Glass Replica Research Articles

Oedipus Riddles

The paper discusses an interesting group of glass intaglios with the motif of Oedipus and the Sphinx. They are known from sites between the Adriatic, the Danube and the Black Sea, and occur in various colors and cuts, which suggests production in different molds or even workshops. Probably modeled on an intaglio made in an Italian officina gemmaria, the glass replicas may have been produced at Aquileia. The style points to the Late Republican or Augustan era, whereas the material of the glass copies and the funerary context from Aquincum show they were in use and probably produced till the 4 th century. The paper also discusses the possible meanings of the motif, from a simple illustration of the famous heroic adventure to a metaphoric depiction representing the mystic message of the key to a blessed afterlife.

A novel hot embossing process for producing high-quality glass micro-pillar arrays

Hot embossing is an efficient technology for the fabrication of glass micro- and nanostructures. However, the long cycle time, high energy consumption, and high nitrogen emissions in traditional hot embossing approach hinders sustainable production of glass micro-optics. Therefore, this paper proposes a novel two-stage gravity-assisted hot embossing process that enables the fabrication of high-quality glass micro-pillar arrays in a rapid, green manner. In this approach, the two-stage gravity loading unit provides accurate force on glass preform through a simple control system, and the tailor-made heating module based on Si3N4 ceramic heaters requires an energy consumption of just 700 kJ per molding cycle. As a result, the proposed approach is featured by low energy consumption and high manufacturing efficiency. In this study, the effects of the embossing temperature, force, and time on the replication accuracy of a K9 glass micro-pillar array were investigated through a series of hot embossing experiments. Afterward, the form accuracy, uniformity of microstructures, and warpage of glass replicas under the optimal process parameters were evaluated separately. Finally, repeated hot embossing experiments were conducted to demonstrate the reproducibility of the hot embossing process. The experimental results show that embossing temperature had the most significant effect on the replication accuracy of glass micro-pillars. By optimizing the process parameters, the embossed glass micro-pillars could achieve transfer ratios of 99.00% and 95.14% in height and diameter, respectively. Moreover, the surface roughness of glass micro-pillars was less than 5 nm, and the warpage amplitude of glass replicas in a 3.9 × 3.9 mm area was smaller than 1 μm. The small discrepancy in geometric features of glass replica in the repeated trails reflects the satisfactory reproducibility of this hot embossing process on the micro and nano scales. The results indicate the strong industrialization potential of the proposed two-stage gravity-assisted hot embossing machine and hot embossing process for fabricating high-quality glass microstructures more cleanly and sustainably.

Study on warpage and filling behavior of glass in non-isothermal hot embossing

Non-isothermal hot embossing has great potential in the mass production of glass micro optical components due to the relatively short heating-cooling cycle time. However, warpage was induced by the temperature gradient inside the glass replica during hot embossing, resulting in a deteriorated optical performance. Therefore, it is non-trivial to investigate the effects of process parameters on warping and filling behaviors of glass in non-isothermal hot embossing. Firstly, a high-quality microhole was fabricated on monocrystalline silicon carbide (SiC) mold by focused ion beam (FIB) lithography. By using a novel home-made gravity-assisted hot embossing machine, the geometric information (i.e., warpage and microstructures) on SiC mold was transferred into the surface of N-BK7 glass replica. The experimental results indicate that high embossing temperature enables not only the minimization of warpage but also the enhancement of microstructure replication accuracy. Furthermore, increasing embossing force enhances filling capacity but increases warpage amplitude. Interestingly, fast heating/cooling rates and short embossing time enable a small warpage as well as a high embossing efficiency. By optimizing the process parameters, especially the embossing temperature, a small warpage amplitude of 3 μm and a high transfer ratio of 99.11% were achieved, which can meet the high requirement of precision optical components.

Holding on or falling off: The attachment mechanism of epiphytic Anthurium obtusum changes with substrate roughness.

