Ga‐Based Liquid Metal Micro/Nanoparticles: Recent Advances and Applications

Liquid metals are emerging as fluidic inorganic materials in various research fields. Micro‐ and nanoparticles of Ga and its alloys have received particular attention in the last decade due to their non toxicity and accessibility in ambient conditions as well as their interesting chemical, physical, mechanical, and electrical properties. Unique features such as a fluidic nature and self‐passivating oxide skin make Ga‐based liquid metal particles (LMPs) distinguishable from conventional inorganic particles in the context of synthesis and applications. Here, recent advances in the bottom‐up and top‐down synthetic methods of Ga‐based LMPs, their physicochemical properties, and their applications are summarized. Finally, the current status of the LMPs is highlighted and perspectives on future directions are also provided.     

Hollow Metal–Organic‐Framework Micro/Nanostructures and their Derivatives: Emerging Multifunctional Materials

Hollow metal–organic framework (MOF) micro/nanostructures and their derivatives are attracting a great amount of research interest in recent years because their hierarchical porous structures not only provide abundant, easily accessed metal sites but also endow 3D channels for rapid mass transport. As a result, they demonstrate significant advantages in many applications including catalysis, gas sensors, batteries, supercapacitors, and so on. Nevertheless, studies on hollow MOFs and their derivatives are still at the beginning of this field, and the relationship between their structures and application performances is not yet reviewed comprehensively. Herein, the synthetic strategies and practical applications of hollow micro/nanostructured MOFs and their derivatives are summarized, and their corresponding prospects are also discussed.     

Hollow Micro/Nanostructured Ceria‐Based Materials: Synthetic Strategies and Versatile Applications

Hollow micro/nanostructured CeO₂‐based materials (HMNCMs) have triggered intensive attention as a result of their unique structural traits, which arise from their hollowness and the fascinating physicochemical properties of CeO₂. This attention has led to widespread applications with improved performance. Herein, a comprehensive overview of methodologies applied for the synthesis of various hollow structures, such as hollow spheres, nanotubes, nanoboxes, and multishelled hollow spheres, is provided. The synthetic strategies toward CeO₂ hollow structures are classified into three major categories: 1) well‐established template‐assisted (hard‐, soft‐, and in situ template) methods; 2) newly emerging self‐template approaches, including selective etching, Ostwald ripening, the Kirkendall effect, galvanic replacement, etc.; 3) bottom‐up self‐organized formation synthesis (namely, oriented attachment and self‐deformation). Their underlying mechanisms are concisely described and discussed in detail, the differences and similarities of which are compared transversely and longitudinally. Niche applications of HMNCMs in a wide range of fields including catalysis, energy conversion and storage, sensors, absorbents, photoluminescence, and biomedicines are reviewed. Finally, an outlook of future opportunities and challenges in the synthesis and application of CeO₂‐based hollow structures is also presented.     

The Micro Pirani™: A solid-state vacuum gauge with wide range

For measuring pressures in the range 1 × 10^?2 to 100 mbar, thermal conductivity gauges are commonly used. The widespread Pirani gauge with a thin wire suffers from problems with temperature drift, low accuracy, requirement for adjustment, large measuring volume, filament contamination, and sensitivity to mounting position. Recently, Wenzel Electronics has introduced the Micro Pirani?, which is based on a newly developed solid-state sensor element and which eliminates or significantly reduces the problems. A temperature compensation improves the stability and extends the useful range of operation to the high vacuum range at 1 × 10^?5 mbar. The geometry of the basic sensor element, close to “infinite slab geometry”, facilitates the introduction of a fairly accurate mathematical model of the sensor. The sensor is insensitive to mounting position since no convection can take place in the sensor due to its small dimensions. Furthermore, the internal volume (“dead volume”) has been significantly reduced as compared to traditional Pirani sensors. The conversion from transmitter output voltage to pressure is achieved by a simple and fast algorithm. The selection of a particular gas species is simple, since the algorithm contains only 3 gas-dependent constants. An excellent reproducibility in production eliminates the need for an individual calibration of individual sensors in most applications.     

Micro gradient-index conical lenses: simulation and fabrication methods

In this paper, a micro gradient-index conical lens, which has a larger acceptance angle than a conventional microlens, is presented. Methods on how to simulate these lenses in commercial optical design software CodeV are introduced, and the effects of several index profiles and cone shapes are compared in simulation. Results show that a micro gradient-index conical lens has a four times larger acceptance angle compared with a microlens. Additionally, conical lenses with a Gaussian-index profile show a larger acceptance angle than those with a solid refractive index. Fabricated conical lenses show an acceptance angle of more than 27 degrees for a detection threshold of 50%, which agrees with the simulation result.     

Self‐Propelled Micro/Nanomotors for Sensing and Environmental Remediation

Self‐propelled micro/nanomotors have gained attention for successful application in cargo delivery, therapeutic treatments, sensing, and environmental remediation. Unique characteristics such as high speed, motion control, selectivity, and functionability promote the application of micro/nanomotors in analytical sciences. Here, the recent advancements and main challenges regarding the application of self‐propelled micro/nanomotors in sensing and environmental remediation are discussed. The current state of micro/nanomotors is reviewed, emphasizing the period of the last five years, then their developments into the future applications for enhanced sensing and efficient purification of water resources are extrapolated.     

