Multi‐scale methods

In this paper four multiple scale methods are proposed. The meshless hierarchical partition of unity is used as a multiple scale basis. The multiple scale analysis with the introduction of a dilation parameter to perform multiresolution analysis is discussed. The multiple field based on a 1‐D gradient plasticity theory with material length scale is also proposed to remove the mesh dependency difficulty in softening/localization problems. A non‐local (smoothing) particle integration procedure with its multiple scale analysis are then developed. These techniques are described in the context of the reproducing kernel particle method. Results are presented for elastic‐plastic one‐dimensional problems and 2‐D large deformation strain localization problems to illustrate the effectiveness of these methods. Copyright © 2000 John Wiley & Sons, Ltd.     

Multi‐University Design Projects

We describe a multi‐university design project in which teams of students across different campuses collaborate on a design and manufacturing project. We show how such projects sensitize students to issues in concurrent engineering and train them in interpersonal skills, communications, and system integration. We believe that this approach allows us to simulate real‐world conditions by imposing realistic boundary conditions on the student teams.     

Light‐Activated,Multi‐Semiconductor Hybrid Microswimmers

Using a dynamic fabrication process, hybrid, photoactivated microswimmers made from two different semiconductors, titanium dioxide (TiO₂) and cuprous oxide (Cu₂O) are developed, where each material occupies a distinct portion of the multiconstituent particles. Structured light‐activated microswimmers made from only TiO₂ or Cu₂O are observed to be driven in hydrogen peroxide and water most vigorously under UV or blue light, respectively, whereas hybrid structures made from both of these materials exhibit wavelength‐dependent modes of motion due to the disparate responses of each photocatalyst. It is also found that the hybrid particles are activated in water alone, a behavior which is not observed in those made from a single semiconductor, and thus, the system may open up a new class of fuel‐free photoactive colloids that take advantage of semiconductor heterojunctions. The TiO₂/Cu₂O hybrid microswimmer presented here is but an example of a broader method for inducing different modes of motion in a single light‐activated particle, which is not limited to the specific geometries and materials presented in this study.     

Multi‐Fuel Driven Janus Micromotors

Here the first example of a chemically powered micromotor that harvests its energy from the reactions of three different fuels is presented. The new Al/Pd Janus microspheres—prepared by depositing a Pd layer on one side of Al microparticles—are propelled efficiently by the thrust of hydrogen bubbles generated from different reactions of Al in strong acidic and alkaline environments, and by an oxygen bubble thrust produced at their partial Pd coating in hydrogen peroxide media. High speeds and long lifetimes of 200 μm s^?1 and 8 min are achieved in strong alkaline media and acidic media, respectively. The ability to autonomously adapt to the presence of a new fuel (surrounding environment), without compromising the propulsion behavior is illustrated. These data also represent the first example of a chemically powered micromotor that propels autonomously and efficiently in alkaline environments (pH > 11) without additional fuels. The ability to use multiple fuel sources to power the same micromotor offers a broader scope of operation and considerable promise for diverse applications of micromotors in different chemical environments.     

Multi‐precision Laplace transform inversion

For the numerical inversion of Laplace transforms we suggest to use multi‐precision computing with the level of precision determined by the algorithm. We present two such procedures. The Gaver–Wynn–Rho (GWR) algorithm is based on a special sequence acceleration of the Gaver functionals and requires the evaluation of the transform only on the real line. The fixed Talbot (FT) method is based on the deformation of the contour of the Bromwich inversion integral and requires complex arithmetic. Both GWR and FT have only one free parameter: M, which is the number of terms in the summation. Both algorithms provide increasing accuracy as M increases and can be realized in a few lines using current Computer Algebra Systems. Copyright © 2004 John Wiley & Sons, Ltd.     

Multi‐Stable Mechanical Structural Materials

Energy absorbing is an important and desirable property in mechanical and civil engineering. Here, a proof‐of‐concept method is presented as a new approach to achieve artificial mechanical materials with tunable compressive behavior for energy absorbing constructed from unit cells with a snap fit structure. The artificial structure undergoes a series of stable configurations derived from the sequential insertion of the plug into the groove of the snap fit. Both, experimental and simulation results manifest the multi‐stable and tunable mechanical properties of the structure. The mechanical energy dissipated by the proposed structure is demonstrated to be dependent on the lead‐in angle of the snap fit and the deflection ratio of the groove, as well as on the coefficient of friction between the plug and the groove of the snap fit. The system designed, herein, exhibits mechanical properties that can be tuned not only by adjusting the geometric parameters, but also by tuning the coefficient of friction between the plug and the groove, allowing the mechanical properties to be tailored post‐fabrication. Furthermore, the proposed model can be extended to the macro‐, micro‐, or nanoscales. These findings provide a simple method to obtain artificial materials with tunable energy absorbing properties, which can be applied in areas such as the design of automobile bumpers and foldable devices that facilitate their transportation.

     

Women Engineering Students and Self‐Efficacy: A Multi‐Year,Multi‐Institution Study of Women Engineering Student Self‐Efficacy

As our nation's need for engineering professionals grows, educators and industry leaders are increasingly becoming concerned with how to attract women to this traditionally male career path. Self‐efficacy has been shown to be related to positive outcomes in studying and pursuing careers in non‐traditional fields. This paper describes the results of two years of engineering self‐efficacy data collected from women engineering students at five institutions across the U.S. This study adds to the growing body of self‐efficacy literature via its multi‐year, multi‐institution design and helps to clarify the impact of the engineering curriculum on self‐efficacy. Results indicate that while women students show positive progress on some self‐efficacy and related subscales, they show a significant decrease on feelings of inclusion from the first to second measurement period and further suggest a relationship between ethnicity and feelings of inclusion. Additionally, correlations show that self‐efficacy is related to women students' plans to persist in this predominantly male discipline.     

