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Two kind of on-chip integrated fatigue bending test structures are designed through system-level simulation method based on macromodels to measure the fracture strength and fatigue mechanical properties of polysilicon thin films. The first on-chip fatigue test structure is actuated by V-beam thermal actuator, and the other test structure actuated by electrostatic comb. The static and dynamic analysis was performed by Coventorware Architect module using self-bulid reduced order model described with the MAST hardware language and some other commercial parts from Coventorware parts library. The structural dimension parameters are determined and optimized according to system-level simulation and the computing result has shown that the self-build macromodels and the on-chip integrated test system are efficient and reliable. Two kinds of polysilicon on-chip fatigue bending test structure were fabricated with two-layer polysilicon surface micromachining process in Institute of Microelectronics, Peking University.

Avian feather is the outstanding protein fiber structure that still lacks an interpretation generally acceptable in any detail. In this paper, asio otus feathers were morphological represented and their barbs were mechanical characterized by a developed micro-tensile tester with a load resolution of 0.25 mN and a displacement resolution of 10 nm. With a tensile loading speed at 0.02 μm/s, Young’s modulus of the flight feather barbs with length of 1450-1900 μm was calculated to be 3.13-3.66 GPa, higher than 1.47-2.04 GPa for the down feather barbs with length of 520-710 μm. It is concluded that the asio otus’s flight feathers on its wing and tail are more rigid than the down feathers on its body.

A refined approach producing MEMS numerical macromodels is proposed in this paper by generating the iterative Krylov subspace using a refined Arnoldi algorithm, which can reduce the degrees of freedom of the original system equations described by the state space method. Projection of the original system matrix onto the Krylov subspace which is spanned by a refined Arnoldi algorithm is still based on the transfer function moment matching principle. The idea of the iterative version is to expect that a new initial vector will contain more and more information on the required eigenvectors that is called refined vector. The refined approach improves approximation accuracy of the system matrix eigenvalues equivalent to a more accurate approximation to the poles of the system transfer function, obtaining a more accurate reduced-order model. The clamped beam model and the FOM model are reduced order by classical Arnoldi and refined Arnoldi algorithm in numerical experiments. From the computing result it is concluded that the refined Arnoldi algorithm based Krylov subspace technique for MEMS model order reduction has more accuracy and reaches lower order number of reduced order model than the classical Arnoldi process.

The methods of on-chip integrated testing have a wide application with the development of the study for MEMS materials properties measurement in microscale. A novel on-chip integrated micro-tensile testing system is designed through system-level simulation based on macromodels to measure the fracture strength and fatigue mechanical properties of polysilicon thin films. The structure of testing instrument consists of V-beam electrothermal actuator, differential capacitance sensor, supporting spring and specimen. The capacitance signal is sensed and controlled by a second sigma-delta modulator circuit. The analytic macromodel of polysilicon thin film specimen considering geometric nonlinearity and the numerical reduced-order model of V-beam electrothermal actuator based on Krylov subspace projection are created separately and described in the MAST hardware language. The mechanical structure dimension size and circuit components parameters are determined and optimized according to system-level simulation. The computing result has shown that the self-build macromodels and the on-chip integrated test system are efficient and reliable.

Wood-polymer composite was prepared by a novel combined two-step method with maleic anhydride (MAN) for the first treatment, and mixed monomers of glycidyl methacrylate (GMA)/ methyl methacrylate (MMA) (1:5 of molar ratio) for the second treatment. SEM and FTIR technologies were employed to characterize the interfacial compatibility between resultant polymer and wood matrix, and the dimensional stability of the resultant wood-polymer composite was also tested. The results indicated that polymers fully filled up wood cell lumina and chemically bonded to wood cell wall, resulting in the improvement of interfacial compatibility between polymer and wood matrix without obvious lacunae. The dimensional stability of poplar wood was significantly improved after the combined two-step treatment, and became more stable than that of PEG-1000 treated Poplar Wood.

It is generally agreed that adipocytes originate from mesenchymal stem cells in what can be divided into two processes: determination and differentiation. In the past decade, many factors associated with epigenetic signals have been proved to be pivotal for the appropriate timing of adipogenesis progression. A large number of coregulators at critical gene promoters set up specific patterns of DNA methylation, histone acetylation and methylation, and nucleosome rearrangement, that act as an epigenetic code to modulate the correct progress of adipocyte differentiation and adipogenesis during adipogenesis. In this review, we focus on the functions and roles of epigenetic processes in preadipocyte differentiation and adipogenesis.

