Thin Glass Sheets Research Articles

Low insertion loss interposer approach for RF applications based on commercial LTCC tape, alkaline-free glass and printed metallization

Materials with high RF performance are in increasing demand due to the needs of modern telecommunications. Glass and low-temperature co-fired ceramics (LTCCs) are both interesting candidates for the design of complex signal transmission systems. Glass can be processed in large panels, and has suitable structure dimensions for silicon processing, but its multilayer capability is limited. LTCC is a mature technology for complex multilayer assemblies, but the structure dimensions and conductor line resolution are restricted by the need to use screen printing technology. The approach presented here combines the advantages of both technological domains: a thin glass sheet is bonded with no additional material to a LTCC multilayer ceramic and sintered to form a tight joint. Metallization of the glass is created using printable pastes and electroplating. Two fabrication routes are compared: etching of printed thick film metal layers, and semi-additive structuring. The results of RF measurements show a low attenuation per unit length for both types of metallization, indicating that our approach is a promising one for the integration of heterogeneous systems of RF transmission modules.

Guided axon outgrowth of neurons by molecular gradients generated from femtosecond laser-fabricated micro-holes

ObjectiveTransplantation of scaffold-embedded guided neurons has been reported to increase neuronal regeneration following brain injury. However, precise axonal integration between host and transplant neurons to form functional synapses remains a major problem. Thus, a high-precision tool to actuate neuronal axon outgrowth in real-time conditions is required to attain robust axon regeneration. This study aims to establish a microfluidic platform for precise and real-time axon outgrowth guidance. Methods: A microfluidic device with a 4 μm thick thin-glass sheet as the neuron culture substrate is fabricated. Surface of the glass sheet is chemically modified to facilitate neuron attachment. Femtosecond (fs) laser is used to engrave the glass sheet to achieve micro-holes, where netrin-1 is released for directing the movement of the neuronal axon. Results: Numerical simulation and experimental data demonstrate that netrin-1 gradient is formed after it passes through the micro-hole. The neuronal response results show the outgrowth rate of the axon is significantly increased by netrin-1 gradient. Furthermore, a majority of neuronal axons exhibit guided outgrowth characterized by positive turning angles of axon displacement in the direction of netrin-1 gradients. Conclusion: Integrating fs laser and microfluidic device facilitates controlled and instantaneous axon outgrowth in a non-invasive manner. Significance: The developed real-time microfluidic platform shows potential in the application for on-site neuronal transplantation, which is significant for the treatment of a range of neurological disorders and injuries.

A comparative analysis of the impact of Bi, Ga, Cr, In, or Sm ions on the Na-B-Te glasses network for UV block in smart windows and optoelectronic applications

Five samples of glass were fabricated, each with the corresponding composition (60%B2O3 + 25%Na2Co3 + 10%TeO2 + 5% M) mol%, M represents one of the following oxides [Cr2O3/ Ga2O3/ In2O3/ Bi2O3/ Sm2O3]. Each glass sample mixture was placed in a porcelain crucible and prepared using the fast quenching technique at 1373 K for one hour. Two brass discs were used to pour each sample at room temperature to obtain a thin glass sheet of each. Several approaches were used to measure the samples in their as-prepared state. The XRD verified that the produced samples were amorphous. For each sample, FTIR studies revealed a large number of absorption bands. The band observed for the studied glass samples at 700 cm−1 is attributed to the B-O-B asymmetric stretching vibration bond of [BO3], a peak at 1430 cm−1 indicates the presence of the asymmetric stretching vibration of the BOB bonds in [BO3]. A peak at 460 cm−1 indicates the presence of Te O Te or O Te O bending mode as well as other characteristic peaks for other ions present in the glass matrix. The glass sample having 5mol% Bi, according to optical measurements, completely absorbs UVA and UVB rays; however, it does not absorb visible light, which is a benefit for lowering the need for artificial lighting throughout the day. This promotes energy efficiency and qualifies it for use in green (sustainable) construction applications. For each processed glass sample, Urbach energies, band gaps for direct and indirect transitions, and refractive index were determined. Based on AC data, a DC plateau was seen at low temperatures, which was followed by an increase in conductivity, reaching a maximum of 10−8 S/m for the Cr sample. It was realised that the Bi glass sample is an effective UV radiation blocker for green life.

Gap design to enable functionalities into nested antiresonant nodeless fiber based systems.

