Controlling three‐dimensional ice template via two‐dimensional surface wetting

Directional freezing (DF) is a fast, scalable, and environmental friendly technique for fabricating monoliths with long‐range oriented pores, which can be applied toward a wide variety of materials. However, the pore size is typically larger than 20 μm and cannot be spatially controlled, which prevent the technique from being used more widely. In this work, effect of wettability of the freezing substrate on the pore size of monolithic polyethylene glycol cryogels is studied. Smaller pores can be generated via more hydrophilic substrates, and tubular pores smaller 5 μm can be created using a poly(vinyl alcohol) coated copper substrate. A numerical fitting between water contact angle of the substrates and pore size is then obtained. Moreover, pore size can be locally varied duplicating wetting patterns of the substrates. The concept of using two dimensional patterns to build monoliths with three dimensional microstructures can probably be extended to other material systems. DF is an effecient and scalable processing method for fabricating materials with long‐range oriented pores. However, the smallest pore feature size reported is around 20 µm, which is in many cases too large for application such as separation and catalysis. We show here, with exemplary cryogels, that both spatial control and feature size reduction (by one order of magnitude) can be realized in DF by controlling the wettability of the ice growth substrate. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4186–4192, 2016     

Photopolymer resins for luminescent three‐dimensional printing

Liquid resins‐based three‐dimensional (3D) printing techniques such as stereolithography and digital light processing (DLP) show higher resolution and accuracy than other printing techniques, but their applications have been impeded by the limited materials selection and lack of functions. We here reported the preparation of luminescent resins for DLP‐based 3D printing. Homogeneous dispersion of the fluorescent dyes was achieved by small acrylate molecules screening, and the cure depth studies was used to optimize both resin composition and printing parameters setting. In addition, we showed that the optical analysis of absorption and emission spectra is an important tool to reduce the complex mutual‐interference of the light absorption of dye, photoinitiator and photo‐absorber in the printable resin. We also developed the mater batch technique to tune the emitting colors in the whole visible range, together with white emitting. By using the developed resins, different 3D structures with different emitting colors were successfully printed by DLP technique. These results will further widen the applications of the liquid resins‐based 3D printing techniques, and these luminescent resins show highly potential applications in education, lighting, UV converters, and so on. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44988.     

Electrospun three‐dimensional silk fibroin nanofibrous scaffold

Practical application to three‐dimensional (3‐D) tissue culture has been limited by the structural restriction of two‐dimensional (2‐D) nature of electrospun nanofiber mat. In this study, for constructing 3‐D nanofibrous structure as real 3‐D tissue engineering scaffold, we developed new fabrication process with silk fibroin (SF) by electrospinning and evaluated the features of this SF nanofiber scaffold (SFNS) through morphological and cell‐culture analyses. Foam type of the SFNS exhibited high porosity as well as large pores and its cell proliferation well occurred inside (inner spaces of pores), which makes this suitable for 3‐D cell‐culture scaffold. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Ionic‐liquid‐assisted three‐dimensional caged silica ablative nanocomposites

In this study, we demonstrated a novel three‐dimensional network of thermally stable fumed silica (FS)–resorcinol formaldehyde (RF) nanocomposites via an ionic‐liquid (IL)‐assisted in situ polycondensation process. The study involved subjecting the tailored nanocomposites to thermogravimetric analysis and oxyacetylene flame environment as per ASTM test standards for thermal ablative performance. X‐ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, high‐resolution transmission electron microscopy, Raman spectroscopy, and wettability studies were undertaken to underline the improvement correlation in the microstructure and material properties. Significant reductions in the linear ablation rate (66%) and mass ablation rate (26.6%), along with lower back‐face temperature profiles, marked enhanced ablative properties. The increased char yield (33.3%) and higher temperatures for weight losses evinced the improved thermal stability of the modified RF resin. The uniformly dispersed fused nanosilica with a glassy coating morphology on the ablative surface acted as barrier to oxidation. The results signify that the IL‐assisted modification of the RF resin with FS significantly enhanced ablative performance. A viable replacement to the conventional phenolic nanocomposites for thermal ablative applications to buy critical time for the containment and suppression of thermal‐heat‐flux threats is of paramount importance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45328.     

