Construction of 3D Shape-Changing Hydrogels via Light-Modulated Internal Stress Fields

The 3D shape-changing hydrogels are highly pursued for numerous applications.However,up to now,the construction of complex 3D shape-changing hydrogels remains a challenge.The reported design strategies are mainly applied to fabricate 2D ones by introducing anisotropic microstructures into hydrogel sheets/membranes.Herein,we present a convenient photolithography strategy for constructing complex 3D shape-changing hydrogels by simultaneously modulating anisotropic microstructures and internal stress fields of gel sheets.When the precursor solution containing ultraviolet(UV)absorber is irradiated by single-side UV light,the attenuated polymerization rate can cause the generation of asymmetric internal stress field in the resulting hydrogel sheet.In the meantime,the directional diffusion of unpolymerized monomers allows for the formation of vertical gradient structure within hydrogel.Therefore,by applying different photomasks to modulate the local gradient structures and internal stress fields of the gel sheets,they can spontaneously transform into various complex 3D shape-changing hydrogels in the air.Response to the external stimuli,these 3D shape-changing hydrogels(e.g.,fighter plane,birdie,and multi-storey origami lattices)can deform in a novel 3D_(1)-to-3D_(2)-to-3D_(3)mode.This new design strategy contributes to the development of complex biomedical implants and soft robotics.

Harnessing the collective properties of nanoparticle ensembles for cancer theranostics

单个无机的 nanoparticles (NP ) 广泛地在药交货，癌症成像和治疗的地里被使用了。仍然有许多障碍，为这些应用程序限制单个 NP 的性能。高度订的 NP 整体的利用打开一扇门解决这些问题，由于他们的新或先进的集体性质。装配 NP 在单个基于 NP 的系统上显示出几个优点，例如指向的改进房间成为主观和肿瘤，提高的 multimodality 成像能力，优异联合治疗从 synergistic 产生完成，从由进原来的小 NP 积木的集会的降级的整个身体的可能的完全的清理等等。在这评论，我们讨论由拿 plasmonic 为癌症成像和治疗利用装配 NP 整体的潜力 Au NP 的小囊的集会作为一个例子。我们首先总结最近的开发在 plasmonic 自己组装从 amphiphilic 的 NP 的小囊的结构拴住聚合物的 NP 积木。我们进一步为癌症成像考察 NP 的 plasmonic 泡的利用(例如多光子导致了光， photothermal，和 photoacoustic 成像) ，并且癌症治疗(例如， photothermal 治疗，和化疗) 。最后，我们沿着这根线构画出当前的挑战和我们的观点。

Influence of the rolling-resistance-based shape of coarse particles on the shear responses of granular mixtures

Shear responses of dense granular mixtures of spherical coarse particles with the rolling resistance and spherical fine particles are studied via triaxial compression tests using the discrete element method.The macroscale responses(shear strength and dilatancy)are examined.Comparing the results with those in the literature indicates that granular mixtures with a rolling resistance coefficient of 0.5 have similar macroscale responses to those of gravel-shaped coarse particle mixtures.We quantify the microscale responses including the percentage contributions of contact types,partial coordination number,average particle rotation,average degree of interlocking,and local structural properties,A detailed analysis of the force-fabric anisotropy reveals the mechanisms of the variations in the shear strength with the rolling resistance coefficient and the fines content.The mechanism of the variation in the shear strength with the fines content for granular mixtures with a rolling resistance coefficient of 0.5 is different from that for gravel-shaped coarse particle mixtures.Finally,we find that a rolling resistance linear model weakens the linear relationship between the stress ratio and the fabric anisotropy of strong and non-sliding contacts when the fines content is 30% and 40%.

Shear behaviours of cohesionless mixed soils using the DEM:The influence of coarse particle shape