By modifying the interconnection design between standard single-mode fiber (SSMF) and nested antiresonant nodeless type hollow-core fiber (NANF), we create an air gap between SSMF and NANF. This air gap enables the insertion of optical elements, thus providing additional functions. We show low-loss coupling using various graded-index multimode fibers acting as mode-field adapters resulting in different air-gap distances. Finally, we test the gap functionality by inserting a thin glass sheet in the air gap, which forms a Fabry-Perot interferometer and works as a filter with an overall insertion loss of only 0.31 dB.

Designing, fabrication and evaluation of a rapid, point-of-care and noninvasive system for the detection of lead (Pb2+).

Non-invasive collection of biological sample such as sweat, urine, saliva, hairs and, stool and onsite detection of anlaytes in those samples is an interesting and viable approach for rapid screening of various toxicants in body. Environmental exposure/presence of lead (82Pb) and its rapid detection provide one such opportunity. A chemical spot based colorimetric method and a transdermal patch device based on this spot test, is developed for rapid and qualitative assessment of inorganic lead (Pb2+) in non-coloured biological or environmental liquid samples. The transdermal patch system contains two important parts, a chemical spot prepared on a thin glass sheet and, an absorbent paper (11µm pore size). A one step colour development reaction is able to identify the presence or absence of Pb2+. In-vitro evaluation for sensitivity and cut-off value determination, within run and between run precision testing, specificity testing were done. In-vivo evaluation of the developed patch system was performed in occupationally lead-exposed subjects and in control volunteers. In-vivo field testing results were further validated with gold standard test for lead detection. Blood lead levels and patch lead levels were found to be positively correlated (r = 0.57, P < 0.0001). In addition, the sensitivity and specificity of device in identification of Pb2+ was found to be 75.93% (95% CI = 62.36%-86.51%) and 95.24% (95% CI = 76.18%-99.88%). The developed system appears as a reliable, non-invasive rapid test with minimum step involve for identification of Pb2+ in a given system.

Thermal strengthening of low‐expansion glasses and thin‐walled glass products by ultra‐fast heat extraction

AbstractThermal strengthening remains the primary method for enhancing the practical strength of commodity glass products, however, the process is limited in terms of applicable glass thickness and coefficient of thermal expansion. The primary reasons for this limitation are the achievable heat transfer coefficient when using conventional gas cooling, and the occurrence of transient surface tension in the early stages of rapid quenching. We revisit this problem for the case of thin borosilicate glass sheet. Using liquid gallium as the cooling medium, ultra‐fast heat extraction is achieved, with a heat transfer coefficient exceeding 5000 Wm−2 K−1. The low vapor pressure of gallium even at high temperatures enables preheating to a wide range of sheet entrant temperatures. We demonstrate thermal strengthening of low‐expansion borosilicate glass with persistent surface compression of up to 85 MPa, and quenching to a fictive temperature of ~190 K above the glass transition temperature. Glass sheet obtained in this way exhibits notably enhanced surface defect resistance to sharp indentation. In addition to thermal strengthening, the extraordinarily high heat extraction rates achieved by liquid metal immersion enable exploitation of high‐Tf glass properties beyond small and thin sample geometry.

Physical properties of chemically strengthened thin glass prepared by the spray method using an original KNO3–Al2O3 slurry

In this study, we developed a novel KNO3–Al2O3 slurry for the chemical strengthening of thin glass sheets using a spray process, and investigated the physical properties of the strengthened glass. A 1 μm particle size α-Al2O3 powder is mixed with a KNO3 solution to obtain the novel slurry. Controlling the temperature and duration of the chemical strengthening process effectively tunes the compressive stress and depth of layer. The strengthened thin glass sheet produced in this study exhibits similar strength properties as commercial products. The highest compressive stress (CS) value (868 MPa) is obtained for the sample heated at 400 °C for 1.5 h, and the highest depth of layer value (60 μm) is observed for the sample at 480 °C for 4 h. The strengthened glass shows good hardness and bending strength. The glass sample heated at 400 °C for 1.5 h exhibits the highest hardness (680 HV) and bending strength (630 MPa).

