Probing the dynamic evolution of catalyst structure and chemical state under operating conditions is highly important for investigating the reaction mechanism of catalysis more in depth, which in turn advances the rational design of redox catalysis in using renewable energy to produce fuels. Herein, the evolution of atomically dispersed Cu species supported by mesoporous TiO2 (mTiO2) during the in situ photocatalytic reduction of CO2 with H2O to valuable solar fuels has been reported. The results unveil that the initial atomically dispersed Cu­(II) undergoes reduction to Cu­(I) and ultimately to Cu(0); the Cu­(I)/Cu(0) mixture is proposed to be more effective for CH4 formation. In addition, the enhanced CO2 adsorption ability benefited from the structural advantage of mTiO2 and the elevated charge carrier transfer synergistically contributes to the CO2 photoreduction. It is anticipated that this work would guide the rational design of Cu-based light-harvesting catalysts for artificial CO2 reduction to value-added feedstocks and inspire further interest in using in situ techniques to study the structure–activity interplay of photocatalysts under operating reaction conditions.

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Carbon-MEMS (C-MEMS) have emerged as a new category of devices for micro/nano technology with many potential applications. Dielectrophoretic manipulation of micro/nanoparticles with C-MEMS is studied in this paper. Through electric field distribution modeling in carbon electrode array, we analyze the strongest simulation effect results of electric field in three dimensional (3-D) surface plots depicting the magnitude of electric field in various cross sections at different heights above the channel floor for 2, 10, 30 and 50 μm high carbon electrodes. It is represented here that maximum intensity of electric field generates with the equality between the height above the channel floor and the height of the electrodes. Simulation parameters involved are for dielectrophoretic manipulation of micro/nano particles based on 3-D C-MEMS. The advantages of using 3-D C-MEMS electrodes over other techniques of creating high-throughput systems for dielectrophoretic manipulation environment surrounded by micro/nano horizons are: (i) complex microscale 3-D electrodes with high-aspect ratios can easily be shaped and patterned using conventional lithography (ii) carbon has a high window of stability thus allowing application of higher voltages (iii) there is no need for bulk micromachining or patterning electrodes on multiple planes (iv) the distance between electrodes can precisely be controlled through the lithography process. FEMLAB 3.4 Multiphysics Modeling software (COMSOL, Stockholm, Sweden) is used for the modeling of electric fields and one-layer C-MEMS microelectrode array was fabricated with SU-8 photoresist.

Engineering medical applications are enriched by the fabrication potential of the growing technology of Micro-Electro-Mechanical Systems (MEMS). Within this technological expansion, device manufacturing costs, failure and long-term performance reliability are critical issues that have to be resolved using basic probabilistic design methodologies which are yet largely unexploited by industrial and service companies at the mature innovation level. Modeling and testing of high-performance MEMS is a promising route, based upon these methodologies, to enhancing reliability and preventing surface failure. In this paper, we focus on the modeling of the mechanical properties of MEMS, as exemplified by a capacitive accelerometer, using probabilistic techniques. The accuracy of these techniques is also evaluated for the accelerometer with regard to those parameters that affect mainly reliability and failure. The simulated analysis of the mechanical properties is performed with easy-to-use probabilistic software known as “NESSUS”. It is concluded that probabilistic design methodologies are very effective and balanced for making design decisions that can, with both reliability and ease, ensure component or system efficiency.

It is critical to understand multiphase flow applications with regard to dynamic behavior. In this paper, a systematic approach to the study of these applications is pursued, leading to separated flows comprising the effects of free surface flows and wetting. For the first time, wetting phenomena (three wetting regimes such as no wetting, 90 º wetting angle and absolute wetting) are added in the separated flow model. Special attention is paid to computational fluid dynamics (CFD) in order to envisage the relationship between complex metallurgical practices such as mass and momentum exchange, turbulence, heat, reaction kinetics and electromagnetic fields. Simulations are performed in order to develop sub-models for studying multiphase flow phenomena at larger scales. The outcomes show that a proper mixture of techniques is valuable for constructing larger-scale models based upon sub-models for recreating the hierarchical structure of a detailed CFD model applicable throughout the process.

Micro/nano outcrops generated on hydrophobic surfaces are vital outcomes of the super-hydrophobic mechanism in the fabrication of miniature batteries, super-capacitors, field effect transistors and electrochemical and biological sensors. In systematized posts positioned on superhydrophobic surfaces, it is critical to alter the contact angle, whilst the retreating one depends upon the post size and spacing. In this paper, it is shown that calculation of the apparent surface free energy concerned with the probe liquid surface tension, and both advancing and receding contact angles (a and r respectively), is useful for bringing special attention to shedding more light on the wetting properties of superhydrophobic surfaces. A simulation is performed, in order to present this interesting phenomenon, which is in reasonable agreement with experiment. It is concluded that the computation supports categorizing the wetting phenomena as well as encouraging further progress in the fabrication of MEMS/NEMS structures with high efficiency, degree of precision, accuracy, uniformity, aspect ratio and through-put.

A growing scientific effort is being devoted to the study of nanoscale interface aspects such as thin-film adhesion, abrasive wear and nanofriction at surfaces by using the nanoscratching technique but there remain immense challenges. In this paper, a three-dimensional (3D) model is suggested for the molecular dynamics (MD) simulation and experimental verification of nanoscratching initiated from nano-indentation, carried out using atomic force microscope (AFM) indenters on Al-film/Si-substrate systems. Hybrid potentials such as Morse and Tersoff, and embedded atom methods (EAM) are taken into account together for the first time in this MD simulation (for three scratching conditions: e.g. orientation, depth and speed, and the relationship between forces and related parameters) in order to determine the mechanisms of nanoscratching phenomena. Salient features such as nanoscratching velocity, direction and depth - as well as indenter shape- and size-dependent functions such as scratch hardness, wear and coefficient of friction - are also examined. A remarkable conclusion is that the coefficient of friction clearly depends upon the tool rake-angle and therefore increases sharply for a large negative angle.

Silicon postsare fabricated by inductively coupled plasmaetching (ICP). Then, a SU-8 layer is spin-coated. During the photolithography, the opening areas of mask are aligned to the top surface of the underlying silicon posts.SU-8 fibers that interconnect the underlying silicon postsare created due to the mask-induced diffraction effect. After pyrolysis, SU-8 photoresist is transformedinto carbon, and as the results, carbon fibers that interconnect the underlying silicon postsare created.