Micrometer Accuracy Research Articles

Digital Holographic Interferometry for Micro-Deformation Analysis of Morpho Butterfly Wing

In this study, we present an analysis of deflections in a Morpho butterfly wing using digital holographic interferometry (DHI). Our methodology revolves around an off-axis lensless Fourier holographic setup, using laser excitation to induce deflections in the object. The implementation of a DHI setup, tailored for rapid monitoring of micro-deformation, is a central aspect of our research. We offer an overview of the theoretical foundations of this technique, complemented by both experimental and numerical results aimed at validating our findings. We designed an optical setup that enhanced both laser illumination and hologram reconstruction for the sample. The experimental findings decisively show that the proposed method is effective for rapid deformation analysis. The deformation of the wing can be measured with micro-meter accuracy thanks to numerical analysis.

Milling and Grinding to Single-Figure Micron Accuracy on One Machining Platform

Gerhard Rauch utilises high-tech 5-axis machine tools that enable it to machine to extremely tight tolerances and produce the high standards expected from its customers

Experimental analysis of failure modes depending on different loading conditions applied on cylindrical polyamide 66 gears

Abstract Engineering plastics are increasingly used for gearing systems, such as in the automotive sector, e-mobility sector, and household appliances. The basic task of the gearing system is to efficiently transfer power from the source to the application user. The use of engineering plastics for gearing applications is conditioned by the lack of tribological characteristics of material pairs which influence on fatigue and wear behaviour of the whole gearing system. The paper presents testing of the steel/Polyamide 66-gear by determining fatigue life in an infinite area, considering high precision optical measurements in the range of micro-meter accuracy of abrasion flank wear together with surface temperature in contact, providing an important database for engineers about material suitability for appropriate mechanical systems. Observing the results, gear flank wear of PA66 HT is directly proportional to the meshing temperature and torque. Thermal melting is a characteristic failure mode of the polymer gears which are exposed to higher load levels. In the middle torques, the dominant failure mode is flank fracture known as pitch point fracture. The greater impact of the gear wear mechanism occurs at lower torques where initial crack propagation starts at the pitch point and ends in the tooth root area.

A novel quasi-static compression test set-up with micron order accuracy for small specimens

Accurate displacement measurements during compression tests on small specimens using large standard universal testing machines are adversely affected by the compliance of the apparatus. The influence of compliance becomes more acute when conducting tests on quasi-brittle materials, such as cortical bone, that exhibit low failure strains and for which accurate modulus values are required. This paper presents a custom compression test set-up (i.e., a subpress) that facilitates routine quasi-static compression tests on small specimens by eliminating the effect of testing machine compliance on the results. The displacement of the compression test set-up was recorded using a combination of Hall effect sensors and multipole magnetic strips, which offers a resolution of less than one micron. The results of quasi-static compression tests on small polymer specimens are reported where the displacements were measured using the custom compression test set-up, the integrated displacement measurement system of a universal testing machine and a visual extensometer. Additional tests on cortical bone specimens demonstrate the effectiveness of the compression test set-up. Based on the results, the compression test set-up appeared to yield more consistent and accurate measurements compared to both the integrated measurement system of a universal testing machine and a visual extensometer. Novel data regarding the incipient fracture of cortical bone were obtained. The compression test set-up allows for the routine testing of a large number of bone specimens with micron accuracy in a short time frame, thus reducing the effects of degradation on biological specimens.

High‐Quality Micropattern Printing by Complex‐Amplitude Modulation Holographic Femtosecond Laser

AbstractHolographic femtosecond laser printing technology is widely used in the fabrication of micropatterns because of its high efficiency and flexibility. However, speckle noise and energy fluctuations limit the quality of the printed structure. In this study, an improved complex‐amplitude modulation holographic femtosecond laser printing method for high‐quality micropattern fabrication is proposed. The holographic light field is divided into a signal area and a surrounding noise area. To improve laser uniformity, phase modulation is applied in the signal region to eliminate the speckle noise caused by unconstrained phase interference, and weighted amplitude modulation is introduced in the signal area to improve the calculation accuracy. To precisely control laser energy density, weighted energy efficiency modulation is introduced in the noise region to disperse the energy that exceeds the material damage threshold. Under the synergistic control of laser uniformity and energy density, high‐quality micro‐pattern structures are printed efficiently. A high‐quality millimeter‐sized multifocal zone plate with micron accuracy is fabricated with the splicing printing method, demonstrating the potential of micropattern processing and the fabrication of functional devices such as binary optics.