For vascular epiphytes, secure attachment to their hosts is vital for survival. Yet studies detailing the adhesion mechanism of epiphytes to their substrate are scarce. Examination of the root hair-substrate interface is essential to understand the attachment mechanism of epiphytes to their substrate. This study also investigated how substrate microroughness relates to the root-substrate attachment strength and the underlying mechanism(s). Seeds of Anthurium obtusum were germinated, and seedlings were transferred onto substrates made of epoxy resin with different defined roughness. After 2 months of growth, roots that adhered to the resin tiles were subjected to anchorage tests, and root hair morphology at different roughness levels was analyzed using light and cryo scanning electron microscopy. The highest maximum peeling force was recorded on the smooth surface (glass replica, 0 µm). Maximum peeling force was significantly higher on fine roughness (0, 0.3, 12 µm) than on coarse (162 µm). Root hair morphology varied according to the roughness of the substrate. On smoother surfaces, root hairs were flattened to achieve large surface contact with the substrate. Attachment was mainly by adhesion with the presence of a glue-like substance. On coarser surfaces, root hairs were tubular and conformed to spaces between the asperities on the surface. Attachment was mainly via mechanical interlocking of root hairs and substrate. This study demonstrates for the first time that the attachment mechanism of epiphytes varies depending on substrate microtopography, which is important for understanding epiphyte attachment on natural substrates varying in roughness.

Toluene NAPL Oxidation by Ferrous Activated Persulfate in a Fractured Rock Glass Replica

AbstractNon‐aqueous phase liquids (NAPLs), such as toluene, often contaminate the subsurface. In this study, we focus on the transformation of toluene NAPL trapped in a single glass replica of a rock fracture via in situ chemical oxidation (ISCO) with ferrous activated persulfate. The trapped toluene consisted of a main trapped blob surrounded by smaller blobs. Over 53 days, successive persulfate injections into the fracture were interspersed with periods of water flushing. During persulfate injections, effluent toluene concentrations were below 0.04 mM. The rebound toluene concentrations during intervening water flushing periods decreased from 0.9 to 0.3 mM over the study. The smaller toluene blobs were removed by dissolution and partial oxidation. The main toluene blob was reduced in area by 35.5% and in volume by 37.3% due to dissolution and partial oxidation. The main blob changed in shape with reduction in size and there was also formation of an oxidation by‐product zone around the blob. The reduction in toluene effluent concentrations with time over successive persulfate injections and periods of water flushing was attributed to reductions in the NAPL‐water interfacial area of the blob and the formation of the by‐product zone surrounding the blob, which resulted in limited toluene dissolution. Analysis of by‐products of toluene oxidation by ferrous activated persulfate suggests that oligomers were part of the by‐product zone formed in the fracture. Gas bubbles were also observed in the fracture and may have formed from toluene oxidation and persulfate decomposition.

Evidence for different behaviors of atmospheric glass alteration as a function of glass composition

The glass composition is a determining parameter that influences the glass chemical durability, particularly in atmospheric conditions (defined by the relative humidity, RH, < 100%). This is obvious in the field of the cultural heritage (CH), where some glass compositions qualified as unstable show advanced signs of degradation under atmosphere, while others seem, on the contrary, stable. This study investigates the differences between stable and unstable glass compositions regarding the phenomenology of the atmospheric glass alteration, by means of accelerated ageing of three glass replicas followed by the characterization of their alteration layers at different scales. Over the same ageing period and experimental conditions, the two glass compositions qualified as unstable develop thick hydrated layers and a thin top layer of carbonate precipitates. Their hydrated layers are depolymerized, and they remarkably retain alkalis and non-bridging oxygens in a dense network of hydrogen bonds, as demonstrated by 29Si and 1H MAS NMR. On the contrary, the stable glass composition shows a considerably thinner hydrated layer and, relatively, a higher amount of carbonates on the surface. In unstable glasses, the retention of a significant proportion of alkalis and NBOs, probably by maintaining a basic character to the hydrated layer, seems comparatively a destabilizing factor sustaining hydration by fast network hydrolysis.

