Fabrication Accuracy Research Articles

Study of thermal stress deformation in hybrid 3D printing and milling process of PEEK material

Hybrid manufacturing can enable rapid production of personalized artificial bones that are made of Polyether-ether-ketone (PEEK) by integrating 3D printing and milling. A main challenge, however, is the thermal stress deformation that arises from the fused deposition process, leading to warping and shrinkage. As a result, the fabrication accuracy is significantly diminished. This work aims to address this challenge by investigating the thermal stress deformation behavior of PEEK in hybrid manufacturing. The main contributions of this work, therefore, include the development of a model for this thermal deformation behavior, and the identification of key parameters such as cross-section length ( Ls), printed layer thickness ( Lh), and current workpiece height ( He). Further, experiments are conducted based on response surface methodology (RSM) to explore the relationships between temperature variation rate (Δ T), end surface height difference (Δ S), and length shrinkage rate (Δ L) with critical hybrid processing parameters. Optimal parameter combinations are then identified. Our experiments demonstrate that the proposed methods effectively reduce the effects of warping and shrinkage.

Influence of Material, Sterilization, and Disinfection on the Accuracy of Three-Dimensional Printed Surgical Templates: An InVitro Study.

To evaluate the influence of the three-dimensional (3D) printing technology, material, sterilization, and disinfection on the accuracy of guided surgical templates. Fifty printed resin surgical templates were designed and fabricated using a digital light processing 3D printer with a photopolymerizing resin, and 50 printed metal surgical templates were designed and fabricated using a selective laser melting 3D printer with a titanium alloy. Templates from both groups were randomly divided into five subgroups involving different sterilization and disinfection procedures. The group without any sterilization or disinfection procedure served as the control group, whereas the other groups were used as the study groups (hydrogen peroxide gas plasma sterilization, 5% povidone-iodine disinfection, 75% ethyl alcohol disinfection, and steam autoclave sterilization). Implant simulations were performed on the 3D-printed resin models, and postoperative impressions were acquired with scan bodies attached to the implants. All surgical templates were digitally scanned. The root mean square was used to determine and quantify fabrication accuracy and reproducibility, and the definitive and planned implant positions were compared. The printed resin templates exhibited lower fabrication accuracy and reproducibility, as well as higher 3D deviations, after steam autoclave sterilization (p < 0.001); however, the printed metal templates were not affected by the different sterilization or disinfection procedures (p > 0.05). Printed metal surgical templates are viable alternatives for guided implant surgery. Preoperative steam or gas plasma sterilization is recommended, especially for metal templates, as resin templates show deformation and decreased accuracy after steam sterilization. chictr.org.cn number: ChiCTR2400081334.

Integrated terahertz topological valley-locked power divider with arbitrary power ratios

Integrated power dividers (PDs) are essential in terahertz (THz) communication and radar systems, but miniaturization often leads to performance degradation due to fabrication inaccuracies and sharp bends. Topological photonics offers a solution to these issues, yet creating THz power dividers with arbitrary splitting ratios remains challenging. We present a design methodology for on-chip topological THz power dividers with customizable splitting ratios using valley-locked photonic crystals. These crystals feature a tri-layered structure with two distinct valley Chern number layers and an intermediate semimetal layer. Utilizing the Jackiw–Rebbi model, we show that the characteristic impedance of the valley-locked photonic crystals, and thus the power division ratio, can be tuned by adjusting the semimetal layer width. Our approach is validated through simulations and experiments for both equal (1:1) and unequal (4:9) power ratios. This method enables efficient navigation around sharp bends and robust THz on-chip connectivity.

