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Acta Mechanica Solida Sinica 2017年第1期30卷 11-19页

作者： Q.F.Lü M.L.Deng W.Q.Zhu Department of Mechanics State Key Laboratory of Fluid Power and Mechatronic SystemsKey Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceZhejiang University

A stochastic averaging method of quasi integrable and resonant Hamiltonian systems under excitation of fractional Gaussian noise （fGn） with the Hurst index 1/2 〈 H 〈 1 is proposed. First, the definition and the basic property of fGn and related fractional Brownian motion （iBm） are briefly introduced. Then, the averaged fractional stochastic differential equations （SDEs） for the first integrals and combinations of angle variables of the associated Hamiltonian systems are derived. The stationary probability density and statistics of the original systems are then obtained approximately by simulating the averaged SDEs numerically. An example is worked out to illustrate the proposed stochastic averaging method. It is shown that the results obtained by using the proposed stochastic averaging method and those from digital simulation of original system agree well.

关键词： Quasi integrable and resonant Hamiltonian system Fractional Brownian motion Fractional Gaussian noise Stochastic averaging method Internal resonant

Laser-driven programmable non-contact transfer printing of objects onto arbitrary receivers via an active elastomeric microstructured stamp

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National Science Review 2020年第2期7卷 296-304页

作者： Hongyu Luo Chengjun Wang Changhong Linghu Kaixin Yu Chao Wang Jizhou Song Department of Engineering Mechanics Soft Matter Research Center and Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University

Transfer printing, as an important assembly technique, has attracted much attention due to its valuable merits to develop novel forms of electronics such as stretchable inorganic electronics requiring the heterogeneous integration of inorganic materials with soft elastomers. Here, we report on a laser-driven programmable non-contact transfer printing technique via a simple yet robust design of active elastomeric microstructured stamp that features cavities filled with air and embedded under the contacting surface, a micro-patterned surface membrane that encapsulates the air cavities and a metal layer on the inner-cavity surfaces serving as the laser-absorbing layer. The micro-patterned surface membrane can be inflated dynamically to control the interfacial adhesion, which can be switched from strong state to weak state by more than three orders of magnitude by local laser heating of the air in the cavity with a temperature increase below 100℃. Theoretical and experimental studies reveal the fundamental aspects of the design and fabrication of the active elastomeric microstructured stamp and the operation of non-contact transfer printing. Demonstrations in the programmable transfer printing of micro-scale silicon platelets and micro-scale LED chips onto various challenging receivers illustrate the extraordinary capabilities for deterministic assembly that are difficult to address by existing printing schemes, thereby creating engineering opportunities in areas requiring the heterogeneous integration of diverse materials such as curvilinear electronics and Micro LED displays.

关键词： tunable adhesion transfer printing heterogeneous integration laser-driven

Analysis of Piezoelectric Semiconductor Structures Considering Both Physical and Geometric Nonlinearities

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Acta Mechanica Solida Sinica 2024年第1期37卷 72-81页

作者： Zhengguang Xiao Shuangpeng Li Chunli Zhang Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Department of Engineering MechanicsZhejiang UniversityHangzhou 310027China Huanjiang laboratory Zhuji 311816China

Piezoelectric semiconductors(PSs),such as ZnO and GaN,known as the third-generation semiconductors,have promising applications in electronic and optoelectronic devices due to the coexistence and interaction of piezoelectricity and semiconductor properties.Theoretical modeling of PS structures under external loads,such as thermal and mechanical loads,plays a crucial role in the design of PS devices.In this work,we propose a nonlinear fully coupling theoretical model and investigate the multi-field coupling behaviors of PS structures and PN junctions under thermal and mechanical loads,considering physical and geometric nonlinearities.The electromechanical and semiconducting behaviors of a PS rod-like structure with flexural deformations under different combinations of temperature changes and mechanical loads are evaluated.The tuning effect of temperature changes and mechanical loads on multi-field coupling behaviors of PSs is revealed.The current–voltage characteristics of PS PN junctions are studied under different combinations of temperature changes and mechanical loads.The obtained results are helpful for the development of novel PS devices.