Improved Reproducibility of Deflection Control Process for Cantilever‐Type MEMS Tactile Sensors

This paper describes an improved process for controlling the initial deflection structure of cantilever‐type MEMS tactile sensors. By using residual stress, deposition sequence, and metal layer patterns, the initial deflection of the cantilever was successfully aligned to the same initial deflection with micron accuracy and 97% yield in a simpler and easier process than previous processes. This enables a reduction in the number of processes and flexible control of deflection, which is expected to improve yield and shorten fabrication time. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Dipole and quadrupole resonance excitation in linear quadrupoles.

In the development of commercial quadrupole mass spectrometers, there is an interest in improving the performance characteristics such as transmission, resolution, and mass range. In particular, parametric and dipolar resonance excitation of trapping ions are used for linear quadrupole mass filters. Theoretical methods and numerical simulation of ion trajectories were applied for study of ion-optical properties. The review is devoted to description of different excitation methods to improve QMF performance and consists of three parts. The first part presents the results of a linear ion trap simulation for various operating conditions and excitation methods. The second part considers the effects of dipole excitation (DE) on the performance of the quadrupole mass filter. The last part analyzes the formation of stability islands by different methods of quadrupole excitation. To date conditions of mass separation in quadrupole mass filters with sin wave supply were described for stability islands of the first and third stability regions formed by quadrupole and DE. By complicating the electronics such methods allow to overcome the destructive influence of electric field distortions and obtain a resolving power and ion transmission efficiency comparable with commercial devices. At quadrupole resonance excitation by a two-frequency signal, it is possible to reduce the length of electrodes three times without losses in resolution and transmission, which reduces the cost of rod set production with micrometer accuracy. Dipole resonance excitation allows controlling the shape of the mass peak by changing amplitude and phase of the auxiliary AC signal. The main factors affecting the resolving power of a linear ion trap are described theoretically. The numerical modeling results are confirmed by experiment.

Precise and Rapid Replication of Complex‐Shaped Fused Silica Optics

AbstractThe high hardness, brittleness, and thermal resistance of fused silica glasses extremely challenge the mass production of complex‐shaped fused silica optics. This paper reports a new process chain for rapidly replicating complex‐shaped fused silica optics from complex molds at ambient temperature. The process chain mainly consists of the ultraprecision diamond turning of the complex‐shaped molds, the rapid shape replication through the silica precursor photopolymerization, and the transparent complex‐shaped optics derivation from the debinding and sintering. The directional shrinkages and surface texture evolutions in the process are comprehensively characterized for the replicated fused silica optics. After the shrinkage compensation, transparent fused silica optics with the spherical, microlens array, and hierarchical freeform surfaces are precisely replicated, exhibiting micrometric form accuracy, nanometric surface roughness, and high imaging quality. The proposed process chain provides a revolutionary approach for the mass production of precise complex‐shaped fused silica optics with fundamentally improved production efficiency and complex shape formation capability.

Process considerations for Aerosol-Jet printing of ultra fine features

In recent years, Aerosol-Jet (AJ) printing has become an increasingly popular technology applied in research ranging from the biomedical field to military applications to printed semiconductors. Extensive efforts have been made to understand the influence of process parameters and the underlying physical principles. Nevertheless, little attention has been paid to the optimization of ultra-small and highly precise printed features. Pushing the printer to its limits and manufacturing structures as small as tens of microns with a micrometer accuracy poses significant challenges, because effects that can be ignored for printing large features play a crucial role. This study demonstrates how the printing speed quickly causes intolerable distortions. In contrast to large-feature printing, the printing speed cannot be used as a free parameter to set the print thickness. We will discuss the non-constant printing behavior induced by the divert/boost shutter and present shutter on the fly as a solution to many problems, but only if the subroutine code is optimized. The modifications made to the code are disclosed in this paper for the first time. Knowing that printing precise features often results in a high print thickness, we will briefly discuss the issue of cracks caused by the drying of thick nanoparticle films. Altogether, this paper presents a range of important considerations for AJ printing ultra-fine features and an interesting insight into the particularities of operating the printer at its limits.

