Search Results (196)

Digital ink Chinese characters (DICCs) written by international students often contain various errors and irregularities, making the recognition of these characters a highly challenging pattern recognition problem. This paper designs a graph convolutional network with agent attention (GCNAA) for recognizing DICCs written by international students. Each sampling point is treated as a vertex in a graph, with connections between adjacent sampling points within the same stroke serving as edges to create a Chinese character graph structure. The GCNAA is used to process the data of the Chinese character graph structure, implemented by stacking Block modules. In each Block module, the graph agent attention module not only models the global context between graph nodes but also reduces computational complexity, shortens training time, and accelerates inference speed. The graph convolution block module models the local adjacency structure of the graph by aggregating local geometric information from neighboring nodes, while graph pooling is employed to learn multi-resolution features. Finally, the Softmax function is used to generate prediction results. Experiments conducted on public datasets such as CASIA-OLWHDB1.0-1.2, SCUT-COUCH2009 GB1&GB2, and HIT-OR3C-ONLINE demonstrate that the GCNAA performs well even on large-category datasets, showing strong generalization ability and robustness. The recognition accuracy for DICCs written by international students reaches 98.7%. Accurate and efficient handwritten Chinese character recognition technology can provide a solid technical foundation for computer-assisted Chinese character writing for international students, thereby promoting the development of international Chinese character education. Full article

Environmental monitoring plays a key role in understanding and mitigating the effects of climate change, pollution, and resource mismanagement. The growth of printed sensor technologies offers an innovative approach to addressing these challenges due to their low cost, flexibility, and scalability. Printed sensors enable the real-time monitoring of air, water, soil, and climate, providing significant data for data-driven decision-making technologies and policy development to improve the quality of the environment. The development of new materials, such as graphene, conductive polymers, and biodegradable substrates, has significantly enhanced the environmental applications of printed sensors by improving sensitivity, enabling flexible designs, and supporting eco-friendly and disposable solutions. The development of inkjet, screen, and roll-to-roll printing technologies has also contributed to the achievement of mass production without sacrificing quality or performance. This review presents the current progress in printed sensors for environmental applications, with a focus on technological advances, challenges, applications, and future directions. Moreover, the paper also discusses the challenges that still exist due to several issues, e.g., sensitivity, stability, power supply, and environmental sustainability. Printed sensors have the potential to revolutionize ecological monitoring, as evidenced by recent innovations such as Internet of Things (IoT) integration, self-powered designs, and AI-enhanced data analytics. By addressing these issues, printed sensors can develop a better understanding of environmental systems and help promote the UN sustainable development goals. Full article

Textile-based wearable devices are rapidly gaining traction in the Internet of Things paradigm and offer distinct advantages for data collection and analysis across a wide variety of applications. Seamlessly integrating electronics in textiles remains a technical challenge, especially when the textiles’ essential properties, such as comfort, breathability, and flexibility, are meant to be preserved. This article investigates screen printing as a textile post-processing technique for electronic integration, and highlights its versatility, cost-effectiveness, and adaptability in terms of design and customization. The study examines two silver-based inks screen-printed on an Oxford polyester textile substrate with a focus on substrate preparation and treatment. Before printing, the textile samples were cleaned with nitrogen gas and then subjected to low-pressure oxygen plasma treatment. For comparative analysis, two samples printed on polyethylene terephthalate (PET) serve as a reference. The findings highlight the importance of plasma treatment in optimizing the printability of textiles and demonstrate that it notably improves the electrical properties of conductive inks. Despite some remaining challenges, the study indicates that screen-printed electronics show promising potential for advancing the development of e-textiles and sensor-integrated wearables. Full article

Celiac disease (CD), a human leukocyte antigen-associated disorder, is caused by gluten sensitivity and is characterized by mucosal alterations in the small intestine. Currently, its diagnosis involves the determination of serological markers. The traditional method for clinically determining these markers is the enzyme-linked immunosorbent assay. However, immunosensors offer sensitivity and facilitate the development of miniaturized and portable analytical systems. This work focuses on developing an amperometric immunosensor for the quantification of IgA antibodies against tissue transglutaminase (IgA anti-TGA) in human serum samples, providing information on a critical biomarker for CD diagnosis. The electrochemical device was designed on a polyimide substrate using a novel solid ink of wax and carbon nanofibers (CNFs). The working electrode microzone was defined by incorporating aminofunctionalized TiO₂ nanoparticles (TiO₂NPs). The interactions and morphology of CNFs/wax and TiO₂NPs/CNFs/wax electrodes were assessed through different characterization techniques. Furthermore, the device was electrochemically characterized, demonstrating that the incorporation of CNFs into the wax matrix significantly enhanced its conductivity and increased the active surface area of the electrode, while TiO₂NPs contributed to the immunoreaction area. The developed device exhibited remarkable sensitivity, selectivity, and reproducibility. These results indicate that the fabricated device is a robust and reliable tool for the precise serological diagnosis of CD. Full article

