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Multiscale tensegrity model for the tensile properties of DNA nanotubes

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Applied Mathematics and Mechanics(English Edition) 2023年第3期44卷 397-410页

作者： Hanlin LIU nenghui zhang Wei LU Shanghai Institute of Applied Mathematics and Mechanics Shanghai Key Laboratory of Mechanics in Energy EngineeringSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China Qishuyan Senior High School of Changzhou Changzhou 213000Jiangsu ProvinceChina

DNA nanotubes(DNTs)with user-defined shapes and functionalities have potential applications in many *** far,compared with numerous experimental studies,there have been only a handful of models on the mechanical properties of such *** paper aims at presenting a multiscale model to quantify the correlations among the pre-tension states,tensile properties,encapsulation structures of DNTs,and the surrounding ***,by combining a statistical worm-like-chain(WLC)model of single DNA deformation and Parsegian's mesoscopic model of DNA liquid crystal free energy,a multiscale tensegrity model is established,and the pre-tension state of DNTs is characterized theoretically for the first ***,by using the minimum potential energy principle,the force-extension curve and tensile rigidity of pre-tension DNTs are ***,the effects of the encapsulation structure and surrounding factors on the tensile properties of DNTs are *** predictions for the tensile behaviors of DNTs can not only reproduce the existing experimental results,but also reveal that the competition of DNA intrachain and interchain interactions in the encapsulation structures determines the pre-tension states of DNTs and their tensile *** changes in the pre-tension states and environmental factors make the monotonic or non-monotonic changes in the tensile properties of DNTs under longitudinal loads.

关键词： DNA nanotube(DNT) multiscale model tensegrity structure pre-tension state tensile property

Thickness dependence of viscoelastic stress relaxation of laminated microbeams due to mismatch strain

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Applied Mathematics and Mechanics(English Edition) 2022年第4期43卷 467-478页

作者： Xiaosheng CAI nenghui zhang Hanlin LIU Shanghai Institute of Applied Mathematics and Mechanics Shanghai Key Laboratory of Mechanics in Energy EngineeringSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China

Time-dependent behaviors due to various mismatch strains are very important to the reliability of micro-/*** paper aims at presenting an analytical model to study the viscoelastic stress relaxation of the laminated microbeam caused by mismatch ***,zhang’s two-variable method is used to establish a mechanical model for predicting the quasi-static stress relaxation of the laminated ***,the related analytical solutions are obtained by combining the differential method and the eigenvalue method in the temporal ***,the influence of the substrateto-film thickness/modulus ratio on the relaxation responses of the laminated microbeam subject to a step load of the mismatch strain is *** results show that the present predictions are consistent with the previous theoretical ***,the thickness dependence of stress relaxation time of the laminated microbeam is jointly determined by the intrinsic structural evolution factors and tension-bending coupling state;the stress relaxation time can be controlled by adjusting the substrate-to-film thickness/modulus ratio.

关键词： laminated structure stress relaxation mismatch strain tension-bending coupling effect analytical method

Quasi-static and dynamical analyses of a thermoviscoelastic Timoshenko beam using the differential quadrature method

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Applied Mathematics and Mechanics(English Edition) 2019年第4期40卷 549-562页

作者： Qiang LYU Jingjing LI nenghui zhang Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Department of Mechanics College of Sciences Shanghai University

The quasi-static and dynamic responses of a thermoviscoelastic Timoshenko beam subject to thermal loads are analyzed. First, based on the small geometric deformation assumption and Boltzmann constitutive relation, the governing equations for the beam are presented. Second, an extended differential quadrature method(DQM)in the spatial domain and a differential method in the temporal domain are combined to transform the integro-partial-differential governing equations into the ordinary differential equations. Third, the accuracy of the present discrete method is verified by elastic/viscoelastic examples, and the effects of thermal load parameters, material and geometrical parameters on the quasi-static and dynamic responses of the beam are discussed. Numerical results show that the thermal function parameter has a great effect on quasi-static and dynamic responses of the beam. Compared with the thermal relaxation time, the initial vibrational responses of the beam are more sensitive to the mechanical relaxation time of the thermoviscoelastic material.