Digital analysis of fabrication accuracy and fit in additively and subtractively manufactured implant-supported fixed complete dentures

ObjectivesTo digitally evaluate the trueness and fit of additively and subtractively manufactured fixed complete dentures in materials intended for definitive use. MethodsAn edentulous maxillary model with implants at the left first molar, left canine, right canine, and right first molar site was digitized and a fixed complete denture was designed. This design was used to fabricate fixed dentures in an additively manufactured resin for definitive use (AM), a high-impact polymer composite (SM-CR), and a strength gradient zirconia (SM-ZR) (n = 10). Each fixed denture was digitized and the surface (overall, occlusal, except occlusal, and abutments), linear, and interimplant distance deviations were analyzed. The fit was assessed with the triple-scan protocol. Data were analyzed with Welch analysis of variance and Games-Howell tests (α = 0.05). ResultsSM-ZR led to lower overall deviations than AM, which had the highest occlusal and the lowest abutments deviations (P ≤ 0.007). SM-ZR had the lowest occlusal and SM-CR had the highest except occlusal deviations (P ≤ 0.002). AM mostly had higher linear and SM-CR mostly had higher interimplant distance deviations (P ≤ 0.043). AM led to the highest marginal gap at the left canine site, while SM-CR had the highest and SM-ZR had the lowest gaps at the right canine site (P ≤ 0.022). ConclusionsSM-ZR dentures mostly had trueness and marginal fit similar to or better than the other groups. Tested fixed complete dentures were mostly smaller than the design file in terms of interimplant distances.

Epitaxial Growth of Two-Dimensional Organic Crystals with In-Plane Heterostructured Domain Regulation.

Complex organic lateral heterostructures (OLHs) with spatial distribution of two or more chemical components are crucial for designing and realizing unique structure-dependent optoelectronic applications. However, the precise design of well-defined OLHs with flexible domain regulation remains a considerable challenge. Herein, we present a stepwise solution self-assembly method to synthesize two-dimensional (2D) OLHs with a central rhombus domain and a lateral region featuring tunable blue and green emission based on the sequential nucleation and growth of 2D crystals. By controlling the initial crystallization time of 2,6-diphenylanthracene, the rhombic length ratio (α) of the multicolor-emissive part of the 2D OLHs is precisely modified. Furthermore, a third lateral layer is constructed on the resulting OLHs, demonstrating scalable lateral regulation. Significantly, these prepared 2D OLHs exhibit great excitation position-dependent waveguide characteristics and enable a 0.06 dB/μm low-loss waveguiding, which are conducive to photon transport and conversion for photonic integrated circuits. This work provides a stepwise strategy for the accurate fabrication of 2D OLHs, fabricating the developments of next-generation optoelectronics devices.

Biphilic Functional Surfaces for Frost Prevention and Efficient Active Defrosting

AbstractThe present work addresses the systematic accurate fabrication and design of biphilic surfaces having superhydrophobic circular islands surrounded by a hydrophilic background by investigating their condensation frosting and defrosting behavior. A significant delay in frost formation is observed on samples with higher superhydrophobicity ratio A*, defined as superhydrophobic area to total area ratio. As the superhydrophobic island diameter D increases from D = 500 µm to D = 700 µm (A* from 19.62% to 38.46%), a 50% improvement/delay is observed in terms of frost formation or densification. Besides delaying icing/frosting, the presence of superhydrophobic areas empowers the formation of porous and nonuniform frost structure, which facilitates ice removal during the defrosting process. To this end, as the surface is recovered the ambient temperature, almost complete passive cleaning performance within only 23 s is observed on the biphilic design having superhydrophobic islands with the diameter of D = 500 µm, that is, a superhydrophobicity ratio A* of 19.62%. This work concludes on the optimum biphilic ratio, which is not only effective as a passive method by hindering frosting but also leads to a slush/water free surface after defrosting eased by the Laplace pressure gradient which is imposed by the different biphilic wettability patterns.

Realization of equivalent multi-level DOEs by the stack of two few-level DOEs using phase dividing

Multi-level DOEs are always desired for the wider application. However, they require more accurate fabrication and expensive production costs. This paper presents an improved stacked DOEs method. Based on the phase distribution of t-level DOEs, a phase dividing method is used to divide the phase of t-level DOEs into m and n-level DOEs (t = n × m), the equivalent t-level DOEs can be realized by the stack of m and n-level DOEs. A 16-level beam shaping DOE is taken as an example to explore the method. The 4 and 4-level (or 2 and 8-level) stacked DOEs show the CV of 3.69% and diffractive efficiency of 98.11%, which is similar to 3.58% and 98.11% of a 16-level DOE. In addition, the tolerance of the stack method is also analyzed in horizontal displacement, vertical displacement, and angular deviation of stacked DOEs. The proposed stacked DOEs method can eliminate the need to directly manufacture multi-level DOEs with more steps, thus providing the possibility of reducing cost and fabricating difficulty.