Newton ring interferometry application for 2D lens array alignment with micrometer accuracy.

The dense packing of two-dimensional (2D) lens arrays with high tilt and decentration accuracies is a technological challenge in coherent beam combining, as the collimator lens parameters and 2D lens array alignment must satisfy stringent requirements. A method for 2D lens array alignment based on Newton ring interferometry (NRI) is proposed. The analytical model and the algorithm presented in this study enabled the estimation of alignment sensitivity. An optical setup for alignment tests using NRI was developed and experimentally verified, and micrometer sensitivity was demonstrated. Analytical and experimental results showed that micrometer accuracy was achieved. Its limitations and prospects for improvement are also discussed.

Record field in a 10 mm-period bulk high-temperature superconducting undulator

A 10 mm-period, high-temperature superconducting (HTS) undulator consisting of 20 staggered-array GdBa2Cu3O7−x (GdBCO) bulk superconductors has been fabricated and tested successfully. Each GdBCO disk was machined into a half-moon shape with micro-meter accuracy and shrink-fitted into a slotted oxygen-free copper disk which provided pre-stress and effective conduction-cooling. The HTS undulator prototype, consisting of GdBCO disks, copper disks, and CoFe poles fitted in a long copper shell, was field-cooled magnetized in fields of up to 10 T at 10 K. An undulator field of 2.1 T in a 4 mm magnetic gap was obtained. This field is the largest reported yet for the same gap and period length and exceeds the target value of 2 T for the meter-long HTS undulator scheduled for the hard x-ray I-TOMCAT beamline in the Swiss Light Source 2.0. We have demonstrated that bulk superconductor based undulators can provide significantly improved performance over alternative technologies.

Absolute wavelength scanning interferometry for measuring the thickness of optical elements.

A technique for measurement of the thickness of optical elements using absolute wavelength scanning interferometry is presented in this paper. To achieve high-grade optical components and systems, the thickness of both planar and non-planar optical components must be measured with an accuracy of a few micrometers. The proposed technique is based on the Fizeau interferometer and interconnects data from three different tunable laser diodes yielding a long effective wavelength range and thus low measurement uncertainty. The uncertainty of the central thickness measurement ranges from hundreds of nanometers to a few microns. The method allows to measure the thickness of both flat optical elements as well as lenses with curved surfaces. Moreover, the areal information provided by the interferometry and its high angle sensitivity help to quickly and precisely align the measured component and reduce misalignment errors. The results of thickness measurements have been validated and cross-tested with other techniques. In addition to the thickness, the technique provides some additional information (wedge, surface form error) in the case of flat samples and can be easily and quickly modified (mounting of a Fizeau transmission sphere) to measure other essential parameters of optical elements. Thus, this one approach can replace many single-purpose measuring devices while maintaining high accuracy.

PS-BPC01-4: NONINVASIVE CONTINUOUS BLOOD PRESSURE MONITORING BASED ON WEARABLE RADAR SENSOR WITH PRELIMINARY CLINICAL VALIDATION

This paper proposes a novel sensing system for noninvasive and continuous estimation of blood pressure (BP), which is based on a custom designed wearable 120 GHz Doppler radar sensor. With radar signals detected from brachial artery at the elbow, the moving trajectory of the pulses can be accurately demodulated with micrometer accuracy, and thus the reflective pulse transit time(RPTT) can be obtained for the prediction model to estimate blood pressure. Clinical trials have been launched with invasive blood pressure as reference. Patients keep their arms straight with palms facing upward, and a transducer set for medical invasive blood pressure measurement called DTXPlus is set up. DTXPlus has one end connected to a monitor, and the other end connected to the arterial catheter that reaches the brachial artery. The blood pressure signals for reference standard are collected by a data acquisition card (DAQ) from the transmission wire between DTXPlus and monitor. Meanwhile, the 120 GHz radar sensor with concentrated energy and high frequency is used to obtain the pulse wave signals from the brachial artery at the elbow, which is almost the same place detected by both invasive and noninvasive methods. The radar sensor continuously transmits electromagnetic signals to the human body, and the throb of the artery modulates the electromagnetic waves in the phase and the backscattered signals return to the radar receiver. For comparison later, the radar outputs are acquired by the DAQ in synchronization with the blood pressure signals. Experiments were carried out in the operating room with permission, patients with cardiovascular diseases were tested for several minutes after operations. The experimental results show a great performance of the designed wearable radar sensor in the detection of weak pulse signatures. Compared to the ground truth of the invasive blood pressure, the estimated blood pressures by radar have mean errors below 3mmHg for most subjects. The results reveal the possibility for the proposed radar-based BP estimation technique to be employed inside and outside the clinic, such as applications in the vast internet-of-things (IoT) and in-home health monitoring.

