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A theory of mechanobiological sensation:strain amplification/attenuation of coated liquid inclusion with surface tension

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Acta Mechanica Sinica 2021年第1期37卷 145-155,I0004页

作者： Fei Ti Xin Chen Haiqian Yang Shaobao Liu tian jian lu State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing210016China Xi’an Modern Chemistry Research Institute Xi’an710065China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi’an Jiaotong UniversityXi’an710049China Bioinspired Engineering&Biomechanics Center(BEBC) Xi’an Jiaotong UniversityXi’an710049China

Cells are compressible and can be regarded as a kind of coated liquid inclusion embedded in a three-dimensional elastic *** the presence of far-field loading,how the coating influences the mechanical response(e.g.,volume change)of the liquid inclusion remains elusive,especially when surface tension effects become significant at cell size *** developed a theoretical model to characterize the mechanical amplification or attenuation role of coating on spherical liquid inclusions,with surface tension and liquid compressibility accounted *** found that surface tension could increase the volumetric strain of the inclusion through decreasing its effective bulk *** further found that,when there is a monotonic stiffness variation(either decreasing or increasing)from matrix via coating to inclusion,the presence of coating amplified the volumetric strain compared with the case without coating;in the opposite,when there is a non-monotonic stiffness change from matrix via coating to inclusion,the volumetric strain is attenuated by the *** results are useful for understanding and exploring the mechanobiological sensation of certain types of cell,e.g.,osteocytes and cancer cells.

关键词： Surface tension Liquid inclusion Mechanobiological sensation Cancer cell

A three-layer structure model for the effect of a soft middle layer on Love waves propagating in layered piezoelectric systems

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Acta Mechanica Sinica 2012年第4期28卷 1087-1097页

作者： Peng Li Feng Jin tian-jian lu State Key Laboratory for Mechanical Structure Strength and Vibration Xi'an Jiaotong University710049 Xi'anChina

A three-layer structure model is proposed for investigating the effect of a soft elastic middle layer on the propagation behavior of Love waves in piezoelectric layered systems, with ＂soft＂ implying that the bulk-shear-wave velocity of the middle layer is smaller than that of the upper sensitive layer. Dispersion equations are obtained for unelectroded and traction-free upper surfaces which, in the limit, can be reduced to those for classical Love waves. Systematic parametric studies are subsequently carried out to quantify the effects of the soft middle layer upon Love wave propagation, including its thickness, mass density, dielectric constant and elastic coefficient. It is demonstrated that whilst the thickness and elastic coefficient of the middle layer affect significantly Love wave propagation, its mass density and dielectric constant have negligible influence. On condition that both the thickness and elastic coefficient of the middle layer are vanishingly small so that it degenerates into an imperfectly bonded interface, the three-layer model is also employed to investigate the influence of imperfect interfaces on Love waves propagating in piezoelectric layer/elastic sub- strate systems. Upon comparing with the predictions ob- tained by employing the traditional shear-lag model, the present three-layer structure model is found to be more ac- curate as it avoids the unrealistic displacement discontinuity across imperfectly bonded interfaces assumed by the shearlag model, especially for long waves when the piezoelectric layer is relatively thin.

关键词： Piezoelectric structure Love waves Soft mid-dle layer, shear-lag model

Localization of elastic waves in one-dimensional detuned phononic crystals with flexoelectric effect

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International Journal of Smart and Nano Materials 2022年第2期13卷 244-262页

作者： Cheng Shen Yifan Kong tian jian lu Shasha Yang State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjingPRChina MIIT Key Laboratory of Multifunctional Lightweight Materials and Structures Nanjing University of Aeronautics and AstronauticsNanjingPRChina Space Structure and Mechanism Technology Laboratory of China Aerospace Science and Technology Group Co.Ltd ShanghaiP.R China School of Mechanical Engineering Nanjing Vocational University of Industry TechnologyNanjingP.R China

Although forbidden band effect in perfectly periodic phononic crystals(PC)is very attractive,random disordered(***)phenomenon is inevitable in engineering processing,thus explor-ing the effect of detuning on the wave characteristics of PC becomes a *** this study,fundamental governing equa-tions and boundary conditions are derived from the principle of virtual *** characteristics and localization factor of one-dimensional(1D)detuned nano-PC are investigated based on the transfer matrix method,with flexoelectric effect duly accounted ***,with BaTiO_(3)􀀀SrTiO_(3) nano-PC taken for illustration,forbidden band properties and localization factor of 1D elastic waves in harmonic and detuned states are systematically *** is demonstrated that localization factor can characterize the energy band structure of 1D PC *** effect tends to widen the width of forbidden band with increasing detuning,and detuning is linearly related to the *** forbidden band is more sensitive to flexoelectric coefficient detuning than thickness *** research results provide useful theoretical guidance for designing high-frequency nanoscaled devices with the function of filtering based on band gap effect of nano-PC.

