Digital Processing Research Articles

Chromatic aberration compensation in a digital camera lens for fringe projection profilometry

This work presents a simplified method for compensating the chromatic aberration of a digital camera lens using orthogonal fringe patterns displayed on an LCD monitor. The proposed compensation method drastically reduces the complex mathematical calculations to an arithmetic procedure of the simple rule of three. First, the implemented method is simulated, and then the experimental results confirm the simulated model. The mean squared error and standard deviation of the chromatic aberration compensation are calculated. Additionally, an arrangement is presented to avoid systematic errors when calculating the chromatic aberration of the lens to be compensated without additional digital processing.

Toward In Vitro Vascular Wall Models: Digital Light Processing of Acrylate‐Endcapped Urethane‐Based Polymers into Tubular Constructs

Toward In Vitro Vascular Wall Models: Digital Light Processing of Acrylate‐Endcapped Urethane‐Based Polymers into Tubular Constructs

Tuning crosslinking of hybrid preceramic polymers in vat photopolymerization toward controlled ceramic yields

Control of preceramic polymer crosslinking for UV-curable processing is essential for fine 3D printing with high ceramic conversion for sustainable polymer-derived ceramics (PDC) engineering. While various factors influencing ceramic yield have been studied, the systematic exploration of the relationship between crosslinking and ceramic yield, especially when crosslinking increases volatile elements, remains open for further investigation. This study addresses this gap by utilizing vat photopolymerization (VP) additive manufacturing (AM) as a versatile platform for controlling preceramic crosslinking and ceramic yield. By rationally designing and tuning the photochemical crosslinking through digital light processing (DLP), we demonstrate that the ceramic yield can be enhanced from 64% to over 86%, even with added volatile elements. We reveal that the post-pyrolysis ceramic yield can be closely correlated with the pre-pyrolysis crosslinking of the preceramic network represented by its stiffness. This correlation thereby suggests a fast, energy-efficient, non-destructive methodology to predict and improve ceramic yield. Combined with these findings, our one-pot thiol-ene hybridization of polycarbosilane and polycarbosiloxane via DLP offers an exemplary method to generate hybrid preceramic polymers with tailored material properties toward target applications, and potentially even higher ceramic yields. This study thus contributes to achieving better resource- and energy-efficient preceramic polymer and PDC processing routes toward sustainable, advanced organic–inorganic materials manufacturing.

Streamlining Barkhausen effect measurements: A simplified apparatus approach

The application of the Barkhausen Effect technique is hindered by the complexity and need for standardization in Barkhausen measurement devices. These devices typically comprise several modules for excitation, measurement, conditioning, and signal acquisition/processing, making them more complex than simpler methods such as Eddy Current or Magnetic Flux Leakage. Variations in device parameters among researchers can affect result consistency and interpretation. To address this issue, we propose a streamlined Barkhausen device consisting of a low-complexity measurement-excitation unit directly connected to the power grid. In the proposed device, nearly all signal conditioning and processing are transitioned from hardware, as used in the classic Barkhausen setup, to digital processing. This transition significantly enhances the standardization of the resultant Barkhausen signal. Comparative analysis between this simplified device and a traditional setup revealed no significant differences in signal parameters. The proposed device could function as a portable solution for preliminary tests to determine the feasibility of using the Barkhausen measurement technique. Adopting this simplified device could enhance the utility of the Barkhausen technique across various applications.

Retraction Note: Application of interactive multimedia based on optical imaging equipment in digital calligraphy information processing system

Retraction Note: Application of interactive multimedia based on optical imaging equipment in digital calligraphy information processing system

Super-resolution enhancement and segmentation for digital rock based on multi-task joint deep neural network

