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Shield construction will cause the fluidization of soft soil which is characterized by flow plasticity. This paper presents two theoretical models of soil flow behavior based on a fluid mechanics framework to understand the behavior of soft soil during shield tunneling, especially under the shearing action of the shield skin and the cutting wheel. The characteristics of the flow field are discussed, and their relationships with shield construction parameters such as advancing speed, cutting wheel rotation, applied thrust and torque, and water content are analyzed, while the proposed theory is verified by the results of a numerical simulation. Considering the shear-thinning effect of the soil, a closed four-stage shear path to describe the complete process of the soil behavior during shield tunneling is further interpreted. The results indicate that the sheared region produced by the rotating cutting wheel was larger than that produced by the shield shell shearing and that it was significantly affected by soil properties and tunneling parameters. In addition, it is concluded that the sheared region was significantly expanded due to the shear-thinning effect.

It is sometimes inevitable to cut the parts within the designed tunnel alignment of foundation reinforced concrete (RC) piles with cutting tools of soft ground shield machines when tunneling in densely populated areas. Cutters employed to cut the RC piles of the soft ground shield machines must be modified to do the work. Based on the construction of cutting 14 large diameter RC piles of Guangji Bridge in Suzhou metro construction, damages and wear of the modified rippers to cut the RC piles is thoroughly examined. A test of using the modified rippers to cut two cast-in-place RC piles was conducted to explore the feasibility of the cutting work. Based on the test, height differences between the rippers, and between the rippers and the scrapers were arranged. An analysis of damages and wear of the modified rippers was performed considering cutter installation radii and the arranged height differences. Due to the excessive and repetitive forces acted on the height-increased rippers, breakages of the carbide inserts at the two sides of the cutter top dominated and the damaged cutters suffered substantial wear. Wear amounts of the rippers increased with the increases of their installation radii, and they were in direct variations.

Part I of this study presented a computational model-based approach for enhancing the performance of solid oxide fuel cells (SOFCs) with designed microarchitecture. The performance of such SOFCs was predicted to greatly improve through a systematic computational design and optimization approach. Part II here proves through experimental fabrication and characterization that microarchitectured SOFC performance can be improved as predicted by the model. A real and specific SOFC is chosen, fabricated and characterized to demonstrate the proof-of-concept. Fabrication techniques using sintering and laser ablation are demonstrated. Pore size and geometry are characterized by interferometry-based surface profilometry and scanning electron microscopy. SOFC button cell performance testing including power output performance and electrochemical impedance spectroscopy are performed. The results show that SOFC performance in a microarchitectured cell can be improved over a baseline button cell by 9–17% in current density and by 7–19% in power density.

The photopolymerization of suspensions of ceramic powders in monomer solutions is the fundamental step for forming techniques where a liquid suspension is solidified with UV light. The photopolymerization behavior is determined by the properties of the monomer and photoinitiator and by the transport of photons in the suspension. Photon transport in suspensions involves scattering from the particle and absorption by photoinitiators and inert dyes. The photopolymerization behavior is related to the formulation of the suspensions. Proper formulations are discussed for several applications. Techniques for characterization include cure depth measurements, photocalorimetry, and photorheology.

A simple two-step method of fabricating vertically aligned and periodically distributed ZnO nanowires on gallium nitride (GaN) substrates is described. The method combines laser interference ablation (LIA) and low temperature hydrothermal decomposition. The ZnO nanowires grow heteroepitaxially on unablated regions of GaN over areas spanning 1 cm 2 , with a high degree of control over size, orientation, uniformity, and periodicity. High resolution transmission electron microscopy and scanning electron microscopy are utilized to study the structural characteristics of the LIA-patterned GaN substrate in detail. These studies reveal the possible mechanism for the preferential, site-selective growth ofthe ZnO nanowires. The method demonstrates high application potential for wafer-scale integration into sensor arrays, piezoelectric devices, and optoelectronic devices.

