Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

We demonstrate a layer-by-layer processing scheme that can be utilized to create transparent superhydrophobic films from SiO2 nanoparticles of various sizes. By controlling the placement and level of aggregation of differently sized nanoparticles within the resultant multilayer thin film, it is possible to optimize the level of surface roughness to achieve superhydrophobic behavior with limited light scattering. Transparent superhydrophobic films were created by the sequential adsorption of silica nanoparticles and poly(allylamine hydrochloride). The final assembly was rendered superhydrophobic with silane treatment. Optical transmission levels above 90% throughout most of the visible region of the spectrum were realized in optimized coatings. Advancing water droplet contact angles as high as 160 degrees with low contact angle hysteresis (<10 degrees ) were obtained for the optimized multilayer thin films. Because of the low refractive index of the resultant porous multilayer films, they also exhibited antireflection properties.

Transparent superhydrophobic films based on silica nanoparticles

Inspired by the superhydrophobic lotus surface in nature, special wettability has attracted a lot of interest and attention in both academia and industry In this review, theoretical models and fabrication strategies of superhydrophobic textiles have been discussed in detail The strategies for constructing fabric surfaces with an anti-wetting property are categorized and discussed based on the morphology of particles coated on the textile fibre Such special wettability textile surfaces are demonstrated with self-cleaning, oil/water separation, self-healing, UV-blocking, photocatalytic, anti-bacterial, and flame-retardant performances Correspondingly, potential applications have been illustrated for self-cleaning, oil/water separation, asymmetric/anisotropic wetting janus fabric, microfluidic manipulation, and micro-templates for patterning In each section, representative studies are highlighted with emphasis on the special wetting ability and other relevant properties Finally, the difficulties and challenges for practical application were briefly discussed

/pdf/a-review-on-special-wettability-textiles-theoretical-models-3tl6y6tjp1.pdf

A review on special wettability textiles: theoretical models, fabrication technologies and multifunctional applications

DOI: 10.1002/admt.201800546 manufacturing processes and relatively high production cost.[12,13] PE has been explored for the manufacturing of flexible and stretchable electronic devices by printing functional inks containing soluble or dispersed materials,[14–16] which has enabled a wide variety of applications, such as transparent conductive films (TCFs), flexible energy harvesting and storage, thin film transistors (TFTs), electroluminescent devices, and wearable sensors.[17–24] The global PE market should reach $26.6 billion by 2022 from $14.0 billion in 2017 at a compound annual growth rate of 13.6%.[25] PE devices are manufactured by a variety of printing technologies. Typical printing technologies can be divided into two broad categories: noncontact patterning (or nozzle-based patterning) and contact-based patterning. The noncontact techniques include inkjet printing, electrohydrodynamic (EHD) printing, aerosol jet printing, and slot die coating, while screen printing, gravure printing, and flexographic printing are examples of the contact techniques. Each of these techniques has its own advantages and disadvantages, but they all rely on the principle of transferring inks to a substrate. Understanding the characteristics and recent advances of each printing technique is important to further the progress in PE. Moreover, to promote the lab-scale printing technologies to large-scale production process, roll-toroll (R2R) printing, which is one of the manufacturing methods to obtain large-area films with low cost and excellent durability, has drawn much attention from both industry and the research community. Nearly all of devices based on PE require conductive structures, interconnects, and contacts; therefore, highly conductive patterns, usually with high transparency and/or high resolution, fabricated by means of printing conductive materials are one of the most critical components in PE devices. Various printable conductive nanomaterials, such as metal nanomaterials (e.g., metal nanoparticles and metal nanowires) and carbon nanomaterials (e.g., graphene and carbon nanotubes (CNTs)), have been explored and used as major materials for PE. Applying printing technology to deposition of the conductive nanomaterials requires formulation of suitable inks. After depositing inks on different substrates, post-printing treatment, Printed electronics is attracting a great deal of attention in both research and commercialization as it enables fabrication of large-scale, low-cost electronic devices on a variety of substrates. Printed electronics plays a critical role in facilitating widespread flexible electronics and more recently stretchable electronics. Conductive nanomaterials, such as metal nanoparticles and nanowires, carbon nanotubes, and graphene, are promising building blocks for printed electronics. Nanomaterial-based printing technologies, formulation of printable inks, post-printing treatment, and integration of functional devices have progressed substantially in the recent years. This review summarizes basic principles and recent development of common printing technologies, formulations of printable inks based on conductive nanomaterials, deposition of conductive inks via different printing techniques, and performance enhancement by using various sintering methods. While this review places emphasis on conductive nanomaterials, the printing techniques and ink formulations can be applied to other materials such as semiconducting and insulating nanomaterials. Moreover, some applications of printed flexible and stretchable electronic devices are reviewed to illustrate their potential. Finally, the future challenges and prospects for printing conductive nanomaterials are discussed.

