

《结构与土木工程前沿（英文）》 2014年 第8卷 第2期   页码 194-200 doi: 10.1007/s11709-014-0251-0

摘要： The paper presents a numerical study on the undrained lateral response of a single, free-head, reinforced concrete pile in soft clays. Soil conditions simulating normally consolidated clays are examined—undrained shear strength increasing with depth—and the pile-soil interaction under static lateral loading is analyzed. The nonlinear ? curves proposed in literature for soft clays are imported into a beam-on-nonlinear-Winkler-foundation simulation in order to predict the pile head lateral load—displacement curve and the distribution of the horizontal displacement and bending moment along the pile. The striking differences among these methods require further investigation via 3D finite element analyses. The determination of the ultimate soil resistance from the results of the finite element analyses aims at providing the estimation of a range of values for the ultimate soil resistance coefficient with depth and the comparison of the derived values to the corresponding ones proposed by existing methodologies.

关键词： laterally loaded     pile     soft clay     p?y curves     finite element method (FEM)    

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标题 作者 时间 类型 操作

Surface tension of liquid metal: role, mechanism and application

Xi ZHAO, Shuo XU, Jing LIU

期刊论文

Preparation and performance of soft actuator based on IPMC with silver electrodes

Qi CHEN, Ke XIONG, Kan BIAN, Ning JIN, Bangfeng WANG,

期刊论文

Perspective on gallium-based room temperature liquid metal batteries

期刊论文

Application of MoS in the space environment: a review

期刊论文

Development of soft kernel durum wheat

Craig F. MORRIS

期刊论文

液态金属科技与工业的崛起：进展与机遇

刘静

期刊论文

Al-NaOH复合液态金属——一种具有热和气动特性且快速响应的水触发材料

袁博, 孙旭阳, 刘静

期刊论文

Performance of soft-hard-soft (SHS) cement based composite subjected to blast loading with consideration

Jun WU,Xuemei LIU

期刊论文

Design and modeling of a novel soft parallel robot driven by endoskeleton pneumatic artificial muscles

期刊论文

Analysis of load and adaptability of disc cutters during shield tunneling in soft–hard varied strata

期刊论文

Risk stratification system for skin and soft tissue infections after allogeneic hematopoietic stem cell

期刊论文

Design and experiment of a novel pneumatic soft arm based on a deployable origami exoskeleton

期刊论文

Crack evolution of soft–hard composite layered rock-like specimens with two fissures under uniaxial compression

期刊论文

Seismic responses of subway station with different distributions of soft soil in Tianjin

Dejian YANG,Meiling DUAN

期刊论文

Numerical investigation of the ultimate lateral resistance of piles in soft clay

Konstantinos P. TZIVAKOS,Michael J. KAVVADAS

期刊论文