Dentofacial deformities and their management in prosthodontic practice

Dentofacial deformities encompass a wide range of skeletal and dental discrepancies that can significantly impact a patient's oral function, aesthetics, and overall quality of life. These deformities can arise from congenital, developmental, or acquired factors, each contributing to the complexity of diagnosis and treatment. Congenital conditions, such as cleft lip and palate and genetic syndromes, often result in significant craniofacial anomalies. Developmental disturbances, including hormonal imbalances and nutritional deficiencies, can further exacerbate these conditions. Additionally, trauma, infections, and neoplasms play a critical role in the etiology of acquired dentofacial deformities. Effective management of dentofacial deformities in prosthodontics requires a multidisciplinary approach, integrating orthodontics, oral and maxillofacial surgery, and advanced prosthodontic techniques. Diagnostic advancements, including 3D imaging and digital workflows, facilitate precise planning and customization of prosthetic solutions. Orthodontic treatment and orthognathic surgery are pivotal in correcting skeletal discrepancies and establishing a stable foundation for prosthodontic rehabilitation. Post-surgical prosthodontic interventions involve the use of high-strength ceramics, zirconia, and biocompatible implant materials to restore dental function and aesthetics. Technological advancements have revolutionized prosthodontic practice. computer-aided design and computer-aided manufacturing (CAD/CAM) technology allows for the accurate design and fabrication of prosthetic components, enhancing treatment predictability and efficiency. The development of minimally invasive techniques, such as guided implant surgery and laser applications, has reduced procedural invasiveness and improved patient outcomes. The integration of digital tools and advanced materials has significantly enhanced the precision, durability, and aesthetic quality of prosthetic restorations. Overall, the advances in prosthodontic techniques and materials have greatly improved the management of dentofacial deformities, offering patients better functional and aesthetic results. Continued innovation and research are essential to address the complex challenges associated with these deformities, ultimately enhancing patient care and outcomes in prosthodontic practice.

Optimization of Grayscale Lithography for the Fabrication of Flat Diffractive Infrared Lenses on Silicon Wafers.

Grayscale lithography (GSL) is an alternative approach to the standard binary lithography in MEMS fabrication, enabling the fabrication of complicated, arbitrary 3D structures on a wafer without the need for multiple masks and exposure steps. Despite its advantages, GSL's effectiveness is highly dependent on controlled lab conditions, equipment consistency, and finely tuned photoresist (PR) exposure and etching processes. This works presents a thorough investigation of the challenges of GSL for silicon (Si) wafers and presents a detailed approach on how to minimize fabrication inaccuracies, aiming to replicate the intended design as closely as possible. Utilizing a maskless laser writer, all aspects of the GSL are analyzed, from photoresist exposure parameters to Si etching conditions. A practical application of GSL is demonstrated in the fabrication of 4-μm-deep f#/1 Si Fresnel lenses for long-wave infrared (LWIR) imaging (8-12 μm). The surface topography of a Fresnel lens is a good case to apply GSL, as it has varying shapes and size features that need to be preserved. The final fabricated lens profiles show a good match with the initial design, and demonstrate successful etching of coarse and fine features, and demonstrative images taken with an LWIR camera.

The Effect of Selecting a Saw Blade on the Cutting Process in the Fabrication of 2-G-(F)-750 Iron Girders

In the fabrication process of a series of piperacks, accurate workpiece results are needed in a fast time, therefore procedures are needed that can support the speed and accuracy of fabrication to fulfill PT Pertamina's wishes so that the RDMP RU V Balikpapan project takes place quickly. One part of the piperack fabricated by PT Arkha Jayanti Persada is iron girders. Because the process of checking the quality of parts of the piperack series is carried out by PT Pertamina very strictly, the results of the fabricated iron girders are also required to obtain precision iron girders at the right time but not injuring the tools and machines owned by PT Arkha Jayanti Persada. The purpose of this study is to analyze the results of 4 different blades. From the research results, it was found that cutting the 2-G-(F)-750 girder took 119 minutes using a saw blade 41 x 1.3 x 5300 – 10 TPI. With the same blade speed, replacing the saw blade with a 14 TPI tooth profile speeds up the cutting time to 85 minutes (29 %).

