Antibacterial and osteogenic thin films on Ti-6Al-4V surface formed by passivation process in copper hydroxide solution.

Implant-associated infections are threatening and devastating complications that lead to bone destruction and loss. As a smooth surface is suitable for inhibiting bacterial adhesion, endowing antibacterial activity to the Ti surface without any structural changes in the surface topography is an effective strategy for preventing infection. The thin film on the Ti-6Al-4 V surface was functionalized to endow antibacterial activity by immersion in a Cu(OH)2 solution. The resulting surface maintains the surface topography with a surface roughness of 0.03 µm even after the immersion in the Cu(OH)2 solution. Moreover, Cu was detected at approximately 10 atom% from the surface and was present up to a depth of 30 nm of thin film. In vitro experiments revealed that the resulting surface exhibited antibacterial activity against methicillin-resistant Staphylococcus aureus and allowed the cellular proliferation, differentiation, and calcification of MC3T3-E1 cells. Furthermore, in vivo experiments determined that the presence of Cu in the thin film on the Ti-6Al-4 V surface led to no inflammatory reactions, including bone resorption. Thus, immersion in a Cu(OH)2 solution incorporates and immobilizes Cu into the thin film on the Ti-6Al-4 V surface without any structural alternations in the surface topography, and the resulting smooth surface exhibits antibacterial activity and osteogenic cell compatibility without cytotoxicity or inflammatory reactions. Our findings provide fundamental insights into the surface design of Ti-based medical devices, to achieve bone reconstruction and infection prevention.

Passivation of Ti-6Al-4V in Cu(OH)2 solution endowed smooth thin film with antibacterial activity and osteogenic cell compatibility for potentially achieving both bone reconstruction and infection prevention.

Impact of five floor coverings on the orthostatic balance of healthy subjects.

Plantar skin sensitivity contributes to the regulation of postural control and, therefore, changing the characteristics of the plantar support surface can modify this control. This study aimed at assessing the impact of five different floor coverings on the orthostatic balance in 48 healthy subjects. Static posturography was performed with eyes open or closed on a platform in a control condition (no covering) and with five different covering surfaces: foam, silicone, ethyl vinyl acetate, and two textured mats with small (height 2 mm) or large pimples (7 mm). The average velocity of center of pressure (CoP) displacement was the primary endpoint measure and ten other posturographic variables were assessed. Comfort and pain produced by the covering were also scored. In eyes open condition, the average velocity of CoP displacement was increased when subjects stood on the foam mat, the silicone mat, and especially the textured mat with large pimples. Several other posturographic variables showed significant changes with different types of floor coverings with eyes open. These changes were not correlated to the comfort or pain scores associated with the different surfaces. In contrast, no difference was observed compared to the control condition (no covering) with eyes closed. This study shows that adding smooth or textured floor covering can alter balance in eyes open condition. In eyes closed condition, although more disturbing for balance, healthy subjects achieved better postural adaptation, probably by mobilizing more of their proprioceptive resources. This posturographic examination procedure could, therefore, be used to assess "proprioceptive reserve" capacities in clinical practice.

Effect of external electric field on ultraviolet-induced nanoparticle colloid jet machining.

Electric field enhanced ultraviolet (UV)-induced nanoparticle colloid jet machining is proposed to improve the material removal efficiency of UV-induced nanoparticle colloid jet machining by applying an external electric field. The influences of TiO2nanoparticle concentration, applied electric field voltage and pH value for the photocatalytic activity of the polishing slurry was investigated by orthogonal experiments. Terephthalic acid (TPA) was used as a fluorescent molecular probe to reflect the relative concentration of hydroxyl radical groups (·OH) in polishing slurry, which directly affects the material removal rate in the UV-induced nanoparticle colloid jet machining process. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and x-ray photoelectron spectroscopy (XPS) were employed to inspect the interaction variations between the TiO2nanoparticles and the SiC workpiece surface. The SEM and XPS results exhibit that the external electric field can enhance the adsorption of TiO2nanoparticles on the SiC workpiece surface, which can create more interfacial reaction active centers in the polishing process. The FT-IR spectra results indicate that TiO2nanoparticles were chemically bonded to the SiC surface by oxygen-bridging atoms in Ti-O-Si bonds. The results of fixed-point polishing experiment show that due to the enhancement effect of external electric field on the photocatalytic activity of the polishing slurry, the material removal efficiency of electric field enhanced UV-induced nanoparticle colloid jet machining is 15% higher than that of UV-induced nanoparticle colloid jet machining, and is 28% higher than that of pure nanoparticle colloid jet machining. Atomic force microscope micromorphology show that an ultra-smooth SiC workpieces with surface roughness of Rms 0.84 nm (Ra 0.474 nm) has been obtained by electric field enhanced UV-induced nanoparticle colloid jet machining.

