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Conventional approaches to creating high‐resolution electric circuits face challenges such as the requirement for skilled personnel and expensive equipment. In response, we propose an innovative strategy that leverages a photochemically modified porous polymer skeleton for in‐situ circuit fabrication. By developing maskless surface energy manipulation that guides PEDOT:PSS‐based conductive ink deposition, electric circuits with high precision, density, stability and adaptability are effortlessly engineered within or atop the porous skeleton, enabling transitions between 2D and 3D circuit configurations. This process simplifies prototyping while significantly reducing costs and maintaining efficiency, promising advancements across various technological sectors. [ABSTRACT FROM AUTHOR]

With the constant increase of electronic waste globally, society is demanding and governments are boosting the development of electronics with less pollutant materials and reduced environmental impact. One way to achieve this is to implement materials that are functional and structural at the same time, reducing material use and assembling parts. Further, printing techniques, such as screen printing, reduce considerably costs and time compared with conventional electronics; combined with methods to conform printed electronics to a 3D shape, such as thermoforming, allow to obtain nonplanar surface electronics simply and efficiently. Herein, screen‐printable inks made of styrene–ethylene/butylene–styrene and different aspect‐ratio carbon‐based materials for conformable electronics are reported. The inks are prepared with carbon black, carbon nanotubes, and reduced graphene oxide as conductive fillers, printed on a flexible substrate and thermoformed. Carbon black and carbon nanotube samples are functional after the process, with conductivities of 96 and 141 S m−1 for the best performing sample of each filler, respectively. Rheological, morphological, thermal, and electrical properties of the materials are also characterized. This study shows the influence of the filler's type and aspect ratio on the morphology and electrical conductivity of the printed materials before and after thermoforming. [ABSTRACT FROM AUTHOR]

Carbon-based conductive inks, with their low cost, ease of fabrication, and environmental friendliness, have a wide range of applications. In this study, we present the development of a candle-soot-based conductive ink through a simple and cost-effective synthesis process. The composite was formulated by incorporating candle-soot with PVDF-HFP polymer using DMF as a solvent. The study evaluates the performance of different amounts of carbon present in a candle-soot-polymer composite. The conductive ink was also filled in a ballpoint refill, circuits were drawn, and I–V responses were studied. The conductive films were thoroughly characterized using SEM, EDX, TGA, and IV characteristics. XRD and FTIR analyses were performed to assess the properties of the conductive film (CPC4) and candle-soot. Four distinct conductive ink formulations were synthesized by varying the percentage of candle-soot. I-V studies revealed that the electrical resistance of the composite films decreased with increasing candle-soot content. The results demonstrated excellent conductivity, enabling the fabrication of simple and functional conductive circuits on paper using the developed CPC4 ink. Candle-soot, as filler, exhibited promising results comparable to expensive conductive fillers such as graphene and multi-walled carbon nanotubes. The developed conductive ink shows promising performance in flexible electronic devices, offering a cost-effective and environmentally friendly alternative. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs), owing to their superior electrical and mechanical properties, are a promising alternative to nonmetallic electrically conducting materials. In practice, cellulose as a low‐cost sustainable matrix has been used to prepare the aqueous dispersion of cellulose‐CNT (C‐CNT) nanocomposites. However, the compatibility with conventional solution‐processing and structural rearrangement for improving conductivity has yet to be determined. Herein, a straightforward route to prepare a conductive composite material from single‐walled CNTs (SWCNTs) and natural pulp is reported. High‐power shaking realizes the self‐alignment of individual SWCNTs in a cellulose matrix, resulting from the structural change in molecular orientations owing to countless collisions of zirconia beads in the aqueous mixture. The structural analysis of the dried C‐CNT films confirms that the entanglement and dispersion of C‐CNT nanowires determine the mechanical and electrical properties. Moreover, the rheological behavior of C‐CNT inks explains their coating and printing characteristics. By controlling shaking time, the electrical conductivity of the C‐CNT films with only 9 wt.% of SWCNTs from 0.9 to 102.4 S cm−1 are adjusted. the optimized C‐CNT ink is highly compatible with the conventional coating and printing processes on diverse substrates, thus finding potential applications in eco‐friendly, highly flexible, and stretchable electrodes is also demonstrated. [ABSTRACT FROM AUTHOR]