Development of diffraction binary grating using hot embossing processing with electroformed nickel mold for broadband IR optics

In this paper we report on cost-effective fabrication of glass diffractive optical elements dedicated to work over a spectral range from the visible to the mid-infrared. As a test we have developed of checker-board diffraction grating using the hot embossing process. The nickel (Ni) shim fabricated using low-cost electroforming method was used as a mold. We synthesised in-house a new composition of lead-free bismuth-silicate glass, labelled SAB-1A, with good rheological properties and high transmittance up to 3.5 μm. Glass composition and parameters of hot embossing process were optimised to accurately replicate the grating and separate the glass replica from the mold. The quality of the fabricated elements was discussed and examined using a white light interferometer and in experimental setup for generation of diffractive pattern at different wavelengths.

Carbide-bonded graphene-based Joule heating for embossing fine microstructures on optical glass

This paper reports the fabrication of high-quality microstructures on optical glass via hot embossing using carbide-bonded graphene (CBG) based Joule heating for the first time. In this study, a tailor-made micro hot embossing tool equipped with a modified CBG-based Joule heating system was designed and developed for transferring microstructures (e.g., microlens arrays, MLAs for short) from the CBG-coated silicon mold insert into the optical glass (P-SK57). Initially, the surface topographies of a typical 3 × 3 MLA from a bare silicon mold to an embossed glass replica were compared for evaluating form errors brought in during different preparation stages. The feasibility of the CBG-based Joule heating technique for the non-equilibrium thermal imprinting of optical glass was evaluated by the surface integrity and replication fidelity of the embossed MLA features. Thermally induced residual stress and imaging performance of the embossed glass lens were assessed as well. Experimental results indicate that the proposed CBG-assisted hot embossing technique, in combination with single point diamond turning technology, has the capability of producing high-quality glass MLAs. Moreover, this technique allows notably fine replication of surface shapes at the microscale, as well as roughness information at the nanoscale. Consequently, the embossed MLA replica shows satisfactory imaging performance.

Boundary control in computational haemodynamics

In this work, a data assimilation method is proposed following an optimise-then-discretise approach, and is applied in the context of computational haemodynamics. The methodology aims to make use of phase-contrast magnetic resonance imaging to perform optimal flow control in computational fluid dynamic simulations. Flow matching between observations and model predictions is performed in luminal regions, excluding near-wall areas, improving the near-wall flow reconstruction to enhance the estimation of related quantities such as wall shear stresses. The proposed approach remarkably improves the flow field at the aortic root and reveals a great potential for predicting clinically relevant haemodynamic phenomenology. This work presents model validation against an analytical solution using the standard 3-D Hagen–Poiseuille flow, and validation with real data involving the flow control problem in a glass replica of a human aorta imaged with a 3T magnetic resonance scanner.In vitroexperiments consist of both a numerically generated reference flow solution, which is considered as the ground truth, as well as real flow MRI data obtained from phase-contrast flow acquisitions. The validation against thein vitroflow MRI experiments is performed for different flow regimes and model parameters including different mesh refinements.

Fabrication of Glass Microchannel via Glass Imprinting using a Vitreous Carbon Stamp for Flow Focusing Droplet Generator.

This study reports a cost-effective method of replicating glass microfluidic chips using a vitreous carbon (VC) stamp. A glass replica with the required microfluidic microstructures was synthesized without etching. The replication method uses a VC stamp fabricated by combining thermal replication using a furan-based, thermally-curable polymer with carbonization. To test the feasibility of this method, a flow focusing droplet generator with flow-focusing and channel widths of 50 µm and 100 µm, respectively, was successfully fabricated in a soda-lime glass substrate. Deviation between the geometries of the initial shape and the vitreous carbon mold occurred because of shrinkage during the carbonization process, however this effect could be predicted and compensated for. Finally, the monodispersity of the droplets generated by the fabricated microfluidic device was evaluated.