In this article, inconsistency of the association of polymorphisms of fibroblast growth factor receptor 2 (FGFR2) with breast cancer is noted. Three commonly studied FGFR2 polymorphisms including rs1219648 (AG), rs2420946 (CT), and rs2981582 (CT) were selected to explore their association with risk of development of breast cancer by meta-analysis of published case-control studies. The results showed that all these three polymorphisms were significantly associated with altered breast cancer risk in any model (co-dominant, dominant, or recessive model) and in stratification based on ethnicity and study design. In the subgroup analyses for postmenopausal women, significantly increased risks were found for rs1219648 and rs2420946 in any model. This meta-analysis suggests that FGFR2 is likely an important genetic marker contributing to susceptibility of breast cancer. We recommend that these single nucleotide polymorphisms to be included in future association studies and functional assays.

Fe/Cu nanometer-scale multilayers with nominal modulation wavelengths ranging from 5 to 40 nm are deposited by direct current magnetron sputtering on Si (100) substrates. Modulation structures of the multilayers are examined by small angle / wide angle x-ray diffraction (SA/WAXRD) and cross-sectional transmission electron microscopy (XTEM). Hardness of the multilayers is measured by using nanoindentation. All the multilayers have Fe (110) and Cu (111) textures. Interface coherency is observed in the multilayers with designed modulation wavelengths of 5 and 10 nm. The hardness increases firstly and then deceases with increasing the modulation wavelength, and reaches peak value of 7.29±0.29 GPa in the multilayers with nominal modulation wavelength of 10 nm. The evolution of the hardness of the mulitlayers is explained by interface width and modulus difference between sublayers.

Flight feather shaft of long-eared owl is characterized by a three-parameter model for linear viscoelastic solids to reveal its damping ability. Uniaxial tensile tests of the long-eared owl, pigeon, and golden eagle flight feather shaft specimens were carried out based on Instron 3345 single column material testing system, respectively, and viscoelastic response of their stress and strain was described by the standard linear solid model. Parameter fitting result obtained from the tensile tests shows that there is no significant difference in instantaneous elastic modulus for the three birds’ feather shafts, but the owl shaft has the highest viscosity, implying more obvious viscoelastic performance. Dynamic mechanical property was characterized based on the tensile testing results. Loss factor (tanδ) of the owl flight feather shaft was calculated to be 1.609 ± 0.238, far greater than those of the pigeon (0.896 ± 0.082) and golden eagle (1.087 ± 0.074). It is concluded that the long-eared owl flight feather has more outstanding damping ability compared to the pigeon and golden eagle flight feather shaft. Consequently, the long-eared owl flight feathers can dissipate the vibration energy more effectively during the flying process based on the principle of damping mechanism, for the purpose of vibration attenuation and structure radiated noise reduction.

SU-8 is not only an epoxy-based negative-tone photoresist but also a potential building structural material which can be directly used as movable parts in micro structures for its unique UV curing characters and high-aspect ratio. It is particularly suitable for the fabrication of a wide range of low-temperature processes objects, such as micro valves, micro gear wheels and micro grippers. A standard mechanical property parameter database of SU-8 in microscale has not been established while its characters can vary significantly depending on the process conditions. The Young's modulus is one of the important parameters to evaluate the mechanical properties of this novel structural material, especially for the optimum design, performance realization and reliability analysis of micro devices. This paper presents the design of free-standing SU-8 thin film specimens with different sizes. The fabrication processing is demonstrated and the Young's modulus is achieved through tensile testing. The experiments are operated on a micro-tensile testing system. The force is measured by a load cell with accuracy of 0.25 mN and elongation of specimen is obtained from a displacement sensor with accuracy of 0.1 um. The measured Young's modulus of 60um wide SU-8 specimens from force-displacement curves is about 2.2±0.1 GPa. The behavior of plastic deformation is also detected before elastic deformation during the experimental process.

This work presents the mechanical characterization of SU-8 photoresists studied in the form of microscaled free-standing thin films with various effective length/width (aspect) ratios, achieved by a tensile testing method. Specimens were designed with gauge segments measuring 240 to 540 μm long and 40 to 80 μm wide with thickness fixed at 20 μm, all fabricated in the same processing conditions. The experiments were carried out on a microtensile testing system which had a load and displacement resolution of 0.25 mN and 10 nm, respectively. With a tensile loading speed of 0.02 μm/s, the average fracture strength of SU-8 photoresist was measured to be 66.34 MPa, and the calculated Young's modulus ranged from 0.86 to 2.33 GPa and the maximum strain from 1.02% to 9.70%, with variation dependent on the effective aspect ratio of the tested films. As a result, effective aspect ratio is concluded to be a significant factor mechanically charactering the size effect of SU-8 photoresist in microscale.