Munsell reflectance spectra represented in three‐dimensional Euclidean space

In this article we describe the results of an investigation into the extent to which the reflectance spectra of 1269 matt Munsell color chips are well represented in low dimensional Euclidean space. We find that a three dimensional Euclidean representation accounts for most of the variation in the Euclidean distances among the 1269 Munsell color spectra. We interpret the three dimensional Euclidean representation of the spectral data in terms of the Munsell color space. In addition, we analyzed a data set with a large number of natural objects and found that the spectral profiles required four basis factors for adequate representation in Euclidean space. We conclude that four basis factors are required in general but that in special cases, like the Munsell system, three basis factors are adequate for precise characterization. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 182–196, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10144     

Shear properties of three‐dimensional woven composite reinforcements

This paper presents a comprehensive experimental study and detailed mechanistic interpretations of the shear deformation of three‐dimensional (3D) reinforcements. Six types of 3D angle interlock glass fiber preforms (3DAP) were fabricated using a range of weave parameters including the fabric density, fabric layer, and yarn linear density. A modified picture frame was developed to ensure a pure shear load during the test. Through a series of comprehensive tests, our results demonstrated that the fabric density played a key role in the mechanical properties of 3DAP and that the reinforcements with low fabric density and yarn linear density were easy to shear. The shear deformation mechanism was analyzed based on the meso‐structure. It is expected that this research will provide preliminary work for building a theoretical model of 3D woven preform. POLYM. COMPOS., 38:244–251, 2017. © 2015 Society of Plastics Engineers     

Modeling viscoelastic secondary flows in three‐dimensional noncircular ducts

As process capabilities become more advanced, the need to predict flow phenomena at a smaller scale increases significantly. Viscoelastic secondary flows in square ducts were simulated using a finite volume approach. Single mode and multimode Giesekus and Phan‐Thien Tanner (PTT) models were implemented and were able to reproduce full three‐dimensional (3D) flow through a square duct. Results for low density polyethylene (LDPE), polystyrene, and polycarbonate are all in agreement with experiments [Dooley, Viscoelastic flow effects in multilayer polymer coextrusion, PhD Thesis, Technische Universiteit Eindhoven (2002)] as well as numerical results using a finite element method (FEM) and a meshless radial function method (RFM), [Lopez et al., SPE ANTEC Tech. Pap. (2010)]. The mathematical model presented here has shown the potential to model full 3D flow in more complex geometries. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Colour appearance shifts in two different‐sized viewing conditions

This study assessed the effect of size on colour appearance, using a colour matching paradigm where two sizes were presented in a setting similar to a normal colour selection interface. Twelve colours sampling the entire range of the colour spectrum were chosen as target stimuli. The target stimuli consisted of either a large (30° by 50°) or a small (0.5° by 0.5°) test field displayed on a cathode ray tube (CRT). In the experiment, a set of small colour samples consisting of the target and its neighboring colours was presented on the screen. Fifty‐seven participants were asked to pick a colour from the sample set that appeared to exactly match the target. Results in CIECAM02 showed a consistent increase in the apparent brightness (Q) but some decrease in saturation (s) for the larger field. Hue shifts were observed to form a systematic pattern. We noticed a discernable trend showing that, for targets of bluish or purplish colour hues, the accuracy of colour matching is lower and colour difference is greater in the condition of the large viewing field. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2010     

Experiments and progressive damage analyses of three‐dimensional full five‐directional braided composites under three‐point bending

Experimental and numerical studies on the bending properties of three‐dimensional full five‐directional (3DF5D) braided composites are presented in this article. Three‐point bending tests of the braided specimens with different braiding angles were first preformed. Then, the full‐scale specimen model was constructed and a strength analysis method based on repeated unit‐cell (RUC) model was established to describe the strength characteristics of the 3DF5D braided composites. The differences between yarn configurations in corner, surface and interior RUCs were considered and continuum damage models were introduced into the components such as yarns and matrix of the RUCs in the method. This linked the macroscopic nonlinear response with the damages in the microstructures. Good agreements were achieved in the load‐deflection curves and damage morphology between experimental and numerical results. POLYM. COMPOS., 37:2478–2493, 2016. © 2015 Society of Plastics Engineers     

Assessing the affective feelings of two‐ and three‐dimensional objects

The aim of this study is to investigate the impact of physical appearance attributes (in terms of color and shape) on our affective feelings of 2D and 3D objects. Twelve colors were studied, each consisting of 12 two‐dimensional and 12 three‐dimensional shapes. This resulted in 144 2D and 144 3D color‐shape combinations. Each color‐shape combination was assessed using 20 emotion scales in a viewing cabinet by a panel of observers with normal color vision. The results show that there are five underlying factors of these 20 scales, i.e., “activity,” “weight,” “heat,” “softness,” and “complexity”. The first three factors were mainly related to color and the other two were linked with shape. © 2008 Wiley Periodicals, Inc. Col Res Appl, 34, 75–83, 2009.     

