Fused Silica Micro Research Articles

Mitigating rim bending in fused silica micro shell resonators by a chamfered mold

In this work, we addressed the bending of a micro shell resonator’s rim toward the stem during glass-blowing process. This phenomenon occurs due to increased heat loss at the mold’s edge and reduced heat flux at the side of the Gaussian heat source. To mitigate rim bending and the subsequent reduction in capacitance between the rim and 3D electrodes, which can degrade performance in micro glass-blown shell resonators for gyroscopes, we propose two potential mold solutions, using short-stem mold and chamfered mold. To quantitatively compare resonators created by these two types of molds, we calculated the noise factor for predicting its gyroscope performance. From these calculations, we find out that using the chamfered mold enables us to increase in the resonator’s effective mass, eigenfrequency, angular gain, and quality factor, consequently reducing the noise factor compared to using the short-stem mold. We also demonstrated these results by manufacturing shell resonators and measuring its vibrational characteristics. After metalization of the glass shell resonator, Q factor and eigen frequency of n = 2 vibration mode along the primary (secondary) axis were measured to 622,466 ± 6,427 (619,793 ± 6,402) and 4,343 ± 40 Hz (4,350 ± 40 Hz), respectively. This simulation process will assist us in getting insight into understanding a shell resonator as a gyroscope, designing a mold and determining experimental conditions.

Controllable Preparation of Fused Silica Micro Lens Array through Femtosecond Laser Penetration-Induced Modification Assisted Wet Etching.

As an integrable micro-optical device, micro lens arrays (MLAs) have significant applications in modern optical imaging, new energy technology, and advanced displays. In order to reduce the impact of laser modification on wet etching, we propose a technique of femtosecond laser penetration-induced modification-assisted wet etching (FLIPM-WE), which avoids the influence of previous modification layers on subsequent laser pulses and effectively improves the controllability of lens array preparation. We conducted a detailed study on the effects of the laser single pulse energy, pulse number, and hydrofluoric acid etching duration on the morphology of micro lenses and obtained the optimal process parameters. Ultimately, two types of fused silica micro lens arrays with different focal lengths but the same numerical aperture (NA = 0.458) were fabricated using the FLPIM-WE technology. Both arrays exhibited excellent geometric consistency and surface quality (Ra~30 nm). Moreover, they achieved clear imaging at various magnifications with an adjustment range of 1.3×~3.0×. This provides potential technical support for special micro-optical systems.

Fused Silica Micro Shell Resonators by a Wafer-Level Thermal Reflow Process

Fused Silica Micro Shell Resonators by a Wafer-Level Thermal Reflow Process

The influence of photothermal effect on the resonance frequency of fused silica micro hemispherical resonator

Micro-electro mechanical system resonant gyroscope plays a more and more important role in inertial navigation. As a core sensing component of micro resonant gyroscope, fused silica micro hemispherical resonator (FS-MHR) is widely concerned because of its great performance potential. The resonance frequency is one of the important characteristic parameters of micro resonators, and laser vibration measurement technology is often used for high-precision measurement of this parameter. During the measurement process, it is inevitably affected by the interference of some light sources. To explore how light affects the resonance characteristics of FS-MHR, this paper establishes a relevant theoretical model; and verifies and analyzes the influence of the photothermal effect on the resonance characteristics of FS-MHR through simulation and experiment. Revealed the trend of temperature and resonance frequency changes over time under the same lighting conditions for uncoated and metal-coated films. The measured data shows that the resonance frequency of FS-MHR coated with the metal film is more susceptible to the influence of the photothermal effect. After 60 s of illumination, the resonance frequency will increase by 6.13 Hz, and frequency splitting will also cause a deviation fluctuation of 2.35 Hz under continuous illumination. This will introduce certain errors in the measurement results, and corresponding measures need to be taken to avoid interference from the light source.

