Montmorillonite based artificial nacre prepared via a drying process

Taking advantage of the specific behaviour of Na/Ca montmorillonite in aqueous dispersion, textured films were prepared by progressive evaporation of dispersions with low concentrations of delaminated platelets. The increase of the concentration of ions during evaporation changes the nature of the clay mineral platelet face interactions from repulsive to attractive. After complete drying, a dense brick-like structure is obtained when a sodium salt is used as deflocculant.

The bending strength of the textured film is strongly affected by cracks formation during drying, specially when the sample thickness increases. After optimisation, crack-free textured samples with a 140 μm thickness, 20 cm × 25 cm area and 120 MPa bending strength were obtained.     

An efficient biomimetic assembly of a macroscopic polyhedral shell from identical subunits

A model system is presented for efficiently assembling a convex polyhedral shell from identical subunits under agitation. The system draws upon two elements of viral assembly. First, the subunits have built-in instructions for shell formation. Second, a flexible template—equivalent to the viral genome—is used to capture the subunits and then orchestrate their assembly into the final structure. Capturing the subunits on the template was achieved by shaking them (1.5 shell equivalents) onto the template lying extended in a shallow planar cavity. Agitating the template/subunit complex in a tumbler resulted in it rapidly folding (seconds). The complete assembly process, which is mediated by reversible magnetic bonds, took approximately 10 s to 5 min, and always resulted in the formation of a closed shell. When the subunits were agitated in the tumbler in the absence of template, a complete shell was produced only 10% of the time. Although the model system as demonstrated here generates a macroscopic dodecahedral shell, the principle could be applied to other polyhedra containing larger numbers of subunits and the system as a whole automated and miniaturised to build optically interesting structures or autonomous electronic devices.     

An advanced fabrication route for alkali silicate glass by non-firing process

An amorphous silica powder surface was treated separately and combining mechanical and chemical treatment processes. The raw silica powder was mechanically modified using a planetary type mill at a rotation speed of 200 rpm for 15 min using a 5 mm size ball. The raw and the mechanically modified silica powders were hydrothermally treated for 5, 15 and 24 h lengths of time. Silanol surface groups successfully produced by the treatments were measured by diffuse reflectance infrared fourier transform (DRIFT) spectroscopy. The results show that the combination of mechanical and chemical, so call mechanochemical treatment, is the most efficient in enhancing the quantity of surface silanol groups. The mechanochemically treated powder was used for the fabrication of glass. Silica glasses were successfully fabricated without firing by mixing the treated powders with KOH 5 M solutions. Morphology and transparency of the obtained glasses were analyzed using SEM and UV–VIS–NIR techniques. Possible mechanism reactions of powder surface activation occurring during the mechanochemical and condensation processes are also discussed.     

An efficient adaptive EWMA control chart for monitoring the process mean

In recent years, the memory‐type control charts—exponentially weighted moving average (EWMA) and cumulative sum (CUSUM)—along with the adaptive and dual control‐charting structures have received considerable attention because of their excellent ability in providing an overall good detection over a range of mean‐shift sizes. These adaptive memory‐type control charts include the adaptive exponentially weighted moving average (AEWMA), dual CUSUM, and adaptive CUSUM charts. In this paper, we propose a new AEWMA chart for efficiently monitoring the process mean. The idea is to first design an unbiased estimator of the mean shift using the EWMA statistic and then adaptively update the smoothing constant of the EWMA chart. The run length profiles of the proposed AEWMA chart are computed using extensive Monte Carlo simulations. Based on a comprehensive comparative study, it turns out that the proposed AEWMA chart performs better than the existing AEWMA, adaptive CUSUM, dual CUSUM, and Shewhart‐CUSUM charts, in terms of offering more balanced protection against mean shifts of different sizes. An example is also used to explain the working of the existing and proposed control charts.     