Identification and characterization of three‐dimensional turbulent flow structures

Many phenomena in chemical processes for example fast mixing, coalescence and break‐up of bubbles and drops are not correctly described using average turbulence properties as the outcome is governed by the interaction with individual vortices. In this study, an efficient vortex‐tracking algorithm has been developed to identify thousands of vortices and quantify properties of the individual vortices. The traditional algorithms identifying vortex‐cores only capture a fraction of the total turbulent kinetic energy, which is often not sufficient for modeling of coalescence and break‐up phenomena. In the present algorithm, turbulent vortex‐cores are identified using normalized Q‐criterion, and allowed to grow using morphological methods. The growth is constrained by estimating the influence from all neighboring vortices using the Biot‐Sawart law. This new algorithm allows 82% of the total turbulent kinetic to be captured, at the same time the individual vortices can be tracked in time. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1265–1277, 2016     

Through‐thickness embossing process for fabrication of three‐dimensional thermoplastic parts

The standard embossing process is limited to the fabrication of surface structures on relatively large polymer substrates. To overcome this limitation, a hybrid punching and embossing process was investigated for through‐thickness embossing of three‐dimensional parts. The embossing tool included a punching head and to‐be‐ replicated features in the socket behind the punching head. The built‐in punching head facilitated a through‐thickness action and provided a closed‐die environment for embossing pressure buildup. The method was used to emboss multichannel millimeter waveguides which requires uniform edges and accurate dimensions. With a tool temperature of 140°C, an embossing time of 3 min and a total cycle time of 7 min, discrete 4‐channel waveguides were successfully embossed from a room‐temperature ABS substrate. A computer model was established to study the flow behavior during through‐thickness embossing. It was found that nonisothermal embossing conditions help confine the polymer in the cavity and reduce the outflow into the surrounding region, thus achieving complete fill of the cavity. POLYM. ENG. SCI., 47:2075–2084, 2007. © 2007 Society of Plastics Engineers     

Transversal patterns in three‐dimensional packed bed reactors: Oscillatory kinetics

Formation of transversal patterns in a 3D cylindrical reactor is studied with a catalytic reactor model in which an exothermic first‐order reaction of Arrhenius kinetics occurs with a variable catalytic activity. Under these oscillatory kinetics, the system exhibits a planar front (1D) solution with the front position oscillating in the axial direction. Three types of patterns were simulated in the 3D system: rotating fronts, oscillating fronts with superimposed transversal (nonrotating) oscillations, and mixed rotating–oscillating fronts. These solutions coexist with the planar front solution and require special initial conditions. We map bifurcation diagrams showing domains of different modes using the reactor radius as a bifurcation parameter. The possible reduction of the 3D model to the 2D cylindrical shell model is discussed. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Nano‐sio2‐reinforced ultraviolet‐curing materials for three‐dimensional printing

As an additive manufacturing technology, ultraviolet (UV)‐curing three‐dimensional printing, which requires the use of a photocurable resin, is increasingly being used to produce customized end‐user parts of many complex shapes. In this study, to improve the strength and ductility of printing materials, nano‐SiO₂‐reinforced photocurable resins were prepared by a planetary ball mill; then, the morphology, photochemistry, thermal property, and mechanical properties of the nanocomposites were investigated and characterized. Transmission electron microscopy analysis indicated that the modified nano‐SiO₂ was well dispersed in the photocurable resin. The glass‐transition temperature increased from 67.2°C for the unfilled resin to 71.7 and 80.1°C for nanocomposites with nano‐SiO₂ contents of 0.3 and 0.7 wt %, respectively. The tensile strength and impact strength were increased by 46.7 and 165.3% for nanocomposites with 0.3 wt % nano‐SiO₂. The flexural modulus of the nanocomposites increased from 1.7 to 8.0 GPa when 0.7 wt % nano‐SiO₂ was added to the photocurable resin; this appeared to originate from the relatively high level of dispersion and the intimate combination of the nano‐SiO₂ with the matrix. The investigation of the physical and chemical properties of such UV‐curing materials showed that the low filler concentration (<1 wt %) of nano‐SiO₂ did not affect the processability of the nanocomposites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42307.     

Numerical simulation of three‐dimensional gas‐solid particle flow in a horizontal pipe

A three‐dimensional model of particulate flows using the Reynolds Averaged Navier‐Stokes method is presented. The governing equations of the gas–solids flow are supplemented with appropriate closure equations to take into account all the relevant forces exerted on the solid particles, such as particle‐turbulence interactions, turbulence modulation, particle–particle interactions, particle–wall interactions, as well as gravitational, viscous drag, and lift forces. A finite volume numerical technique was implemented for the numerical solution of the problem. The method has been validated by comparing its results with the limited number of available experimental data for the velocity and turbulence intensity of the gas–particle flow. The results show that the presence of particles in the flow has a significant effect on all the flow variables. Most notably, the distribution of all the parameters becomes asymmetric, because of the gravitational effect on the particles and particle sedimentation. © 2011 American Institute of Chemical Engineers AIChE J, 2011     

UV‐assisted three‐dimensional printing of polymer nanocomposites based on inorganic fillers