Reliable segmentation of pores and minerals from high-resolution (HR) digital rock data is the fundamental prerequisite for accurately characterizing the digital rock's physical properties. Limited by the complexity of the super-resolution (SR) issues and the user bias for segmentation, conventional SR enhancement and segmentation methods are generally brutal in satisfying the research demands. In recent years, with the introduction of deep learning technology into digital rock research, deep learning-based approaches for SR enhancement or segmentation methods have emerged and achieved significantly better effects than conventional approaches. Most deep learning-based digital rock SR enhancement and segmentation processing steps are currently separate. Still, preliminary studies have demonstrated that an end-to-end approach that integrates the two steps could achieve better performance. However, the training cost of 3D deep neural networks that can be directly applied to 3D digital rock processing is usually expensive. In contrast, 2D networks cannot be effectively applied to SR segmentation of 3D digital rocks. Here, we present an end-to-end SR segmentation framework for 3D digital rock based on a 2D multi-task joint deep neural network. The multi-task joint networks utilize a parallel architecture that integrates the SegNet for the segmentation task and the EDSR for the SR task. We also improved the loss function to address the issue of category imbalance and proposed an approach to utilize the 2D network for 3D digital rock processing. We demonstrate the effectiveness of the proposed network framework, the improved loss function, and the 3D digital rock processing strategies through ablation experiments on the high and low-resolution (LR) CT image datasets captured by imaging devices. The results show that the evaluation metrics and physical properties of the SR-segmented 2D\\3D digital rocks align with the HR-segmented results (ground truth). It indicates that the proposed framework can improve the performance of digital rock SR enhancement and segmentation and that it is essential to integrate deep learning frameworks into digital rock analysis.

PMMA light channels facilitate the additive manufacturing of complex-structured SiC reflector mirrors

The rapid manufacturing of lightweight SiC reflector mirrors has always posed a formidable challenge. We have successfully solved the problem of SiC slurry’s difficulty in vat photopolymerization by using highly transparent organic particles to construct the light channels for the first time. Through the integration of digital light processing with reaction sintering, we manufactured complex-structured SiC/Si reflector mirrors. Utilizing the light channels constructed with PMMA, ultraviolet light can effectively penetrate SiC slurry, thereby significantly enhancing the curing depth. During subsequent reaction sintering, PMMA particles induce the formation of numerous spherical silicon through dissolution-precipitation mechanism, alleviating stress concentration in the matrix and enhancing the flexural strength of SiC/Si ceramics. The method achieves significantly higher curing depth for SiC slurry and greater flexural strength for ceramic compared to similar materials. Extending the success above further, we have demonstrated their potential as high-quality products for practical applications.

A New Right to Procedural Accuracy: A Governance Model for Digital Evidence in Criminal Proceedings

This paper motivates and studies the feasibility of a new digital right to procedural accuracy (RPA) for digital evidence processing in criminal investigations. The need to guarantee a new principle of procedural accuracy under Art. 6 of the European Convention on Human Rights (ECHR) is based on the concern that digital forensic science and AI technology have a significant impact on individuals’ rights in criminal proceedings, which are neither coherently nor comprehensively addressed. The personal and material scope of RPA are examined and include: (i) protection against unreliable digital evidence processing; (ii) right to access the chain of evidence, explanation, and forensic assistance; and (iii) the right to participate in the determinative stages of the digital evidence processing. Limitations of the RPA are also discussed.

The oleaginous voice: Auto-Tune, linear predictive coding, and the security-petroleum complex

ABSTRACT In the twentieth century, exploration geophysics and digital vocal processing each underwent key technical transformations based on formally similar signal processing techniques derived from prior work in statistics and information theory. Engineers at Texas Instruments (TI) and the Massachusetts Institute of Technology (MIT) developed deconvolution filtering as a way to model geological strata from seismograph recordings in order to facilitate oil exploration. Meanwhile, engineers at Bell Laboratories and Nippon Telegraph and Telephone (NTT) used similar techniques to digitally encode and transmit speech signals more efficiently – a method known as linear predictive coding (LPC). These cognate approaches to modeling geophysical and vocal signals provided a practical basis for subsequent forays by oil industry figures into the world of digital audio. Tracing the histories of four technologies – LPC secure voice transmission terminals, the TI Speak & Spell educational toy, automatic speech recognition, and the vocal pitch correction software Auto-Tune – I analyze the role of security interests in facilitating spillovers between technologies of oil and the voice. I argue that, by approaching both geophysical and vocal signals as matters of national security, the United States’ defense and intelligence services furnished the bulk of socio-economic connective tissue between petroleum geophysics and vocal processing research.

Multi-stage and multi-colour liquid crystal reflections using a chiral triptycene photoswitchable dopant.