关键词： Timoshenko beam thermoviscoelasticity thermal load dynamic response,differential quadrature method(DQM)

SURFACE STRESS PROPERTIES OF DNA-MICROCANTILEVER SYSTEMS

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Acta Mechanica Solida Sinica 2014年第2期27卷 122-128页

作者： Zouqing Tan nenghui zhang Jingjing Li Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Department of Mechanics College of Sciences Shanghai University

For the first time, the connection between surface stress and nanoscopic interac- tions of DNA adsorbed on microcantilever is established by combining Strey＇s mesoscopic liquid crystal theory and Stoney＇s formula. It is shown that surface stress depends not only on biomolec- ular interactions of DNA biofilm but also on mechanical properties of cantilever. Considering the correlativity between grafting density and chain length of DNA chain, we discuss the differences between DNA-microcantilever system and DNA solution system. The major theoretical achieve- ment of this model is to identify the main contributions to surface stress under different detection conditions. This provides guidelines for designing new biosensors with high sensitivity and improved reliability.

关键词： surface stress DNA hybridization microcantilever biosensor energy method biomolecular interaction

Thermal-induced snap-through buckling of simply-supported functionally graded beams

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Applied Mathematics and Mechanics(English Edition) 2020年第12期41卷 1821-1832页

作者： Yongyong XI QiangLYU nenghui zhang Junzheng WU School of Mechanics and Engineering Science Shanghai UniversityShanghai 200444China Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai Institute of Applied Mathematics and MechanicsShanghai UniversityShanghai 200072China

The instability of functionally graded material(FGM)structures is one of the major threats to their service safety in engineering *** paper aims to clarify a long-standing controversy on the thermal instability type of simply-supported FGM ***,based on the Euler-Bernoulli beam theory and von K′arm′an geometric nonlinearity,a nonlinear governing equation of simply-supported FGM beams under uniform thermal loads by zhang’s two-variable method is ***,an approximate analytic solution to the nonlinear integro-differential boundary value problem under a thermal-induced inhomogeneous force boundary condition is obtained by using a semiinverse method when the coordinate axis is relocated to the bending axis(physical neutral plane),and then the analytical predictions are verified by the differential quadrature method(DQM).Finally,based on the free energy theorem,it is revealed that the symmetry breaking caused by the material inhomogeneity can make the simply-supported FGM beam under uniform thermal loads occur snap-through postbuckling only in odd modes;furthermore,the nonlinear critical load of thermal buckling varies non-monotonically with the functional gradient index due to the stretching-bending coupling *** results are expected to provide new ideas and references for the design and regulation of FGM structures.

关键词： functionally graded beam simply-supported boundary buckling thermal load snap-though free energy theorem

A VARIATIONAL PRINCIPLE OF PERTURBED MOTION ON VISCOELASTIC THIN PLATES WITH APPLICATIONS

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Acta Mechanica Solida Sinica 1999年第2期12卷 121-128页

作者： zhang nenghui Cheng Changjun Shanghai Univ Shanghai Inst Appl Math & Mech Shanghai 200072 Peoples R China Shanghai Univ Dept Mech Shanghai 200072 Peoples R China

In this paper, in the light of the Boltzmann superpositionprinciple in linear viscoelastic- ity, a mathematical model ofperturbed motion on viscoelastic thin place is established. Thecorre- sponding variational principle is obtained in a convolutionbilinear form. For application the problems of free vibration, forcedvibration and stability of a viscoelastic simply-supportedrectangular thin plate are considered. The results show thatnumerical solutions agree well with analytical solutions.