AbstractIn the rapidly evolving wireless communication landscape, achieving full-dimensional coverage poses a gamut of challenges such as intricacy, high hardware costs and energy consumption. In addressing these issues, reconfigurable metasurfaces are being considered as a potential solution. However, traditional methods of producing reconfigurable metasurfaces via printed circuit board (PCB) technologies possess limitations such as high cost and extended production cycles. Particularly, in the context of large-scale communication scenarios, reconfigurable metasurfaces can also present high energy consumption issues. Therefore, this paper proposes a novel type of intelligent reflection surface (IRS) characterized by lower production costs, reduced energy consumption, enhanced flexibility, ease of manufacture, and superior electromagnetic wave modulation capabilities. The proposed reconfigurable smart metasurface is a paper-based metasurface printed with conductive ink, which uses conductive ink to draw base metal blocks on a flexible substrate, and uses silver-tin as a metal patch between the metal blocks, and the phase response is reconstructed with silver ink. By adjusting the distribution of these metallic patches, we tailor the phase and amplitude distributions to generate specific scattering effects. This paper presents designs of six patterns that yield single-beam and dual-beam, with experimental results aligning closely with simulated results, validating the feasibility of the proposed method. This low-power, low-cost, and efficient IRS is expected to pave a new path for advanced 5 G/6G wireless communication technologies. [ABSTRACT FROM AUTHOR]

Natural polymer substrates are gaining attention as substitutes for plastic substrates in electronics, aiming to combine high performance, intricate shape deformation, and environmental sustainability. Herein, natural wood veneer is converted into a transparent wood film (TWF) substrate. The combination of 3D printing and origami technique is established to create programmable wood-based origami electronics, which exhibit superior flexibility with high tensile strength (393 MPa) due to the highly aligned cellulose fibers and the formation of numerous intermolecular hydrogen bonds between them. Moreover, the flexible TWF electronics exhibit editable multiplexed configurations and maintain stable conductivity. This is attributed to the strong adhesion between the cellulose-based ink and TWF substrate by non-covalent bonds. Benefiting from its anisotropic structure, the programmability of TWF electronics is achieved through sequentially folding into predesigned shapes. This design not only promotes environmental sustainability but also introduces its customizable shapes with potential applications in sensors, microfluidics, and wearable electronics. Wood-based electronics are typically constrained in their ability to undergo complex shape deformation. Here, authors integrate transparent wood film and cellulose-based conductive ink for flexible electronic origami devices that have been demonstrated as a proof-of-concept for human motion sensors. [ABSTRACT FROM AUTHOR]

Herein we introduce a novel water-based graphite ink modified with multiwalled carbon nanotubes, designed for the development of the first wearable self-powered biosensor enabling alcohol abuse detection through sweat analysis. The stencil-printed graphite (SPG) electrodes, printed onto a flexible substrate, were modified by casting multiwalled carbon nanotubes (MWCNTs), electrodepositing polymethylene blue (pMB) at the anode to serve as a catalyst for nicotinamide adenine dinucleotide (NADH) oxidation, and hemin at the cathode as a selective catalyst for H2O2 reduction. Notably, alcohol dehydrogenase (ADH) was additionally physisorbed onto the anodic electrode, and alcohol oxidase (AOx) onto the cathodic electrode. The self-powered biosensor was assembled using the ADH/pMB-MWCNTs/SPG||AOx/Hemin-MWCNTs/SPG configuration, enabling the detection of ethanol as an analytical target, both at the anodic and cathodic electrodes. Its performance was assessed by measuring polarization curves with gradually increasing ethanol concentrations ranging from 0 to 50 mM. The biosensor demonstrated a linear detection range from 0.01 to 0.3 mM, with a detection limit (LOD) of 3 ± 1 µM and a sensitivity of 64 ± 2 μW mM−1, with a correlation coefficient of 0.98 (RSD 8.1%, n = 10 electrode pairs). It exhibited robust operational stability (over 2800 s with continuous ethanol turnover) and excellent storage stability (approximately 93% of initial signal retained after 90 days). Finally, the biosensor array was integrated into a wristband and successfully evaluated for continuous alcohol abuse monitoring. This proposed system displays promising attributes for use as a flexible and wearable biosensor employing biocompatible water-based inks, offering potential applications in forensic contexts. A novel water-based graphite ink modified with multiwalled carbon nanotubes designed for the development of a wearable self-powered biosensor enabling alcohol abuse detection through sweat analysis. [ABSTRACT FROM AUTHOR]