Ni-Ti supermirror coated onto a curved substrate for nested neutron-focusing optics

Low neutron intensity is a critical problem for neutron scattering measurements at compact sources Among various other methods, reflection-based neutron-focusing devices have been developed to increase the neutron flux on samples. In this study, we utilized nested neutron-focusing optics to converge a neutron beam with large divergence. These optics consisted of nested full conical shells that were assembled from supermirror-coated thin glass sheets with an initially cylindrical form. Specifically, an optimized m = 2 Ni/Ti supermirror coating was applied to the concave sides of cylindrical thin glass substrates utilizing a dedicated DC magnetron sputtering system. A particle collimation system was also incorporated into the deposition process to achieve excellent thickness uniformity for the supermirror coating. As a result, the characterized thickness variation was within 2% on the inner sides of the curved substrates. The internal stress of the supermirror coating was effectively reduced to approximately -135 MPa under a 0.4 Pa working gas pressure. The supermirror coating provided a reflectivity of over 78% with a momentum transfer Q ranging from 0.1 to 0.45 nm−1. Consequently, the neutron flux collected by the focusing optics was enhanced by a factor of 26 compared to a conventional pinhole design according to our experimental results.

Effect of α-Al2O3 Particle Size in a Slurry on the Physical Properties of Chemically Strengthened Thin Glass Prepared by the Spray Method.

Chemical strengthening is considered as the most suitable method for strengthening thin glass sheets used in mobile phones. The spray method of chemical strengthening requires a slurry to be sprayed on the glass sample to be strengthened. This slurry is prepared by mixing various compounds. In this study, the influence of α-Al2O3 particle size in the slurry on the physical properties of the chemically strengthened glass prepared by the spray method was investigated. The compressive stress (CS) was dramatically enhanced as the particle size of Al2O3 in the slurry decreased. The glass sample with 13 nm α-Al2O3 including the KNO3-Al2O3 slurry exhibited the highest CS of 905 MPa, and the depth-of-layer (DOL) of this sample was 37 μm. The same slurry composition also achieved the highest bending strength of 640 MPa under different heat treatment conditions. The optimization of the heat treatment conditions, such as temperature and time duration, resulted in the highest value of CS (916 MPa) obtained for the sample heated at 400 °C for 1.5 h, and the maximum DOL (65 μm) was obtained for the sample at 480 °C for 4 h.

Implementation of a nanochannel open/close valve into a glass nanofluidic device

In micro-/nanofluidics, channel open/close valves are fundamental to integrating fluid operations and realizing highly integrated analytical devices. Recently, we proposed a nanochannel open/close valve utilizing glass deformation and verified the principle of opening and closing nanochannels. Glass deformation sufficient to close the valve was achieved using a 45-µm-thick glass sheet as a material of a nanofluidic device. However, since the device incorporates the thin glass sheet and is not robust enough to be used for repeated analyses, fluid operations utilizing the valve have not been verified sufficiently. Thus, in the present study, we fabricated a nanofluidic device implemented with a nanochannel open/close valve using rigid glass substrates of thicknesses on the order of 100 μm, and verified fluid operations utilizing the valve. On a small part of the substrate, we designed and fabricated a 30-µm-thick deformation section for the valve. The open/close operation and the performance of the valve were verified. The leakage of the valve was measured to be 2%, the response time was 0.9 s, and the number of repetitions was over 100,000. By utilizing the fabricated valve, we demonstrated fluid operations with femtoliter to picoliter volumes. Flow-switching within approximately 1 s and a flow control rate in the 63-1341 fL/s range was achieved. In addition, the fluid resistance of the valve was investigated both experimentally and numerically to establish a guideline for designing the valve. The valve developed and the design guidelines obtained will greatly contribute to integrated nanofluidic analytical devices.

Modeling multivariate dependencies for manufacturing single-mode I/O structures of integrated MMI-based splitters in glass sheets

For the realization of integrated optical interconnect systems, optical waveguide components are needed. A promising approach to manufacturing graded-index waveguide components is their embedding in thin glass sheets by ion-exchange processes. Conventionally, the modeling of integrated waveguide components manufactured by thermal diffusion processes involves the numerical solution of differential equations. In this work, a semi-analytical approach for the modeling of the concentration profile is extended by the Gauss–Newton optimization algorithm. This is done with the specific purpose of accurately modeling single-mode input and output waveguide structures of multimode-interference-based (MMI-based) optical splitters. The constraints imposed by the multivariate manufacturing process for the realization of these MMI-based components are elaborated. Corresponding correlations between these constraints and the according modeling of the devices are established.