On-Machine Measurement System of Tool Topography Using Edge Reversal Principle

Worn tools would wreak havoc on the surface integrity of workpieces in precision machining. This paper develops a new system for on-machine measurements of tool topography with micron accuracy based on the edge reversal principle. An array of experiments has been carried out to verify the system performance amenable to measuring various tools. An initial database of tools has been established as well for rapidly calculating tool wear and recording the topography characteristics of the different stages of tool wear. The on-machine measurement system is capable of achieving an expanded measurement uncertainty of 0.6 μm for tools with corner radii from 200 μm to 800 μm. The work provides equipment and data basis for efficient on-machine measurement of tool topography, which is beneficial to the prediction and management of tool life intelligently.

Distance Measurement Using mmWave Radar: Micron Accuracy at Medium Range

This work provides a proof-of-concept for a linear-position sensor using an ultrawideband (UWB) frequency-modulated continuous wave (FMCW) radar system operating at 126–182 GHz. It is the first work to show environmental compensated and calibration-free distance measurements with micron accuracy at medium range using millimeter-wave (mmWave) radar technology. We addressed hardware imperfections, parameter estimation, and the free-space path, i.e., refractive index and near-field effects. The proposed signal processing chain is robust to interference and of low computational cost. Experiments reveal a systematic error of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm 1~\mu \text{m}$ </tex-math></inline-formula> over 4.8 m (0.8–5.6 m), and a random error at a minimum of 30 nm, providing very high sensitivity.

Micro-patterns of gold nanoparticles assembled by photovoltaic optoelectronic tweezers: application to plasmonic fluorescence enhancement.

Noble metal nanostructures are well-known for their ability to increase the efficiency of different optical or physical phenomena due to their plasmonic behavior. This work presents a simple strategy to obtain Au plasmonic patterns by optically induced nanoparticle assembly and its application as fluorescence enhancement platforms. This strategy is based on the so-called photovoltaic optoelectronic tweezers (PVOT) being the first time they are used for fabricating Au periodic micro-patterns. Fringe patterns with a sub-structure of aggregates, assembled from individual spherical nanoparticles of 3.5 or 170 nm diameters, are successfully obtained. The spatial distribution of the aggregates is controlled with micrometric accuracy and the patterns can be arranged over large-scale active areas (tens of mm2). The outcome for the ultra-small (3.5 nm) particles is particularly relevant because this diameter is the smallest one manipulated by PVOT so far. Testing experiments of plasmonic fluorescence enhancement show that the 170-nm patterns present a much better plasmonic behavior. For the 170-nm platform they reveal a 10-fold enhancement factor in the fluorescence of Rhodamine-B dye molecules and a 3-fold one for tagged DNA biomolecules. Hence, the results suggest that these latter plasmonic platforms are good candidates for efficient bio-imaging and biosensing techniques, among other applications.

Defects localization using the data fusion of laser Doppler and image correlation vibration measurements

This work proposes a defects localization method based on the combination of laser Doppler vibrometry (LDV) and Digital image correlation (DIC). DIC and LDV are the dominant non-contact vibration measurement methods with a matured theory and high stability. DIC gives a high spatial resolution with a measurement accuracy of several microns, whereas the Multipoint LDV has a limited spatial resolution with high-precision results for the sparse points up to nanometer level. However, the vibration-based defect localization (VBDL) necessitates certain measurement methods with both the high spatial resolution and measurement accuracy. Unfortunately, the accuracy of DIC is not sufficient to detect the data anomalies caused by the structural defects. Nevertheless, LDV cannot achieve a high-precision defect localization owing to the limited spatial resolution. In this study, a nonlinear weighted least-squares fitting has been proposed to improve the measurement accuracy and reliability. A Chebyshev polynomial has been employed as the basis function in the fitting process. The effective signal-to-noise ratio (SNR) and the correlation coefficient are employed as the weight basis of the LDV points and the DIC subsets, respectively. Based on the simulation analysis, the determination of the optimal polynomial order at multiple noise levels and the influence of the LDV points distribution are discussed. The experiment proves that the data fusion method can significantly improve spatial resolution and measurement accuracy. From the data fusion results, the reference-free defects localization in cantilever beams and plates based on residuals have been presented.