The photomodulation of the helical pitch of cholesteric liquid crystals results in dynamic and coloured canvases that can potentially be used in applications ranging from energy-efficient displays to colour filters, anti-counterfeiting tags and liquid crystal (LC) lasers. Here we report on the analysis of a series of photoswitchable chiral dopants that combine the large geometrical change and bistability of hydrazone switches with the efficient helical pitch induction of the chiral motif, triptycene. We elucidate the effects that conformational flexibility, dispersion forces and π-π interactions have on the chirality transfer ability of the dopant. We then use the irradiation time with visible light (442 nm) combined with a simple digital light processing microscope projection set-up to draw numerous stable multi-coloured images on an LC canvas, showcasing the fine control this dopant yields over the LC assembly.

4D-printed shape-programmable [H+]-responsive needles for determination of urea

Four-dimensional printing (4DP) technologies are revolutionizing the fabrication, functionality, and applicability of stimuli-responsive analytical devices. More practically, 4DP technologies are effective in fabricating devices with complex geometric designs and functions, and the degree of shape programming of 4D-printed stimuli-responsive devices can be optimized to become a reliable analytical strategy. Although shape-programming modes play a critical role in determining the analytical characteristics of 4D-printed stimuli-responsive sensing devices, the effect of shape-programming modes on the analytical performance of 4D-printed stimuli-responsive devices remains an unexplored subject. We employed digital light processing three-dimensional printing (3DP) with acrylate-based photocurable resins and 2-carboxyethyl acrylate (CEA)-incorporated photocurable resins for 4DP of the bending, helixing, and twisting needles. Upon immersion in samples with pH values above the pKa of CEA, the electrostatic repulsion among the dissociated carboxyl groups of polyCEA caused swelling of the CEA-incorporated part and [H+]-dependent shape programming. When coupling with the derivatization reaction of the urease-mediated hydrolysis of urea, the decline in [H+] induced shape programming of the needles, offering reliable determination of urea based on the shape-programming angles. After optimizing the experimental conditions, the helixing needles provided the best analytical performance, with the method's detection limit of 0.9 μM. The reliability of this analytical method was validated by determining urea in samples of human urine and sweat, fetal bovine serum, and rat plasma with spike analyses and comparing these results with those obtained from a commercial assay kit. Our demonstration and analytical results suggest the importance of optimizing the shape-programming modes to improve the analytical performance of 4D-printed stimuli-responsive shape-programming sensing devices and emphasize the benefits and applicability of 4DP technologies in advancing the development and fabrication of stimuli-responsive sensing devices for chemical sensing and quantitative chemical analyses.

Mechanistic understanding of enhancing bioactivity via bio-ionic liquid functionalization of biomaterials

The selection of biomaterials is a pivotal criterion for designing tissue engineering scaffolds, crucial for diverse biomedical applications. While natural biomaterials offer inherent bioactivity and biocompatibility, fine-tuning their properties for specific applications poses challenges. Conversely, synthetic biomaterials, while highly customizable, are often bio-inert. Functionalizing materials with bioactive molecules can improve cell-material interactions. Prevailing approaches utilizing RGD peptides or natural/synthetic composites have drawbacks including cost and immunogenicity. Bio-ionic liquids (BILs), a class of biocompatible ionic liquids derived from natural or synthetic biomolecules, offer a potential alternative. Herein, we present the biofunctionalization of a bio-inert polyethylene glycol diacrylate (PEGDA) with an acrylated choline-based BIL (“BioPEG”) as a method for enhancing the bioactivity of biomaterials. Cell studies using mouse myoblast C2C12 and human mesenchymal stem cells (hMSCs) revealed the excellence of BioPEG hydrogels in promoting cell attachment, growth, proliferation, and differentiation. Computational molecular dynamics (MD) simulations elucidated the mechanism by which BIL facilitates cell interaction with PEGDA. 3D printability of BioPEG hydrogel was showcased using a digital light processing (DLP) bioprinter, with printed scaffolds demonstrating excellent cytocompatibility. Collectively, these findings present BIL as a versatile bioactive agent for augmenting cell adhesion to materials, thus enriching the repertoire of biomaterials for advanced tissue engineering.

Integrating Clay Modeling in Implant Fabrication for Craniofacial Defect.