Multi‐Step Crystallization of Self‐Organized Spiral Eutectics

A method for the solidification of metallic alloys involving spiral self‐organization is presented as a new strategy for producing large‐area chiral patterns with emergent structural and optical properties, with attention to the underlying mechanism and dynamics. This study reports the discovery of a new growth mode for metastable, two‐phase spiral patterns from a liquid metal. Crystallization proceeds via a non‐classical, two‐step pathway consisting of the initial formation of a polytetrahedral seed crystal, followed by ordering of two solid phases that nucleate heterogeneously on the seed and grow in a strongly coupled fashion. Crystallographic defects within the seed provide a template for spiral self‐organization. These observations demonstrate the ubiquity of defect‐mediated growth in multi‐phase materials and establish a pathway toward bottom‐up synthesis of chiral materials with an inter‐phase spacing comparable to the wavelength of infrared light. Given that liquids often possess polytetrahedral short‐range order, our results are applicable to many systems undergoing multi‐step crystallization.     

Nonadditive Transport in Multi‐Channel Single‐Molecule Circuits

As stated in the classic Kirchhoff's circuit laws, the total conductance of two parallel channels in an electronic circuit is the sum of the individual conductance. However, in molecular circuits, the quantum interference (QI) between the individual channels may lead to apparent invalidity of Kirchhoff's laws. Such an effect can be very significant in single‐molecule circuits consisting of partially overlapped multiple transport channels. Herein, an investigation on how the molecular circuit conductance correlates to the individual channels is conducted in the presence of QI. It is found that the conductance of multi‐channel circuit consisting of both constructive and destructive QI is significantly smaller than the addition of individual ones due to the interference between channels. In contrast, the circuit consisting of destructive QI channels exhibits an additive transport. These investigations provide a new cognition of transport mechanism and manipulation of transport in multi‐channel molecular circuits.     

Multi‐level hp‐adaptivity for cohesive fracture modeling

Discretization‐induced oscillations in the load–displacement curve are a well‐known problem for simulations of cohesive crack growth with finite elements. The problem results from an insufficient resolution of the complex stress state within the cohesive zone ahead of the crack tip. This work demonstrates that the hp‐version of the finite element method is ideally suited to resolve this complex and localized solution characteristic with high accuracy and low computational effort. To this end, we formulate a local and hierarchic mesh refinement scheme that follows dynamically the propagating crack tip. In this way, the usually applied static a priori mesh refinement along the complete potential crack path is avoided, which significantly reduces the size of the numerical problem. Studying systematically the influence of h‐refinement, p‐refinement, and hp‐refinement, we demonstrate why the suggested hp‐formulation allows to capture accurately the complex stress state at the crack front preventing artificial snap‐through and snap‐back effects. This allows to decrease significantly the number of degrees of freedom and the simulation runtime. Furthermore, we show that by combining this idea with the finite cell method, the crack propagation within complex domains can be simulated efficiently without resolving the geometry by the mesh. Copyright © 2016 John Wiley & Sons, Ltd.     

Click‐Chemistry Based Multi‐Component Microarrays by Quill‐Like Pens

We demonstrate the generation of multi‐component spot microarrays by blotting different ink solutions via quill‐like pens. The obtained arrays are immobilized by click‐chemistry in form of the copper(I)‐catalyzed azide‐alkyne cycloaddition and remain stable against washing and immersion in aqueous solution. The average spot radius ranges from 10 to 20 μm and is about an order of magnitude smaller than in currently commercially applied arraying techniques, effectively bridging the gap to high resolution methods as dip‐pen nanolithography and polymer pen lithography. The use of the quill‐like‐pen‐generated spot microarrays as binding assay is demonstrated by capturing of streptavidin from solution and by bioactive sandwich structures from neutravidin and biotin‐labeled fibronectin. Thus, our multi‐component spot microarrays have ideal dimensions and biochemical properties to accommodate (single) cells. Additionally, the building up of the cell‐recruiting protein sandwich structure on top of the basic spot microarray allows for the highly selective adhesion of fibroblasts. This results then in ordered (single) cell arrays, demonstrating the bio‐compatibility and high throughput of this multi‐component spot microarray platform.     

Cooling‐Triggered Shapeshifting Hydrogels with Multi‐Shape Memory Performance

Heating‐triggered shape actuation is vital for biomedical applications. The likely overheating and subsequent damage of surrounding tissue, however, severely limit its utilization in vivo. Herein, cooling‐triggered shapeshifting is achieved by designing dual‐network hydrogels that integrate a permanent network for elastic energy storage and a reversible network of hydrophobic crosslinks for “freezing” temporary shapes when heated. Upon cooling to 10 °C, the hydrophobic interactions weaken and allow recovery of the original shape, and thus programmable shape alterations. Further, multiple temporary shapes can be encoded independently at either different temperatures or different times during the isothermal network formation. The ability of these hydrogels to shapeshift at benign conditions may revolutionize biomedical implants and soft robotics.