Millimetre Length Scales Research Articles

Evaluation of cataract formation in fish exposed to environmental radiation at Chernobyl and Fukushima

Recent studies apparently finding deleterious effects of radiation exposure on cataract formation in birds and voles living near Chernobyl represent a major challenge to current radiation protection regulations. This study conducted an integrated assessment of radiation exposure on cataractogenesis using the most advanced technologies available to assess the cataract status of lenses extracted from fish caught at both Chernobyl in Ukraine and Fukushima in Japan. It was hypothesised that these novel data would reveal positive correlations between radiation dose and early indicators of cataract formation.The structure, function and optical properties of lenses were analysed from atomic to millimetre length scales. We measured the short-range order of the lens crystallin proteins using Small Angle X-Ray Scattering (SAXS) at both the SPring-8 and DIAMOND synchrotrons, the profile of the graded refractive index generated by these proteins, the epithelial cell density and organisation and finally the focal length of each lens.The results showed no evidence of a difference between the focal length, the epithelial cell densities, the refractive indices, the interference functions and the short-range order of crystallin proteins (X-ray diffraction patterns) in lens from fish exposed to different radiation doses. It could be argued that animals in the natural environment which developed cataract would be more likely, for example, to suffer predation leading to survivor bias. But the cross-length scale study presented here, by evaluating small scale molecular and cellular changes in the lens (pre-cataract formation) significantly mitigates against this issue.

Chiral Polymer Dots Show Unexpected Versatility of Highly Ordered Self-Assembly into Chiroptical Liquid Crystals, Ultra-Thin Films, and Long-Ribbons.

Compared to the organic counterparts, chiral self-assembly of nanomaterials shows persistency to kinetic factors such as solvent environments, and consequently, dynamic modulation of self-assembly and functions remains major challenge. Here, it is shown that alkylated, chiral polymer dots (c-PDs) give highly ordered self-assemblies with amplified chirality adaptive to solvent environments, and one-to-many hierarchical aggregation can be realized. The c-PDs tended to self-assemble into nanohelices with cubic packing in the solid state, which, thanks to the thermo-responsiveness, transformed into thermic liquid crystals upon heating. Cotton effects and circularly polarized luminescence evidenced the chirality transfer from central chirality to supramolecular chirality. At the air-water interface, the c-PDs are self-assembled into monolayers, which further stack into multiple layers with chirality transfer and highly ordered packing. In addition, undergoing a good/poor solvent exchange, the c-PDs afforded ultra-long microribbons up to a length scale of millimeters, which are constituted by the bilayer lamellar stacking. The versatile chiral self-assembly modalities with long-range ordered packing arrays of carbonized c-PDs via solvent strategy are realized. This feature is comparable to the organic species, although the c-PDs have no atomic precise structures. This work would surely expand the applications of quantum dot ordered self-assembly with adaptiveness to kinetic factors.

Composite fast scintillators based on high-Z fluorescent metal–organic framework nanocrystals

Scintillators, materials that produce light pulses upon interaction with ionizing radiation, are widely employed in radiation detectors. In advanced medical-imaging technologies, fast scintillators enabling a time resolution of tens of picoseconds are required to achieve high-resolution imaging at the millimetre length scale. Here we demonstrate that composite materials based on fluorescent metal–organic framework (MOF) nanocrystals can work as fast scintillators. We present a prototype scintillator fabricated by embedding MOF nanocrystals in a polymer. The MOF comprises zirconium oxo-hydroxy clusters, high-Z linking nodes interacting with the ionizing radiation, arranged in an orderly fashion at a nanometric distance from 9,10-diphenylanthracene ligand emitters. Their incorporation in the framework enables fast sensitization of the ligand fluorescence, thus avoiding issues typically arising from the intimate mixing of complementary elements. This proof-of-concept prototype device shows an ultrafast scintillation rise time of ~50 ps, thus supporting the development of new scintillators based on engineered fluorescent MOF nanocrystals. Composites of fluorescent metal–organic framework nanocrystals in a polymer are exploited to create fast scintillators with a rise time of about 50 ps.