Novel designed mechanical-mechanochemical synergistic micro-grinding technology and compounded abrasive micro-grinding tools

The mechanical and mechanochemical synergistic micro-grinding technology was proposed for grinding hard and brittle materials, especially for fused silica micro parts in this work. Compounded abrasive micro-grinding tools with diamond abrasives on the outer layer and cerium oxide abrasives on the inner layer were designed and fabricated. Efficient grinding was initially achieved by mechanical processing of super hard abrasives, and then ultra-precision processing was obtained by mechanochemical process to remove surface or subsurface damage. This study firstly analyzed the contact model of single diamond abrasive particle and theoretically evaluated ground surface roughness. The mechanism of abrasive layer wear was investigated for accurate error compensation. The formulation of cerium oxide abrasive layer and its processing efficiency were further analyzed. The material removal mechanisms of fused silica during mechanochemical grinding were also studied. Results showed that the material removal rate was 1.924 μm/min and the surface roughness Ra was 0.248 μm after mechanical processing. Subsequently, the surface roughness Ra was improved to 38 nm after mechanochemical processing. The study indicates that this technique is a promising approach for high-efficiency and high-quality grinding of fused silica.

Three-Dimensional Digital Reconstruction Geometric Analysis for Fused Silica Microshell Resonators

This paper reports, for the first time, a 3D digital reconstruction method for geometric characterization of fused silica microshell resonators. Three-dimensional digital geometric information of fused silica microshell resonators prepared by a chemical foaming process is acquired by X-ray microscope. The surface points of the microshell are selected by pixel contrast to reconstruct the 3D geometric model. The 4th harmonics distribution of spatial radius and thickness at different shell heights are successfully calculated with the reconstruction model. The finite element method based on the reconstruction model is also established to analyze the resonant frequency and frequency split of the wineglass mode. Results show that the relative 4th radius harmonic decreases with the height increase, indicating that the chemical foaming process has the capability to restrain the asymmetry for fused silica micro shell resonators. Besides, the wineglass frequency difference between the digital reconstruction model and the experiment is within 3%. The frequency splits from the digital model also correspond well with the experiments. This work provides new insights in 3D shell information, and may enable manufacturing precision improvement of 3D microshell resonators.

Ultrafast laser in fabrication of micro hemispherical resonators with quality factor over millions

Fused silica (FS) micro hemispherical resonators have attracted considerable interest for application in high-performance sensors. Manufacturing of resonators with extremely high quality factor and acceptable cost is currently the main challenge. Here, we demonstrate the application of ultrafast laser in manufacturing of three-dimensional (3D) FS micro hemispherical resonators with unrestricted edge shapes. The 3D FS structures fabricated from micro glassblowing are detached from substrates by direct laser ablation with amplification tines, which is useful for improving the performance of the resonators. Resonators fabricated from direct laser ablation are experimentally characterized, exhibiting quality factors over millions via electrostatically characterization. This is the first time that ultrafast lasers are exploited in the manufacturing of mechanical resonators, while obtaining satisfactory performance. Effective integration of the laser ablation into current devices will greatly improve the fabrication ability, generating important implications for future micro electronic devices.

Frequency split suppression of fused silica micro shell resonator based on rotating forming process

This paper demonstrates the impact of harmonic error on the natural frequency of micro shell resonator (MSR). Parameterized 3D model is established to analyze the frequency split of resonator with deviation along the circumferential and height direction. Both the n = 1 tilt mode and n = 2 wineglass modes are considered. The simulation results show that frequency split significantly increases as the growth of the 2nd and 4th harmonic errors. At the same time, the influence of frequency split on MSR output is analyzed. The increasing of frequency split will lead to the increasing of quadrature error and decreasing of mechanical sensitivity. The uniformity of the temperature field during processing is considered, a rotary platform is used to reduce the harmonic error of the resonator by improving symmetry of the shell structure. After measurement, the error of 2nd harmonic and 4th harmonic errors have been suppressed by using rotating platform. Finally, more than 10 samples are electrostatically characterized and well matched with the simulation results, the initial frequency symmetry of n = 1 and n = 2 modes is greatly promoted.

Experimental and numerical studies of the diluent influence (N2, Ar, He, Xe) on stable premixed methane flames in micro-combustion

This work focuses on the diluent influence on stable methane flames in a fused silica micro flow reactor (MFR). Experimental and numerical investigations are performed. The first part presents the method of performing experiments and extracting data from an MFR in order to increase the reliability of the experimental results necessary for subsequent numerical simulations. Those methods are applied to premixed stoichiometric methane flames diluted by nitrogen, argon, helium and xenon. Methods to point out the influence of mixture thermodynamic and transport properties influence is presented. A numerical study of the influence of diluent on stable flames is also undertaken to support the experimental observations difficult to realize in such micro-devices.