This study investigates the application of additive manufacturing (AM) in fabricating transverse thermoelectric (TTE) composites, demonstrating the feasibility of this methodology for TTE material synthesis. Zinc oxide (ZnO), a wide-bandgap semiconductor with moderate thermoelectric performance, and copper (Cu), a highly conductive metal, were selected as base materials. These were formulated into stable paste-like feedstocks for direct ink writing (DIW). A custom dual-nozzle 3D printer was developed to precisely deposit these materials in pre-designed architectures. The resulting structures exhibited measurable transverse Seebeck effects. Unlike prior TE research primarily focused on longitudinal configurations, this work demonstrates a novel AM-enabled strategy that integrates directional compositional anisotropy, embedded metal–semiconductor interfaces, and scalable multi-material printing to realize TTE behavior. The approach offers a cost-effective and programmable pathway toward next-generation energy harvesting and thermal management systems. Full article

An electrochemical aptasensor was developed for the rapid and sensitive detection of ciprofloxacin (CPX) in milk samples. The device was fabricated on a polyethylene terephthalate (PET) substrate using a screen-printing technique with carbon-based conductive ink. Gold nanoparticles (AuNPs) were incorporated to enhance aptamer immobilization and facilitate electron transfer at the electrode surface. The sensor’s analytical performance was optimized by adjusting key parameters, including AuNP volume, DNA aptamer concentration, and incubation times for both the aptamer and the blocking agent (6-mercapto-1-hexanol, MCH). Differential pulse voltammetry (DPV) measurements demonstrated a linear response ranging from 10 to 50 nmol L⁻¹ and a low detection limit of 3.0 nmol L⁻¹. When applied to real milk samples, the method achieved high recovery rates (101.4–106.7%) with a relative standard deviation below 3.1%, confirming its robustness. This disposable and cost-effective aptasensor represents a promising tool for food safety monitoring, with potential for adaptation to detect other pharmaceutical residues in dairy products. Full article

The development of biocompatible, conductive hydrogels via direct ink writing (DIW) has gained increasing attention for strain sensor applications. In this work, a hydrogel matrix composed of polyvinyl alcohol (PVA) and κ-carrageenan (KC) was formulated and enhanced with polyvinylidene fluoride (PVDF) and silver nanoparticles (AgNPs) to impart piezoelectric properties. The ink formulation was optimized to achieve shear-thinning and thixotropic recovery behavior, ensuring printability through extrusion-based 3D printing. The resulting hydrogels exhibited high water uptake (~280–300%) and retained mechanical integrity. Rheological assessments showed that increasing PVDF content improved stiffness without compromising printability. Electrical characterization demonstrated that AgNPs were essential for generating piezoelectric signals under mechanical stress, as PVDF alone was insufficient. While AgNPs did not significantly alter the crystalline phase distribution of PVDF, they enhanced conductivity and signal responsiveness. XRD and SEM-EDX analyses confirmed the presence and uneven distribution of AgNPs within the hydrogel. The optimized ink formulation (5% PVA, 0.94% KC, 6% PVDF) enabled the successful fabrication of functional sensors, highlighting the material’s strong potential for use in wearable or biomedical strain-sensing applications. Full article

Printed electronics employ established printing methods to create low-cost, mechanically flexible devices including batteries, supercapacitors, sensors, antennas and RFID tags on plastic, paper and textile substrates. This review focuses on the specific contribution of screen printing to that landscape, examining how ink viscosity, mesh selection and squeegee dynamics govern film uniformity, pattern resolution and ultimately device performance. Recent progress in advanced ink systems is surveyed, highlighting carbon allotropes (graphene, carbon nano-onions, carbon nanotubes, graphite), silver and copper nanostructures, MXene and functional oxides that collectively enhance mechanical robustness, electrical conductivity and radio-frequency behavior. Parallel improvements in substrate engineering such as polyimide, PET, TPU, cellulose and elastomers demonstrate the technique’s capacity to accommodate complex geometries for wearable, medical and industrial applications while supporting environmentally responsible material choices such as water-borne binders and bio-based solvents. By mapping two decades of developments across energy-storage layers and functional electronics, the article identifies the key process elements, recurring challenges and emerging sustainable practices that will guide future optimization of screen-printing materials and protocols for high-performance, customizable and eco-friendly flexible devices. Full article