关键词： Flexoelectric effect phononic crystal detuning localization factor forbidden band

Three-point bending of honeycomb sandwich beams with facesheet perforations

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Acta Mechanica Sinica 2018年第4期34卷 667-675页

作者： Pengbo Su Bin Han Zhongnan Zhao Qiancheng Zhang tian jian lu State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong University MOE Key Laboratory for Multifunctional Materials and Structures Xi'an Jiaotong University School of Mechanical Engineering Xi'an Jiaotong University

A novel square honeycomb-cored sandwich beam with perforated bottom facesheet is investigated under threepoint bending,both analytically and *** square holes in the bottom facesheet are characterized by the area ratio of the hole to intact facesheet（perforation ratio）.While for large-scale engineering applications like the decks of cargo vehicles and transportation ships,the perforations are needed to facilitate the fabrication process（e.g.,laser welding）as well as service maintenance,it is demonstrated that these perforations,when properly designed,can also enhance the resistance of the sandwich to *** illustration,fair comparisons among competing sandwich designs having different perforation ratios but equal mass is achieved by systematically thickening the core ***,the perforated sandwich beam is designed with a relatively thick facesheet to avoid local indention failure so that it mainly fails in two competing modes：（1）bending failure,i.e.,yielding of beam cross-section and buckling of top facesheet caused by bending moment;（2）shear failure,i.e.,yielding and buckling of core webs due to shear *** sensitivity of the failure loads to the ratio of core height to beam span is also discussed for varying perforation *** the perfo-ration ratio is increased,the load of shear failure increases due to thickening core webs,while that of bending failure decreases due to the weakening bottom *** of a sandwich beam with optimal perforation ratio is realized when the two failure loads are equal,leading to significantly enhanced failure load（up to 60%increase）relative to that of a non-perforated sandwich beam with equal mass.

关键词： Honeycomb sandwich Facesheet perforation Three-point bending Analytical model

Optomechanical soft metamaterials

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Acta Mechanica Sinica 2017年第3期33卷 575-584页

作者： Xiangjun Peng Wei He Yifan Liu Fengxian Xin tian jian lu State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong University MOE Key Laboratory for Multifunctional Materials and Structures Xi'an Jiaotong University

We present a new type of optomechanical soft metamaterials, which is different from conventional mechanical metamaterials, in that they are simple isotropic and homogenous materials without resorting to any complex nano/microstructures. This metamaterial is unique in the sense that its responses to uniaxial forcing can be tailored by programmed laser inputs to manifest different nonlinear constitutive behaviors, such as monotonic, S-shape, plateau, and non-monotonic snapping performance. To demonstrate the novel metamaterial, a thin sheet of soft material impinged by two counterpropagating lasers along its thickness direction and stretched by an in-plane tensile mechanical force is considered. A theoretical model is formulated to characterize the resulting optomechanical behavior of the thin sheet by combining the nonlinear elasticity theory of soft materials and the optical radiation stress theory. The optical radiation stresses predicted by the proposed model are validated by simulations based on the method of finite elements. Programmed optomechanical behaviors are subsequently explored using the validated model under different initial sheet thicknesses and different optical inputs, and the first- and second-order tangential stiffness of the metamaterial are used to plot the phase diagram of its nonlinear constitutive behaviors. The proposed optomechanical soft metamaterial shows great potential in biological medicine, microfluidic manipulation, and other fields.

关键词： Optomechanics Soft metamaterial Optical radiation stress Programmable constitutive relation

Biomechanics in plant resistance to drought

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Acta Mechanica Sinica 2020年第5期36卷 1142-1157,I0004页

作者： Shaobao Liu Han Liu Jiaojiao Jiao Jun Yin tian jian lu Feng Xu State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China Nanjing Center for Multifunctional Lightweight Materials and Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China MOE Key Laboratory of Biomedical Information Engineering School of Life Science and TechnologyXi'an Jiaotong UniversityXi’an 710049China Bioinspired Engineering and Biomechanics Center(BEBC) Xi'an Jiaotong UniversityXi'an 710049China

During drought,plant functions at multi-levels(i.e.,tissue,.cellular and molecular)are adjustable with the change of water condition,which is known as drought *** biological,chemical and physical mechanisms have been found in plant drought resistance,among which the role of physical cues(especially mechanics)has attracted significantly increasing *** studies have shown that mechanics is one of the fundamental factors that control the responses and self-adaptation from tissue to molecular levels in plant when the external conditions *** the review,we examine how the factor of mechanics acts on the multi-level plant functions under drought stress,including water transport,tissue deformation,cell growth,cell movements,molecules interaction and signal pathway.

