Screen Printing Technology Research Articles

Multilevel Stimuli-Responsive Smart "Sandwich" Label with Physical Unclonable Functions Bionic Wrinkles and Space-Selective Fluorescence Patterns.

With the increasing popularity of the internet, it brings convenience to lives while also increases security risks. Physical Unclonable Functions (PUFs) can generate random, unclonable, and unique identifiers using their inherent physical characteristics, which have broad prospects in anti-counterfeiting. Herein, inspired by the irregular tree bark fissures and random skin wrinkles found in nature, a method for creating complex micro-wrinkles with unclonable random patterns is proposed by simply stretching hydrogels. The random texture information contained in the micro-wrinkles is digitized into binary codes using an adaptive threshold algorithm. Additionally, a novel "sandwich" label with a multilevel intelligent anti-counterfeiting system is proposed. The first-level involves photoluminescence encryption with adjustable luminescence within visible light range and modulated luminescence at different excitation wavelengths; the second-level includes strain-related mechanical encryption, and the third-level consists of highly random and unclonable micro-wrinkles. The certification difficulty increases as the anti-counterfeiting grade increases, thereby enhancing label security. Furthermore, space-selective doping of rare earth metal-organic framework (RE-MOF) fluorescent materials in hydrogels is achieved through the use of screen-printing technology. The concept of novel multilevel smart anti-counterfeiting PUF labels will further enhance current levels of counterfeiting prevention.

Portable alkaloid discrimination via nanozyme-mediated colorimetric paper-based sensor array integrated with smartphone detection.

Apaper-based colorimetric sensor array mediated by a novel nanozyme (CuCo2O4) was developed using a screen-printing technology. The aim was to facilitate the identification of different kinds of alkaloids. Typically, three chromogenic substrates (3,3',5,5'-tetramethylbenzidine, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid), and o-phenylenediamine) were selected as sensing elements, which can be catalyzed by a CuCo2O4 nanozyme with peroxidase-like activity to yield corresponding oxidized products, thereby inducing color changes. Owing to the varying inhibitory ability of different alkaloids on acetylcholinesterase (AChE), a decrease in choline (Ch) concentration occurs and subsequently results in the restoration of color within the units of sensor array. Color data can be transformed into hue information with a smartphone. The above color variations generated a unique "fingerprint" pattern on five alkaloids (berberine, palmatine, jatrorrhizine, eserine, and harmane), which can be successfully discriminated through linear discriminant analysis in the range0.2 to 20µM. Furthermore, the sensor arrays allowed successful discrimination of the above five alkaloids in Chinese herbal medicine samples and recognition of 22 blind samples. This work presents a novel nanozyme-based paper sensor array, which is a user-friendly and reliable platform for probing different alkaloids. In addition, the developed sensing strategy enables the identification of AChE-related diseases, positively contributing to the screening available of AD-associated drugs.

Donor–π bridge-acceptor dyes featuring dual chromophoric groups for enhanced sensitivity in wearable sweat sensor

The pH value of human sweat serves as a crucial biomarker for disease diagnosis, rendering wearable sweat sensors an innovative tool for monitoring human health. However, the commercialization of these devices is seriously impeded by their low sensitivity, poor wearing comfort, and limited reusability. In this work, a reactive dye capable of color change under pH change has been synthesized. Due to the unique molecular structure, the dye molecule exhibits remarkable color change recognition and high sensitivity. To fabricate a wearable pH sensor, screen printing technology was employed for depositing the color-changing dye onto cotton fabric. The resulting sensor demonstrated excellent performance attributes including high color sensitivity, robust cyclic stability in response to pH changes, and exceptional resistance against washing, friction, and sunlight-induced fading. Therefore, this study presents a highly promising approach for achieving real-time monitoring of human sweat pH levels.

Enabling High Strength and Toughness Polyurethane through Disordered-Hydrogen Bonds for Printable, Recyclable, Ultra-Fast Responsive Capacitive Sensors.

