A Gibbs‐energy‐barrier‐based computational micro‐sphere model for the simulation of martensitic phase‐transformations

We introduce a material model for the simulation of polycrystalline materials undergoing solid‐to‐solid phase‐transformations. As a basis, we present a scalar‐valued phase‐transformation model where a Helmholtz free energy function depending on volumetric and deviatoric strain measures is assigned to each phase. The analysis of the related overall Gibbs energy density allows for the calculation of energy barriers. With these quantities at hand, we use a statistical‐physics‐based approach to determine the resulting evolution of volume fractions. Though the model facilitates to take into account an arbitrary number of solid phases of the underlying material, we restrict this work to the simulation of phase‐transformations between an austenitic parent phase and a martensitic tension and compression phase. The scalar model is embedded into a computational micro‐sphere formulation in view of the simulation of three‐dimensional boundary value problems. The final modelling approach necessary for macroscopic simulations is accomplished by a finite element formulation, where the local material behaviour at each integration point is governed by the response of the micro‐sphere model.Copyright © 2014 John Wiley & Sons, Ltd.     

Moving‐least‐squares‐particle hydrodynamics—I. Consistency and stability

The Smooth‐Particle‐Hydrodynamics (SPH) method is derived in a novel manner by means of a Galerkin approximation applied to the Lagrangian equations of continuum mechanics as in the finite‐element method. This derivation is modified to replace the SPH interpolant with the Moving‐Least‐Squares (MLS) interpolant of Lancaster and Saulkaskas, and define a new particle volume which ensures thermodynamic compatibility. A variable‐rank modification of the MLS interpolants which retains their desirable summation properties is introduced to remove the singularities that occur when divergent flow reduces the number of neighbours of a particle to less than the minimum required. A surprise benefit of the Galerkin SPH derivation is a theoretical justification of a common ad hoc technique for variable‐h SPH. The new MLSPH method is conservative if an anti‐symmetric quadrature rule for the stiffness matrix elements can be supplied. In this paper, a simple one‐point collocation rule is used to retain similarity with SPH, leading to a non‐conservative method. Several examples document how MLSPH renders dramatic improvements due to the linear consistency of its gradients on three canonical difficulties of the SPH method: spurious boundary effects, erroneous rates of strain and rotation and tension instability. Two of these examples are non‐linear Lagrangian patch tests with analytic solutions with which MLSPH agrees almost exactly. The examples also show that MLSPH is not absolutely stable if the problems are run to very long times. A linear stability analysis explains both why it is more stable than SPH and not yet absolutely stable and an argument is made that for realistic dynamic problems MLSPH is stable enough. The notion of coherent particles, for which the numerical stability is identical to the physical stability, is introduced. The new method is easily retrofitted into a generic SPH code and some observations on performance are made. Copyright © 1999 John Wiley & Sons, Ltd.     

Virion‐Like Membrane‐Breaking Nanoparticles with Tumor‐Activated Cell‐and‐Tissue Dual‐Penetration Conquer Impermeable Cancer

Poor drug penetration into tumor cells and tissues is a worldwide difficulty in cancer therapy. A strategy is developed for virion‐like membrane‐breaking nanoparticles (MBNs) to smoothly accomplish tumor‐activated cell‐and‐tissue dual‐penetration for surmounting impermeable drug‐resistant cancer. Tailor‐made dendritic arginine‐rich peptide prodrugs are designed to mimic viral protein transduction domains and globular protein architectures. Attractively, these protein mimics self‐assemble into virion‐like nanoparticles in aqueous solution, having highly ordered secondary structure. Tumor‐specific acidity conditions would activate the membrane‐breaking ability of these virion‐like nanoparticles to perforate artificial and natural membrane systems. As expected, MBNs achieve highly efficient drug penetration into drug‐resistant human ovarian (SKOV3/R) cancer cells. Most importantly, the well‐organized MBNs can pass through endothelial/tumor cells and spread from one cell to another one. Intravenous injection of MBNs into nude mice bearing impermeable SKOV3/R tumors suggests that the MBNs can recognize the tumor tissue after prolonged blood circulation, evoke the membrane‐breaking function for robust transvascular extravasation, and penetrate into the deep tumor tissue. This work provides the first demonstration of sophisticated molecular and supramolecular engineering of virion‐like MBNs to realize the long‐awaited cell‐and‐tissue dual‐penetration, contributing to the development of a brand‐new avenue for dealing with incurable cancers.     