关键词： Piezoelectric semiconductor Nonlinearity Multi-field Coupling Tuning

A Microstructural Damage Model toward Simulating the Mullins Effect in Double-Network Hydrogels

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Acta Mechanica Solida Sinica 2022年第4期35卷 682-693页

作者： Lin Zhan Rui Xiao State key laboratory of Fluid Power and Mechatronic System Key Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceDepartment of Engineering MechanicsZhejiang UniversityHangzhou310027China

The damage models based on the eight-chain model and the affine full-chain network model are not adequate to describe the damage behaviors in double-network(DN)hydrogels.To overcome this limitation,we propose a combined chain stretch model with new damage flow rules.It is demonstrated that the new proposed micro-chain stretch is a reduced form of the complete representation for the transversely isotropic tensor function.As a result,the damage models based on the eight-chain model and the affine model are incorporated as special cases.The effects of chain affineness and network entangling are simultaneously involved in the new model,while only one of these two effects can be characterized in either the eight-chain model or the affine model.It is further shown that the new model can effectively capture the Mullins features of the DN hydrogels and achieve better agreement with the experimental data than the affine model and the eight-chain model.

关键词： Mullins effect Double-network hydrogel Full-network model Microstructural model

Effects of domain unfolding and catch-like dissociation on the collective behavior of integrin-fibronectin bond clusters

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Acta Mechanica Sinica 2021年第2期37卷 229-243页

作者： Ji Lin Yanzhong Wang Jin Qian Department of Engineering Mechanics Key Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceZhejiang UniversityHangzhou 310027China

To gain more understanding of cell-matrix adhesion,we consider an idealized theoretical model of a cluster of integrin-fibronectin bonds at the cell-matrix interface subjected to a dynamic ramping.The distributions of bond traction and interfacial deformation are assumed to obey classical elastic equations,whereas the dissociation/association of individual bonds as well as unfolding/refolding of fibronectin domains are described by stochastic equations.Through stochastic-elasticity coupling,we perform Monte Carlo simulations to investigate how the collective behavior and adhesion performance of the integrin-fibronectin-mediated interface are influenced by two characteristics newly incorporated in the modeling,i.e.,catchlike dissociation between integrin and fibronectin,and unfolding of repeated domains in fibronectin.The probable unfolding of fibronectin domains is found to have profound effects on the resultant adhesion energy of the integrin-fibronectin-mediated interface,and governs the failure model transiting between uniform decay and catastrophic crack-like rupture.

关键词： Integrin-fibronectin complex Cell-matrix adhesion Domain unfolding Catch bond Rate dependence Modulus effect

Influence of surface scattering on the thermal properties of spatially confined GaN nanofilm

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Chinese Physics B 2016年第8期25卷 301-307页

作者：侯阳朱林利 Department of Engineering Mechanics and Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University

Gallium nitride（GaN）, the notable representative of third generation semiconductors, has been widely applied to optoelectronic and microelectronic devices due to its excellent physical and chemical properties. In this paper, we investigate the surface scattering effect on the thermal properties of GaN nanofilms. The contribution of surface scattering to phonon transport is involved in solving a Boltzmann transport equation（BTE）. The confined phonon properties of GaN nanofilms are calculated based on the elastic model. The theoretical results show that the surface scattering effect can modify the cross-plane phonon thermal conductivity of GaN nanostructures completely, resulting in the significant change of size effect on the conductivity in GaN nanofilm. Compared with the quantum confinement effect, the surface scattering leads to the order-of-magnitude reduction of the cross-plane thermal conductivity in GaN nanofilm. This work could be helpful for controlling the thermal properties of Ga N nanostructures in nanoelectronic devices through surface engineering.