Electromagnetic interference (EMI) shielding is critical for maintaining signal integrity in high-speed electronic packaging. However, conventional shielding approaches face limitations in process complexity and spatial efficiency. In this study, an EMI shielding film based on trimodal silver (Ag) ink and low-dielectric polyimide (PI) resin was developed and comprehensively evaluated. The fabricated film exhibited an average shielding effectiveness (SE) of −99.7 dB in the 6–18 GHz frequency range and demonstrated a 50% increase in electrical conductivity after lamination (from 0.752 × 10⁵ S/m to 1.13 × 10⁵ S/m). The horizontal thermal conductivity reached 34.614 W/m·K, which was 3.4 times higher than the vertical value (10.249 W/m·K). Signal integrity simulations showed significant reductions in near-end crosstalk (NEXT, 77.8%) and far-end crosstalk (FEXT, 65%). Moreover, cyclic bending tests confirmed excellent mechanical durability, with a normalized resistance change below 0.6 after 1000 cycles at a bending radius of 4 mm. Notably, the film enabled a 50% reduction in signal line spacing while maintaining signal integrity, even without strict compliance with the 3W Rule. These results demonstrate the potential of the proposed EMI shielding film as a high-performance solution for advanced packaging applications requiring high-frequency operation, thermal management, and mechanical flexibility. Full article

High-performance flexible sensors capable of direct integration with biological tissues are essential for personalized health monitoring, assistive rehabilitation, and human–machine interaction. However, conventional devices face significant challenges in achieving conformal integration with biological surfaces, along with sufficient biomechanical compatibility and biocompatibility. This research presents an in situ 3D biomanufacturing strategy utilizing Direct Ink Writing (DIW) technology to fabricate functional bioelectronic interfaces directly onto human skin, based on a novel annealing PEDOT:PSS/PVA composite bio-ink. Central to this strategy is the utilization of a novel annealing PEDOT:PSS/PVA composite material, subjected to specialized processing involving freeze-drying and subsequent thermal annealing, which is then formulated into a DIW ink exhibiting excellent printability. Owing to the enhanced network structure resulting from this unique fabrication process, films derived from this composite material exhibit favorable electrical conductivity (ca. 6 S/m in the dry state and 2 S/m when swollen) and excellent mechanical stretchability (maximum strain reaching 170%). The material also demonstrates good adhesion to biological interfaces and high-fidelity printability. Devices fabricated using this material achieved good conformal integration onto a finger joint and demonstrated strain-sensitive, repeatable responses during joint flexion and extension, capable of effectively transducing local strain into real-time electrical resistance signals. This study validates the feasibility of using the DIW biomanufacturing technique with this novel material for the direct on-body fabrication of functional sensors. It offers new material and manufacturing paradigms for developing highly customized and seamlessly integrated bioelectronic devices. Full article

The development of printable, conductive, and biocompatible hydrogels has emerged as a promising strategy for the next generation of flexible and soft sensor platforms. In this study, we present a systematic investigation of alginate-based hydrogels incorporating different carbonaceous materials, natural graphite, carbon black (Vulcan V3), and activated carbon (PCO1000C), to evaluate their suitability for sensor applications. Hydrogels were formulated with varying concentrations of sodium alginate and a fixed loading of carbon additives. Each composite was characterized in terms of electrical conductivity under compression, rheological behavior, and mechanical strength. Printability was assessed using a custom-designed extrusion platform that allowed for the precise determination of the minimum force and optimal conditions required to extrude each formulation through a standard 20G nozzle. Among all tested systems, the alginate–graphite hydrogel demonstrated superior extrudability, shear-thinning behavior, and shape fidelity, making it well-suited for 3D printing or direct ink writing. A simple conductivity-testing device was developed to verify the electrical response of each hydrogel in the hydrated state. The effects of different drying methods on the final conductivity were also analyzed, showing that oven drying at 50 °C yielded the highest restoration of conductive pathways. Mechanical tests on printed structures confirmed their ability to maintain shape and resist compressive forces. Finally, the biocompatibility of the printed alginate–graphite hydrogel was validated using a standard cytotoxicity assay. The results demonstrated high cell viability, confirming the material’s potential for use in biomedical sensing environments. This work offers a robust framework for the development of sustainable, printable, and biocompatible conductive hydrogels. The combined performance in printability, mechanical integrity, electrical conductivity, and cytocompatibility highlights their promise for flexible biosensors and wearable sensor technologies. Full article