Three-dimensional imaging of integrated circuits with macro- to nanoscale zoom

The imaging of integrated circuits across different length scales is required for failure analysis, design validation and quality control. At present, such inspection is accomplished using a hierarchy of different probes, from optical microscopy on the millimetre length scale to electron microscopy on the nanometre scale. Here we show that ptychographic X-ray laminography can provide non-destructive, three-dimensional views of integrated circuits, yielding both images of an entire chip volume and high-resolution images of arbitrarily chosen subregions. We demonstrate the approach using chips produced with 16 nm fin field-effect transistor technology, achieving a reconstruction resolution of 18.9 nm, and compare our results with photolithographic mask layout files and more conventional imaging approaches such as scanning electron microscopy. The technique should also be applicable to other branches of science and engineering where three-dimensional X-ray images of planar samples are required. A technique that combines X-ray ptychography with laminography can provide three-dimensional views of integrated circuits, yielding both images of entire chip volumes and high-resolution images of arbitrarily chosen subregions, and is applicable to any imaging problem where the samples are planar.

Computed tomography porosity and spherical indentation for determining cortical bone millimetre-scale mechanical properties

The cortex of the femoral neck is a key structural element of the human body, yet there is not a reliable metric for predicting the mechanical properties of the bone in this critical region. This study explored the use of a range of non-destructive metrics to measure femoral neck cortical bone stiffness at the millimetre length scale. A range of testing methods and imaging techniques were assessed for their ability to measure or predict the mechanical properties of cortical bone samples obtained from the femoral neck of hip replacement patients. Techniques that can potentially be applied in vivo to measure bone stiffness, including computed tomography (CT), bulk wave ultrasound (BWUS) and indentation, were compared against in vitro techniques, including compression testing, density measurements and resonant ultrasound spectroscopy. Porosity, as measured by micro-CT, correlated with femoral neck cortical bone’s elastic modulus and ultimate compressive strength at the millimetre length scale. Large-tip spherical indentation also correlated with bone mechanical properties at this length scale but to a lesser extent. As the elastic mechanical properties of cortical bone correlated with porosity, we would recommend further development of technologies that can safely measure cortical porosity in vivo.

Understanding the mechanisms of root-reinforcement in soils: soil shear tests using X-ray computed tomography and digital volume correlation

Soil containing plant roots may be expected to exhibit a greater shearing resistance compared with the same ‘unreinforced’ soil, providing enhanced stability and effective erosion control, particularly for earth slopes. To be able to rely on the improved shearing resistance and stiffness of root-reinforced soils, it is important to understand and quantify the effectiveness of root reinforcement. This requires sophisticated multiscale models, building understanding at different length scales, from individual soil-root interaction through to full soil-profile or slope scale. One of the challenges with multiscale models is ensuring that they are representative of real behaviour, and this requires calibration to detailed high-quality experiments. The focus of the work presented was to capture and quantify root-reinforcement behaviour and associated soil and root deformation mechanisms during direct shear at the macroscopic to millimetre length scales. A novel shear box was developed to operate within a large-scale X-ray computed tomography (CT) scanner. Tests were interrupted to be scanned at a series of shear displacements from 0-20 mm to capture the chronology of behaviour in three-dimensions. Digital volume correlation (DVC) was applied to the CT dataset to obtain full-field 3D displacement and strain component information. The study demonstrates feasibility of the technique and presents preliminary DVC results.

Synergistic mode II delamination toughening of composites using multi-scale carbon-based reinforcements

This paper presents an investigation into the synergistic improvements to the mode II interlaminar fracture toughness of composites using multi-scale carbon reinforcements spanning the nano to millimetre length scales. Varying volume fractions of carbon nanofibres (CNFs) and millimetre-long carbon fibre z-pins were used to increase the mode II delamination resistance of multi-scale reinforced composites. The results reveal that adding CNFs into the epoxy matrix and transversely inserting z-pins creates a synergistic, rather than additive, improvement to the mode II fracture toughness. The magnitude of the synergistic toughening effect depends on the volume contents of both the nanofibres and z-pins, with the measured synergistic improvement to the mode II toughness being up to 26% (i.e. greater than the expected additive toughening contribution from each filler type). A finite element (FE) numerical model has been developed to accurately predict the mode II fracture properties and the synergistic toughening effect exhibited by the multi-scale reinforced epoxy composites.