Printing Conductive Nanomaterials for Flexible and Stretchable Electronics: A Review of Materials, Processes, and Applications

Flexible electronics incorporate all the functional attributes of conventional rigid electronics in formats that have been altered to survive mechanical deformations. Understanding the evolution of device performance during bending, stretching, or other mechanical cycling is, therefore, fundamental to research efforts in this area. Here, we review the various classes of flexible electronic devices (including power sources, sensors, circuits and individual components) and describe the basic principles of device mechanics. We then review techniques to characterize the deformation tolerance and durability of these flexible devices, and we catalogue and geometric designs that are intended to optimize electronic systems for maximum flexibility.

Flexible electronics under strain: a review of mechanical characterization and durability enhancement strategies

https://dr.ntu.edu.sg/bitstream/10220/9448/1/64.%20A%20Study%20Towards%20Improving%20Mechanical%20Properties%20of%20Sol-Gel%20Coatings%20for%20Polycarbonate.pdf

A study towards improving mechanical properties of sol–gel coatings for polycarbonate

There has been intensive interest in studying the behavior of hard and brittle thin films on compliant substrates under scratch action. The examples include sol–gel protective coatings on plastic optical lenses, safe windows, and flexible electronic devices and displays. Hard ceramic coatings have been widely used to prolong the life of cutting tools and biomedical implants. In this work, the scratch resistance of sol–gel coatings with different amount of colloidal silica on polycarbonate substrates was tested by the pencil scratch test following the ISO 15184 standard. The scratch failure was found to be tensile trailing cracking in the coating and substrate gouging. The indentation hardness, elasticity modulus and fracture toughness of the coatings were determined and correlated to the observed pencil scratch hardness. Based on the analysis, the main factors to improve the scratch resistance are the elasticity modulus, thickness and fracture toughness of the coatings. General consideration for the improvement of scratch resistance of hard coatings on compliant substrates was also discussed.

/pdf/scratch-resistance-of-brittle-thin-films-on-compliant-1xff5met72.pdf

Scratch resistance of brittle thin films on compliant substrates

https://dr.ntu.edu.sg/bitstream/10220/9386/1/40.%20Quantitative%20Test%20Method%20for%20Evaluation%20of%20Anti-Fingerprint%20Property%20of%20Coated%20Surfaces.pdf

Quantitative test method for evaluation of anti-fingerprint property of coated surfaces

Transparent photochromic (PC) films can be used for smart window applications to partially block the sunlight and provide comfort vision However, for large area applications, the high cost and delicate manufacturing processes are the major challenges faced by the prior-art technologies This paper reports a development of cost effective PC coatings with effective reduction of visible light transmission and total energy transmittance at tinted states The coating material was prepared by embedding organic PC dyes, 1,2-b Naphthopyran, in sol-gel based organic-inorganic mesoporous coating matrix The degree of crosslinking of coating matrix and types of organic groups can effectively influence the visible light transmittance and bleaching speed Visible light transmission reduction at tinted state can be tuned from 30% to 60% by varying the dye concentration in coating and coating thickness The thermal properties of the PC coatings are evaluated by UV–Vis-NIR and FTIR measurements and further calculation to obtain solar heat gain coefficient (G value) and thermal transmittance (U value) For a glass in thickness of 3 mm coated with a PC layer in thickness of 12 μm, the G value at tinted state was reduced to 078 as compared with a G value of 087 for an uncoated glass A double glazed smart window prototype consisting of a commercial low-E glass and a PC coated glass showed G value of 026, and U value of 158 as compared to the G value of 087 and U value of 52 of a single uncoated glass This demonstrates a significant reduction of energy transmittance through the smart window resulting in high potential energy saving for end users especially in tropical climate

Sol-gel based photochromic coating for solar responsive smart window

We report a study on the treatment of flat glass surfaces by ambient air atmospheric pressure plasma, generated by a dielectric barrier discharge of coplanar arrangement of the electrode system—the diffuse coplanar surface barrier discharge (DCSBD). The plasma treatment of glass was performed in both static and dynamic modes. With respect to wettability of the glass surface, treatment in static mode resulted in non-uniform surface properties, whereas dynamic mode provided a fully uniform treatment. A water contact angle measurement was used to determine the efficiency of plasma treatments in dynamic mode and also to investigate a hydrophobic recovery of plasma treated glass surfaces. The X-ray photoelectron spectroscopy measurements showed a decrease of overall carbon concentrations after plasma treatment. A deconvolution of C1s peak, showed that a short plasma treatment led to decrease of C–C bonds concentration and increases of C–O and O–C=O bond concentrations. An enhancing influence of the glass surface itself on DCSBD diffuse plasma was observed and explained by different discharge onsets and changes in the electric field distribution.

Linda Y. L. Wu

Papers

A study towards improving mechanical properties of sol–gel coatings for polycarbonate

Scratch resistance of brittle thin films on compliant substrates

Quantitative test method for evaluation of anti-fingerprint property of coated surfaces

Sol-gel based photochromic coating for solar responsive smart window

Plasma Treatment of Glass Surfaces Using Diffuse Coplanar Surface Barrier Discharge in Ambient Air