A Dual‐Organic‐Transistor‐Based Tactile‐Perception System with Signal‐Processing Functionality

Organic‐device‐based tactile‐perception systems can open up new opportunities for the next generation of intelligent products. To meet the critical requirements of artificial perception systems, the efficient construction of organic smart elements with integrated sensing and signal processing functionalities is highly desired, but remains a challenge. This study presents a dual‐organic‐transistor‐based tactile‐perception element (DOT‐TPE) with biomimetic functionality by the construction of organic synaptic transistors with integrated sensing transistors. The unique geometry of the DOT‐TPE permits instantaneous sensing of pressure stimuli and synapse‐like processing of an electric signal in a single element. More importantly, these organic‐transistor‐based tactile‐perception elements can be built into arrays to serve as bionic tactile‐perception systems. The combined biomimetic functionality of tactile‐perception systems, together with their promising features of flexibility and large‐area fabrication, makes this work represent a step forward toward novel e‐skin devices for artificial intelligence.     

Templated Sub‐100‐nm‐Thick Double‐Gyroid Structure from Si‐Containing Block Copolymer Thin Films

The directed self‐assembly of diblock copolymer chains (poly(1,1‐dimethyl silacyclobutane)‐block‐polystyrene, PDMSB‐b‐PS) into a thin film double gyroid structure is described. A decrease of the kinetics of a typical double‐wave pattern formation is reported within the 3D‐nanostructure when the film thickness on mesas is lower than the gyroid unit cell. However, optimization of the solvent‐vapor annealing process results in very large grains (over 10 µm²) with specific orientation (i.e., parallel to the air substrate) and direction (i.e., along the groove direction) of the characteristic (211) plane, demonstrated by templating sub‐100‐nm‐thick PDMSB‐b‐PS films.     

A Colloidal‐Quantum‐Dot‐Based Self‐Charging System via the Near‐Infrared Band

A novel self‐charging platform is proposed using colloidal‐quantum‐dot (CQD) photovoltaics (PVs) via the near‐infrared (NIR) band for low‐power electronics. Low‐bandgap CQDs can convert invisible NIR light sources to electrical energy more efficiently than wider spectra because of reduced thermalization loss. This energy‐conversion strategy via NIR photons ensures an enhanced photostability of the CQD devices. Furthermore, the NIR wireless charging system can be concealed using various colored and NIR‐transparent fabric or films, providing aesthetic freedom. Finally, an NIR‐driven wireless charging system is demonstrated for a wearable healthcare bracelet by integrating a CQD PVs receiver with a flexible lithium‐ion battery and entirely embedding them into a flexible strap, enabling permanent self‐charging without detachment.     

A Role of α′ Martensite Introduced by Thermo‐Mechanical Treatment in Improving Shape Memory Effect of an Fe‐Mn‐Si‐Cr‐Ni Alloy

The evolution of α′ martensite with different thermo‐mechanical treatment and its effect on the shape memory effect were studied in an Fe‐14Mn‐5Si‐8Cr‐4Ni alloy. The α′ martensite was introduced by only 5% pre‐deformation, and its amount increased with increasing pre‐deformation up to 20%. The α′ martensite started to transform into austenite when the annealing temperature was 773 K. As the annealing temperature increased to 1 073 K, the α′ martensite almost transformed fully into austenite. The α′ martensite introduced by the thermo‐mechanical treatment could prevent collisions between different ε martensite bands during deformation. The intrusion of α′ martensite was another key reason that the stress‐induced ε martensite bands in Fe‐Mn‐Si based shape memory alloys formed in a domain‐specific manner in addition to that of uniformly distributed stacking faults after thermo‐mechanical treatment.     

A Retina‐Like Dual Band Organic Photosensor Array for Filter‐Free Near‐Infrared‐to‐Memory Operations

Human eyes use retina photoreceptor cells to absorb and distinguish photons from different wavelengths to construct an image. Mimicry of such a process and extension of its spectral response into the near‐infrared (NIR) is indispensable for night surveillance, retinal prosthetics, and medical imaging applications. Currently, NIR organic photosensors demand optical filters to reduce visible interference, thus making filter‐free and anti‐visible NIR imaging a challenging task. To solve this limitation, a filter‐free and conformal, retina‐inspired NIR organic photosensor is presented. Featuring an integration of photosensing and floating‐gate memory modules, the device possesses an acute color distinguishing capability. In general, the retina‐like photosensor transduces NIR (850 nm) into nonvolatile memory and acts as a dynamic photoswitch under green light (550 nm). In doing this, a filter‐free but color‐distinguishing photosensor is demonstrated that selectively converts NIR optical signals into nonvolatile memory.     