An optimized process for fabrication of high-aspect-ratio photoresist-derived carbon microelectrode array on silicon substrate

An optimized process was developed for fabrication of high-aspect-ratio photoresist-derived carbon microelectrode array on silicon substrate. This process consisted of conventional photolithography, three-step linear pyrolyzing process and micromechanical interlocking. Comparing with previous two-step pyrolysis, three-step linear pyrolysis process can better preserve the geometry of microstructure during pyrolysis, and micromechanical interlocking was introduced to improve bonding strength between carbon microstructure and substrate. As a result, it can be achieved that high-aspect-ratio carbon microelectrode array remained upright and robustly with substrate. The experimental results confirmed that the optimized process is very effective, and the technology will be helpful for integration of 3-dimensional carbon-based devices in the fields of bioMEMS and electrochemical analysis.     

An efficient hybrid artificial bee colony algorithm for disassembly line balancing problem with sequence-dependent part removal times

This study deals with a sequence-dependent disassembly line balancing problem by considering the interactions among disassembly tasks, and a multi-objective mathematical model is established. Subsequently, a novel hybrid artificial bee colony algorithm is proposed to solve the problem. A new rule is used to initialize a bee colony population with certain diversity, and a dynamic neighbourhood search method is introduced to guide the employed/onlooker bees to promising regions. To rapidly leave the local optima, a global learning strategy is employed to explore higher quality solutions. In addition, a multi-stage evaluation method is designed for onlookers to effectively select employed bees to follow. The performance of the proposed algorithm is tested on a set of benchmark instances and two case scenarios, and the results are compared with several other metaheuristics in terms of solution quality and computation time. The comparisons demonstrate that the proposed algorithm exhibits superior performance.     

A geometry controllable approach for the fabrication of biomimetic hierarchical structure and its superhydrophobicity with near-zero sliding angle

A simple, geometry controllable method is presented for fabricating multiscale hierarchical polymer structures that exhibit superhydrophobic water-repellent properties with near-zero sliding angle over a large area. A UV-assisted micromolding technique is used to create a microtexture with an ultraviolet (UV)-curable resin containing Al(2)O(3) nanoparticles. A subsequent treatment of ultraviolet ozone (UVO) leads to the formation of nanoscale roughness over the as-formed microstructured surface, resulting in a dual-scale surface texture similar to a lotus leaf, in a reproducible manner. After hydrophobization with a self-assembled monolayer (SAM) in the liquid phase, this hierarchical surface exhibits stable superhydrophobic characteristics, having a water contact angle close to 160° and a contact angle (CA) hysteresis as low as 1°. These characteristics did not change even after exposure to ambient conditions for 6?months.     

Chemical liquid deposition process for microstructure fabrication

Scientists and engineers are currently moving into a new era to develop precise and intelligent mini-structures and microsystems. The study of mini-structures and microsystems is a rapidly growing area of research with a great potential to accomplish useful tasks in numerous applications. In this paper, a new fabrication technology for microstructures based on the chemical liquid deposition (CLD) is presented. This technology is based on the following principles: micro-droplets of a cold (room temperature) solution or liquid reactant are sprayed from a nozzle and make contact with a hot substrate, the droplets will evaporate, decompose, or react, and then the reacted solid products will deposit on the substrate. By controlling the motion of the nozzle and the spray time, a desired 3D microstructure of the deposited material can be formed through a layer-by-layer scanning technique. The working principle, available materials as well as the process control and modeling is discussed and some preliminary results are presented.     

Formation of opaque films by biomimetic process

The preparation of opaque white films with amorphous aluminium polyphosphate, crystalline calcium carbonate and poly(vinyl acetate) latex is described. Film optical properties were characterized by diffuse reflectance spectrophotometry; morphological film features were examined by SEM, TEM, STM and AFM. Domain organization and void formation were detected, with dimensions of the same order of magnitude as the wavelength of visible light and can thus account for the film optical properties. Calcium carbonate consumption was monitored by X-ray diffraction and is assigned to a chemical reaction with aluminium polyphosphate, in which a mixed Al-Ca carbonate-polyphosphate is formed. The process of film opacification is interpreted as a result of dispersion, chemical reaction and orientation of solid inorganic particles within the polymer network during the film drying process. A model is proposed for void formation, based on volume contraction of the swollen inorganic particles, at a stage when their rigid surfaces are bound to the polymeric matrix. This revised version was published online in November 2006 with corrections to the Cover Date.     