We have developed a patterning procedure based on selective ablation using interference patterns with ns-laser pulses to fabricate periodic arrays on large areas of poly(3,4-ethylene dioxythiophene)-poly(4-styrene sulfonic acid) (PEDOT-PSS) thin films over a metallic gold–palladium layer. Single pulse laser-ablation experiments were performed to study the ablation characteristics of the thin films as a function of the film thickness. The ablation threshold fluence of the PEDOT-PSS films was found to be dependent on thickness with values ranging from 43 mJ/cm 2 to 252 mJ/cm 2 . Additionally, fluences at which the PEDOT-PSS films could be ablated without inducing damage in the underlying metallic films were observed (128 mJ/cm 2 and 402 mJ/cm 2 for film thicknesses of 70 nm and 825 nm, respectively). Linear periodic arrays with line spacings of 7.82 μm and 13.50 μm were also fabricated. The surface topography of these arrays was analyzed using scanning electron and atomic force microscopy. For thicker polymeric layers, several peeled sub-layers of the conjugated polymer with average thicknesses of about 165–185 nm were observed in the ablation experiments. The size and scale of structures produced by this technique could be suitable for several biomedical applications and devices in which controlling cell adhesion, promoting cell alignment, or improving biocompatibility are important.

We report on the laser interference patterning of as-spun block copolymer films on silicon and silicon dioxide substrates. Our process involves the use of a pulsed laser light source of 266 nm wavelength and any type of diblock copolymer as a positive tone photoresist, resulting in the generation of sub-micron domains of different geometries and periodicity. This non-solvent based method is robust, and when combined with the inherent nano-scaled periodicity in block copolymers, can produce hierarchical patterns on substrates with potential use in the electronics and semiconductor industries.

PS-b-PEO block co-polymers have been reported to form cylindrical, lamellar, gyroidic, and supramolecular architectures due to several reasons: some of the reasons include the chemical incompatibility between the lipophilic and lipophobic covalently cross-linked blocks resulting in a high Flory-Huggins interaction parameter, the annealing solvent, and the interfacial boundary conditions between the substrate and the phase separating blocks. We report here for the first time on the spontaneous formation of nanopores and nanorings in PS-b-PEO block co-polymers. The mean size and depth of the pores are about 150nm and 40nm, respectively, while the pores occur randomly placed in clusters of about 2-5 pores. The pore clusters leave behind a breath-like architecture replicated by the phase separating block co-polymer. These breath architectures, in the shape of nanorings, are formed during the initial period of phase separation and do not disappear after phase separation has been achieved, leaving behind a PS-enriched circular framework. The diameter of the nanorings is in the 200-700nm range, as measured from AFM phase and height images. This range falls within the reported size of water droplets forming breath structures on polymer films. The resulting nanoarchitectured materials could find potential applications where biocompatibility and water permeability of the PEO block within the nanopores is desirable. In addition, the slightly elevated nanorings could also provide semi-enclosed barriers that can serve as micro/nano-enclosed cell and tissue cultures.

A method for the large-scale fabrication of patterned organic nanowire (NW) arrays is demonstrated by the use of laser interference patterning (LIP) in conjunction with inductively coupled plasma (ICP) etching. The NW arrays can be fabricated after a short ICP etching of periodic patterns produced through LIP. Arrays of NWs have been fabricated in UV-absorbent polymers, such as PET (polyethylene terephthalate) and Dura film (76% polyethylene and 24% polycarbonate), through laser interference photon ablation and in UV transparent polymers such as PVA (polyvinyl acetate) and PP (polypropylene) through laser interference lithography of a thin layer of photoresist coated atop the polymer surface. The dependence of the structure and morphology of NWs as a function of initial pattern created by LIP and the laser energy dose in LIP is discussed. The absence of residual photoresist atop the NWs in UV-transparent polymers is confirmed through Raman spectroscopy.

This article presents an effective approach for patterned growth of vertically aligned ZnO nanowire (NW) arrays with high throughput and low cost at wafer scale without using cleanroom technology. Periodic hole patterns are generated using laser interference lithography on substrates coated with the photoresist SU-8. ZnO NWs are selectively grown through the holes via a low-temperature hydrothermal method without using a catalyst and with a superior control over orientation, location/density, and as-synthesized morphology. The development of textured ZnO seed layers for replacing single crystalline GaN and ZnO substrates extends the large-scale fabrication of vertically aligned ZnO NW arrays on substrates of other materials, such as polymers, Si, and glass. This combined approach demonstrates a novel method of manufacturing large-scale patterned one-dimensional nanostructures on various substrates for applications in energy harvesting, sensing, optoelectronics, and electronic devices.

In this article, we report on the fabrication of periodic arrays using multibeam laser interference patterning (MLI) with both nanosecond and femtosecond lasers on hydrogel materials. Configurations involving two, four, and five laser beams were utilized being able to produce a wide range of periodic arrays.

