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micromechanical properties of poly(N-isopropylacrylamide)hydrogel microspheres determined using a simple method

Particuology 2015年第2期13卷 164-172页

作者： Mei Yuan Xiaojie Ju Rui Xie Wei Wang Liangyin Chu School of Chemical Engineering Sichuan University

Temperature-responsive poly（N-isopropylacrylamide）（PNIPAM） hydrogel microspheres have attracted extensive attention because of their promising diverse biomedical applications. A quantitative understanding of the micromechanical properties of these microspheres is essential for their practical application. Here, we report a simple method for the characterization of the elastic properties of PNIPAM hydrogel microspheres. The results show that PNIPAM hydrogel microspheres exhibit elastic deformation and the obtained force-deformation experimental data fits the Hertz theory well. The moduli of elasticity of the PNIPAM hydrogel microspheres prepared under different conditions were systematically investigated in this work for the first time. The PN1PAM hydrogel microsphere composition significantly affects their micromechanical properties and their temperature sensitivity behavior. PNIPAM hydrogel microspheres with a larger equilibrium volume change have a lower modulus of elasticity. The modulus of elasticity of the PNIPAM hydrogel microspheres at body temperature （37 ℃, above the lower critical solution temperature （LCST） of PNIPAM） is much higher than that at room temperature （25 ℃, below the LCST of PNIPAM） because ofthermo-induced volume shrinkage and an increase in stiffness. These results provide valuable guidance for the design of smart materials for practical biomedical applications. Moreover, the simple microcompression method presented here also provides a versatile way to investigate the micromechanical properties of microscopic biomedical materials.

关键词： Poly（N-isopropylacrylamide） Microspheres micromechanical properties Modulus of elasticity Temperature-responsive volume change Lower critical solution temperature

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Design and application of the dynamic detection platform for testing the micromechanical properties of agricultural products

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International Journal of Agricultural and Biological Engineering 2022年第6期15卷 8-15页

作者： Yifeng Hao Yongwei Wang Qianjing Jiang Jing Zhang Jun Wang Department of Biosystems Engineering Zhejiang UniversityHangzhou 310058China Key Laboratory of Intelligent Equipment and Robotics for Agriculture of Zhejiang Province Hangzhou 310058China

The micromechanical properties of agricultural products can be used to formulate simulation models and optimize processing parameters for harvest,packaging,and storage.In this study,a detection platform was designed for conducting mechanical tests on different specimens at the tissue level.The system provided controllable and precise displacements;the relative error was less than±1.0%.The displacement and force measurements were calibrated.micromechanical tests of apple parenchyma tissues were conducted to evaluate the performance of the proposed platform.The stress-strain curves of the specimens and the micrographs of the microstructures can be obtained simultaneously during the tests.The proposed platform has the capability to test mechanical properties and obtain micro behaviors of agricultural products at the tissue level,which helps in studying the failure mechanism of agricultural products under external loading.

关键词： elasticity module micro tensile parenchyma tissue micromechanical properties agricultural products

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Study of the Climbing Behavior of the Flagella of Calamus Simplicifolius Based on Micro-CT and Nanoindentation

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Journal of Bionic Engineering 2022年第6期19卷 1790-1796页

作者： Fukuan Dai Ziwei Wang Tuhua Zhong Hankun Wang Genlin Tian Institute of New Bamboo and Rattan Based Biomaterials International Center for Bamboo and RattanBeijing100102China Key Laboratory of National Forestry and Grassland Administration/Beijing for Bamboo&Rattan Science and Technology Beijing100102China

Rattan is a typical tropical climbing plant that uses flagella to climb supports to grow.A comprehensive understanding of the anatomic structure and micromechanics of rattan flagella might inspire more research on biomimetic climbing materials.Here,the structure and micromechanical properties of flagella in calamus simplicifolius were examined by Micro-Computed Tomography(Micro-CT)and nanoindentation techniques,respectively.The results showed that the rachis of the flagella mainly comprised vascular bundles surrounded by basic tissues,which had a gradient density decreasing from outsides to insides.The prickles are derived from the epidermis or the epidermis and cortical tissue of the flagellum,which do not possess vascular tissue.The entire tip of the prickle was composed almost of fibrous cells.The indentation modulus of elasticity of the prickle was 17.03 GPa,which was 17.93%higher in comparison with the rachis.The hardness of the prickle was 539.27 MPa and was slightly higher than that of the rachis.The results indicated that the discrepancy of micromechanical strengths in different parts of flagella reflects on their unique roles in the process of climbing.