Development of Microwave Components Using Additive Manufacturing: A Review

In modern telecommunication, there is a growing demand for lightweight, low-cost, and compact microwave components with high transmission functionalities, especially for applications requiring multiple high-performance antennas to provide multi-beam capabilities. Additive manufacturing (AM), also known as three-dimensional (3D) printing, has emerged as a promising solution to meet these demands due to its simplicity, fast prototyping capabilities, and enhanced fabrication accuracy. AM technology has found widespread adoption across various industries, including space-borne, satellite, handheld wireless systems, biomedical, mechanical, electrical, optical, and environmental applications. In particular, AM-based microwave components offer significant advantages, including reduced weight compared to traditional aluminum prototypes, with savings of up to two-thirds of the weight. This paper presents a comprehensive review of the AM process, materials used, and microwave components developed using AM technology. The review encompasses various aspects, including fabrication techniques, performance characteristics, and applications of AM-based microwave components, providing insights into the advancements, and potential future directions of this innovative approach.

Size-Effect-Based Dimension Compensations in Wet Etching for Micromachined Quartz Crystal Microstructures.

Microfabrication technology with quartz crystals is gaining importance as the miniaturization of quartz MEMS devices is essential to ensure the development of portable and wearable electronics. However, until now, there have been no reports of dimension compensation for quartz device fabrication. Therefore, this paper studied the wet etching process of Z-cut quartz crystal substrates for making deep trench patterns using Au/Cr metal hard masks and proposed the first quartz fabrication dimension compensation strategy. The size effect of various sizes of hard mask patterns on the undercut developed in wet etching was experimentally investigated. Quartz wafers masked with initial vias ranging from 3 μm to 80 μm in width were etched in a buffered oxide etch solution (BOE, HF:NH4F = 3:2) at 80 °C for prolonged etching (>95 min). It was found that a larger hard mask width resulted in a smaller undercut, and a 30 μm difference in hard mask width would result in a 17.2% increase in undercut. In particular, the undercuts were mainly formed in the first 5 min of etching with a relatively high etching rate of 0.7 μm/min (max). Then, the etching rate decreased rapidly to 27%. Furthermore, based on the etching width compensation and etching position compensation, new solutions were proposed for quartz crystal device fabrication. And these two kinds of compensation solutions were used in the fabrication of an ultra-small quartz crystal tuning fork with a resonant frequency of 32.768 kHz. With these approaches, the actual etched size of critical parts of the device only deviated from the designed size by 0.7%. And the pattern position symmetry of the secondary lithography etching process was improved by 96.3% compared to the uncompensated one. It demonstrated significant potential for improving the fabrication accuracy of quartz crystal devices.

Efficient full-aperture mirror polishing method with variable orbital radius in computer-controlled optical surfacing

Optical systems in astronomy have extremely high requirements on the full-aperture surface precision and fabrication efficiency of aspherical mirrors. However, the current full-aperture optics fabrication method suffers from both fabrication and computation inefficiency. The former is caused by the isolated polishing strategy for the inner and edge regions of the mirror with different tools, while the latter is caused by the global computation strategy for the two regions. In this paper, a full-aperture mirror polishing method with the reversed strategy is proposed to solve this problem. Firstly, the dwell time of inner/edge regions are respectively calculated by the deconvolution method and the linear equations method based on the space-variant tool influence function. Therefore, both the computation cost and the edge polishing error can be reduced. Then, a fused tool path is developed to achieve variable orbital radius in the inner/edge region so the full aperture can be polished in one round. Simulations and experiments using a SiC aspherical mirror and large segmented mirrors demonstrate that the surface error can converge quickly in the full aperture. As a consequence, the full-aperture fabrication accuracy and efficiency can be greatly improved through the proposed method.