In this work, nanocomposites based on a UV‐curable polymeric resin and different inorganic fillers were developed for use in UV‐assisted three‐dimensional (UV‐3D) printing. This technology consists in the additive multilayer deposition of a UV‐curable resin for the fabrication of 3D macro structures and microstructures of arbitrary shapes. A systematic investigation on the effect of filler concentration on the rheological properties of the polymer‐based nanocomposites was performed. In particular, the rheological characterization of these nanocomposites allowed to identify the optimal printability parameters for these systems based on the shear rate of the materials at the extrusion nozzle. In addition, photocalorimetric measurements were used to assess the effect of the presence of the inorganic fillers on the thermodynamics and kinetics of the photocuring process of the resins. By direct deposition of homogeneous solvent‐free nanocomposite dispersions of different fillers in a UV‐curable polymeric resin, the effect of UV‐3D printing direction, fill density, and fill pattern on the mechanical properties of UV‐3D printed specimens was investigated by means of uniaxial tensile tests. Finally, examples of 3D macroarchitectures and microarchitectures, spanning features, and planar transparent structures directly formed upon UV‐3D printing of such nanocomposite dispersions were reproducibly obtained and demonstrated, clearly highlighting the suitability of these nanocomposite formulations for advanced UV‐3D printing applications. POLYM. COMPOS., 38:1662–1670, 2017. © 2015 Society of Plastics Engineers     

Flow pattern variations of viscoelastic fluid flows in three‐dimensional branching channel

Transport phenomena in three‐dimensional branching channel are important because of their relevance in polymer processing. In this article, an experimental study on viscoelastic flow in a three‐dimensional cylindrical branching channel is carried out to investigate variations of flow pattern. Flow visualization in representative symmetric planes is made both for the viscoelastic fluid and Newtonian flow. From the results of the present investigation, the flow field in the three‐dimensional cylindrical branching channel is clarified within the range of laminar flow. It is confirmed that corner vortex, shedding vortex, and secondary vortex flow are all obviously changed with the fluid concentration and the Reynolds number, which are much more three‐dimensional and complex than the Newtonian fluid, and the flow pattern of the viscoelastic fliud flow largely depends on the Reynolds number and fluid concentration. Even for the viscoelastic flow at the low Reynolds number, shedding vortex and secondary vortex and complex three‐dimensional flow occur in the cylinder. The flow field is not symmetric space for the viscoelastic flow and however is fairly symmetric for the Newtonian fluid. The above reasons explain why the flow deflection happens even at the low Reynolds number flow. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Experimental study of flow regimes in three‐dimensional confined impinging jets reactor

Dynamic behaviors in a three‐dimensional confined impinging jets reactor (CIJR) were experimentally studied by a flow visualization technique at 100 ≤ Re ≤ 2000 and 2 ≤ D/d ≤ 12 (where D is the reactor diameter and d is the nozzle diameter). The effects of inlet Reynolds numbers (Re) and geometry configurations of the CIJR on the flow regimes have been investigated by a particle image velocimetry and a high‐speed camera. Results show that with the increasing Re, a segregated flow regime, a radial deflective oscillation, an axial oscillation and a vortex shedding regime emerge in turns in CIJR. A map of parameter space formed by the inlet Reynolds number (Re) and the normalized reactor diameter (D/d) has been presented. The effects of jet instability and confined boundary of the chamber on the flow regimes and their transition are also investigated and discussed. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3033–3045, 2014     

A three‐dimensional analysis of coextrusion in a single manifold flat die

The coextrusion of two polymers through a single manifold flat die is examined. The three components of velocity and the pressure are determined in each layer along with the interface between the layers. It is shown that even when the viscosity ratio is one (i.e., single layer), flat “layers” entering the die will not remain flat but will be distorted by the die. For coextrusion of two polymers, the distortion of the interface profile at the exit of the die and thus the uniformity of the layers depends upon the viscosity and flow rate ratios of the two polymers as well as the geometry of the die.     

Fabrication of porous three‐dimensional fibroin structures through a freezing process

Silk fibroin has been investigated for various biomedical applications. In this research, through a green process, without using freeze‐drying, which is energy consuming during a single step process that is completely aqueous‐based, without using any additional materials during or after structure formation, water‐insoluble silk fibroin sponges have been obtained; these achieved only through keeping fibroin solutions frozen at a suitable temperature for a sufficient time. The effect of solution concentration and freezing conditions on the pore morphology and size, microstructure, and mechanical properties was investigated. A discussion has been proposed for the formation of structures. The average measured pore sizes were approximately from 4 to 77 μm. Elastic modules of the investigated structures varied from about 100 to 900 kPa. Cyclic mechanical tests were performed; the remaining strain of the structures reached to about 1%. A less considered issue which can be considered as the possible significant change of the mechanical behavior of as‐prepared samples after one or more times of loading and unloading should be noted. The used method in this study as a cost effective and convenient procedure could have the potential for application in the production of porous structures for biomedical applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46537.