Ability of a Blue Hemoglobin-Based Liquid as a Novel Technology to Stain Initial Enamel Demineralization: A Proof-of-Concept in vitro Study.

During orthodontic treatment, enamel demineralization can occur. Its early detection is the basis for efficient preventive measures to arrest or remineralize lesions. In the present study, the application of a novel blue hemoglobin-based liquid (BlueCheck) was evaluated as proof of concept for detection of artificially demineralized smooth surfaces. 60 samples from extracted human posterior teeth were randomly assigned to four groups (15 per group). In 30 of these samples (groups A and B), superficial enamel was removed to create a ground surface. On the surface of other 30 samples (group C and D), orthodontic metal brackets were bonded. On each surface, BC liquid was applied and rinsed with water after 3 min (baseline). All surfaces were checked by two independent observers for presence of blue areas. On each sample, one side was covered by nail varnish to protect this enamel part from demineralization. The samples were demineralized with lactic acid (pH 4.6) for 7 days (group A and C) and 14 days (group B and D), respectively. Mineral loss was determined using quantitative light-induced fluorescence after demineralization. BlueCheck dye was again applied on the samples and evaluated for presence of stained areas. Histological sections were prepared from randomly selected samples and lesion depth was measured. Kruskal-Wallis test was used for group comparison (α = 0.05). After demineralization, median ΔF value for all samples was -8.25% indicating the presence of an initial demineralization. The difference of ΔF values was not statistically significant between samples at 7 or 14 days of demineralization, nor for samples with and without orthodontic brackets (p = 0.13). At baseline, none of the sample surfaces showed discoloration, whereas a distinctive blue color was visible after demineralization in all samples exposed to acid-exposed areas, corresponding to 100% sensitivity. The internal control surfaces (without demineralization) did not show any staining, corresponding to 100% specificity. Histologically measured lesion depths ranged between 200 and 254 µm. In this in vitro study, staining of demineralized enamel surface areas were shown to be reliable. Based on our results, this easily applicable product seems useful to be an adjuvant method to clinical examination to monitor oral health during an orthodontic treatment on tooth surfaces after removal of dental biofilm.

Depth Data Denoising in Optical Laser Based Sensors for Metal Sheet Flatness Measurement: A Deep Learning Approach.

Surface flatness assessment is necessary for quality control of metal sheets manufactured from steel coils by roll leveling and cutting. Mechanical-contact-based flatness sensors are being replaced by modern laser-based optical sensors that deliver accurate and dense reconstruction of metal sheet surfaces for flatness index computation. However, the surface range images captured by these optical sensors are corrupted by very specific kinds of noise due to vibrations caused by mechanical processes like degreasing, cleaning, polishing, shearing, and transporting roll systems. Therefore, high-quality flatness optical measurement systems strongly depend on the quality of image denoising methods applied to extract the true surface height image. This paper presents a deep learning architecture for removing these specific kinds of noise from the range images obtained by a laser based range sensor installed in a rolling and shearing line, in order to allow accurate flatness measurements from the clean range images. The proposed convolutional blind residual denoising network (CBRDNet) is composed of a noise estimation module and a noise removal module implemented by specific adaptation of semantic convolutional neural networks. The CBRDNet is validated on both synthetic and real noisy range image data that exhibit the most critical kinds of noise that arise throughout the metal sheet production process. Real data were obtained from a single laser line triangulation flatness sensor installed in a roll leveling and cut to length line. Computational experiments over both synthetic and real datasets clearly demonstrate that CBRDNet achieves superior performance in comparison to traditional 1D and 2D filtering methods, and state-of-the-art CNN-based denoising techniques. The experimental validation results show a reduction in error than can be up to 15% relative to solutions based on traditional 1D and 2D filtering methods and between 10% and 3% relative to the other deep learning denoising architectures recently reported in the literature.

Optical Dual Laser Based Sensor Denoising for OnlineMetal Sheet Flatness Measurement Using Hermite Interpolation.