Three-dimensional numerical analysis and experimental confirmation for investigating the ground-based lateral droplet ejection toward microgravity simulation

Rapid in situ manufacturing is significant in space exploration. Droplet-based printing technology with micrometer accuracy has great potential in space due to the advantages of convenient transportation, customized metal material, and good environmental adaptability. It could achieve the ground microgravity simulation by a small Bond number (Bo &amp;lt; 1). The present work proposes a new method to evaluate the reliability of the ground microgravity simulation in the lateral metallic droplet-based ejection. The three-dimensional model is developed to numerically analyze the droplet ejection dynamic process coupled with the volume of fluid method and the k–ω shear stress transport model. The model accuracy and efficiency are improved by the local fine grid. In addition, the computation is validated by the cryogenic alloy droplet ejection experiments and theoretical analysis. The proposed theoretical analysis equation has good agreement with the SnPb alloy droplet ejection trajectory. Reynolds number (Re), Weber number (We), Froude number (Fr), Ohnesorge number (Oh), and breakup length (Lb) are used to analyze the gravity influences on the droplet ejection process of different materials, nozzle length–diameter ratios, and crucible fluid unfilled heights. The ejection direction has little effect on the aluminum droplet formation time and breakup length and the gravity effect increases with the length–diameter ratio and unfilled heights. In simulated results, the minimum We number of the aluminum droplet formation is 0.22 and the cryogenic alloy droplet formation is 0.19. The reliability of ground physical microgravity simulation is dependent on material selection, and aluminum is more suitable than the cryogenic and SnPb alloys.

Diffraction From Metallic Objects in Radar Imaging—Theory, Simulation, and Experimental Verification

The paper describes the modelling of diffraction effects in radar imaging scans at and near sharp-edged metallic objects as the aperture dimension is close to the dimension of the object to be scanned. We evaluate the Fresnel-Kirchhoff integral within the process of radar imaging for an <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><inline-formula><tex-math notation="LaTeX">$\mathbf {1}$</tex-math></inline-formula></b> D synthetic aperture radar. The resulting compact imaging model describes the diffraction effects in a single convolution-based formula. This is the basis for the simulative analysis in which the derived model is compared to a numerical radar imaging model. Further, we test our derived diffraction model experimentally. It confirms the developed theory and opens up additional areas of application for diffraction effect impacted radar imaging. This might be: high precision cross-range measurement with micrometer accuracy; highly precise surface reconstruction unveiling surface uncertainties in the low double-digit micrometer range; and model-based radar image enhancement.

Controlled Continuous Patterning of Spherical Stainless Steel by Multi-Axis Linkage Laser Milling.

While laser surface texturing is promising for the fabrication of planar surface microstructures, the continuously patterning with micrometer accuracy of non-planar surface on miniature parts with large curvature by laser ablation is challenging. In the present work, we demonstrate the feasibility of applying the proposed multi-axis laser milling in continuous patterning of 25 mm diameter spherical stainless steel with high uniformity and precision, based on a strategy of simultaneously adjusting the position and the posture of laser-surface interaction point for enabling the constant coincidence of laser beam with ablated surface normal. Specifically, a miniaturized five-axis platform for controlling workpiece motion with high degree-of-freedom is designed and integrated with a fixed nanosecond pulsed laser beam operating at 1064 nm. The precise path of laser-surface interaction point is derived based on the projection and transformation of pre-determined planar pattern on spherical surface. Meanwhile, a virtual prototype of the multi-axis laser milling with embedded interpolation algorithm is established, which enables the generation of NC codes for subsequent laser milling experiments. Furthermore, the sampling of laser processing parameters particularly for spherical surface is carried out. Finally, complex patterns are continuously structured on the spherical surface by employing the proposed multi-axis laser milling method, and subsequent characterization demonstrates both long range uniformity and local high accuracy of the fabricated patterns. Current work provides a feasible method for the continuous laser surface texturing of non-planar surfaces for miniature parts with large curvature.