Design and Fabrication of Wolter-type 4-mirror system

A Wolter-type 4-mirror system was designed and evaluated by ray-trace calculation. The design and fabrication process were developed. The master mandrel of oxygen-free copper was shaped by diamond turning. The Pyrex glass replica was made by a vacuum replication technique. A visible light image of a metal mesh could be obtained using this replica mirror.

Retraction Note to: DNAPL Migration in a Rough Fracture Under Various Wettability and Flow Conditions

We conducted laboratory experiments to investigate the influence of surface wettability on Dense Nonaqueous Phase Liquid (DNAPL) migration in a rough-walled fracture at various groundwater flow conditions. A glass replica of a granite sample containing a rough-walled single fracture was made, and DNAPL migration experiments were carried out with the replica whose surface wettability was controlled by using several NAPL exposures. In the experiments, we observed different migration paths of DNAPL among the hydrophilic, weakly hydrophobic, and strongly hydrophobic surfaces in the linear flow regime, whereas there was little difference in the nonlinear flow regime. The modified invasion percolation model was used to analyze the quantitative influence of the wettability change and groundwater flow on DNAPL migration paths in a rough-walled fracture, and suggested that the wettability is important to determine the DNAPL migration path in the linear flow regime but inertial force of groundwater becomes strong enough to overcome the influence of the wettability in the nonlinear flow regime.

DNAPL Migration in a Rough Fracture Under Various Wettability and Flow Conditions

We conducted laboratory experiments to investigate the influence of surface wettability on Dense Nonaqueous Phase Liquid (DNAPL) migration in a rough-walled fracture at various groundwater flow conditions. A glass replica of a granite sample containing a rough-walled single fracture was made, and DNAPL migration experiments were carried out with the replica whose surface wettability was controlled by using several NAPL exposures. In the experiments, we observed different migration paths of DNAPL among the hydrophilic, weakly hydrophobic, and strongly hydrophobic surfaces in the linear flow regime, whereas there was little difference in the nonlinear flow regime. The modified invasion percolation model was used to analyze the quantitative influence of the wettability change and groundwater flow on DNAPL migration paths in a rough-walled fracture, and suggested that the wettability is important to determine the DNAPL migration path in the linear flow regime but inertial force of groundwater becomes strong enough to overcome the influence of the wettability in the nonlinear flow regime.

Nanomoulding with amorphous metals

Nanoimprinting promises low-cost fabrication of micro- and nano-devices by embossing features from a hard mould onto thermoplastic materials, typically polymers with low glass transition temperature. The success and proliferation of such methods critically rely on the manufacturing of robust and durable master moulds. Silicon-based moulds are brittle and have limited longevity. Metal moulds are stronger than semiconductors, but patterning of metals on the nanometre scale is limited by their finite grain size. Amorphous metals (metallic glasses) exhibit superior mechanical properties and are intrinsically free from grain size limitations. Here we demonstrate direct nanopatterning of metallic glasses by hot embossing, generating feature sizes as small as 13 nm. After subsequently crystallizing the as-formed metallic glass mould, we show that another amorphous sample of the same alloy can be formed on the crystallized mould. In addition, metallic glass replicas can also be used as moulds for polymers or other metallic glasses with lower softening temperatures. Using this 'spawning' process, we can massively replicate patterned surfaces through direct moulding without using conventional lithography. We anticipate that our findings will catalyse the development of micro- and nanoscale metallic glass applications that capitalize on the outstanding mechanical properties, microstructural homogeneity and isotropy, and ease of thermoplastic forming exhibited by these materials.

Fabrication of nanodot array molds for photonanoimprint using anodic porous alumina

This article reports on the fabrication of a transparent nanodot array mold for nanoimprint and so on. In the mold fabrication, the combination of a porous alumina master mold made by anodization of an Al plate and spin on glass replica process is utilized to pattern nanodot array on a transparent mold with large area. Using this method, the authors could obtain transparent nanodot array mold pattern with a pitch of about 100nm and height/depth of 90nm. When this nanodot array mold was used for photonanoimprint, a pitch of the photonanoimprinted pattern was found to be about 100nm. The pitch is considered quite comparable to the pitch of the patterns on the porous alumina master mold.