Label-free detection of thiram in trace quantity in fruits and vegetables using chemically made SERS-active substrate

Surface-enhanced Raman spectroscopy (SERS) provides a sensitive, rapid, and accurate mechanism to detect and classify the analytes in trace concentrations. Numerically optimized design and its accurate fabrication plays an important role in realization of a SERS-active substrates, used to enhance the Raman signals. Thiram (tetramethyl-thiuram disulfide) is a fungicide that is used to protect the crops from fungal infections. However, excessive use of thiram can cause several health-related complications and must be avoided. In this study, we have laid out a simple but fast and sensitive SERS technique and demonstrated its application for the detection of thiram residues in vegetable and fruit peels. This study employs silver nanoparticles decorated with reduced graphene as SERS-active substrate to detect R6G and thiram in trace amount in tomato and apple peels. The proposed substrate yielded an enhancement factor of about 1016 for the most prominent Raman mode. We were able to achieve the detection limit of 1000 pM and 100 pM concentrations of thiram in tomato and apple peels respectively, using the proposed SERS-active substrate. It was also able to detect PNBA, an explosive analyte, up to nanomolar concentration, demonstrating the versatility of the proposed substrate. The proposed scheme has a great potential for detection of adulterants in fruits and vegetables and can also be implemented for trace detection in various other fields such as narco-analysis, defence and medicine etc.

3D printing of ferromagnetic passive shims for field shaping in magnetic resonance imaging

Magnetic Resonance Imaging (MRI) often encounters image quality degradation due to magnetic field inhomogeneities. Conventional passive shimming techniques involve the manual placement of discrete magnetic materials, imposing limitations on correcting complex inhomogeneities. To overcome this, we propose a novel 3D printing method utilizing binder jetting technology to enable precise deposition of a continuous range of concentrations of ferromagnetic ink. This approach grants complete control of the magnitude of the magnetic moment within the passive shim enabling tailored corrections of B0 field inhomogeneities. By optimizing the magnetic field distribution using linear programming and an in-house written Computer-Aided Design (CAD) generation software, we printed shims with promising results in generating low spherical harmonic corrections. Experimental evaluations demonstrate feasibility of these 3D printed passive shims to induce target magnetic fields corresponding to second-order spherical harmonic, as evidenced by acquired B0 maps. The electrically insulating properties of the printed shims eliminate the risk of eddy currents and heating, thus ensuring safety. The dimensional fabrication accuracy of the printed shims surpasses previous methods, enabling more precise and localized correction of subject-specific inhomogeneities. The findings highlight the potential of binder-jetted 3D printed passive shims in MRI shimming as a versatile and efficient solution for fabricating passive shims, with the potential to enhance the quality of MRI imaging while also being applicable to other types of Magnetic Resonance systems.

Study on the Flow Field Distribution in Microfluidic Cells for Surface Plasmon Resonance Array Detection.

This research is dedicated to optimizing the design of microfluidic cells to minimize mass transfer effects and ensure a uniform flow field distribution, which is essential for accurate SPR array detection. Employing finite element simulations, this study methodically explored the internal flow dynamics within various microfluidic cell designs to assess the impact of different contact angles on flow uniformity. The cells, constructed from Polydimethylsiloxane (PDMS), were subjected to micro-particle image velocimetry to measure flow velocities in targeted sections. The results demonstrate that a contact angle of 135° achieves the most uniform flow distribution, significantly enhancing the capability for high-throughput array detection. While the experimental results generally corroborated the simulations, minor deviations were observed, likely due to fabrication inaccuracies. The microfluidic cells, evaluated using a custom-built SPR system, showed consistent repeatability.

Bevel-edge epitaxy of ferroelectric rhombohedral boron nitride single crystal.

Within the family of two-dimensional dielectrics, rhombohedral boron nitride (rBN) is considerably promising owing to having not only the superior properties of hexagonal boron nitride1-4-including low permittivity and dissipation, strong electrical insulation, good chemical stability, high thermal conductivity and atomic flatness without dangling bonds-but also useful optical nonlinearity and interfacial ferroelectricity originating from the broken in-plane and out-of-plane centrosymmetry5-23. However, the preparation of large-sized single-crystal rBN layers remains a challenge24-26, owing to the requisite unprecedented growth controls to coordinate the lattice orientation of each layer and the sliding vector of every interface. Here we report a facile methodology using bevel-edge epitaxy to prepare centimetre-sized single-crystal rBN layers with exact interlayer ABC stacking on a vicinal nickel surface. We realized successful accurate fabrication over a single-crystal nickel substrate with bunched step edges of the terrace facet (100) at the bevel facet (110), which simultaneously guided the consistent boron-nitrogen bond orientation in each BN layer and the rhombohedral stacking of BN layers via nucleation near each bevel facet. The pure rhombohedral phase of the as-grown BN layers was verified, and consequently showed robust, homogeneous and switchable ferroelectricity with a high Curie temperature. Our work provides an effective route for accurate stacking-controlled growth of single-crystal two-dimensional layers and presents a foundation for applicable multifunctional devices based on stacked two-dimensional materials.