Quasi‐Solid‐State Single‐Atom Transistors

The single‐atom transistor represents a quantum electronic device at room temperature, allowing the switching of an electric current by the controlled and reversible relocation of one single atom within a metallic quantum point contact. So far, the device operates by applying a small voltage to a control electrode or “gate” within the aqueous electrolyte. Here, the operation of the atomic device in the quasi‐solid state is demonstrated. Gelation of pyrogenic silica transforms the electrolyte into the quasi‐solid state, exhibiting the cohesive properties of a solid and the diffusive properties of a liquid, preventing the leakage problem and avoiding the handling of a liquid system. The electrolyte is characterized by cyclic voltammetry, conductivity measurements, and rotation viscometry. Thus, a first demonstration of the single‐atom transistor operating in the quasi‐solid‐state is given. The silver single‐atom and atomic‐scale transistors in the quasi‐solid‐state allow bistable switching between zero and quantized conductance levels, which are integer multiples of the conductance quantum G₀ = 2e²/h. Source–drain currents ranging from 1 to 8 µA are applied in these experiments. Any obvious influence of the gelation of the aqueous electrolyte on the electron transport within the quantum point contact is not observed.     

Interface‐Directed Self‐Assembly of Cell‐Laden Microgels

Cell‐laden hydrogels show great promise for creating engineered tissues. However, a major shortcoming with these systems has been the inability to fabricate structures with controlled micrometer‐scale features on a biologically relevant length scale. In this Full Paper, a rapid method is demonstrated for creating centimeter‐scale, cell‐laden hydrogels through the assembly of shape‐controlled microgels or a liquid–air interface. Cell‐laden microgels of specific shapes are randomly placed on the surface of a high‐density, hydrophobic solution, induced to aggregate and then crosslinked into macroscale tissue‐like structures. The resulting assemblies are cell‐laden hydrogel sheets consisting of tightly packed, ordered microgel units. In addition, a hierarchical approach creates complex multigel building blocks, which are then assembled into tissues with precise spatial control over the cell distribution. The results demonstrate that forces at an air–liquid interface can be used to self‐assemble spatially controllable, cocultured tissue‐like structures.     

A contact detection algorithm for multi‐sphere particles by means of two‐level‐grid‐searching in DEM simulations

In discrete element method simulations, multi‐sphere particle is extensively employed for modeling the geometry shape of non‐spherical particle. A contact detection algorithm for multi‐sphere particles has been developed through two‐level‐grid‐searching. In the first‐level‐grid‐searching, each multi‐sphere particle is represented by a bounding sphere, and global space is partitioned into identical square or cubic cells of size D, the diameter of the greatest bounding sphere. The bounding spheres are mapped into the cells in global space. The candidate particles can be picked out by searching the bounding spheres in the neighbor cells of the bounding sphere for the target particle. In the second‐level‐grid‐searching, a square or cubic local space of size (D + d) is partitioned into identical cells of size d, the diameter of the greatest element sphere. If two bounding spheres of two multi‐sphere particles are overlapped, the contacts occurring between the element spheres in the target multi‐sphere particle and in the candidate multi‐sphere particle are checked. Theoretical analysis and numerical tests on the memory requirement and contact detection time of this algorithm have been performed to verify the efficiency of this algorithm. The results showed that this algorithm can effectively deal with the contact problem for multi‐sphere particles. Copyright © 2015 John Wiley & Sons, Ltd.     

NIR‐Responsive Polycationic Gatekeeper‐Cloaked Hetero‐Nanoparticles for Multimodal Imaging‐Guided Triple‐Combination Therapy of Cancer

Responsive multifunctional organic/inorganic nanohybrids are promising for effective and precise imaging‐guided therapy of cancer. In this work, a near‐infrared (NIR)‐triggered multifunctional nanoplatform comprising Au nanorods (Au NRs), mesoporous silica, quantum dots (QDs), and two‐armed ethanolamine‐modified poly(glycidyl methacrylate) with cyclodextrin cores (denoted as CD‐PGEA) has been successfully fabricated for multimodal imaging‐guided triple‐combination treatment of cancer. A hierarchical hetero‐structure is first constructed via integration of Au NRs with QDs through a mesoporous silica intermediate layer. The X‐ray opacity and photoacoustic (PA) property of Au NRs are utilized for tomography (CT) and PA imaging, and the imaging sensitivity is further enhanced by the fluorescent QDs. The mesoporous feature of silica allows the loading of a typical antitumor drug, doxorubicin (DOX), which are sealed by the polycationic gatekeepers, low toxic hydroxyl‐rich CD‐PGEA/pDNA complexes, realizing the co‐delivery of drug and gene. The photothermal effect of Au NRs is utilized for photothermal therapy (PTT). More interestingly, such photothermal effect also induces a cascade of NIR‐triggered release of DOX through the facilitated detachment of CD‐PGEA gatekeepers for controlled chemotherapy. The resultant chemotherapy and gene therapy for glioma tumors are complementary for the efficiency of PTT. This work presents a novel responsive multifunctional imaging‐guided therapy platform, which combines fluorescent/PA/CT imaging and gene/chemo/photothermal therapy into one nanostructure.     