Flatness sensors are required for quality control of metal sheets obtained from steel coils by roller leveling and cutting systems. This article presents an innovative system for real-time robust surface estimation of flattened metal sheets composed of two line lasers and a conventional 2D camera. Laser plane triangulation is used for surface height retrieval along virtual surface fibers. The dual laser allows instantaneous robust and quick estimation of the fiber height derivatives. Hermite cubic interpolation along the fibers allows real-time surface estimation and high frequency noise removal. Noise sources are the vibrations induced in the sheet by its movements during the process and some mechanical events, such as cutting into separate pieces. The system is validated on synthetic surfaces that simulate the most critical noise sources and on real data obtained from the installation of the sensor in an actual steel mill. In the comparison with conventional filtering methods, we achieve at least a 41% of improvement in the accuracy of the surface reconstruction.

Removal Mechanism Investigation of Ultraviolet Induced Nanoparticle Colloid Jet Machining.

Ultraviolet induced nanoparticle colloid jet machining is a new ultra-precision machining technology utilizing the reaction between nanoparticles and the surface of the workpiece to achieve sub-nanometer ultra-smooth surface manufacturing without damage. First-principles calculations based on the density functional theory (DFT) were carried out to study the atomic material removal mechanism of nanoparticle colloid jet machining and a series of impacting and polishing experiments were conducted to verify the mechanism. New chemical bonds of Ti-O-Si were generated through the chemical adsorption between the surface adsorbed hydroxyl groups of the TiO2 cluster and the Si surface with the adsorption energy of at least -4.360 eV. The two Si-Si back bonds were broken preferentially and the Si atom was removed in the separation process of TiO2 cluster from the Si surface realizing the atomic material removal. A layer of adsorbed TiO2 nanoparticles was detected on the Si surface after 3 min of fixed-point injection of an ultraviolet induced nanoparticle colloid jet. X-ray photoelectron spectroscopy results indicated that Ti-O-Si bonds were formed between TiO2 nanoparticles and Si surface corresponding to the calculation result. An ultra-smooth Si workpiece with a roughness of Rq 0.791 nm was obtained by ultraviolet induced nanoparticle colloid jet machining.

Optical coherence tomography to evaluate variance in the extent of carious lesions in depth.

Evaluation of variance in the extent of carious lesions in depth at smooth surfaces within the same ICDAS code group using optical coherence tomography (OCT) in vitro and in vivo. (1) Verification/validation of OCT to assess non-cavitated caries: 13 human molars with ICDAS code 2 at smooth surfaces were imaged using OCT and light microscopy. Regions of interest (ROI) were categorized according to the depth of carious lesions. Agreement between histology and OCT was determined by unweighted Cohen's Kappa and Wilcoxon test. (2) Assessment of 133 smooth surfaces using ICDAS and OCT in vitro, 49 surfaces in vivo. ROI were categorized according to the caries extent (ICDAS: codes 0-4, OCT: scoring based on lesion depth). A frequency distribution of the OCT scores for each ICDAS code was determined. (1) Histology and OCT agreed moderately (κ = 0.54, p ≤ 0.001) with no significant difference between both methods (p = 0.25). The lesions (76.9% (10 of 13)) _were equally scored. (2) In vitro, OCT revealed caries in 42% of ROI clinically assessed as sound. OCT detected dentin-caries in 40% of ROIs visually assessed as enamel-caries. In vivo, large differences between ICDAS and OCT were observed. Carious lesions of ICDAS codes 1 and 2 vary largely in their extent in depth.

Histologic validation of ICDAS-II and polarization sensitive optical coherence tomography to detect smooth surface early carious lesions.

AIM: This in vitro study aimed to histologically validate and compare the methods for detection of smooth surface early carious lesions (ECLs) that is, International caries detection and assessment system for the smooth surface (ICDAS-II-SSC), Polarization sensitive optical coherence tomography (PS-OCT), and radiography. METHODOLOGY: PS-OCT images for scores 0-3 of ICDAS-II-SSC were standardized according to ECLs' depth. Preliminary PS-OCT images for ICDAS-II-SSC score-2 of pigmented ECLs showed reduced lesion depth and therefore were dichotomized into scores 2 and 2p for white and pigmented lesions (ICDAS-II-SSCm). ECLs on one hundred freshly extracted teeth were scored by three examiners for ICDAS-II-SSCm, PS-OCT, radiography, and histology. RESULTS: Compared to histology, ICDAS-II-SSCm showed a strong positive correlation followed by PS-OCT and radiographic evaluation. ICDAS-II-SSCm had a strong positive correlation with PS-OCT, while both variables had a weak positive correlation with radiography. PS-OCT detected the activity of ECLs by directly relating the image depth of ECLs to their mineral volume content. CONCLUSION: The current scope of ICDAS-II should be reviewed since the pigmentation can be misinterpreted as an active lesion. Till then, ICDAS-II-SSC is an effective visual method for early caries detection. PS-OCT has the potential to become a probe with the proper algorithm for diagnostic purposes.