In this research, an interdigitated gear-shaped working electrode is presented for cortisol sensing. Overall, the sensor was designed in a three-electrode system and was fabricated using direct laser scribing. A synthesized conductive ink based on graphene and polyaniline was further employed to enhance the electrochemical performance of the sensor. Scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were employed for physicochemical characterization of the laser-induced graphene (LIG) sensor. Cortisol, a biomarker essential in detecting stress, was detected both in phosphate-buffered saline (PBS, pH = 7.4) and human serum within a linear range of 100 ng/mL to 100 µg/mL. Ferri/ferrocyanide was employed as the redox probe to detect cortisol in PBS. The electrochemical performance of the developed sensor was assessed via differential pulse voltammetry (DPV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. The electrochemical performance demonstrates high sensitivity and selectivity alongside strong repeatability (relative standard deviation (RSD) = 3.8%, n = 4) and reproducibility (RSD = 5.85%, n = 5). Overall, these results highlight the sensor’s reliability, high sensitivity, and repeatability and reproducibility in the detection of cortisol. The sensor successfully detected cortisol in the complex medium of human serum and effectively distinguished it in a ternary mixture containing cortisol and dopamine. Also, the use of direct laser writing on Kapton film makes the approach cost-effective and thus disposable, making it suitable for chronic stress diagnostics and neurological research applications. Full article

Printing technology has revolutionized manufacturing by enabling high-volume, multipurpose, low-cost production with minimal environmental impact. This advancement has led to the integration of flexible electronic devices, such as displays, actuators, and sensors, into various consumer markets. Over the past few decades, printed electronics have garnered significant interest from both academic and industrial communities. Among these, flexible strain sensors stand out due to their adaptability and potential for large-scale applications. However, a comprehensive analysis of their sensing performance, particularly with respect to printability, remains lacking. This review aims to systematically explore the development of flexible strain sensors produced through printing technology, focusing on key aspects such as the formulation of conductive inks, the use of diverse substrate materials, and the challenges associated with printability. Additionally, it delves into the practical applications of these sensors across multiple industries. By providing an in-depth examination of these factors, this review offers valuable insights into the current state of printed electronics and highlights their future potential in advancing flexible sensing technologies. Full article

A newly developed series of polylactide (PLA)-based composites filled with hybrid lignin–carbon nanotube (CNTs) particles were studied using thermal and dielectric techniques. The low CNT content (up to 3 wt%) aimed to create conductive networks while enhancing particle–polymer adhesion. For comparison, PLA composites based on lignin and CNTs were also examined. Although infrared spectroscopy showed no significant interactions, calorimetry and dielectric spectroscopy revealed a rigid interfacial PLA layer exhibiting restricted mobility. The interfacial polymer amount was found to increase monotonically with the particle content. The hybrid-filled PLA composites exhibited electrical conductivity, whereas PLA/Lignin and PLA/CNTs remained insulators. The result was indicative of a synergistic effect between lignin and CNTs, leading to lowering of the percolation threshold to 3 wt%, being almost ideal for sustainable conductive printing inks. Despite the addition of lignin and CNTs at different loadings, the glass transition temperature of PLA (60 °C) decreased slightly (softer composites) by 1–2 K in the composites, while the melting temperature remained stable at ~175 °C, favoring efficient processing. Regarding crystallization, which is typically slow in PLA, the hybrid lignin/CNT particles promoted crystal nucleation without increasing the total crystallizable fraction. Overall, these findings highlight the potential of eco-friendly conductive PLA composites for new-generation applications, such as printed electronics. Full article

Purpose: Pharmaceutical parenteral drug products (PDPs) and orally inhaled nasal drug products (OINDPs) are critical medications for patient care, for which the route of administration is intravenous or oral/nasal inhalation, and the drug products directly infuse into the bloodstream or lungs, but they are categorized as high-risk for leachables. Method: These external foreign chemical substances (leachables) may adversely affect and alter patient safety. Results: These primary container closure systems and manufacturing process equipment mainly comprise rubber elastomers, polypropylene, resin, ink, adhesives, glass, or plastic material. To establish the ID of detected compounds and their quantity in the finished parenteral drug formulation and then to assess the formulation for toxicological safety, broad-scope non-specific analytical screening methods are required that are capable of screening out and quantifying the predicted/unpredicted leachable compounds at the levels that pose anticipated toxicological concerns for human patients. Before the selection of the final primary packaging system for the parenteral drug product, their extractable screening profile/knowledge is required to minimize leachable compounds in the finished drug product formulation and to develop and manufacture a safe product for human patients. The adverse effect or toxicity of leachables proportionally increases with an increase in the dose of the drug product or the duration of therapy because the volume of the drug product administered to a patient in a larger quantity is directly proportional to the concentration of the detected leachable. Conclusion: This document outlines the detailed process/scientific approach for conducting an organic leachable screening profile for parenteral drug products with respect to the chemical nature of leachables, i.e., polarity, propensity, volatility, and techniques. Full article