An efficient process to reduce infrastructure vulnerabilities facing malevolence

In daily life, we are all used to frequent ‘systems’: public transports, industrial parks, shopping areas, stadiums or many others. And with the exponential increase of technologies, we are now living in a kind of ‘open World’ within which goods, persons or information are moving increasingly faster. The consequence is an amazing new way of life and also a number of new threats for our society. To insure the security of all citizens, and also of infrastructures, national skills or anything else, we need to secure our systems efficiently. To do so, we need appropriate tools to accurately analyze vulnerabilities in order to counter all kinds of malevolence. After giving an overview of different methods linked to that problem, we will explain our process to analyze the vulnerabilities of a complex infrastructure and what points are fundamental to take into account facing human aggressions.     

Facile fabrication of gold nanoparticle arrays for efficient surface-enhanced Raman scattering

An effective and facile method for the fabrication of a surface-enhanced Raman scattering (SERS)-active film with closely packed gold nanoparticle (AuNP) arrays is proposed by self-assembly of different sizes (16, 25, 40 and 70?nm) of AuNPs at a toluene/water interface with ethanol as the inducer. The as-prepared AuNP arrays exhibit efficient Raman scattering enhancement, and the enhancement factors estimated using p-aminothiophenol as a probe molecule range from 10(5) to 10(7). This is attributed to the coupling electromagnetic SERS enhancement mechanism with additional localization field within closely packed AuNPs, which have greater SERS activity and reproducibility than that on aggregates and on self-assembled monolayers of isolated AuNPs on glass.     

Comparison of nacre with other ceramic composites

Mother-of-pearl, the highly filled ceramic composite of mollusc shell, is compared with other, less highly filled, artificial ceramics. Stiffness is fairly simply related to volume fraction of ceramic, but no model seems to be adequate to describe this relationship. Strength, stress-intensity factor and the work of fracture are also dependent on the ceramic content but in a much more complex manner. Nacre has the highest value for all these parameters.     

An application of artificial neural networks for modeling formaldehyde emission based on process parameters in particleboard manufacturing process

Volatile organic compounds refer to a large class of carbon-based chemicals capable of evaporating easily into the air at room temperature. Formaldehyde is one of the best known volatile organic compounds, and long-term exposure to formaldehyde emission from wood-based building products in indoor air may cause many adverse health effects. This paper presents an implementation of artificial neural networks for modeling the formaldehyde emission from particleboard as a wood-based product based on wood-glue moisture content, density of board and pressing temperature, with the experimental data collected from Petinarakis and Kavvouras (Wood Res 51(1):31–40, 2006). With the constructed model, formaldehyde emission of particleboard could be predicted successfully, and the intermediate formaldehyde emission values not obtained from experimental investigation could be predicted for different combinations of manufacturing parameters. The results proved that the artificial neural network is a promising technique in predicting the formaldehyde emission from particleboard. In this regard, the findings of this study will help the manufacturing industries in obtaining the intermediate values of the formaldehyde emission without performing further experimental activity. The model thus may save time, reduce the consumption of experimental materials and design costs.     

Multivariate statistical process control with artificial contrasts

A multivariate control region can be considered to be a pattern that represents the normal operating conditions of a process. Reference data can then be generated and used to learn the difference between this region and random noise. Then multivariate statistical process control can be converted to a supervised learning task. This can dramatically reshape the control region and open the control problem to a rich collection of supervised learning tools. Such tools provide generalization error estimates that can be used to specify error rates. The effectiveness of such an approach is shown here. Such a computational approach is now easily accomplished with modern computing resources. Examples use random forests and a regularized least squares classifier as the learners.     

Computer-aided process planning for fabrication of three-dimensional microstructures for bioMEMS applications

In recent years, there has been increasing interest from both academies and industries in developing micro-electromechanical system (MEMS) technology for biological applications, known as bioMEMS or biochips. Targeting at high throughput biomolecule analysis, drug compound screening, and reduction of reagent and sample volume, today's bioMEMS devices come with miniaturised design and increased complexity of microstructures. Fabrication of such a complex bioMEMS structure involves a number of layer fabrication cycles. Moreover, a two-dimensional (2D) mask is required for each process. Thus, manually generating such a complex process plan has become a difficult task. With recent advances in material technology, polydimethylsiloxane (PDMS) silicone material has been widely applied in nowadays bioMEMS fabrication. This paper proposes a novel automated process planning approach for fabrication of three-dimensional (3D) microstructures in bioMEMS. This approach can handle both PDMS casting and traditional micro fabrication processes. It integrates a novel solid decomposition method and a feasibility search algorithm. Also, it can directly handle the solid model of an integrated microstructure with B-rep representation, and automatically generate the data of the fabrication process plan along with masks. A process planner prototype has been implemented. An application example is presented to demonstrate the functionality of the prototype.     