Micro and nano-structured surfaces

The study of cell reaction to micro and nanotopography is dependent on the method of manufacture available. Several methods of manufacture have been developed: polymer demixing, embossing and photolithography. Surfaces obtained with these different techniques, having micro and/or nanodomains, have been studied toward the same type of cells, i.e. human endothelial cells (HGTFN) and mouse fibroblasts (3T3). Polymer demixing of polystyrene (PS) and poly(4-bromostyrene) (PBrS) producing nanometrically islands of 18, 45 and 100 nm height, polycarbonate (PC) and polycaprolactone (PCL) grooved with grooves 450 nm wide and 190 high, the natural polysaccharide hyaluronic acid (Hyal) and its sulfated derivative (HyalS) photoimmobilized on silanized glass as grooves 250 nm high and 100, 50, 25 or 10 m wide have been obtained. The morphology and polarization of the cells has been studied by optical microscopy and scanning electron microscopy. Cells respond in different way to the topography of the materials, but the surface chemistry is dominant in inducing different cell behavior.     

聚合物基微纳米复合材料的制备及微型注塑加工研究

微型高分子功能器件具有独特优点,发展迅速,应用广泛,是当今科学技术的重要前沿,迫切需要发展高性能多功能聚合物基微纳米复合材料,实现其微型注塑加工。介绍了近年来作者课题组在聚合物基微纳米复合材料制备及其微型注塑加工方面的研究进展:通过有机/无机杂化、固相剪切碾磨、纳米复合、分子复合及熔融共混技术等制备适合于微成型加工的高性能多功能聚合物基微纳米复合材料,如尼龙11/钛酸钡压电复合材料、聚乙烯醇/羟基磷灰石生物医用纳米复合材料、聚氨酯/碳纳米管导电复合材料等。解决了微纳米填料难分散、复合体系难加工的难题,实现了聚合物基微纳米功能复合材料的微型注塑加工,研究了其流变行为和充填行为,调控和优化了微型制品的结构与性能,为制备高性能多功能的聚合物微型器件提供了新材料、新技术和新理论。     

Enhanced Intercalation Dynamics and Stability of Engineered Micro/Nano‐Structured Electrode Materials: Vanadium Oxide Mesocrystals

An additive and template free process is developed for the facile synthesis of VO₂(B) mesocrystals via the solvothermal reaction of oxalic acid and vanadium pentoxide. The six‐armed star architectures are composed of stacked nanosheets homoepitaxially oriented along the [100] crystallographic register with respect to one another, as confirmed by means of selected area electron diffraction and electron microscopy. It is proposed that the mesocrystal formation mechanism proceeds through classical as well as non‐classical crystallization processes, and is possibly facilitated or promoted by the presence of a reducing/chelating agent. The synthesized VO₂(B) mesocrystals are tested as a cathodic electrode material for lithium‐ion batteries, and show good capacity at discharge rates ranging from 150–1500 mA g^?1 and a cyclic stability of 195 mA h g^?1 over fifty cycles. The superb electrochemical performance of the VO₂(B) mesocrystals is attributed to the porous and oriented superstructure that ensures large surface area for redox reaction and short diffusion distances. The mesocrystalline structure ensures that all the surfaces are in intimate contact with the electrolyte, and that lithium‐ion intercalation occurs uniformly throughout the entire electrode. The exposed (100) facets also lead to fast lithium intercalation, and the homoepitaxial stacking of nanosheets offers a strong inner‐sheet binding force that leads to better accommodation of the strain induced during cycling, thus circumventing the capacity fading issues typically associated with VO₂(B) electrodes.     

基于硅材料的微型气体涡轮机中微型燃烧器的设计和加工

由微型燃烧器、微型压缩机和涡轮组成的微型气体涡轮发动机有望成为微机电系统的能源系统.阐述了一种微型燃烧器的设计和加工.设计时力图增加流路的长度,其目的是减少微型燃烧腔的热损失和有效地对燃料和空气进行预热.该微型燃烧器由7片厚度不同的单晶硅片组成,通过ICP DRIE干刻蚀加工而成.组装后的微燃烧器的样件尺寸为21.5 mm×21.5 mm×4.4 mm,已成功地进行了氢气燃烧实验和测试.该微型燃烧器和转子组合后可以应用于微型气体涡轮发动机,与压电元件组合后可用于微型发电机.     

Self‐Propelled Micro/Nanomotors for On‐Demand Biomedical Cargo Transportation

Micro/nanomotors (MNMs) are miniaturized machines that can perform assigned tasks at the micro/nanoscale. Over the past decade, significant progress has been made in the design, preparation, and applications of MNMs that are powered by converting different sources of energy into mechanical force, to realize active movement and fulfill on‐demand tasks. MNMs can be navigated to desired locations with precise controllability based on different guidance mechanisms. A considerable research effort has gone into demonstrating that MNMs possess the potential of biomedical cargo loading, transportation, and targeted release to achieve therapeutic functions. Herein, the recent advances of self‐propelled MNMs for on‐demand biomedical cargo transportation, including their self‐propulsion mechanisms, guidance strategies, as well as proof‐of‐concept studies for biological applications are presented. In addition, some of the major challenges and possible opportunities of MNMs are identified for future biomedical applications in the hope that it may inspire future research.