The rapid advancement of smart, flexible electronic devices has paralleled a surge in electronic waste (e-waste), exacerbating massive resource depletion and serious environmental pollution. Recyclable materials are extensively investigated to address these challenges. Herein, this study designs a unique polyurethane (SPPUs) with ultra-high strength up to 60MPa and toughness of 360MJ m-3. This synthetic SPPUs can be fully recycled at room temperature by using green solvents of ethanol. Accordingly, the resultant SPPU-Ni composites, created by mixing the ethanol-dissolved SPPUs solution with nickel (Ni) powder, effectively combine the flexibility and recyclability of SPPUs with the electrical conductivity of the nickel filler. Notably, this work develops the printable capacitive sensors (PCBS) through transcribing the paste of SPPUs-Ni slurry onto PET film and paper using screen-printing technology. The devised PCBS have fast response time ≈50ms, high resolution, and multiple signal recognition capabilities. Remarkably, SPPUs and Ni powder can be fully recycled by only dissolving the waste PCBS in ethanol. This work offers a sustainable solution to the growing e-waste problem in recyclable flexible electronics.

Characterization of Silver Conductive Ink Screen-Printed Textile Circuits: Effects of Substrate, Mesh Density, and Overprinting

This study explores the intricate interaction between the properties of textile substrates and screen-printing parameters in shaping fabric circuits using silver conductive ink. Via analyzing key variables such as fabric type, mesh density, and the number of overprinted layers, the research revealed how the porous structure, large surface area, and fiber morphology of textile substrates influence ink absorption, ultimately enhancing the electrical connectivity of the printed circuits. Notably, the hydrophilic cotton staple fibers fabric effectively absorbed the conductive ink into the fabric substrate, demonstrating superior electrical performance compared with the hydrophobic polyester filament fabric after three overprinting, unlike the results observed after a single print. As mesh density decreased and the number of prints increased, the electrical resistance of the circuit gradually reduced, but ink bleeding on the fabric surface became more pronounced. Cotton fabric, via absorbing the ink deeply, exhibited less surface bleeding, while polyester fabric showed more noticeable ink spreading. These findings provide valuable insights for improving screen printing technology for textile circuits and contribute to the development of advanced fabric circuits that enhance the functionality of smart wearable technology.

Strategy for co-enhancement of interface adhesion and coercivity of Nd-Fe-B grain boundary diffusion magnet: TbH3 nanopowders used in screen printing

Screen printing technology (SPT) was applied to conduct grain boundary diffusion sintered Nd-Fe-B magnets using TbH3 and TbF3 nanopowders as diffusion sources. TbH3 grain boundary diffusion (HGBD) coating had better adhesion to the magnet surface than TbF3 grain boundary diffusion (FGBD) coating. When the weight gain ratio was 1.0 wt%, the HGBD magnet achieved a coercivity increment of 11.07 kOe under non-pressurized heat treatment, while effectively controlling the magnet’s residual C and O elements. However, pressure heat treatment was necessary for the FGBD magnet to improve the coercivity due to the poor adhesion between the coating and the magnet surface, resulting in more residual C and O elements inside the magnet. Moreover, the coercivity of the FGBD magnet only increased by 7.96 kOe. Compared to the FGBD magnet, Tb diffused deeper into the HGBD magnet and formed more (Nd, Tb)2Fe14B-Nd2Fe14B core–shell structures. The formation of core–shell structures greatly enhanced the nucleation field of the reverse domain, thereby increasing the coercivity. Hence, the HGBD magnet had a higher coercivity increment. In addition, the HGBD magnet possessed better coercivity temperature stability than the original and FGBD magnets. Using TbH3 nanopowders as a diffusion source for SPT can achieve higher magnetic properties and simplified processes without pressure.

Design and investigation of indium tin oxide-based transparent broadband microwave absorbers

This paper presents the design of a novel wideband transparent microwave absorber based on indium tin oxide (ITO). The absorber adopts a multilayer structure, with the top layer composed of a nested square structure made of ITO material, an intermediate dielectric layer of polyvinyl chloride (PVC), and a bottom layer of polyethylene terephthalate (PET) coated with ITO as the reflector. By optimizing structural parameters such as the thickness of the ITO film and the dimensions of the spacer layer, efficient broadband microwave absorption exceeding 90% is achieved within the frequency range of 2.43 to 5.67 GHz, while simultaneously meeting requirements for optical transparency and broadband performance. Simulation experiments and theoretical analyses demonstrate excellent polarization and incident angle stability of the absorber structure. Finally, samples are fabricated using screen printing technology, and free-space testing results are consistent with simulation predictions, validating the feasibility of the design.