The coarse particles in mixed soils can be cobbles or gravels,with the main difference being their roundness(an indicator describing particle shape characteristics at an intermediate scale).The influence of coarse particle shape(i.e.,roundness)on the macroscopic and microscopic shear behaviours of cohesionless mixed soils with various fines contents(FCs)was investigated via the discrete element method in this study.The shapes of coarse particles were formed using the rotation-invariant spherical harmonic method proposed by previous investigators.An equation was proposed to predict the initial void ratios of samples in this study.A decrease in the roundness of coarse particles can increase the peak friction angle(FC≤40%)and critical friction angle(FC≤30%).As the roundness of coarse particles decreases,the peak dilatancy angle initially increases and then decreases(FC≤20%).Furthermore,it was found that the roundness of coarse particles hardly affects the classification of cohesionless mixed soils,as determined by probing the percentage contributions of coarse-coarse,coarse-fine,and fine-fine contacts.When cohesionless mixed soils change from an underfilled structure to an interactive-underfilled structure at the critical state,the main forms of coarse-coarse contacts were discovered.Additionally,the force-fabric anisotropy mechanisms of the influences of the roundness and rolling resistance coefficient of coarse particles on the shear strengths of cohesionless mixed soils were found to be different.

Discrete element simulation of effects of multicontact loading on single particle crushing

Particle crushing commonly occurs in granular materials and affects their structures and mechanical properties.Unlike idealized particles in experimental single particle crushing tests with two loading points,natural particles are crushed under multicontact loading.To date,the criteria and patterns of par-ticle crushing under multicontact conditions are not fully understood.By using the three-dimensional discrete element method,this report explores the effect of multicontact loading on the crushing criterion of a single particle,the crushing pattern,and the relationship between the particle crushing strength and loading distribution.The particles are modelled as aggregates of glued Voronoi polyhedra.The numer-ical results indicate that the logarithm of the mean principal stress has a good linear correlation with the coordination number.For a specific coordination number,the number of child particles presents a significant normal distribution.For a specific number of child particles,the volumes of child particles can be statistically described as normal or gamma distribution.Three typical models are proposed to qual-itatively analyse the relationship between the loading distribution and crushing strength.The relevant conclusions can be helpful in engineering practice and in further studies on crushable granular materials via the discrete element method.

Effect of particle type on the shear behaviour of granular materials

In discrete element method(DEM)simulations,multi-sphere(MS)clumped and convex particles are two main particle models that are used to study the mechanical behaviours of granular materials.Of interest is the evaluation of the effect of multiple contacts between clumped particles or single contacts between convex particles on the mechanical behaviours of granular materials.In this context,a series of drained triaxial compression tests were conducted on convex true(CT)ellipsoids and MS ellipsoids with aspect ratios(ARs)ranging from 1.0-2.0.The microscale results indicate that at a given AR,the critical friction angleφ_(c)changes with the particle type,whereas the peak friction angleφ_(p)is nearly independent of the particle type.The anisotropic analysis provides underlying mechanisms of the shear strength evolution from two perspectives.First,the anisotropies of granular materials are essential to shear strength as the deviatoric(q)-to-effective mean(p′)stress ratio can be expressed as the sum of the anisotropies,i.e.,q/p'≈0.4a_(c)+0.4a_(n)+0.6a_(t),where ac,an and at are the normal contact anisotropy,normal contact force anisotropy and tangential contact force anisotropy,respectively.For all samples,a_(c)and a_(n)underpin the shear strength and are influenced by the particle type.The similarφ_(p)displayed by the CT and MS ellipsoids does not translate to similar a_(n)and a_(c)but similar a_(c)+a_(n)for the two particle types.In addition,owing to their larger a_(c)+a_(n),the CT ellipsoids have a higherφ_(c)than the MS ellipsoids.Second,there is a satisfactory linear relationship between q/p'and ac within strong and non-sliding(sn)contacts a_(c)^(sn)(i.e.,q/p′=ka_(c)^(sn)),where k is the fitting parameter.Accordingly,in the peak state,the subtle difference in shear strength is attributed to the greater acsn in the CT ellipsoids than in the MS ellipsoids that is counteracted by the smaller k.However,in the critical state,the greater difference in a_(c)^(sn)between the CT and MS ellipsoids is partially offset by the smaller difference in k,causing a higherφ_(c)in the CT ellipsoids than in the MS ellipsoids.

Effect of local non-convexity on the critical shear strength of granular materials determined via the discrete element method

Multi-sphere clumps are commonly used to simulate non-spherical particles in discrete element method simulations.It is of interest whether the degree of local non-convexity λ affects the mechanical behaviour of granular materials with the same non-convexity η.A series of discrete-element-method biaxial shear tests are conducted on rough particle packings with rη=0.075 and different λ values(ranging from 0.134 to 0.770).The microscale results show that the contact type changes with an increase in λ.However,the critical strength is independent of λ.The evaluation of the contributions of different contact types to the critical shear strength and a detailed analysis of the anisotropies help clarify the microscopic mechanisms that result in the independence of the critical shear strength from λ.