Spontaneous Structuration in Coacervate‐Based Protocells by Polyoxometalate‐Mediated Membrane Assembly

Molecularly crowded, polyelectrolyte/ribonucleotide‐enriched membrane‐free coacervate droplets are transformed into membrane‐bounded sub‐divided vesicles by using a polyoxometalate‐mediated surface‐templating procedure. The coacervate to vesicle transition results in reconstruction of the coacervate micro‐droplets into novel three‐tiered micro‐compartments comprising a semi‐permeable negatively charged polyoxometalate/polyelectrolyte outer membrane, a sub‐membrane coacervate shell, and an internal aqueous lumen. We demonstrate that organic dyes, ssDNA, magnetic nanoparticles and enzymes can be concentrated into the interior of the micro‐compartments by sequestration into the coacervate micro‐droplets prior to vesicle formation. The vesicle‐encapsulated proteins are inaccessible to proteases in the external medium, and can be exploited for the spatial localization and coupling of two‐enzyme cascade reactions within single or between multiple populations of hybrid vesicles dispersed in aqueous media.     

Ultrahigh‐Water‐Content,Superelastic, and Shape‐Memory Nanofiber‐Assembled Hydrogels Exhibiting Pressure‐Responsive Conductivity

High‐water‐content hydrogels that are both mechanically robust and conductive could have wide applications in fields ranging from bioengineering and electronic devices to medicine; however, creating such materials has proven to be extremely challenging. This study presents a scalable methodology to prepare superelastic, cellular‐structured nanofibrous hydrogels (NFHs) by combining alginate and flexible SiO₂ nanofibers. This approach causes naturally abundant and sustainable alginate to assemble into 3D elastic bulk NFHs with tunable water content and desirable shapes on a large scale. The resultant NFHs exhibit the integrated properties of ultrahigh water content (99.8 wt%), complete recovery from 80% strain, zero Poisson's ratio, shape‐memory behavior, injectability, and elastic‐responsive conductivity, which can detect dynamic pressure in a wide range (>50 Pa) with robust sensitivity (0.24 kPa^?1) and durability (100 cycles). The fabrication of such fascinating materials may provide new insights into the design and development of multifunctional hydrogels for various applications.     

Vakuum‐Drehdurchführungen mit Magnetflüssigkeitsdichtungen. Magnetic‐liquid‐sealed vacuum rotary feedthrough

Most vacuum manufacturing processes require some type of motion to take place within the chamber. A magnetic liquid sealed feedthrough is a device that transmits rotary motion into a vacuum chamber with minimal torque requirements and minimal contamination level. The are widely employed in high and ultra‐high vacuum conditions, such as: semiconductor fabrication industry, coating equipment, high power X‐ray generators, robotics applications and the others. In the paper is given principle of operation of a magnetic liquid seal and various standard and special designs of vacuum rotary feedthroughs, sealed with magnetic liquid are described.     

Microstructures and corrosion resistance of as‐cast aluminum‐10 wt.% silicon and aluminum‐20 wt.% silicon alloys

The microstructures and corrosion resistance of two as‐cast alloys, aluminum‐10 wt.% silicon hypoeutectic alloy and aluminum‐20 wt.% silicon (weight percent) hypereutectic alloy are investigated by conventional casting, the scanning electron microscope equipped with oxford X‐ray energy dispersive spectroscopy system and transmission electron microscope are applied for analysis. The results show that the microstructures change from the strip‐like into lump shape with the increase of silicon content from 10 % to 20 %. The electrochemical polarization curves prove that the aluminum‐20 wt.% hypereutectic silicon alloy had the better resistance with the corrosion potential of ?1.414 V and corrosion current density of 5.41 ? 10^?5 ampere compared with the aluminum‐10 wt.% silicon hypoeutectic alloy.     