Towards using a focussed phased array of millimetre length scale elements for ultrasound imaging

Sparse phased array ultrasound transducers with millimetre length scale elements have previously been proposed for generating hyperthermia but not for imaging. Numerical simulation with a pseudospectral solver was used to investigate: (a) how the position of the maximum pressure in the focal region changed with element diameter and frequency; (b) how the size and position of the focal region changed with focal distance under steering; and (c) the imaging performance of 15 element random arrays. These analyses were performed for both piston-like and non piston-like millimetre diameter elements since previous work has shown a shift in the distance to the maximum pressure in the focal region with the latter. The results for these elements were compared with elements where the diameter was <λ/2. The distance from the array to the position of maximum pressure in the focal region diverged from the value with element diameter <λ/2; values for piston-like elements increased positively whilst values for non piston-like elements increased negatively. With distances expressed in λ, no difference was found for arrays at 1 MHz and 2.5 MHz. For piston-like elements, but not for non piston-like elements, two peaks were found in the focal region which were in-line with the direction of propagation for a focus on the central axis but which rotated to become parallel with the direction of propagation when steering exceeded 20°. The size and position of the focal region under steering was similar for the non piston-like elements and elements with diameter <λ/2. Little difference was found in image quality or the size of the point spread function (PSF) between images at 2.5 MHz with piston-like and non piston-like behaviour for steering angles less than 20° when compared with a linear array of similar size. These results suggest that imaging with random arrays of millimetre length scale elements is possible.

Osseointegration of porous apatite-wollastonite and poly(lactic acid) composite structures created using 3D printing techniques

A novel apatite-wollastonite/poly(lactic acid) (AW/PLA) composite structure, which matches cortical and cancellous bone properties has been produced and evaluated in vitro and in vivo. The composites structure has been produced using an innovative combination of 3D printed polymer and ceramic macrostructures, thermally bonded to create a hybrid composite structure. In vitro cell assays demonstrated that the AW structure alone, PLA structure alone, and AW/PLA composite were all biocompatible, with the AW structure supporting the proliferation and osteogenic differentiation of rat bone marrow stromal cells. Within a rat calvarial defect model the AW material showed excellent osseointegration with the formation of new bone, and vascularisation of the porous AW structure, both when the AW was implanted alone and when it was part of the AW/PLA composite structure. However, the AW/PLA structure showed the largest amount of the newly formed bone in vivo, an effect which is considered to be a result of the presence of the osteoinductive AW structure stimulating bone growth in the larger pores of the adjacent PLA structure. The layered AW/PLA structure showed no signs of delamination in any of the in vitro or in vivo studies, a result which is attributed to good initial bonding between polymer and ceramic, slow resorption rates of the two materials, and excellent osseointegration. It is concluded that macro-scale composites offer an alternative route to the fabrication of bioactive bone implants which can provide a match to both cortical and cancellous bone properties over millimetre length scales.

On the inhomogeneous hydration kinetics and stiffness evolution of HNBR‐MgO reactive elastomer composites

ABSTRACTSwellable elastomers are widely used in oilfield industry for sealing and zonal isolation applications. These materials need to sustain a large amount of external load after swelling. A newly developed reactive hydrogenated nitrile butadiene rubber (HNBR) based elastomer composite with magnesium oxide (MgO) as filler can swell and stiffen when exposed to water, which makes it ideal for oil field applications. However, both the filler hydration and the stiffness evolution inside this composite material are observed to be highly inhomogeneous even for samples on the length scale of millimeters. To understand this coupled diffusion‐hydration process is critical for applications of these materials with larger length scales. In this work, the hydration kinetics and stiffness evolution of the HNBR‐MgO composite are quantitatively studied on microscopic level. The extent of MgO hydration along the thickness of the sample are measured at the different stage of swelling. These results are used to determine the diffusion coefficient of water inside the composite. The diffusivity increases orders of magnitude after the filler hydration. In addition, the modulus change is non‐proportional to the degree of filler hydration as demonstrated by instrumented grid indentation on the hydrated composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43420.

Long‐Range Proton Conduction across Free‐Standing Serum Albumin Mats

Free-standing serum-albumin mats can transport protons over millimetre length-scales. The results of photoinduced proton transfer and voltage-driven proton-conductivity measurements, together with temperature-dependent and isotope-effect studies, suggest that oxo-amino-acids of the protein serum albumin play a major role in the translocation of protons via an "over-the-barrier" hopping mechanism. The use of proton-conducting protein mats opens new possibilities for bioelectronic interfaces.

Hard-Soft Tissue Interface Engineering.