In this Letter, we report on the experimental development and computational modeling of a simple, one-step method for the fabrication of diverse 2D and 3D periodic nanostructures derived from gold films on silicon substrates and over areas spanning 1 cm2. These nanostructures can be patterned on films of thickness ranging from 50 nm to 500 nm with pulsed interfering laser beams. A finite volume-based inhomogeneous multiphase model of the process shows reasonable agreement with the experimentally obtained topographies and provides insights on the flow physics including normal and radial expansion that results in peeling of film from the substrate.

We report on the formation of hierarchical nanostructures of Au, PtOx, FexOy and PdOx using a hybrid technique by combining laser interference ablation (LIA) and block copolymer phase separation (BCPS). Different types of hierarchical arrays can be obtained including square, triangular, linear and circular arrays by varying the loading time of the block co-polymer with metallic salts, and the laser interference technique. The primary ordering of the as-generated nanoarrays (30-100 nm) is tunable by changing either the composition of the block copolymer spun from solution or by changing other parameters that affect the phase separation kinetics of the block copolymer, while the secondary ordering of the features can be tuned from 200 nm to 2 μm, by changing the angle of convergence of the laser beams on the patterned substrate. Such a robust method can be applied to the fabrication of other metallic and ceramic materials including Ag, Co, and Ni (O) and has potential use in the large scale fabrication of hierarchical arrays of catalysts that can be used to grow germanium, silicon nanowires using the vapour-liquid-solid growth (VLS) technique. The as-generated arrays can also find use in optical as well as sensor applications for biodetection and biosensing.

A single-step method for the fabrication of large-area microlens arrays on flexible polycarbonate sheets is described. On areas of approximately 1 cm2, 17 million to 120 million microlenses ranging in size from sub-micrometer to several micrometers are fabricated via deep-UV pulsed laser interference ablation. The uniformity and surface quality of fabricated microlens arrays are examined and confirmed through atomic force microscopy and scanning electron microscopy. Optical imaging performance of the microlenses, and their use in massively parallel, pulsed laser nanofabrication on silicon is demonstrated. The microlens arrays can be fabricated in a matter of seconds, suggesting the potential for fast and low-cost production on flexible plastic substrates.

We report on rapid fabrication of two-dimensional periodic structures in pentaerythritol triacrylate (PETIA) through laser interference patterning with 10 ns pulses from a frequency-tripled Nd:YAG laser emitting at 355 nm. Different periodic arrays including line-, cross-, honeycomb-, and dotlike structures were fabricated using two and three interfering laser beams. The composition of the photoinitiator was changed from 2% to 15% w/w to determine the threshold laser fluences necessary to photopolymerize the PETIA solution. The effects of the PETIA layer thickness and periodic geometries on the mechanical stability of the fabricated structures as well as self-organization processes are reported.

The growth of semiconductor ZnO nanowires in a periodic fashion is of great interest for many applications such as solar cells, field emission devices, light emitting diodes, and piezo-nanogenerators. Novel laser interference lithography techniques for the site-selective growth of ZnO nanowires on Gallium Nitride (GaN) substrate are described. A nanosecond pulsed Nd:YAG laser with 266nm wavelength is used in the experiments. Both laser interference ablation of GaN substrates and laser interference lithography of photoresist masks on GaN substrates are conducted to control the position and periodicity of grown individual ZnO nanowires. Simulations of both processes are presented. The nanowires, grown using a low temperature hydrothermal decomposition method on both types of substrates, follow the designed pattern, with a high degree of control in size, dimensionality, and uniformity. Well patterned and aligned individual ZnO nanowires on areas spanning one square-centimeter scale and onesquare-decimeter scale can be achieved by laser interference ablation and lithography respectively.The growth of semiconductor ZnO nanowires in a periodic fashion is of great interest for many applications such as solar cells, field emission devices, light emitting diodes, and piezo-nanogenerators. Novel laser interference lithography techniques for the site-selective growth of ZnO nanowires on Gallium Nitride (GaN) substrate are described. A nanosecond pulsed Nd:YAG laser with 266nm wavelength is used in the experiments. Both laser interference ablation of GaN substrates and laser interference lithography of photoresist masks on GaN substrates are conducted to control the position and periodicity of grown individual ZnO nanowires. Simulations of both processes are presented. The nanowires, grown using a low temperature hydrothermal decomposition method on both types of substrates, follow the designed pattern, with a high degree of control in size, dimensionality, and uniformity. Well patterned and aligned individual ZnO nanowires on areas spanning one square-centimeter scale and onesquare-decimeter sc...