Super-aperture metrology: overcoming a fundamental limit in imaging smooth highly curved surfaces.

The imaging of smooth, highly curved or tilted surfaces is widely recognized as one of the most challenging and unsolved problems in optical imaging and metrology today. The reason is that even when such surfaces are imaged using high aperture microscope objectives the steepness of the features causes the light to be reflected in such a way that it is not captured by the lens. This is true even in the limiting case of unity numerical aperture since the illuminating light may also be reflected in the forward direction. In order to overcome this fundamental problem we have developed a method whereby such specimens are covered with a readily removable organic fluorescent film thereby creating an isotropic scattering surface. We show that we are readily able to detect slopes with angles close 90° using a 0.75 NA objective--an 82% improvement over the theoretical aperture limit. Issues of variation in film thickness deposition are shown to be readily accommodated. This approach may be used with other fluorophore materials, organic or inorganic, since there is no need for biocompatibility in this application.

Adhesive pad differentiation in Drosophila melanogaster depends on the Polycomb group gene Su(z)2.

The ability of many insects to walk on vertical smooth surfaces such as glass or even on the ceiling has fascinated biologists for a long time, and has led to the discovery of highly specialized adhesive organs located at the distal end of the animals' legs. So far, research has primarily focused on structural and ultrastructural investigations leading to a deeper understanding of adhesive organ functionality and to the development of new bioinspired materials. Genetic approaches, e.g. the analysis of mutants, to achieve a better understanding of adhesive organ differentiation have not been used so far. Here, we describe the first Drosophila melanogaster mutant that develops malformed adhesive organs, resulting in a complete loss of climbing ability on vertical smooth surfaces. Interestingly, these mutants fail to make close contact between the setal tips and the smooth surface, a crucial condition for wet adhesion mediated by capillary forces. Instead, these flies walk solely on their claws. Moreover, we were able to show that the mutation is caused by a P-element insertion into the Su(z)2 gene locus. Remobilization of the P-element restores climbing ability. Furthermore, we provide evidence that the P-element insertion results in an artificial Su(z)2 transcript, which most likely causes a gain-of-function mutation. We presume that this transcript causes deregulation of yet unknown target genes involved in pulvilli differentiation. Our results nicely demonstrate that the genetically treatable model organism Drosophila is highly suitable for future investigations on adhesive organ differentiation.

Preparation of robust polyamide microcapsules by interfacial polycondensation of p-phenylenediamine and sebacoyl chloride and plasticization with oleic acid.

Microcapsules produced by interfacial polycondensation of p-phenylenediamine (PPD) and sebacoyl chloride (SC) were studied. The products were characterized in terms of morphology, mean diameter and effectiveness of dodecane encapsulation. The use of Tween 20 as dispersion stabilizer, in comparison with polyvinyl alcohol (PVA), reduced considerably the mean diameter of the microcapsules and originated smoother wall surfaces. When compared to ethylenediamine (EDA), microcapsules produced with PPD monomer were more rigid and brittle, prone to fracture during processing and ineffective retention of the core liquid. The use of diethylenetriamine (DETA) cross-linker in combination with PPD did not decrease capsule fragility. On the other hand, addition of a small fraction of oleic acid to the organic phase remarkably improved wall toughness and lead to successful encapsulation of the core-oil. Oleic acid is believed to act as a plasticizer. Its incorporation in the polymeric wall was demonstrated by FTIR and (1)H-NMR.

Experimental Study on the Adhesion of Abalone to Surfaces with Different Morphologies.