Real-time Monitoring of Carbon Dioxide with IoT ThingSpeak using TiO2 Thick Film Gas Sensor

Carbon dioxide is a colorless, odorless, and non-flammable gas and is claimed to be the fourth most abundant in the earth's atmosphere. Carbon dioxide emission is mainly generated by human and animal exhalation, decomposition of organic matter, and forest fires. Moreover, human activities in the industrial sector emit high levels of carbon dioxide gas, such as through fossil fuel burning, transportation, and deforestation. It is also an asphyxiant and high exposure to it may lead to health effects in humans such as headaches, breathing difficulty, tiredness, coma, and elevated blood pressure. Therefore, in this paper, a carbon dioxide gas sensor with IoT using TiO2 is proposed to observe varying concentrations of carbon dioxide gas at room temperature. Three similar gas sensors were fabricated via screen-printing technology to compare their performance towards carbon dioxide. The hardware development consisted of an Arduino Uno R3 with ESP 8266 Wi-Fi module, wires, LCD display, red and green LEDs, and a 5V power supply. The ThingSpeak application was integrated with the gas sensor and hardware parts to monitor the carbon dioxide concentration in a real-time system. Gas sensor G1 produced the highest response and highest sensitivity with values of 2.120 and 0.245, respectively.

Study on luminescence properties and anti-counterfeiting application of Sr3Y2Ge3O12 doped Mn2+ long afterglow materials

Traditional anti-counterfeiting materials have the characteristics of static display of anti-counterfeiting patterns and are easy to be disturbed by background patterns. Consequently, the development of novel luminous materials represents an imperative objective. As a novel class of matrix material, Sr3Y2Ge3O12 has demonstrated considerable potential for application in the field of anti-counterfeiting. In this study, strontium yttrium germanate doped manganese ion long afterglow material was prepared by the high temperature solid phase method, and its afterglow performance and dynamic anti-counterfeiting application were studied. The experimental results show that the sample exhibits excellent luminescence characteristics. It is observed that the sample excited at 260 nm shows an emission band centred at 634 nm and a high-energy turning point at 578 nm. Using screen printing technology, design a variety of anti-counterfeiting labels. The prepared samples after ultraviolet excitation can maintain the pattern for a long time, and with the passage of time, the pattern shows dynamic attenuation, which is important in enhancing the anti-counterfeiting effect and improving product safety.

All-printed MXene/WS2-based flexible humidity sensor for multi-scenario applications

As non-contact sensing, non-invasive medical diagnostics and environmental humidity monitoring technologies advance, the demand for high-performance humidity sensors is becoming increasingly apparent. Ti3C2Tx MXene is an attractive humidity-sensitive candidate due to its excellent chemical activity and hydrophilic surface. However, achieving fast responsiveness and high sensitivity of dynamic changes in humidity is still challenging. Herein, this work introduced a WS2-modified Ti3C2Tx MXene composite material as humidity sensing material with superior sensing performance. Then sodium carboxymethyl cellulose solution was added to the Ti3C2Tx MXene/WS2 composite material to adjust viscosity of the composite material, enabling the formulation of printable humidity-sensitive ink. Utilizing screen-printing technology, a mass-producible humidity sensor (CMXW2) was successfully fabricated. Experimental results show that the sensor has short response and recovery times of 4.65 s/1.33 s in the relative humidity of 11–97 % with a high humidity response of 1707 % and excellent mechanical properties. The efficacy of the humidity sensor for skin moisture monitoring, real-time respiration monitoring, and non-contact switch was also evaluated. The successful demonstration of multi-scenario applications using the CMXW2 humidity sensor opens up new possibilities and applications in the fields of smart healthcare and non-contact sensing.