关键词： Calamus simplicifolius micromechanical properties Structure Flagellum Biomaterials

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micromechanical characterization of microwave dielectric ceramic BaO-Sm_(2)O_(3)-5TiO_(2),by indentation and scratch methods

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Journal of Advanced Ceramics 2023年第6期12卷 1136-1165页

作者： Ming Liu Zhitong Xu Fujian Provincial Key Laboratory of Terahertz Functional Devices and Intelligent Sensing School of Mechanical Engineering and AutomationFuzhou UniversityFuzhou 350108China

Mechanical characterization of dielectric ceramics,which have drawn extensive attention in wireless communication,remains challenging.The micromechanical properties with the microstructures of dielectric ceramic BaO-Sm_(2)O_(3)-5TiO_(2)(BST)were assessed by nanoindentation,microhardness,and microscratch tests under different indenters,along with the X-ray diffraction(XRD),scanning electron microscopy(SEM),and Raman spectroscopy.Accurate determination of elastic modulus(Err)(i.e.,260 GPa)and indentation hardness(Hrr)(i.e.,16.2 GPa)of brittle BST ceramic by the instrumented indentation technique requires low loads with little indentation-induced damage.The elastic modulus and indentation hardness were analyzed by different methodologies such as energy-based approach,displacement-based approach,and elastic recovery of Knoop imprint.Consistent values(about 3.1 MPa·m^(1/2))of fracture toughness(Kc)of BST ceramic were obtained by different methods such as the Vickers indenter-induced cracking method,energy-based nanoindentation approaches,and linear elastic fracture mechanics(LEFM)-based scratch approach with a spherical indenter,demonstrating successful applications of indentation and scratch methods in characterizing fracture properties of brittle solids.The deterioration of elastic modulus or indentation hardness with the increase in indentation load(F)is caused by indentation-induced damage and can be used to determine the fracture toughness of material by energy-based nanoindentation approaches,and the critical void volume fraction(f^(*))is 0.27(or 0.18)if elastic modulus(or indentation hardness)of the brittle BST ceramic is used.The fracture work at the critical load corresponding to the initial decrease in elastic modulus or indentation hardness can also be used to assess the fracture toughness of brittle solids,opening new venues of the application of nanoindentation test as a means to characterize the fracture toughness of brittle ceramics.

关键词： brittle ceramics micromechanical properties instrumented indentation microscratch fracture toughness(K_(c)) grid nanoindentation

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Particle shape effects on ductility of SiC particle reinforced LD2 matrix composites investigated by AFM-based nanoindentation

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中国有色金属学会会刊：英文版 2001年第4期11卷 509-512页

作者：刘澄张国定 M.Naka State Key Laboratory of Metal Matrix Composites Shanghai Jiaotong University Joining and Welding Research Institute of Osaka University Osaka 567-0047 Japan

An AFM (Atomic Force Microscope) based nanoindentation method for local measurement of mechanical properties near interfaces in both angular and blunted SiC particle reinforced LD2 composites is presented. The blunted composite exhibits an improved ductility than the angular counterpart. The nanoindentation examination shows that the micromechanical properties near interfaces distribute unevenly and vary with particle shape in the SiC p/LD2 composites. There are a higher nanohardness value and a lower plastic deformation capacity around an angular particle than around a blunted one. It is inferred that the residual stress and strain concentrations are severer around the angular particle, which causes matrix cracking at a lower external strain level and leads to a lower ductility of the angular composite.

关键词： micromechanical properties nanoindentation interface ductility

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玻纤增强聚苯硫醚复合材料界面微观力学性能研究

玻纤增强聚苯硫醚复合材料界面微观力学性能研究

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2012年全国高分子材料科学与工程研讨会

作者：刘钊刘保英王孝军杨杰四川大学高分子科学与工程学院四川大学材料科学技术研究所四川大学高分子材料工程国家重点实验室

＜正＞复合材料的机械性能及稳定性主要受三个方面影响:纤维的自身的强度和刚度;基体的强度及化学稳定性;纤维与基体间界面层的结合程度。作为增强材料与基体的连接桥梁和外加载荷从基体向增强材料传递的纽带,界面层力学性能在很大程度... 详细信息

＜正＞复合材料的机械性能及稳定性主要受三个方面影响:纤维的自身的强度和刚度;基体的强度及化学稳定性;纤维与基体间界面层的结合程度。作为增强材料与基体的连接桥梁和外加载荷从基体向增强材料传递的纽带,界面层力学性能在很大程度上影响到了整体复合材

关键词： microbond plasma micromechanical properties composite

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