关键词： GaN nanofilm elastic model quantum confinement Boltzmann transport equation size effect,phonon thermal conductivity

Growing actin networks regulated by obstacle size and shape

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Acta Mechanica Sinica 2017年第2期33卷 222-233页

作者： Bo Gong Ji Lin Jin Qian Department of Engineering Mechanics Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University Hangzhou 310027 China

Growing actin networks provide the driving force for the motility of cells and intracellular pathogens. Based on the molecular-level processes of actin polymerization, branching, capping, and depolymerization, we have developed a modeling framework to simulate the stochastic and cooperative behaviors of growing actin networks in propelling obstacles, with an emphasis on the size and shape effects on work capacity and filament orientation in the growing process. Our results show that the characteristic size of obstacles changes the protrusion power per unit length, without influencing the orientation distribution of actin filaments in growing networks. In contrast, the geometry of obstacles has a profound effect on filament patterning, which influences the orientation of filaments differently when the drag coefficient of environment is small, intermediate, or large. We also discuss the role of various parameters, such as the aspect ratio of obstacles, branching rate, and capping rate, in affecting the protrusion power of network growth.

关键词： Actin network Growth dynamics Monte Carlo simulation Size effect Shape effect

Coordinated motion of molecular motors on DNA chains with branch topology

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Acta Mechanica Sinica 2021年第10期37卷 1580-1588,I0004页

作者： Di Lu Bin Chen Department of Engineering Mechanics Zhejiang UniversityHangzhou310027China Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Hangzhou310027China

Toward understanding the macroscopic mechanical behaviors of responsive deoxyribonucleic acid(DNA)hydrogels integrated with DNA motors,here we construct the state map for the translocation process of a single C-terminal translocase domain(FtsKC)on a single DNA chain at the molecular level and then investigate the movement of single or multiple FtsKC motors on DNA chains with varied branch topology.Our studies indicate that multiple FtsKC motors can have coordinated motion,which is mainly due to the force responsive behavior of individual FtsKC motor.We further suggest the potential application of motors of FtsKC,together with DNA chains of specific branch topology,to serve as strain sensors in hydrogels.

关键词： DNA Molecular motor Coordinated motion Branch topology Strain sensor

Motion and deformation of immiscible droplet in plane Poiseuille flow at low Reynolds number

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Journal of Hydrodynamics 2016年第4期28卷 702-708页

作者：潘定一林雨青张凌新邵雪明 State key laboratory of Fluid Power and Mechatronic Systems Key Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceDepartment of Engineering MechanicsZhejiang University

Droplet migration in plane Poiseuille flow is numerically investigated with a dissipative particle dynamics method.The single droplet deformation in the channel flow is first studied to verify the current method and the physical model.The effect of the viscosity ratio between the droplet and the solvent and the effect of the confinement are systematically investigated.The droplet is in an off-centerline equilibrium position with a specific selection of the parameters.A large viscosity ratio makes the droplet locate in a near-wall equilibrium position,and a large capillary number makes the droplet migrate to the near-centerline region of the channel.For the droplet migration at the same Capillary number,there is a critical width of the channel,which is less than twice of the droplet diameter,and the droplet will only migrate to the channel centerline if the width is less than this critical value.

关键词： droplet migration migrate viscosity Reynolds locate capillary systematically twice positions

On the role of piezoelectricity in phonon properties and thermal conductivity of GaN nanofilms

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Theoretical & Applied Mechanics Letters 2016年第6期6卷 277-281页

作者： Linli Zhu Haonan Luo Department of Engineering Mechanics and Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University

The effect of piezoelectricity on phonon properties and thermal conductivity of gallium nitride （GaN） nanofilms is theoretically investigated. The elasticity model is utilized to derive the phonon properties in spatially confined GaN nanofilms. The piezoelectric constitutive relation in GaN nanofilms is taken into account in calculating the phonon dispersion relation. The modified phonon group velocity and phonon density of state as well as the phonon thermal conductivity are also obtained due to the contribution of piezoelectricity. Theoretical results show that the piezoelectricity in GaN nanofilms can change significantly the phonon properties such as the phonon group velocity and density of states, resulting in the variation of the phonon thermal conductivity of GaN nanofilms remarkably. Moreover, the piezoelectricity of GaN can modify the dependence of thermal conductivity on the geometrical size and temperature. These results can be useful in modeling the thermal performance in the active region of GaN-based electronic devices.

关键词： GaN nanofilm Phonon properties Elastic model Piezoelectricity Phonon thermal conductivity