关键词： viscoelastic thin plate perturbed motion variational principle

PIEZOELECTRIC PROPERTIES OF SINGLE-STRAND DNA MOLECULAR BRUSH BIOLAYERS

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Acta Mechanica Solida Sinica 2007年第3期20卷 206-210页

作者： zhang nenghui Shah Jinying Xing Jingjing Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China Department of Mechanics College of Sciences Shanghai University Shanghai 200444 China

The paper is devoted to investigations on nanomechanical behaviors of biochips in label-free biodetections. The chip consists of Si-layer, Ti-layer, Au-layer and single-strand DNA （ssDNA） molecular brush biolayer immobilized by self-assembly technology of thiol group. Unlike previous viewpoints, such as force-bending, entropy-bending and curvature electricity effect, etc., the piezoelectric effect of the biopolymer brush layer is viewed as the main factor that induces nanomechanical bending of biochips, and a classical macroscopic piezoelectric constitutive relation is used to describe the piezoelectric effect. A new laminated cantilever beam model with a piezoelectric biolayer in continuum mechanics, the linearized Poisson-Boltzmann equation in statistical mechanics and the scaling method in polyelectrolyte brush theory are combined to es- tablish a relationship between the nanomechanical deflection of DNA chips and the factors such as nanoscopic structural features of ssDNA molecules, buffer salt concentration, macroscopic mechanical/piezoelectric parameters of DNA chips etc. Curve fitting of experimental data shows that the sign of the piezoelectric constant of the biolayer may control the deflection direction of DNA chips during the packaging process.

关键词： DNA chip laminated beam polymer brush piezoelectric effect

Piezoelectric and flexoelectric effects of DNA adsorbed films on microcantilevers

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Applied Mathematics and Mechanics(English Edition) 2023年第9期44卷 1547-1562页

作者： Yuan YANG nenghui zhang Hanlin LIU Jiawei LING Zouqing TAN Shanghai Institute of Applied Mathematics and Mechanics Shanghai Key Laboratory of Mechanics in Energy EngineeringSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China School of Mechanical Engineering and Rail Transit Changzhou UniversityChangzhou 213164Jiangsu ProvinceChina

DNA-based biosensors have played a huge role in many areas,especially in current global coronavirus ***,there is a great difficulty in the characterization of piezoelectric and flexoelectric coefficients of the nanoscale DNA film,because the existing experimental methods for hard materials are almost *** addition,the relevant theoretical models for DNA films only consider a single effect without clarifying the difference between the two electromechanical effects on device detection *** work aims to present multiscale models for DNA-microcantilever experiments to clarify the competitive mechanism in piezoelectric and flexoelectric effects of DNA films on detection ***,a Poisson-Boltzmann(PB)equation is used to predict the potential distribution due to the competition between fixed phosphate groups and mobile salt ions in DNA ***,a macroscopic piezoelectric/flexoelectric constitutive equation of the DNA film and a mesoscopic free energy model of the DNA solution are combined to analytically predict the electromechanical coefficients of the DNA film and the relevant microcantilever signals by the deformation equivalent method and zhang’s two-variable ***,the effects of detection conditions on microscopic interactions,electromechanical coupling coefficients,and deflection signals are *** results not only agree well with the experimental observations,but also reveal that the piezoelectric and flexoelectric effects of the DNA film should be equivalently modeled when interpreting microcantilever detection *** insights might provide opportunities for the microcantilever biosensor with high sensitivity.

关键词： DNA microcantilever biosensor electromechanical coupling effect flexo-electricity piezoelectricity multiscale model

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光伏组件单元的热应力和内力分析

太阳能学报 2020年第8期41卷 215-220页

作者：刘翰林张乘胤张能辉上海大学力学与工程科学学院上海200444 上海大学上海市应用数学和力学研究所上海市力学在能源工程中的应用重点实验室上海200072

由于层间热失配效应和边界效应,在层合结构边缘存在局部剥离应力和界面剪切应力,引起光伏组件单元的破坏。针对此类问题,首先采用张能辉提出的两变量方法,给出层合结构内部轴向正应力和边界区域界面剥离内力的解析模型。随后进行有限元... 详细信息

由于层间热失配效应和边界效应,在层合结构边缘存在局部剥离应力和界面剪切应力,引起光伏组件单元的破坏。针对此类问题,首先采用张能辉提出的两变量方法,给出层合结构内部轴向正应力和边界区域界面剥离内力的解析模型。随后进行有限元数值模拟,通过对比证明解析预测具有较高的准确性;同时讨论硅片层弹性模量和厚度对层间剥离内力和轴向正应力的影响。最后考虑温度变化,讨论导热层对光伏组件单元热应力和剥离内力的影响。

关键词：光伏组件层合结构解析模型热效应热应力