Self‐Assembly of Enzyme‐Like Nanofibrous G‐Molecular Hydrogel for Printed Flexible Electrochemical Sensors

Conducting hydrogels provide great potential for creating designer shape‐morphing architectures for biomedical applications owing to their unique solid–liquid interface and ease of processability. Here, a novel nanofibrous hydrogel with significant enzyme‐like activity that can be used as “ink” to print flexible electrochemical devices is developed. The nanofibrous hydrogel is self‐assembled from guanosine (G) and KB(OH)₄ with simultaneous incorporation of hemin into the G‐quartet scaffold, giving rise to significant enzyme‐like activity. The rapid switching between the sol and gel states responsive to shear stress enables free‐form fabrication of different patterns. Furthermore, the replication of the G‐quartet wires into a conductive matrix by in situ catalytic deposition of polyaniline on nanofibers is demonstrated, which can be directly printed into a flexible electrochemical electrode. By loading glucose oxidase into this novel hydrogel, a flexible glucose biosensor is developed. This study sheds new light on developing artificial enzymes with new functionalities and on fabrication of flexible bioelectronics.     

Temperature‐Enhanced Solvent Vapor Annealing of a C3 Symmetric Hexa‐peri‐Hexabenzocoronene: Controlling the Self‐Assembly from Nano‐ to Macroscale

Temperature‐enhanced solvent vapor annealing (TESVA) is used to self‐assemble functionalized polycyclic aromatic hydrocarbon molecules into ordered macroscopic layers and crystals on solid surfaces. A novel C₃ symmetric hexa‐peri‐hexabenzocoronene functionalized with alternating hydrophilic and hydrophobic side chains is used as a model system since its multivalent character can be expected to offer unique self‐assembly properties and behavior in different solvents. TESVA promotes the molecule's long‐range mobility, as proven by their diffusion on a Si/SiO_x surface on a scale of hundreds of micrometers. This leads to self‐assembly into large, ordered crystals featuring an edge‐on columnar type of arrangement, which differs from the morphologies obtained using conventional solution‐processing methods such as spin‐coating or drop‐casting. The temperature modulation in the TESVA makes it possible to achieve an additional control over the role of hydrodynamic forces in the self‐assembly at surfaces, leading to a macroscopic self‐healing within the adsorbed film notably improved as compared to conventional solvent vapor annealing. This surface re‐organization can be monitored in real time by optical and atomic force microscopy.     

Nanoporous Al‐Ni‐Co‐Ir‐Mo High‐Entropy Alloy for Record‐High Water Splitting Activity in Acidic Environments

Ir‐based binary and ternary alloys are effective catalysts for the electrochemical oxygen evolution reaction (OER) in acidic solutions. Nevertheless, decreasing the Ir content to less than 50 at% while maintaining or even enhancing the overall electrocatalytic activity and durability remains a grand challenge. Herein, by dealloying predesigned Al‐based precursor alloys, it is possible to controllably incorporate Ir with another four metal elements into one single nanostructured phase with merely ≈20 at% Ir. The obtained nanoporous quinary alloys, i.e., nanoporous high‐entropy alloys (np‐HEAs) provide infinite possibilities for tuning alloy's electronic properties and maximizing catalytic activities owing to the endless element combinations. Particularly, a record‐high OER activity is found for a quinary AlNiCoIrMo np‐HEA. Forming HEAs also greatly enhances the structural and catalytic durability regardless of the alloy compositions. With the advantages of low Ir loading and high activity, these np‐HEA catalysts are very promising and suitable for activity tailoring/maximization.     

Mesoporous‐Silica‐Coated Up‐Conversion Fluorescent Nanoparticles for Photodynamic Therapy

Near‐infrared (NIR)‐to‐visible up‐conversion fluorescent nanoparticles have potential to be used for photodynamic therapy (PDT) in deep tissue because NIR light can penetrate thick tissue due to weak absorption in the optical window. Here a uniform layer of mesoporous silica is coated onto NaYF₄ up‐converting nanocrystals, with a large surface area of ≈770 m² g^?1 and an average pore size of 2 nm. A photosensitizer, zinc phthalocyanine, is incorporated into the mesoporous silica. Upon excitation by a NIR laser, the nanocrystals convert NIR light to visible light, which further activates the photosensitizer to release reactive singlet oxygen to kill cancer cells. The photosensitizer encapsulated in mesoporous silica is protected from degradation in the harsh biological environment. It is demonstrated that the photosensitizers loaded into the porous silica shell of the nanoparticles are not released out of the silica while they continuously produce singlet oxygen upon excitation by a NIR laser. The nanoparticles are reusable as the photosensitizers encapsulated in the silica are removed by soaking in ethanol.