Manufacturing craniofacial implants using 3-dimensional (3D) methods and computed tomography data has become popular. The image object for the defect is produced as the first step, followed by several methods to create the implant. The authors have used a novel method that combines clay modeling with 3D scanning to create implants for craniofacial contour reconstruction. This approach does not require complicated resources. The method allows for high customization and immediate modifications, resulting in implants that achieve an accurate fit and high patient satisfaction. It is particularly beneficial for addressing complex defects and achieving aesthetic improvements. In addition, it reduces the need for cumbersome digital processing and expensive materials, making it a practical and feasible solution for a wide range of craniofacial deformities.

Intervertebral osteointegration and biomechanical performance of bioactive lithium disilicate glass-ceramic scaffold fabricated by digital light processing

The high strength of lithium disilicate (LD) glass-ceramic makes it difficult to form complex orthopaedic scaffolds using traditional methods. In addition, the osteointegration behavior of LD has also not been well studied in vivo. This study aimed to investigate the procedure of digital light processing (DLP) for fabricating porous LD glass-ceramic scaffolds and to assess the intervertebral osteointegration and biomechanical performance of the scaffolds. The phase formation, fracture morphology, flexural strength and density of LD glass-ceramics fabricated by DLP were evaluated to optimize the manufacturing process. Cell proliferation, cell differentiation and mineralization on the optimized glass-ceramics were recorded for comparison with traditional cast glass-ceramics (CG). The porous LD glass-ceramics scaffold was implanted into rabbits for 7 w and 14 w and then assessed using micro-CT and histological staining. Compression testing was also used to understand the scaffold’s mechanical properties. Furthermore, the scaffold was inserted into a validated finite element model of a human lumbar spine to study the stress distribution during physiological motions. The results indicated that LD glass-ceramics with step-by-step crystallization formed principal phases of Li2Si2O5 and Li3PO4, which had the highest flexural strength. Cell proliferation, cell differentiation and mineralization on the glass-ceramics formed by DLP were similar to the results of glass-ceramics formed by casting. The porous LD glass-ceramic scaffold promoted osseointegration in rabbits and was capable of withstanding physiological loads that would be experienced in a human lumbar spine. In conclusion, the bioactive LD glass-ceramic developed in this study showed good osteogenesis with sufficient mechanical performance, potentially making it suitable for applications in intervertebral fusion.

Effect of La2O3-MgO ratio on the microstructure and properties of Si3N4 ceramics fabricated via digital light processing

Due to the low powder content characteristic of digital light processing in the preparation of ceramic green bodies, significant challenges arise in obtaining high-density, high-performance Si3N4 ceramic. Sintering aids exert a critical influence on the densification and properties of Si3N4 ceramics. To further improve the performance of 3D-printed Si3N4 ceramics, Si3N4 ceramics were fabricated using DLP technology combined with gas pressure sintering employing different ratios of La2O3-MgO as sintering aids. The ceramic slurries, microstructures, and ceramic performance were studied systematically. The results showed that increasing the proportion of· La2O3 powder enhanced the rheological and curing properties of Si3N4 ceramic slurries. Varying the La2O3-MgO ratio affected the composition of the liquid phase, leading to differences in the densification and grain growth of Si3N4 ceramics. The average grain size increased with higher ratios of La2O3-MgO, and reached a maximum value of 0.91 μm with a ratio of 9:1. With the increase of the La2O3-MgO ratio, the bulk density and shrinkage rate of the ceramics initially increased and then declined. In addition, the flexural strength and fracture toughness of the ceramics peaked at a ratio of 3:7 for La2O3-MgO, measuring 577 ± 16.28 MPa and 5.84 ± 0.17 MPa m1/2, respectively. These results demonstrate that high-performance Si3N4 ceramics can be effectively prepared using DLP technology by adapting the ratio of sintering additives.