金属在高分子-金纳米颗粒复合纳米链上的区域选择性生长（英文）

模板法是可控合成复合纳米材料的一种重要手段.然而,纳米材料在模板,尤其是复合模板上的选择性生长仍面临巨大挑战.本文以自组装聚乙烯-金纳米颗粒一维复合纳米链为软-硬复合模板,实现金属在该模板上可控地选择性沉积、生长.通过选择恰当的表面活性剂来调节金属生长的热力学,金属可以选择性地生长在金纳米颗粒的表面,得到金属间歇包覆的复合纳米链;也可以同时包覆在聚乙烯和金纳米颗粒的表面,得到金属完全包覆的豌豆荚状复合纳米链.不同的包覆方式和包覆材料选择都会导致材料光学性质的变化.时间差分有限元模拟表明,金包覆的豌豆荚状复合纳米链的表面金壳层和内部金纳米颗粒之间存在极强的表面等离子体耦合作用.在表面增强拉曼实验中,该复合纳米链表现出很强的增强信号.

Reservoir Characteristics and Controlling Factors of Silurian Lower Kepingtage Formation in Tahe Area, Tarim Basin, NW China

With the breakthrough of exploration in Well TP16-1, the lower Kepingtage Formation becomes a key target for petroleum exploration of deep clastic reservoir in Tahe area. In this paper we focused on the research of the reservoir characteristics and its controlling factors in two sub-member formations（S1k11 and S1k13）. Based on X-ray diffraction, conventional physical properties data（porosity and permeability） and reservoir storage space data（casting thin section and scanning electron microscope）, we determined that the S1k1 Formation belongs to extra-low porosity and permeability reservoir, although the upper S1k13 Formation shows relative better physical characteristic than the lower S1k11 Formation. The development of storage space in the study area is controlled by sedimentary microfacies, diagenesis process. Reservoirs in S1k1 Formation are mainly located in channel（S1k11 sandstones） and sand flat（S1k13 sandstones）. The sand flat sediments with a more coarse grain size compared with the channel. In diagenesis, compaction is the major controlling factor for reducing the porosity, followed by cementation. Dissolution of diagenesis is the major controlling factor in enhancing the reservoir porosities. Compared with channel（S1k11） sandstones, sand flat sandstones（S1k13） have better reservoir quality for its weaker compaction, cementation and stronger dissolution. On the basis of sedimentary characteristics（grain size and subfacies）, physical property（porosity and permeability） and reservoir storage space, we divide the S1k1 reservoir into three categories（I, II and III）. Type I reservoir is high quality reservoir. It is mainly distributed in the south area of S1k11 and S1k13 reservoir. Type II is moderate reservoir. It is located in the middle of S1k11 reservoir and in the north of S1k13 reservoir. Type III is the poor reservoir. It is only located in the north of S1k11 reservoir.

DEM investigation of strain behaviour and force chain evolution of gravel-sand mixtures subjected to cyclic loading

The strain characteristic and load transmission of mixed granular matter are different from those of homogeneous granular matter.Cyclic loading renders the mechanical behaviours of mixed granular mat-ter more complex.To investigate the dynamic responses of gravel-sand mixtures,the discrete element method(DEM)was used to simulate the cyclic loading of gravel-sand mixtures with low fines contents.Macroscopically,the evolution of the axial strain and volumetric strain was investigated.Mesoscopi-cally,the coordination number and contact force anisotropy were studied,and the evolution of strong and weak contacts was explored from two dimensions of loading time and local space.The simulation results show that increasing fines content can accelerate the development of the axial strain and vol-umetric strain but has little effect on the evolution of contact forces.Strong contacts tend to develop along the loading boundary,presenting the spatial difference.Weak contacts are firstly controlled by confining pressure and then controlled by axial stress,while strong contacts are mainly controlled by axial stress throughout the whole cyclic loading.Once compression failure occurs,the release of axial stress causes the reduction of strong contact proportion in all local regions.These findings are helpful to understand the dynamic responses of gravel-sand mixtures,especially in deformation behaviours and the Spatio-temporal evolution of contact forces.