Disposable electrochemical aptasensor with mesoporous carbon spheres modified screen-printed dual-working electrodes for Pb2+ and Hg2+ detection

Electrochemical biosensing combined with screen-printed paper technology provides an effective strategy for the quantitative analysis of metal ions, particularly suitable for in-situ determination. In this study, a disposable, economical and user-friendly screen-printed dual-working electrodes (SPDEs) aptasensor system for the determination of lead ions (Pb2+) and mercury ions (Hg2+) was described. The sensor system consists of dual-working electrodes, a counter electrode and a reference electrode fabricated using screen printing technology. The aptasensor demonstrates high sensitivity and selectivity towards Pb2+ and Hg2+, owing to the larger specific surface area (1334.7 m2/g) and excellent conductivity of mesoporous carbon nanoparticles (MCNs). Additionally, the specific recognition ability and high affinity of G-quadruplex and T-Hg2+-T structures for Pb2+ and Hg2+, respectively, further enhance the performance. Under optimized experimental conditions, the aptasensor achieves a low limit of detection (LOD) of 0.088 ng/mL for Pb2+ and 0.0007 ng/mL for Hg2+ (S/N = 3), a wide linear range (0.1–1000.0 ng/mL for Pb2+ and 0.001–100.0 ng/mL for Hg2+), and high accuracy (relative standard deviation, RSD≤10.0 %) and selectivity. Importantly, the SPDEs aptasensor can detect Pb2+ and Hg2+ in a sample without competition and interference, achieving accuracy comparable to that of commercial inductively coupled plasma mass spectrometry (ICP-MS). These advantages make the SPDEs aptasensor highly suitable for practical applications in environmental monitoring, food safety, and clinical diagnosis.

Selecting optimal carbon inks for fabricating high-performance screen-printed electrodes for diverse electroanalytical applications

Carbon-based screen-printed electrodes (SPEs) are extensively employed in electrochemistry due to their reproducibility, low-cost production, disposability and versatility. It is commonly accepted that batch to batch variations may occur due to variations in the ink formulation or the use of a different ink to print the electrodes. In this paper, three different commercial carbon-based inks (DuPont, Loctite and SunChemical) were used to manufacture SPEs, referred to respectively as Dup-SPE, Loc-SPE and Sun-SPE, using a semi-automated screen-printing technology. This study focuses on evaluating the quality, characteristics and electrochemical performance of the fabricated SPEs. Furthermore, the study aimed to investigate potential correlations between the ink composition and the nature of different target molecules, as well as their electroanalytical responses. Specifically, phenolic compounds and cocaine cutting agents are tested in alkaline conditions, while benzodiazepines and cephalosporine antibiotics are investigated in acidic media using square wave voltammetry (SWV). This aims to extract insights for the proper selection of inks and SPEs in both conditions. Additionally, a scan rate study of cephalosporine antibiotics using linear sweep voltammetry (LSV) is performed confirming the ion-exchange polymer layer on the electrode surface of Loc-SPE, which impact surface and electrochemical properties, leading to drawbacks in alkaline SWV sensing, but strategic benefits in reductive sensing resulting in an enhanced selective detection of specific targets. The insights on ink-specific influences on the surface and electrochemical properties of the SPEs obtained, may be useful for facilitating the electrode selection in diverse electrochemical applications, emphasizing the critical role of ink composition in achieving desired sensing capabilities.

Sustainable, cytocompatible and flexible electronics on potato starch-based films

Environmental concerns and climate protection are gaining increasing emphasis nowadays. A growing number of industries and scientific fields are involved in this trend. Sustainable electronics is an emerging research strand. Environmentally friendly and biodegradable or biobased raw materials can be used for the development of green flexible electronic devices, which may serve to reduce the pollution generated by plastics and electronics waste. In this work, we present cytocompatible, electrically conductive structures of nanocarbon water-soluble composites based on starch films. To accomplish this goal, potato starch-based films with glycerol as a plasticiser were developed along with a water-soluble vehicle for nanocarbon-based electroconductive pastes specifically dedicated to screen printing technology. Films were characterized by optical microscopy, scanning electron microscopy (SEM) mechanical properties and surface free energy.