A Multigap Resistive Plate Chamber built with thin low-resistive glass:High rate capability with excellent time resolution

Abstract Two Multigap Resistive Plate Chambers (MRPCs) were built with thin (0.4 mm) low-resistive glass sheets for the inner plates and standard 0.28 mm ‘soda lime’ float glass as external plates. The 6-gap MRPC reaches 96.5% efficiency at 15.6 kV and a time resolution of 68 ps at an instantaneous particle flux around 2.5 kHz/cm 2 . The 20-gap MRPC reaches 98% efficiency at 18.8 kV and a time resolution of 32 ps. Compared to a 6-gap MRPC built previously with all plates made with soda-lime float glass, the two MRPCs made with low-resistive inner glass show a much higher count rate capability. A third MRPC with all plates made from low-resistive glass was also constructed to verify the operation at high particle flux. In this paper a relative rate capability comparison between the MRPCs has been performed under a pulsed beam with a small spot on the chamber. Their rate capability under full illumination with continuous particle flux needs to be further studied.

Timing performance study of Multigap Resistive Plate Chamber with different gap size

Abstract This paper reports on the results of time resolution measurements of Multigap Resistive Plate Chamber (MRPC). Three 20 gas gaps MRPCs were built with thin float glass sheets and different gap sizes: 160 μ m , 140 μ m and 120 μ m . These chambers have been tested using a different gas flow configurations. The measurements indicate that to reach a better time resolution for small gap size ( 140 μ m and 120 μ m ), a smaller gas volume of the chamber is preferable. The efficiency of the chambers in both gas flow configurations has been tested. A time resolution of 25 ps comprehensive of the front-end electronics jitter, with an efficiency of 98% has been achieved for the MRPC with 140 μ m gas gaps; this is the best time resolution. Moreover, all the chambers have been tested for different particle flux . At the highest particle flux tested, a time resolution better than 60 ps together with an efficiency higher than 80% has been achieved for all the detectors at an instantaneous particle flux of 30 k H z ∕ c m 2 . From the efficiency and time resolution study, the rate capability for these three MRPC is similar.

Thermal insulation performance of an advanced photovoltaic vacuum glazing: A numerical investigation and simulation

Structural details of an advanced laminated PV (photovoltaic) vacuum glazing are illustrated. The glazing design features low heat gain or loss, while the sandwiched PV film generates electricity and allows daylight and vision. The thin vacuum gap and glass sheets make it slimmer and lighter than conventional designs. Aerogel support pillars and epoxy resin edge seals minimise conductive heat transfer and further reduce the weight of the window. The thermal insulation performance of the PV vacuum glazing is numerically investigated. All the three heat transfer mechanisms are considered in the COMSOL modelling. During the modelling of radiation in participating media, the optical properties of low-e (low-emissivity) and PV coating are considered and a boundary condition for translucence is re-customized in particular. For the verification of the modeling accuracy, a simplified vacuum glazing model is adopted first. The simulation results are consistent with the thermal performance data report of a vacuum glazing manufacturer. Subsequently, comprehensive simulation results with different configurations of the PV vacuum glazing are presented and discussed. Retrofitting of steel pillars with aerogel pillars for conventional vacuum glazing can yield a decrease of 0.3255 W/m2 K in the overall U-value and a decrease of 0.2559 W/m2 K in the central U-value. Besides, the thermal resistances of the laminated structure are calculated layer by layer. Moreover, the influence of the radiative parameters of the PV film on the thermal performance of the glazing is assessed. On the other hand, the simulation of the PV vacuum glazing under solar radiation is carried out to evaluate its working temperature.

20 gas gaps Multigap Resistive Plate Chamber: Improved rate capability with excellent time resolution

A 20 gas gaps multigap resistive plate chamber (MRPC) was built with thin (0.28 mm) glass sheets and 0.16 mm gas gap size. This chamber reaches 97% efficiency at 18.4 kV and a time resolution of 32 ps (sigma) at an instantaneous particle flux around 2.5 kHz/cm2. Compared to a 6 gaps MRPC with 0.22 mm gas gap, this 20-gap MRPC shows a higher rate capability and much better time resolution. The efficiencies of the 20-gap MRPC reach 95%, 93% and 88% at instantaneous fluxes of 10 kHz/cm2, 14.5 kHz/cm2 and 20 kHz/cm2, respectively. The efficiencies of the 6-gap MRPC at the same flux are 90%, 85% and 77%. The time resolution of 20-gap MRPC degrades with the increase of particle flux. However, a time resolution of 39 ps was obtained at an instantaneous flux of 10 kHz/cm2.

