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Flexible Polymeric Semiconductors: Intrinsic Mechanical Properties and Design Strategy
LIN Jinyi, AN Xiang, BAI Lubing, XU Man, WEI Chuanxin, XIE Linghai, LIN Zongqiong, HUANG Wei
Materials Reports    2020, 34 (1): 1001-1008.   DOI: 10.11896/cldb.19110117
Abstract5230)      PDF(pc) (7739KB)(3783)       Save
In the last decade, polymeric semiconductors have attracted wide attentions owing to their potential application in organic light-emitting diodes, organic solar cell and organic field-effect transistors. Some polymer materials, especially elastomers, have excellent flexibility, such as strechability, bendability, etc., so polymeric semiconductors are considered as the most promising kind of materials in the future research of flexible electronics. The key point for the flexibility evaluation of polymeric semiconductors is intrinsic mechanical properties, for which, according to relevant works, researchers have already developed some effective approaches to determine, including stretching method, sinusoidal buckling technique, nanoindentation method, and AFM nanomechanical mapping. On the other hand, a variety of ideas for designing flexible polymeric semiconductor materials have emerged and can be classified into supramolecular strategy, "chain flexibilization" strategy, and doping/blending strategy. It is noteworthy that the orthogonal dynamic non-covalent interaction is a fundamental molecular mechanism to induce the flexibility of conjugated polymers. And the tactic based on this mechanism provides a universal method to design flexible semiconductor materials and deserves further studies. This review gives a summary on the intrinsic mechanical properties and design strategies of flexible polymeric semiconductor materials based on the state-of-the-art researches.
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Flexible Hybrid Electronics: Manufacturing Flexible Electronics by Printing Technique 
CUI Zheng
Materials Reports    2020, 34 (1): 1009-1013.   DOI: 10.11896/cldb.19110099
Abstract2921)      PDF(pc) (5266KB)(2711)       Save
The commercialization of foldable mobile phones makes the year of 2019 been regarded as the starting year of flexible electronics. However, apart from the flexible displays which contribute to the foldable phones, flexible electronics products in a broader sense still remains unrea-lized. One of the key reasons is not all the functional electronic components have been successively flexibilized in commercial level. For example, there are still no flexible alternatives for the transistors and integrated circuits (ICs) which are indispensable to any electronic system. And the complete functions of an electronic system still rely on rigid IC chips and printed circuit boards (PCBs). To overcome this barrier, no other choice is practicable except fabricating flexible electronic systems that integrate traditional rigid ICs. There are currently two approaches to achieving this integration — transferring thin silicon chips onto a flexible substrate; or the so called “flexible hybrid electronics” — in which the latter is based on printing technique and is of simplicity, low cost and high throughput potential. Herein, I sketch out the technical approach of flexible hybrid electronics, and give a summary of the research progress of the ink materials and printing process for flexible electronics printing manufacturing. In addition, I also present a retrospective report showing the achievements of the author's Printable Electronics Research Center in the last 10 years in the area of printed electronics. This paper intends to prove that we can create flexible electronic products closer to practical applications and more competitive through printing conductive interconnects on flexible substrates, which can be an effective methodology, at the current technology level, to greatly advance the commercialization of flexible electronics.
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Functionalization of Diatomite and Its Applications
WANG Xuekai, WANG Jinshu, DU Yucheng, WU Junshu, TENG Weili, CHE Haibing, JIN Cuixin
Materials Reports    2020, 34 (3): 3017-3027.   DOI: 10.11896/cldb.19070130
Abstract1019)      PDF(pc) (37568KB)(489)       Save
Diatomite is an inorganic nonmetallic mineral material. Due to unique ordered pore structures, applications of diatomite have been realized in chemical engineering and building materials industries. The application of diatomite was usually limited by its specific surface area (about 18—28 m2/g). Through the functionalization, diatomite materials could be vested with a certain property, thus improving the performance in environment treatment and advancing applications in the field of energy and bioengineering. Therefore, functionalization of diatomite has become a research focus.
In recent years, researches on functionalization of diatomite mainly focus on three areas: noncovalent functionalization, covalent functionalization and chemical conversion of diatomite. Normally, noncovalent functionalization indicate that using nano metal oxides and metal oxygenates to modify diatomite and the functionalized diatomite can be used in the field of energy, water treatment and sensors. Covalent functionalization of diatomite refers to modifying diatomite with functional monomer through the connection of Si-O covalent bond based on Si-O tetrahedron and Si-OH of diatomite. Functional monomers are classified into silicates and silane coupling agents. Silane coupling agents connect to diatomite through Si-OH, and it could also be used to connect other functional groups to obtain excellent properties. Covalent functionalized diatomite is commonly used in the fields of energy, sensor and water treatment. The chemical conversion of diatomite to silicon source is the other functionalization met-hod. Silicon keeps the morphology of diatomite and can be used in the field of energy and bioengineering.
Functionalization of diatomite is the key to realize the application of diatomite materials in emerging fields. Therefore, researches on diatomite functionalization would advance the application of diatomite and promote the development of emerging areas. Here, the progress of diatomite functionalization at home and abroad in recent years are summarized. The functionalization routes and their applications are introduced in detail in order to provide reference for advanced diatomite functionalization routes and their applications.