Effect of ZrSiO4 as additive on the mechanical properties of DLP printing porous mullite ceramics

In order to satisfy the demand for mullite porous ceramics with complex geometries in the engineering field, the digital light processing (DLP) technology is employed to prepare mullite porous ceramics in this study. However, the poor mechanical properties of the mullite porous ceramics prepared using the DLP technology limits its further application in engineering field. In this work, the microstructure of mullite crystals was regulated by adding the sintering aid ZrSiO4 to enhance the mechanical properties of the mullite ceramics, and the effects of sintering aid ZrSiO4 content and sintering temperature on the internal microstructure evolutions of mullite porous ceramics were investigated. Results showed that the decomposition of ZrSiO4 promoted the generation of the silica-rich liquid phase at high temperatures, which effectively promoted the nucleation and growth of needle-like mullite crystals. When the sintering temperature was 1600 °C and the ZrSiO4 content was 10 wt%, the well-developed elongated crystals formed an interlocking nonwoven structure. The corresponding mullite porous ceramics exhibited a compressive strength of 2.52 MPa and a porosity of 74.51%. The strategy of this study can be a feasible route for preparing lightweight and high-strength mullite porous ceramics via digital light processing.

Shape-programmable hard-magnetic soft actuators with high magnetic particle content via digital light processing method

In this work, we developed a novel hard-magnetic photosensitive suspension with high solid loadings of 50 wt% for digital light processing 3D printing. The suspension combining photosensitive resin and reactive diluent can retain stability for 6 h. The printed materials from the suspension achieve a low modulus of below 900 kPa and high remanence of 83.7 kA/m. The suspension’s cure behavior was studied in detail to obtain the optimal printing parameters. The printing error of the small structures with feature size of about 1000 μm is kept below 20 %. Moreover, we proposed an efficient magnetization programming strategy for hard-magnetic soft actuators with desirable shapes based on the rod model considering the non-magnetic load. The accuracy and reliability of the strategy are verified by the experiment results. Finally, we designed and fabricated a “flower” using our method, achieving its closing action in accordance with the prescribed shape.

Effect of different parameters on mode I fracture toughness of resin samples manufactured by DLP

Abstract Additive manufacturing is spreading rapidly in almost all industries, from household to advanced engineering. Components produced by Digital Light Processing (DLP) are not comprehensively characterized, but exceed the capabilities of many AM processes. Its advantages include the ability to produce highly complex designs, superior precision, fast printing and lower operating costs. The present paper investigates the mode I fracture toughness (KIC) of UV-sensitive resin specimens obtained through DLP process. Single edge notch bending (SENB) specimen were 3D printed and tested according to the ASTM D5045 standard. The influence of printing orientation-PO (0°, 45° and 90°), resin color-RC (white, black and transparent) and corrosive environment-CE (air, water and saline solution) was studied. It was observed that all the studied parameters have some effect on the fracture properties. The highest KIC values were obtained for 45°-PO, white-RC (1.88 MPa•m0.5) and saline solution-CE (2.24 MPa•m0.5). However, the greatest influence is highlighted by RC (∼92%), while CE (∼32%) shows a minimal effect. The fracture surface of the investigated samples is influenced by the printing parameters.

Structural integrity of polymers processed by additive manufacturing techniques using residual strength diagrams

Motivated by the increasingly important role that polymers have in structural applications, this study aims to analyse the structural integrity of polymers through residual strength diagrams. The polymers analysed have been thermoplastics, Polylactic acid (PLA), Polyethylene terephthalate glycol-modified (PET-G) and Polyamide 12 (PA-12), as well as a thermosetting resin, processed through different additive manufacturing techniques: Fused Deposition Modelling (FDM) in the case of PLA, PET-G, Selective Laser Sintering (SLS) for PA-12 and Digital Light Processing (DLP) for the thermosetting resin. In addition, PA-12 manufactured by injection moulding was also included in this study. To obtain the residual strength diagrams, mechanical tests have been carried out on smooth specimens and on specimens with cracks of different lengths. From the analysis of the results, a prediction has been obtained by fitting a semi-empirical model that describes the structural integrity in the areas of microstructurally short cracks, long cracks and physically short cracks.

Production of microneedle patches coated with polyvinyl-alcohol/sucrose/gentamicin sulfate for skin treatment

In this study, resin-based microneedle (MN) patches were fabricated using a digital light processing (DLP) printer. The needles were coated with gentamicin sulfate (GEN)-loaded with 13.3 % PVA/25 % sucrose solution by immersion. The SEM results showed that the coating was homogeneous and uniformly conical. Analysing the in vitro release profiles of GEN, it was found that it was ultimately released within 312 h. The compression test results demonstrated that GEN addition increased the compression strength to the value of 2.17 ± 0.01 N/mm2.