Ultrasensitive electrochemical sensing for simultaneous rapid detection of zearalenone and ochratoxin A in feedstuffs and foodstuffs

Mycotoxins are causing persistent worries regarding food safety worldwide due to their ability to elicit a wide range of harmful effects in both animals and humans. Approaches that can identify a single mycotoxin are not sufficient for addressing the needs of quality control of agricultural products since they are often co-contaminated by multiple mycotoxins. This paper presents the development of an electrochemical sensor that is free of biomolecules and is capable of simultaneously detecting zearalenone (ZEN) and ochratoxin A (OTA) through the incorporation of nickel oxide (NiO) with carboxylated carbon nanotubes (MWCNT(–COOH)).This is the first time that NiO–MWCNT(–COOH) based electrochemical sensor has achieved the simultaneous potential-resolved selective detection of ZEN and OTA. Under optimized conditions, good linear responses were observed in the range of 0.01–10.24 μg mL−1 for ZEN and 0.04–10.24 μg mL−1 for OTA with low detection limit of 6 and 15 ng mL−1, respectively. The proposed electrochemical sensor demonstrated good selectivity, reusability, reproducibility, and shelf-life for the sensitive detection of both mycotoxins. Moreover, the sensor was made utilizing screen-printing technology to demonstrate its potential for commercialization and practical application. Our biomolecule-free electrochemical sensor was successful in evaluating these mycotoxins in actual samples of corn flour and wheat flour, proving its promising application in monitoring ZEN and OTA co-contamination in agricultural products.

Multi-color Na3GaF6:Tm3+,Yb3+@SiO2 for dual-mode security and information encryption

The development of advanced luminescent materials is important for anti-counterfeiting applications, but still faces many challenges. In this study, Na3GaF6:Tm3+,Yb3+@SiO2 core@shell type nanocrystals with cryolite structure were synthesized for the first time by co-precipitation method. By modulating the excitation mode and Tm3+/Yb3+ doping ratio, the Na3GaF6:Tm3+,Yb3+@SiO2 nanocrystals exhibits multicolor up-conversion emission. Multicolor anti-counterfeiting ink was configured with up-conversion nanocrystals, and a variety of multi-colour anti-counterfeiting patterns were printed using screen printing technology. Additionally, multi-colour fluorescent barcodes are combined with binary coding technology to achieve encryption of anti-counterfeiting information. This work not only discovered an excellent up-conversion nanocrystals (Na3GaF6:Tm3+,Yb3+@SiO2) suitable for anti-counterfeiting applications, but also provided an effective encryption strategy for anti-counterfeiting information.

Sandwich probe temperature sensor based on In2O3-IZO thin film for ultra-high temperatures

High-temperature thin-film thermocouples (TFTCs) have attracted significant attention in the aerospace and steel metallurgy industry. However, previous studies on TFTCs have primarily focused on the two-dimensional planar-type, whose thermal sensitive area has to be perpendicular to the test environment, and therefore affects the thermal fluids pattern or loses accuracy. In order to address this problem, recent studies have developed three-dimensional probe-type TFTCs, which can be set parallel to the test environment. Nevertheless, the probe-type TFTCs are limited by their measurement threshold and poor stability at high temperatures. To address these issues, in this study, we propose a novel probe-type TFTC with a sandwich structure. The sensitive layer is compounded with indium oxide doped zinc oxide and fabricated using screen-printing technology. With the protection of sandwich structure on electrode film, the sensor demonstrates robust high-temperature stability, enabling continuous working at 1200 °C above 5 h with a low drift rate of 2.3 °C·h−1. This sensor exhibits a high repeatability of 99.3% when measuring a wide range of temperatures, which is beyond the most existing probe-type TFTCs reported in the literature. With its excellent high-temperature performance, this temperature sensor holds immense potentials for enhancing equipment safety in the aerospace engineering and ensuring product quality in the steel metallurgy industry.