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Recent Progress in Lead-free Environmentally-friendly Brasses
YANG Chao, TAO Qingchi, DING Yanfei
Materials Reports    2019, 33 (13): 2109-2118.   DOI: 10.11896/cldb.19010222
Abstract1082)      PDF(pc) (12094KB)(555)       Save
Due to excellent mechanical properties, corrosion resistance, casting properties and formability, brasses alloys are widely used in many industries such as sanitary ware, electronic product and equipment manufacturing. Generally, 3wt% Pb is added into brasses alloys to improve their cutting performance. As a soft and brittle phase with relative low melting point, Pb acts as a separate phase in the Cu-Zn binary alloy, which can play roles of chip breaking, lubrication and cooling, and thus improve the cutting performance of brasses alloys. However, Pb is a toxic element and can cause environmental pollution during its production, processing and usage processes. Especially, when lead brasses are used as products contacting with water environment, Pb ions are easily precipitated from the matrix. Lead poisoning can damage the blood, nerves, digestion and reproductive systems of the human body. On this account, the development of lead-free environmentally-friendly brasses becomes an urgent and significant problem.
According to the easy-cutting mechanism of lead brasses, in order to obtain excellent cutting performance, new lead-free environmentally-friendly brasses alloys should have dispersed fine particles in the matrix, which can play a role of chip breaking like Pb particles during cutting processing. According to the existing modes of the particles, the elements beneficial to the cutting performance of brasses alloys can be classified into three types, minor solid-soluble ones in Cu that can form eutectics with Cu, insoluble ones in Cu that can form compounds with Cu, and partial solid-soluble ones in Cu that can form compounds with Cu. Currently, systematic researches have been carried out on the first type of substitute elements such as Bi. However, these elements are of limited resources and are mostly toxic. Some research results have been obtained on the second type of substitute elements, which are easily oxidized and formed harmful inclusions, thus increasing the difficulty in the preparation and processing of these materials. A large number of studies have been conducted to improve the cutting performance of brasses alloys by the third type of substitute elements, such as Pb replacer of Sb, Mg and Si. Unfortunately, Sb is a toxic element like Pb; lead-free magnesium brasses are easy to bring in inhaling, oxidizing and other casting defects, making its smelting process very complicated. The element Si has many advantages of large zinc equivalent coefficient, rich resource and non-toxic effect. Tailoring Si content is easy to regulate microstructures of lead-free silicon brasses with simple smelting process. As such, silicon brasses are expected to realize the complete lead-free in brasses products, which is of great significance in protecting human health, ecological environment and realizing green manufacturing.
In summary, based on the selection characteristics of the third component elements and the zinc equivalent rule, this paper reviewed the research progress in lead-free environmentally-friendly free-cutting brasses, including microstructure, cutting performance and corrosion resistance. Meanwhile, the effects of Si and Al additions on microstructure and properties of developed brasses are analyzed. Particularly, the composition and microstructure design, cutting performance and production process of lead-free environmentally-friendly free-cutting silicon brasses are underlined. Finally, prospects for future research trends are pointed out. The progress reviewed herein may provide significant insight into the development and application of lead-free environmentally-friendly free-cutting brasses.
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Bacterial Infection-microenvironment Responsive Polymeric Materials for the Treatment of Bacterial Infectious Diseases: a Review
WANG Yingjun, HUANG Xuelian, CHEN Junjian, LIANG Yangbin, XIONG Menghua
Materials Reports    2019, 33 (1): 5-15.   DOI: 10.11896/cldb.201901001
Abstract2140)      PDF(pc) (3789KB)(964)       Save
Since the discovery of penicillin in 1928, the application of antibiotics has greatly reduced the morbidity and mortality of bacterial infectious di-seases, and numerous lives are survived from bacterial infection. However, with the widespread use and abuse of antibiotics, antimicrobial resistance has become a global public health issue. In addition, there are several problems that traditional antibiotic therapies encounter. Specifi-cally speaking, the antibiotics are rapidly metabolized and excreted from body after administration, only a few drugs reach the infected site and the bioavailability was low. In this case, high doses and long period treatments are required in clinical application, which lead to notable side effects. Besides, the poor therapeutic effect of antibiotics against biofilm infections and intracellular infections is also a pressing issue, leading to chronic infections and recurrent infections.
In view of the problems existing in the traditional antibiotic delivery mode, the delivery of antibiotics by nanoparticles is proposed and shows great potential in the treatment of bacterial infection, which can improve the solubility of poorly soluble drugs, improve the pharmacokinetics and biodistribution of antibiotics, and overcome the tissue and cell barriers. Inspired by the fact that the physiological and physical microenvironment of bacterial infection sites is different from normal tissues, polymeric nanoparticles, that are responsive to the unique infectious microenvironments, have been developed to deliver antibiotics. These strategies remarkably improve the bioavailability and biodistribution of antibiotics, enhance the therapeutic efficacy of antibiotics against intracellular and biofilm infections, as well as attenuate the side effects.
However, the delivery of antibiotics by nanoparticles shows limitations in the treatments of drug-resistant bacteria and especially for multidrug-resistant bacteria. Aiming at the problems of antibiotic resistance, antimicrobial peptides and their analogues have attracted extensive attention worldwide, since they exhibit broad-spectrum antibacterial activity with the less like-hood to develop drug resistance. Nevertheless, the cytotoxicity of these antibacterial agents hinders their clinical applications. For the sake of solving this problem, researchers designed responsive antimicrobial polymers that exhibited low toxicity in normal tissues, and transformed to active form to effectively kill drug-resistant bacteria when triggered by the acid infectious environment or bacterial enzymes in the infectious environment.
In this review, we gave a brief introduction on the existing issues on traditional antimicrobial therapy, and an overview and current perspectives on the development infection-microenvironment responsive polymeric nanoparticles as carriers of antibiotics and the infection-responsive antimicrobial polymers for the treatment of bacterial infectious diseases over the past decade.
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