An Experiment-Based Variable Compensation Method to Improve the Geometric Accuracy of Sub-mm Features Fabricated by Stereolithography (SLA)

In this paper, we present an experimental procedure to enhance the dimensional accuracy of fabrication via stereolithography (SLA) of features at the sub-mm scale. Deviations in sub-mm hemispherical cavity diameters were detected and measured on customized samples by confocal microscopy. The characterization and experimental observations of samples allowed the identification of inaccuracy sources, mainly due to the laser beam scanning strategy and the incomplete removal of uncured liquid resin in post-processing (i.e., IPA washing). As a technology baseline, the measured dimensional errors on cavity diameters were up to −46%. A compensation method was defined and implemented, resulting in relevant improvements in dimensional accuracy. However, measurements on sub-mm cavities having different sizes revealed that a constant compensation parameter (i.e., C = 85, 96, 120 μm) is not fully effective at the sub-mm scale, where average errors remain at −24%, −18.8%, and −16% for compensations equal to 85, 96 and 120 μm, respectively. A further experimental campaign allowed the identification of an effective nonlinear compensation law where the compensation parameter depends on the sub-mm feature size C = f(D). Results show a sharp improvement in dimensional accuracy on sub-mm cavity fabrication, with errors consistently below +8.2%. The proposed method can be extended for the fabrication of any sub-mm features without restrictions on the specific technology implementation.

On-Chip Broadband, Compact TM Mode Mach-Zehnder Optical Isolator Based on InP-on-Insulator Platforms.

An integrated optical isolator is a crucial part of photonic integrated circuits (PICs). Existing optical isolators, predominantly based on the silicon-on-insulator (SOI) platform, face challenges in integrating with active devices. We propose a broadband, compact TM mode Mach-Zehnder optical isolator based on InP-on-insulator platforms. We designed two distinct magneto-optical waveguide structures, employing different methods for bonding Ce:YIG and InP, namely O2 plasma surface activation direct wafer bonding and DVS-benzocyclobutene (BCB) adhesive bonding. Detailed calculations and optimizations were conducted to enhance their non-reciprocal phase shift (NRPS). At a wavelength of 1550 nm, the direct-bonded waveguide structure achieved a 30 dB bandwidth of 72 nm with a length difference of 0.256 µm. The effects of waveguide arm length, fabrication accuracy, and dimensional errors on the device performance are discussed. Additionally, manufacturing tolerances for three types of lithographic processes were calculated, serving as references for practical manufacturing purposes.

Optimization and test of a ring-ring typed atmospheric pressure plasma jet for optical fabrication

In recent years, the atmospheric pressure plasma jet (APPJ) has gained considerable attention in the field of optical fabrication because the chemical etching approach offers the advantage of avoiding mechanical damage to workpieces. This paper presents the development of an atmospheric pressure plasma machining system with a ring-ring typed APPJ, which exhibits several favorable characteristics. It has a relatively low processing temperature, no electrode corrosion, no plasma contamination, and a long discharge plume, etc. Optimization of the dimensional parameters and analysis of reactive gas flow rate are conducted through experimental investigations. Comparative experiments are carried out with the commonly used needle-ring typed APPJ, revealing significant improvements of the ring-ring typed APPJ, i.e., a fourfold increase in machining distance, a tenfold increase in machining efficiency, and a 58% enhancement in the stability of the material volumetric removal rate. Furthermore, on-line temperature monitoring of the footprint has been achieved due to the specific traits of the extended discharge plume. Fabrication experiments are conducted to demonstrate the significant correlation between the temperature and material removal rate, which shows the possibility of improving the accuracy of optical fabrication based on the ring-ring typed APPJ.