And the winner is … 20 years of excellence in research on allergic disease!

And the winner is … 20 years of excellence in research on allergic disease!

Fabrication of Low Line Edge Roughness Mold by Spin On Glass (SOG) Replica Method

This paper reports on the fabrication of a low line edge roughness (LER) mold by the spin on glass (SOG) replica method. The fabrication technique provides a transparent mold with a low LER. In the mold fabrication, the combination of a low LER Si master mold made by anisotropic wet etching and the SOG replica process is effective in reducing fluctuation of the transparent mold pattern. Using this method, we could obtain an LER of SOG replica mold as low as 0.80 nm. When this SOG replica mold was used for photo-nanoimprint, the LER of the patterns on the photocurable polymer, used for the process, was found to be 0.86 nm which is considered quite comparable to the LER of the patterns on the Si master mold. Moreover, using the SOG replica mold, we also nanoimprinted a 60 nm line and space (L/S) pattern with an aspect ratio of 2 and 30 nm L/S patterns.

FABRICATION OF UNIFORM ARRAY OF NANO-DOTS AND ITS APPLICATIONS

We have developed a novel technique to fabricate extremely uniform arrays of nano-sized dots. Regular arrays of nanometer-sized metallic dots are obtianed by magnetron sputtering deposition through a nanochannel glass replica mask. The platinum replica masks are fabricated using thin film deposition on an etched nanochannel glass and contain hexagonally patterned uniform voids with diameters as small as 50 nanometers. The metallic dot density can be as high as 5×1011 per square centimeter. The magnetic properties of Ni and Co dot arrays have been studied by a Alternating Gradient Magnetometer. The magnetic dot array can be used as pinning centers for superconductors and also can be used as the discrete magnetic media for magnetic recording.

Surface Modification of the Channels of Poly(dimethylsiloxane) Microfluidic Chips with Polyacrylamide for Fast Electrophoretic Separations of Proteins

The electrophoresis of proteins was investigated using poly(dimethylsiloxane) (PDMS) microfluidic chips whose surfaces were modified with polyacrylamide through atom-transfer radical polymerization. PDMS microchips were made using a glass replica to mold channels 10 microm high and 30 microm wide, with a T-intersection. The surface modification of the channels involved surface oxidation, followed by the formation of a self-assembled monolayer of benzyl chloride initiators, and then atom-transfer radical polymerization to grow a thin layer of covalently bonded polyacrylamide. The channels filled spontaneously with aqueous buffer due to the hydrophilicity of the coating. The resistance to protein adsorption was studied by open-channel electrophoresis for bovine serum albumin labeled with fluorophor. A plate height of 30 microm, corresponding to an efficiency of 33 000 plates/m, was obtained for field strengths from 18 to 889 V/cm. The lack of dependence of plate height on field strength indicates that there is no detectable contribution to broadening from adsorption. A 2- to 3-fold larger plate height was obtained for electrophoresis in a 50-cm polyacrylamide-coated silica capillary, and the shape of the electropherogram indicated the efficiency is limited by a distribution of species. The commercial capillary exhibited both reversible and irreversible adsorption of protein, whereas the PDMS microchip exhibited neither. A separation of lysozyme and cytochrome c in 35 s was demonstrated for the PDMS microchip.

Magnetic resonance imaging of dense and light non‐aqueous phase liquid in a rock fracture

Magnetic resonance (MR) imaging was used to observe the flow of dense (FC‐75) and light (dodecane) non‐aqueous phase liquids (NAPLs) through a water saturated dolomite fracture. Dynamic two‐phase behavior was influenced by (1) buoyancy of the NAPL relative to the aqueous phase, (2) fracture aperture distribution, and (3) alteration of wettability by long‐term presence of NAPL phase. MR imaging was capable of characterizing the fracture geometry and the fluid flow, but was limited by outlet flow conditions in the sample and acquisition times. This method permits observation of two‐phase flow under natural wettability and matrix porosity, providing significant advantages over plastic or glass replicas.