To date, research on abalone adhesion has primarily analyzed the organism's adhesion to smooth surfaces, with few studies on adhesion to non-smooth surfaces. The present study examined the surface morphology of the abalone's abdominal foot, followed by measuring the adhesive force of the abalone on a smooth force measuring plate and five force measuring plates with different surface morphologies. Next, the adhesion mechanism of the abdominal foot was analyzed. The findings indicated that the abdominal foot of the abalone features numerous stripe-shaped folds on its surface. The adhesion of the abalone to a fine frosted glass plate, a coarse frosted glass plate, and a quadrangular conical glass plate was not significantly different from that on a smooth glass plate. However, the organism's adhesion to a small lattice pit glass plate and block pattern glass plate was significantly different. The abalone could effectively adhere to the surface of the block pattern glass plate using the elasticity of its abdominal foot during adhesion but experienced difficulty in completely adhering to the surface of the quadrangular conical glass plate. The abdominal foot used its elasticity to form an independent sucker system with each small lattice pit, significantly improving adhesion to the small lattice pit glass plate. The elasticity of the abalone's abdominal foot created difficulty in handling slight morphological size changes in roughness, resulting in no significant differences in its adhesion to the smooth glass plate.

Simulation and Structural Analysis of a Flexible Coupling Bionic Desorption Mechanism Based on the Engineering Discrete Element Method.

Soil adhesion is one of the important factors affecting the working stability and quality of agricultural machinery. The application of bionic non-smooth surfaces provides a novel idea for soil anti-adhesion. The parameters of sandy loam with 21% moisture content were calibrated by the Engineering Discrete Element Method (EDEM). The final simulated soil repose angle was highly consistent with the measured soil repose angle, and the obtained regression equation of the soil repose angle provides a numerical reference for the parameter calibration of different soils. By simulating the sinusoidal swing of a sandfish, it was found that the contact interface shows the phenomenon of stress concentration and periodic change, which reflects the effectiveness of flexible desorption and soil anti-adhesion. The moving resistance of the wedge with different wedge angles and different serrated structures was simulated. Finally, it was found that a 40° wedge with a high-tail sparse staggered serrated structure on the surface has the best drag reduction effect, and the drag reduction is about 10.73%.

A Review of Emerging Technologies in Ultra-Smooth Surface Processing for Optical Components.

Advancements in astronomical telescopes and cutting-edge technologies, including deep ultraviolet (DUV) and extreme ultraviolet (EUV) lithography, have escalated demands and imposed stringent surface quality requirements on optical system components. Achieving near-ideal optical components requires ultra-smooth surfaces with sub-nanometer roughness, no sub-surface damage, minimal surface defects, low residual stresses, and intact lattice integrity. This necessity has driven the rapid development and diversification of ultra-smooth surface fabrication technologies. This paper summarizes recent advances in ultra-smooth surface processing technologies, categorized by their material removal mechanisms. A subsequent comparative analysis evaluates the roughness and polishing characteristics of ultra-smooth surfaces processed on various materials, including fused silica, monocrystalline silicon, silicon carbide, and sapphire. To maximize each process's advantages and achieve higher-quality surfaces, the paper discusses tailored processing methods and iterations for different materials. Finally, the paper anticipates future development trends in response to current challenges in ultra-smooth surface processing technology, providing a systematic reference for the study of the production of large-sized freeform surfaces.

Nanoscale Polishing Technique of Biomedical Grade NiTi Wire by Advanced MAF Process: Relationship between Surface Roughness and Bacterial Adhesion.

Nitinol (NiTi), an alloy of nickel and titanium, wires are an important biomedical material that has been used in catheter tubes, guidewires, stents, and other surgical instruments. As such wires are temporarily or permanently inserted inside the human body, their surfaces need to be smoothed and cleaned in order to prevent wear, friction, and adhesion of bacteria. In this study, NiTi wire samples of micro-scale diameters (i.e., Ø 200 µm and Ø 400 µm) were polished by an advanced magnetic abrasive finishing (MAF) process using a nanoscale polishing method. Furthermore, bacterial adhesion (i.e., Escherichia coli (E. coli), and Staphylococcus aureus (S. aureus)) to the initial and final surfaces of NiTi wires were investigated and compared in order to assess the impact of surface roughness on bacterial adhesion to the surfaces of NiTi wires. The finding revealed that the surfaces of NiTi wires were clean and smooth with a lack of particle impurities and toxic components on the final surface polished using the advanced MAF process. The surface roughness Ra values of the Ø 200 µm and Ø 400 µm NiTi wires were smoothly enhanced to 20 nm and 30 nm from the 140 nm and 280 nm initial surface roughness values. Importantly, polishing the surfaces of a biomedical material such as NiTi wire to nano-level roughness can significantly reduce bacterial adhesion on the surface by more than 83.48% in the case of S. aureus, while in the case of E. coli was more than 70.67%.