Utilizing multimode interference effects in integrated graded-index optical waveguides for efficient power splitting

PurposeFor the realization of optical waveguide components, needed for photonic integrated circuits, multimode-interference based (MMI-based) devices are an excellent component class for the realization of low loss optical splitters. A promising approach to the manufacturing of these components is their embedding in thin glass sheets by ion-exchange diffusion processes, which has not yet been extensively studied. This study aims to significantly enhance the modeling of the diffusion process to support manufacturing of graded-index, MMI-based optical splitters.Design/methodology/approachThe methods of design and analysis of MMI-based components are based on a step-index refractive index profile. In this work, fundamental correlations between the properties of the manufacturing ion-exchange process and the characteristics of the graded-index, MMI-based components are established. The refractive index profile is calculated with a proprietary solver based on the finite element method. Any further investigation with respect to parameter influence is based on the beam propagation method, specifically a finite difference based, semi-vectorial, wide-angle beam propagation algorithm. The influence of the parameters of the self-imaging effect is investigated. On this basis, different approaches for efficient power splitting with graded-index, MMI-based waveguide components are evaluated.FindingsEasy approximations – mostly linear – can be found to model the dependencies of the investigated parameters. The resulting graded-index splitters are characterized by their low excess and insertion loss.Originality/valueThese findings are the first step in the direction of the semi-analytical modeling of the respective waveguide components to reduce the numerical effort.

Glass sheet redraw through a long heater zone

Thin glass sheets may be manufactured using a two-part process in which a sheet is first cast and then subsequently reheated and drawn to a required thickness. The dimensions of the heater zone used for the latter ‘redraw’ process determine the relative change in the width and thickness of the sheet. When a product with the same cross-sectional aspect ratio as the original sheet is desired, the heater zone through which the sheet is drawn must be long compared with the sheet width. However, deviations from the original aspect ratio due to the finite length of the heater zone can be significant, and the final product is typically thick at the edge compared to the centre. We present a model for redraw of a thin glass sheet and consider the limit in which the heater zone is long compared with the sheet width. We show that the deviations in aspect ratio and thickness depend linearly on the ratio of sheet width to heater zone length and arise due to boundary layers at the sheet ends where the fluid flow adjusts to satisfy imposed boundary conditions. The behaviour inside the boundary layers can be reduced to a canonical problem that is independent of process parameters, and we thus calculate the final thickness and width of the redrawn sheet.

Low loss optical MMI-based splitter based on a semi-analytical modeling approach

For the realization of optical waveguide components, needed for photonic integrated circuits, a promising approach to manufacturing is their embedding in thin glass sheets by thermal diffusion processes. In this work, a semi-analytical approach to modeling the concentration profile of geometrically large components of a thermal ion-exchange diffusion process is evaluated to reduce the computational requirements to an absolute minimum. Conventionally, the modeling of integrated waveguide components manufactured by diffusion processes is based on solving the diffusion equation numerically. This approach, however, is based on the approximation of the analytical solution of the one-dimensional diffusion equation and its abstraction for a higher dimensionality. After introducing some general constraints with respect to the utilization of multimode interference effects (MMI-effects), the application to the modeling of these waveguide components is validated. The introduced error is evaluated and the excess and insertion loss of the modeled MMI-based splitters are calculated.

Cutting thin glass by femtosecond laser ablation

The femtosecond laser ablation process for cutting thin aluminoborosilicate glass sheets of thickness 100 μm was investigated with emphasis on effective cutting speed (Veff) and mechanical strength of diced samples. The process parameters including the laser fluence (F), overlap ratio (r) of the laser beam and polarization direction were varied at a fixed pulse repetition rate f = 1 kHz to find the optimal process condition that maximizes Veff and edge strength. A three-point bending test was performed to evaluate the front-side and back-side bending (edge) strength of the laser-cut samples. Veff was proportional to F unless r exceeded a critical value, at which excessive energy began to be delivered at the same spot. The front-side edge strength was bigger than the back-side strength because of the back-side damages such as chipping. Good edge strength, as high as ∼280 MPa (front-side) and ∼230 MPa (back-side), was obtained at F = 19 J/m2, r = 0.99, with laser polarization vertical to the cutting path.

ガラスへの圧子押込みにおける応力状態とクラック進展過程の動的観察

Wheel scribing techniques were commonly used for glass separation. We have studied on the internal stress field during/after wheel scribing using the photoelastic method. Internal stress data obtained by photoelastic method was integrated data of the light progression, and internal stress induced by a scribing wheel distributed three-dimensionally. This characteristic complicates the explanation of the photoelastic data. In this paper, we investigate two dimensional internal stress fields by the indentation of a wedge on a thin glass sheet. As a result, birefringence and azimuthal angle was obtained during/after the indentation. Internal stress by the plastic deformation was observed. First, median cracks were propagated after the indentation, then lateral cracks were propagated. The internal stress was released along with the crack propagation.