Utilizing screen printing technology to fabricate tungsten-rhenium thick film thermocouples with a maximum temperature limit of 1600 °C

Tungsten-rhenium thick film thermocouples (TFTCs) show excellent potential for in-situ high-temperature monitoring due to their high-temperature resistance. However, the only reported method for preparing tungsten-rhenium thin film thermocouples is magnetron sputtering. The upper limit of temperature resistance of thetungsten-rhenium thin film thermocouples prepared by this method is low because the thickness is reduced by continuous thermal ablation at high temperatures. In this work, screen printing technology is used to prepare tungsten-rhenium TFTCs. The tungsten-rhenium TFTCs’ temperature accuracy is better than ±1.5 %, repeatability is better than 0.9 %, and drift is only 0.26 %/h at 1600 °C. Finally, the tungsten-rhenium TFTC temperature ring array is installed in a tubular furnace for high-temperature monitoring, and the tungsten-rhenium TFTC is heated in the air using a high-temperature flame gun at approximately 1000 °C for up to 30 s. This method to fabricate tungsten-rhenium TFTCs has the potential for temperature measurement in extremely harsh environments.

Flexible Thermoelectric Wearable Architecture for Wireless Continuous Physiological Monitoring.

Continuous monitoring of physiological signals from the human body is critical in health monitoring, disease diagnosis, and therapeutics. Despite the needs, the existing wearable medical devices rely on either bulky wired systems or battery-powered devices needing frequent recharging. Here, we introduce a wearable, self-powered, thermoelectric flexible system architecture for wireless portable monitoring of physiological signals without recharging batteries. This system harvests an exceptionally high open circuit voltage of 175-180 mV from the human body, powering the wireless wearable bioelectronics to detect electrophysiological signals on the skin continuously. The thermoelectric system shows long-term stability in performance for 7 days with stable power management. Integrating screen printing, laser micromachining, and soft packaging technologies enables a multilayered, soft, wearable device to be mounted on any body part. The demonstration of the self-sustainable wearable system for detecting electromyograms and electrocardiograms captures the potential of the platform technology to offer various opportunities for continuous monitoring of biosignals, remote health monitoring, and automated disease diagnosis.

Controllable decomposition/recrystallization of water-sensitive CsPbBr3 glass ceramics for dynamic anti‐counterfeiting with high security

Due to the sensitivity to water, the all-inorganic CsPbBr3 nanocrystals have been widely applied in information encryption with spatial dimensions. However, the absence of time-dimension information limits the information capacity for the application of CsPbBr3. In this work, the CsPbBr3 nanocrystal was combined with water-sensitive borophosphate glass, achieving decomposing/recrystallization of CsPbBr3 nanocrystal with multi-dimension. The addition of SiO2 confirms that the collapse of the borophosphate glass network structure causes the exposure of the CsPbBr3 nanocrystals. The decomposition and recrystallization mechanism of CsPbBr3 nanocrystals in glass-ceramics upon encountering water has been verified. Finally, an information encryption strategy, using the mixture of CsPbBr3 glass ceramic and sodium carboxymethylcellulose as ink, is designed via adopting screen-printing technology, which not only provides a new idea for the preparation of CsPbBr3 nanocrystals, but also establish a new avenue for the information encryption technology.

Water‐Based Polyurethane Heating Film with Double‐Layer Conductive Network for a Rapid Electrothermal Response

Carbon‐based composite materials have garnered widespread attention in the field of personal thermal management (PTM). In these applications, constructing conductive fillers with a highly cross‐linked network is key to achieving the rapid electrothermal conversion of materials. Herein, a novel carbon‐based composite material is successfully developed using screen printing technology, with a waterborne polyurethane (WPU) matrix embedded with carbon nanotubes (CNTs) and calcein‐modified graphene nanosheets (CAG). Due to the strong π–π conjugation interactions present in the highly cross‐linked carbon‐based network, the resulting CAG‐CNTs/WPU composite forms a 3D conductive network, which not only demonstrates a significant synergistic effect but also facilitates efficient transport of electrons and phonons. Experimental results show that the CAG‐CNTs/WPU composite possesses excellent electrothermal conversion properties and an upper high thermal conductivity (3.10 W m−1 K−1). At a low voltage of 5 V, the composite exhibits a rapid response, increasing to 50 °C in 20 s. This research not only highlights the importance of adopting environmentally friendly preparation methods but also emphasizes the synergistic role played by 2D graphene nanosheets and 1D CNTs in building an efficient 3D electrothermal network, which has significant scientific and application value in advancing PTM applications.