The musculoskeletal system is comprised of three distinct tissue categories: structural mineralized tissues, actuating muscular soft tissues, and connective tissues. Where connective tissues - ligament, tendon and cartilage - meet with bones, a graded interface in mechanical properties occurs that allows the transmission of load without creating stress concentrations that would cause tissue damage. This interface typically occurs over less than 1 mm and contains a three order of magnitude difference in elastic stiffness, in addition to changes in cell type and growth factor concentrations among others. Like all engineered tissues, the replication of these interfaces requires the production of scaffolds that will provide chemical and mechanical cues, resulting in biologically accurate cellular differentiation. For interface tissues however, the scaffold must provide spatially graded chemical and mechanical cues over sub millimetre length scales. Naturally, this complicates the manufacture of the scaffolds and every stage of their subsequent cell seeding and growth, as each region has different optimal conditions. Given the higher degree of difficulty associated with replicating interface tissues compared to surrounding homogeneous tissues, it is likely that the development of complex musculoskeletal tissue systems will continue to be limited by the engineering of connective tissues interfaces with bone.

Halogen-bonded mesogens direct polymer self-assemblies up to millimetre length scale.

Aligning polymeric nanostructures up to macroscale in facile ways remains a challenge in materials science and technology. Here we show polymeric self-assemblies where nanoscale organization guides the macroscopic alignment up to millimetre scale. The concept is shown by halogen bonding mesogenic 1-iodoperfluoroalkanes to a star-shaped ethyleneglycol-based polymer, having chloride end-groups. The mesogens segregate and stack parallel into aligned domains. This leads to layers at ~10 nm periodicity. Combination of directionality of halogen bonding, mesogen parallel stacking and minimization of interfacial curvature translates into an overall alignment in bulk and films up to millimetre scale. Upon heating, novel supramolecular halogen-bonded polymeric liquid crystallinity is also shown. As many polymers present sites capable of receiving halogen bonding, we suggest generic potential of this strategy for aligning polymer self-assemblies.

Apatite alignment and orientation at the Ångstrom and nanometer length scales shed light on the adaptation of dentine to whole tooth mechanical function

Human teeth are capped by a highly mineralized enamel layer that rests on a bone-like material termed dentine. Dentine is composed mainly of collagen and carbonated apatite known to form the biological composite of all types of bone by combining into mineralized collagen fibrils. The apatite mineral is found both within and also encasing the fibrils, but in dentine, particularly in the crown, mineral is also found in regions where there is no collagen, forming peritubular dentine cuffs that surround narrow channels that perforate and render dentine porous. The authors hypothesize that regional variations in the mineral spatial configuration may reflect local adaptation to functional needs of whole teeth. The 3D orientation of the micron-sized tubules and the associated clusters of peritubular mineral vary on the length scale of millimeters. The orientation and degree of coalignment of the nanometer-sized mineral platelets in dentine exhibit marked changes at the same length scale, matching predicted load-trajectories in loaded teeth. However, wide-angle X-ray diffraction mapping shows that there is almost no preferred orientation of the 002 reflection (and hence the c-axis of apatite). The authors thus propose that the orientation of the peritubular and intertubular mineral compensate for localized preferred orientations, to create an overall average, randomly oriented mineral configuration.

Bio-inspired composite structures subjected to underwater impulsive loading

Designing lightweight high-performance materials that can sustain high impulsive loadings is of great interest to marine and civil applications. When designing tough, strong new materials from relatively weak components, mimicking structures from nature can be a highly promising strategy, as illustrated by nacre from red abalone shells. One of nacre’s most impressive features is its ability to laterally spread damage and dissipate energy over millimetre length scales at crack tips and other defects. In this work, a composite panel is redesigned to mimic nacre’s microstructure. The bio-inspired composite panel and the original composite structure, which have identical areal mass, are subjected to an underwater impulsive loading scenario. Their performances are compared numerically in terms of damage and deflection. A finite element fluid–structure interaction model is developed to capture the water impact on E-glass/vinylester composite facets and to provide insights into the deformation modes and failure mechanisms. Damage and degradation in individual unidirectional composite laminas are simulated using Hashin’s composite damage model. The delamination between laminas is modelled by a bilinear cohesive model. Results interpreted from this numerical study will be used as guidance for the future manufacturing and experimental characterisation of bio-inspired composite structures.