High-Efficiency Chemical-Mechanical Magnetorheological Finishing for Ultra-Smooth Single-Crystal Silicon.

To improve the material removal efficiency and surface quality of single-crystal silicon after magnetorheological finishing, a novel green chemical-mechanical magnetorheological finishing (CMMRF) fluid was developed. The main components of the CMMRF fluid are nano-Fe3O4, H2O2, CH3COOH, nanodiamond, carbonyl iron powder, and deionized water. The novel CMMRF fluid can simultaneously achieve Ra 0.32 nm (0.47 mm × 0.35 mm measurement area), Ra 0.22 nm (5 µm × 5 µm measurement area), and 1.91 × 10-2 mm3/min material removal efficiency. Comprehensive studies utilizing a scanning electron microscope and a magnetic rheometer show that the CMMRF fluid has a high mechanical removal effect due to the well-dispersed nanodiamond and nano-Fe3O4 particles. The results of Fourier transform infrared spectra and Young's modulus test reveal the mechanism of the chemical reaction and the mechanical characteristics deterioration of the modified layer. Under co-enhanced chemical and mechanical effects, an ultra-smooth and highly efficient MRF technology for single-crystal silicon is realized.

Tri-Layered Vascular Grafts Guide Vascular Cells' Native-like Arrangement.

Bionic grafts hold great promise for directing tissue regeneration. In vascular tissue engineering, although a large number of synthetic grafts have been constructed, these substitutes only partially recapitulated the tri-layered structure of native arteries. Synthetic polymers such as poly(l-lactide-co-ε-caprolactone) (PLCL) possess good biocompatibility, controllable degradation, remarkable processability, and sufficient mechanical strength. These properties of PLCL show great promise for fabricating synthetic vascular substitutes. Here, tri-layered PLCL vascular grafts (TVGs) composed of a smooth inner layer, circumferentially aligned fibrous middle layer, and randomly distributed fibrous outer layer were prepared by sequentially using ink printing, wet spinning, and electrospinning techniques. TVGs possessed kink resistance and sufficient mechanical properties (tensile strength, elastic modulus, suture retention strength, and burst pressure) equivalent to the gold standard conduits of clinical application, i.e., human saphenous veins and human internal mammary arteries. The stratified structure of TVGs exhibited a visible guiding effect on specific vascular cells including enhancing endothelial cell (EC) monolayer formation, favoring vascular smooth muscle cells' (VSMCs) arrangement and elongation, and facilitating fibroblasts' proliferation and junction establishment. Our research provides a new avenue for designing synthetic vascular grafts with polymers.

Surface analysis of titanium disks with strontium coating.

Peri-implantitis is one of the most common complications after dental implant placement. Researchers have demonstrated that the peri-implantitis tends to occur around dental implants with a rough surface rather than those with a smooth surface. We aimed to investigate the ability of a smooth titanium (Ti) surface containing strontium (Sr) to enhance bone formation as a result of strontium's capacity to support osteoblast proliferation and differentiation. A thin titanium oxide film was formed on an as-mirror polished Ti surface by dipping in 5% sodium hypochlorite (NaOCl) solution for 24 h, followed by thermal treatment at 350°C. The Ti surface was then treated with 1% strontium nitrate (Sr(NO3)2) solution and turned in spin coater. The surface morphology, chemical composition, and release of strontium ions (Sr2+) were evaluated. The results demonstrate that strontium in the form of Sr2+ was successfully doped into the titanium dioxide (TiO2) film by this simple chemical treatment.

Application of Flow Field Analysis in Ion Beam Figuring for Ultra-Smooth Machining of Monocrystalline Silicon Mirror.

X-ray free-electron lasers are large modern scientific devices that play an important role in fields such as frontier physics and biomedicine. In this study, a light source is connected to an experimental station through beam lines, which requires numerous ultra-smooth and high-precision X-ray mirrors. Monocrystalline silicon is an ideal substrate material where ion-beam figuring is required. However, the ultra-smooth surface is damaged after the ion-beam figuring. Through an analysis of the machined surface, it is found that in the process of vacuum pumping, the impurities in the cavity adhere to the machined surface and increase the roughness after processing. Therefore, an optimized vacuum-pumping scheme is proposed. The experiment demonstrates that the original value of the processed surface roughness remains unchanged.