关键词： Water transport Deformation Molecule interaction Multi-level Self-adaptation

Dual-level stress plateaus in honeycombs subjected to impact loading:perspectives from bucklewaves, buckling and cell-wall progressive folding

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Acta Mechanica Sinica 2019年第1期35卷 70-77,I0003页

作者： Lang Li Zhenyu Zhao Rui Zhang Bin Han Qiantheng Zhang tian jian lu State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong UniversityXi'an 710049China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China MOE Key Laboratory for Multifunctional Materials and Structures Xi'an Jiaotong UniversityXi'an 710049China School of Mechanical Engineering Xi'an Jiaotong UniversityXi'an 710049China School of Engineering Brown UniversityProvidenceRI 02912USA Research Institute of Xi'an Jiaotong University ZhejiangHangzhou 311215China

Dual-level stress plateaus (i.e., relatively short peak stress plateaus, followed by prolonged crushing stress plateaus) in metallic hexagonal honeycombs subjected to out-of-plane impact loading are characterized using a combined numerical and analytical study, with the influence of the strain-rate sensitivity of the honeycomb pare nt material accounted for. The predicti ons are validated against existing experimental measurements, and good agreement is achieved. It is demonstrated that honeycombs exhibit dual-level stress plateaus when bucklewaves are initiated and propagate in cell walls, followed by buckling and progressive folding of the cell walls. The abrupt stress drop from peak to crushing plateau in the compressive stress versus strain curve can be explained in a way similar to the quasi-static buckling of a clamped plate. The duration of the peak stress plateau is more evident for strain-rate insensitive honeycombs.

关键词： Honeycomb Impact loading Dual-level stress Strain-rate sensitivity

Characterizing in situ poroelastic properties of cytoplasm by the translation of a rigid spherical inclusion

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Acta Mechanica Sinica 2021年第2期37卷 194-200页

作者： Xuechao Sun Xin Chen Ming Wang Moxiao Li Yonggang Liu Shaobao Liu tian jian lu State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China Xi'an Modern Chemistry Research Institute Xi'an 710065China State Key Laboratory for Strength and Vibration of Mechanical Structures School of AerospaceXi'an Jiaotong UniversityXi'an 710049China Bioinspired Engineering&Biomechanics Center(BEBC) Xi'an Jiaotong UniversityXi'an 710049China Key Laboratory of Biomedical Information Engineering of Ministry of Education School of Life Science and TechnologyXi'an Jiaotong UniversityXi'an 710049China

Poroelasticity of cytoplasm is a rate-and size-dependent biphasic material behavior that reflects the normal activities and pathological states of cells,mainly caused by the migration of fluid molecules and the deformation of porous solid skeleton(protein scaffold).While micro/nano-indentation tests have been extensively used to characterize the poroelasticity of a cell,characterizing the in situ poroelasticity of cytoplasm remains *** this study,based on the theory of the translation of a rigid spherical inclusion,we proposed a new method to characterize the in situ poroelasticity of *** on data from optical/magnetic tweezers tests,we estimated three key poroelasticity parameters-shear modulus,Poisson ratio and diffusion coefficient-of cytoplasm for a variety of cells,including cardiomyocytes,endothelial cells of bovine capillary,and *** proposed method provides a powerful tool for in situ measurement of poroelastic properties of cytoplasm via optical/magnetic tweezers.

关键词： Biot theory Diffusion coefficient Optical/magnetic tweezers.Finite element

Mechanical microenvironments of living cells: a critical frontier in mechanobiology

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Acta Mechanica Sinica 2019年第2期35卷 265-269页

作者： Guoyou Huang Feng Xu Guy M. Genin tian jian lu The Key Laboratory of Biomedical Information Engineering of Ministry of Education School of Life Science and Technology Xi’an Jiaotong University Xi’an 710049 China Bioinspired Engineering and Biomechanics Center (BEBC) Xi’an Jiaotong University Xi’an 710049 China Department of Mechanical Engineering &Materials Science Washington University in St. Louis St. Louis 63130 MO USA NSF Science and Technology Center for Engineering Mechanobiology Washington University in St. Louis St. Louis 63130 MO USA State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Nanjing 210016 China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong University Xi'an 710049 China

The fields of biomechanics and mechanobiology have long been predicated on the premise that mechanics governs cell behavior. However, over the past few years, a growing body of evidence has suggested that the mechanical environment very close to cells–the cell microenvironment–plays the most important role in determining what a cell feels and how it responds to tissue-level stimuli. To complicate matters further, cells can actively manipulate their microenvironments through pathways of recursive mechanobiological feedback. Harnessing this recursive behavior to understand and control cell physiology and pathophysiology is a critical frontier in the field of mechanobiology. Recent results suggest that the key to opening this scientific frontier to investigation and engineering application is understanding a different frontier: the physical frontier that cells face when probing their mechanical microenvironments.

关键词： Mechanical microenvironments living cells mechanobiology