Aesthetically textured, hard latex coatings by fast IR-assisted evaporative lithography

Polymer coatings with periodic topographic patterns, repeating over millimetre length scales, can be created from lateral flows in an aqueous dispersion of colloidal particles. The flow is driven by differences in evaporation rate across the wet film surface created by IR radiative heating through a shadow mask. This new process, which we call IR radiation-assisted evaporative lithography (IRAEL), combines IR particle sintering with the concept of evaporative lithography. Here, a series of experiments has been conducted in which the mass of the latex is measured as a function of the exposure time under infrared radiation through a mask. The water evaporation rates and the minimum exposure time required for a dry film are estimated as a function of the power density of the IR emitter. The temperature of the wet film is monitored to avoid overheating and boiling of the water, which will otherwise cause defects. It is demonstrated that textured films can be created on a variety of substrates (plastics, metals, paper and glass), and processing times can be as short as 5min. We use IRAEL to decorate household goods with an aesthetic coating with the desired texture.

Time resolved chromatograms in ultra-thin layer chromatography

Ultrathin-layer chromatography (UTLC) is a recently developed analytical method intended for compact, rapid separations of nanolitre analyte volumes. Optimizing this method's performance requires new measurement techniques compatible with the millimetre length scales and rapid separation dynamics observed in UTLC. We have designed, implemented and characterized a measurement system which records UTLC separations in full color with 32μm spatial resolution and 33ms temporal resolution. Our code analyzes multiple tracks per plate, filters analyte spots by color, and automatically generates time-resolved figures of merit. The instrument presented here captures a wealth of information from a UTLC separation, and should provide insight into UTLC physics and improved analytical performance.

Highly Oriented Mesoporous Silica Channels Synthesized in Microgrooves and Visualized with Single-Molecule Diffusion

A novel synthesis method for large-pore, well-aligned 2D hexagonal mesoporous silica thin films is reported. The alignment was achieved by confinement in poly(dimethylsiloxane) (PDMS) microgrooves without the necessity of additional forces (such as electric fields). We describe the influence of various experimental conditions including the way the grooves are filled, surface modification at the solid/liquid interfaces, and the height-to-width ratio of the microgrooves on mesopore alignment. With this technique, highly oriented mesoporous silica channels can be obtained at a length scale of several millimeters. For a nondestructive, detailed, and wide-ranging structural and dynamic characterization of the as-synthesized mesochannel silica network, dye molecules were incorporated into the channels at concentrations suitable for single-molecule microscopy. A "maximum projection" of individual frames recorded with a fluorescence microscope immediately gives a global overview ("map") of the pore structure, thus providing direct feedback for tuning synthesis conditions. In addition, deeper insights into the real nanoscale structure of the mesoporous silica framework were obtained through high-accuracy single-molecule tracking experiments. The high spatial accuracy of the experiments allowed for the direct observation of jumps of single dye molecules between individual channels in the mesoporous silica host. Nevertheless, due to the low concentration of defects, the diffusion could be described as a 1D random walk where the molecules diffuse along the highly oriented, parallel channels and sometimes switch from channel to channel through small defects in the pore walls. Furthermore, it could be shown with single-molecule microscopy that template removal and calcination of the aligned films results in an increased defect concentration; however, the overall order of the structures remained intact.

Test of the Gravitational Inverse Square Law at Millimeter Ranges

We report a new test of the gravitational inverse square law at millimeter ranges by using a dual-modulation torsion pendulum. An I-shaped symmetric pendulum and I-shaped symmetric attractors were adopted to realize a null experimental design. The non-Newtonian force between two macroscopic tungsten plates is measured at separations ranging down to 0.4 mm, and the validity of the null experimental design was checked by non-null Newtonian gravity measurements. We find no deviations from the Newtonian inverse square law with 95% confidence level, and this work establishes the most stringent constraints on non-Newtonian interaction in the ranges from 0.7 to 5.0 mm, and a factor of 8 improvement is achieved at the length scale of several millimeters.

Patterning Alloy Precipitates through Tailored Surface Loading

An innovative processing technique that produces distinct, locally patterned microstructures within a single sample is introduced in this article. This technique alters the conventional heat-treatment process by applying a micropatterned external surface load to selected locations during the quench and anneal. In the aluminum-copper system (2 wt pct Cu), spatial control of Al2Cu precipitates within 50 μm features over an aggregate length scale of millimeters is achieved. Chemical interactions among the furnace environment, the alloy sample, and the loading device can affect the experiments adversely and steps used to ameliorate these effects are discussed. The precipitate patterning technique presented in this article is compatible with standard “heat and beat” processing and could be used potentially to develop new multifunctional metallic alloys.