一种制作沟槽型同位素微电池表面电极的新工艺

开发了一种利用SU8胶剥离工艺制作沟槽型同位素微电池表面电极的新工艺,通过使用BP212正胶作为牺牲层,有效地解决了在制作沟槽型同位素微电池表面电极时,堆胶以及沟槽中SU8胶不易去除的难题.该工艺操作简单、可靠,成本低,因此具有很大的实用价值.     

A two-step deposition process for electrode fabrication of CdZnTe detectors

The method of the electrode deposition process plays a vital role in determining the contact characteristics, which is often one of the dominant factors influencing the CdZnTe detector performance. In this work, a modified deposition process named two-step process for the electrode fabrication of CdZnTe detectors, was developed. This deposition process can dramatically increase the adhesion strength and reduce the inhomogeneity of the metal/semiconductor interface, and improve the detection ability of high energy radiation such as X-rays and gamma-rays. Scanning acoustic microscopy, shear tests, current-voltage test and energy spectra characteristics measurements were carried out in this work.     

A novel biomimetic catalyst constructed by axial coordination of hemin with PAN fiber for efficient degradation of organic dyes

A novel biomimetic catalyst was synthesized by supporting hemin onto the amidoximated polyacrylonitrile (PAN) fiber and then used for the oxidative degradation of organic dyes by H₂O₂ activation. SEM, FTIR and XPS results suggested that the OH and NH₂ in amidoxime groups were responsible for hemin immobilization through axial coordination bonds. The fibrous support significantly enhanced the catalytic activity and pH tolerance of pure hemin, and the prepared catalyst also exhibited excellent recycling capability. In addition, the effect of axial ligands on the catalytic mechanism was clarified by employing the modified PAN fiber with amidrazones groups as the support of hemin, and the possible catalytic mechanism was proposed and discussed based on the ESR measurement combined with a series of designed experiments. It is found that OH and NH₂ as axial ligands of hemin might induce H₂O₂ activation through two different pathways, corresponding to the generation of Fe(IV)=O and ^·OH species, respectively.     

Merger of structure and material in nacre and bone – Perspectives on de novo biomimetic materials

In contrast to synthetic materials, evolutionary developments in biology have resulted in materials with remarkable structural properties, made out of relatively weak constituents, arranged in complex hierarchical patterns. For instance, nacre from seashells is primarily made of a fragile ceramic, yet it exhibits superior levels of strength and toughness. Structural features leading to this performance consist of a microstructure organized in a hierarchical fashion, and the addition of a small volume fraction of biopolymers. A key to this mechanical performance is the cohesion and sliding of wavy ceramic tablets. Another example is bone, a structural biological material made of a collagen protein phase and nanoscopic mineral platelets, reaching high levels of toughness and strength per weight. The design and fabrication of de novo synthetic materials that aim to utilize the deformation and hardening mechanism of biological materials such as bone or nacre is an active area of research in mechanics of materials. In this review, our current knowledge on microstructure and mechanics of nacre and bone are described, and a review of the fabrication of nacre-inspired artificial and related materials is presented. Both experimental and simulation approaches are discussed, along with specific examples that illustrate the various approaches. We conclude with a broader discussion of the interplay of size effects and hierarchies in defining mechanical properties of biological materials.     

Graphene resist interlacing process for versatile fabrication of free-standing graphene

We present a graphene resist interlacing process (GRIP) to sandwich graphene between polymer lines in a cloth-like fashion, making it more accessible for experiments and applications. We demonstrate the handling of large-area graphene in this way. Here, GRIP is used to fabricate supports for transmission electron microscopy. These supports improve the imaging quality of nanoparticles, as we show by comparison to imaging on standard lacey carbon supports.