Response Surface Modeling and Optimization of Gelcast Fused Silica Micro Hybrid Ceramic Composites

In the current work, Response Surface Methodology (RSM) was effectively implemented to the technique of fabrication of fused silica (SiO2) advanced hybrid ceramic composites using gelcating, a near net shaping process. The influence of process variables like solid loading (SL), monomer ratio (MR) and monomer content (MC) on flexural strength (FS), porosity (P) and dielectric constant (e) was explored using central composite face centered design (CCFCD) with six centre points approach to an experimental work. The interaction between the process parameters on the responses was studied and modeled. Three mathematical models were created through RSM related independent process parameters to portray the flexural strength, porosity and dielectric constant as the responses. The acceptability of the derived model was examined with the help of Analysis of Variance (ANOVA) at 95% confidence level and through other parameters. The statistical analysis of the outcomes demonstrated that in extend considered the three input factors have critical impact on the response. The RSM models obtained have high R2 values (0.999, 0.994, and 0.995) which demonstrate exceptional relation between the actual and predicted models. The optimum values obtained through RSM was experimentally confirmed and it was 87.36 MPa for flexural strength, 35.66% for porosity and 4.783 for dielectric constant (e) obtained at 52 vol% solid loading, 15:1 monomer ratio and 5 wt% monomer content respectively.

Fused Silica Micro Shell Resonator With T-Shape Masses for Gyroscopic Application

This paper presents a novel micro shell resonator (MSR) with T-shape masses based on fused silica using out-of-plane electrode structures. Eight circular-distributed T-shape masses are designed along the rim of resonator shell to improve transduction efficiency, including drive efficiency and detection efficiency. The dynamic parameters and transduction efficiency are calculated and optimized with finite element method, revealing 3.76 times improvement in drive efficiency, 4.65 times improvement in detection efficiency, and 17.81 times increase in mechanical sensitivity. In addition, it is feasible to trim the frequency by adding or removing mass on the T-shape masses. The key feature of the process is based on micro blow-torching process and whirling platform, which form the resonator structure with smooth roughness and good structure uniformity. Femtosecond laser ablation is used to release the T-shape masses for good symmetry and high processing quality. Then, metalized MSR with T-shape masses is assembled on a glass substrate. Electrostatic transduction is used to detect spatial deformation of resonators by out-of-plane electrodes, which reveals a frequency mismatch of 0.175% at 6904.4 Hz and 6916.5 Hz with quality factors of 20.39 k ( $\tau =0.94$ s) and $Q = 36.94$ k ( $\tau =1.7\text{s}$ ). [2017-0086]

Low Temperature Fabrication and Surface Modification Methods for Fused Silica Micro- and Nanochannels

ABSTRACTElectrokinetic based micro- and nanofluidic technologies provide revolutionary opportunities to separate, identify and analyze biomolecular species. Key to fully harnessing the power of such systems is the development of a robust method for integrated electrodes as well as a thorough understanding of the influence of the electrokinetic surface properties with and without different surface modifications. In this work, we demonstrate a surface micromachined fabrication approach for integrated addressable metal electrodes within centimeter-long nanofluidic channels using a low-temperature, xenon diflouride dry-release method for novel biosensing applications, as well as recent results from a joint theoretical and experimental study of electrokinetic surface properties in nano- and microfluidic channels fabricated with fused silica. The main contribution of this fabrication process involves the addition of addressable electrodes to a novel dry-release channel fabrication method, produced at <300°C, to be used in nanofluidic electronic sensing of biomolecules. Finally, we also show a novel method with which to coat our channels with silane based chemistries. Certain modifications are observed to show improved resistance to non-specific adhesion of both small molecules and proteins, indicating their further use as compatible surfaces in micro- and nanofluidic applications.

Catalysts by the meter: rapid screening approach of N-heterocyclic carbeneligand based catalysts

Here, we demonstrate a versatile screening platform for NHC ligand based catalysts by coating fused-silica micro capillaries with a bonded 1,3-bismesityl-2-imidazolidinylidene ligand. Such micro capillaries can be efficiently converted into (pre)-catalysts from various organometallic precursors by solid-phase chemistry techniques and can be quantitatively screened using on-column reaction chromatography.

High-performance liquid chromatography using flexible fused-silica micro-packed columns

High-resolution flexible fused-silica micro packed columns were prepared by coupling 50-cm columns in series. These columns produced large numbers of theoretical plates (more than 100,000) and were successfully applied to the separations of epoxy oligomers and polychlorobiphenyl mixtures in gel permeation chromatography and reversed-phase liquid chromatography, respectively.