The integration of electronics into textiles, commonly referred to electronic textiles (e-textiles), has sparked significant interest in recent years owing to their vast potential across diverse industries including healthcare, fashion, sports, and wearable technology. This review paper offers an extensive examination of the current landscape of e-textiles, focusing on their types, applications, conductive materials, and fabrication methods. Regarding fabrication methods, two primary approaches as main groups were introduced and are scrutinized in detail: (1) Fabricating/using conductive yarn/thread and inserting it into the textile using traditional textile techniques such as weaving, knitting, embroidery and so on. (2) Direct applying of conductive coatings onto existing textiles which include sub groups such as deposition techniques, wet coating techniques, printing techniques and in situ polymerization for integrated conductivity. Notably, this review not only elucidates these methodologies but also encapsulates the latest advancements in e-textile fabrication, serving as a vital resource for researchers and developers navigating this rapidly evolving domain. It also acknowledges the main challenges that need to be addressed to fabricate high efficent e-textile. These include ensuring durability with has direct relation with long-term washability and flexibility. Different strategies to improve durability such as using elastic substrates, stretchable conductive ink, improving adhesion between conductive layer and textile along with encapsulation of conductive layer on textile are discussed. By offering a comprehensive overview and highlighting recent innovations, this paper aims to propel further advancements in the realm of e-textiles, facilitating the realization of their full potential across various sectors. [ABSTRACT FROM AUTHOR]

The combination of fluidity and metallic conductivity has attracted considerable attention to liquid metal (LM), but its development remains challenging due to enormous surface tension. Here, vinyl‐terminated silicone oil and platinum catalyst are added to LM to reduce its surface tension, which develops a special type of liquid‐metal‐silicone (LMS) ink with a catalyst diffusion effect. Combined with an embedded three‐dimentional (3D) printing method, the LMS ink is printed on the support matrix, and the catalyst diffuses outward along the print path to cure the silicone around it, directly constructing self‐encapsulated conductive composites with excellent conductivity and self‐encapsulated flexible tactile sensors based on triboelectric nanogenerator (TENG). The sensor exhibits excellent sensitivity (0.308 V kPa−1), high linearity (≈0.99), and good durability (over 10 000 cycles). Furthermore, when used in flexible wearable electronics, the sensor demonstrates a good performance with an accuracy of ≈96% in classifying different human postures using a convolutional neural network. Finally, through embedded 3D printing with LMS ink and silicone ink, a somatosensory soft robotic gripper with complex cavity structures is designed and manufactured in one step, achieving the all‐in‐one integration of sensors and actuators. This study shows great application potential in flexible electronics and soft robotic systems. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A modified polyol process was used to produce low-cost silver nanowires, which were analyzed using surface plasmon resonance, x-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. These nanowires were used to create silver ink with specific properties suitable for inkjet and aerosol printing. The ink's electrical resistivity was 140 µΩ cm on paper and 200 µΩ cm on polyethylene terephthalate and polypropylene. [ABSTRACT FROM AUTHOR]

Summary A wearable dual‐band dual‐polarized fabric antenna is screen printed on a cotton polyester substrate to operate at the industrial scientific and medical band at 2.45 GHz and wireless local area network at 5.2 GHz. A rectangular slot with a pair of L‐shaped branches are used to excite dual bands. The rectangular slot is used to achieve lower band resonance at 2.45 GHz with linear polarization, and an L‐shaped branch with a stub is used to obtain the circular polarization at 5.2 GHz. A 3 × 3 electromagnetic bandgap (EBG) structure is enabled behind the antenna to minimize the back radiation and specific absorption rate (SAR). The antenna provides a measured impedance bandwidth (BW) of 25% from 2.1 to 2.7 GHz (600 MHz), and 18% from 4.5 to 5.7 GHz (1.2 GHz), respectively. The antenna also has a 3‐dB axial ratio BW of 15% from 4.6 to 5.35 GHz (750 MHz). The antenna exhibits a measured gain of 5.1 dB at 5.2 GHz and 6.4 dB at 2.45 GHz. The SAR is validated by using a CST (computer simulation technology) voxel human body model and found to be 0.0949 and 0.127 W/kg for 1 g tissue at 5.2 and 2.45 GHz, respectively. The dimension of the proposed EBG integrated antenna is (0.52 λ × 0.52 λ × 0.07 λ). The antenna and EBG structure are screen printed with silver conductive ink, which provides good conductivity, conformability, comfort, wearability, and being lightweight. [ABSTRACT FROM AUTHOR]

Liquid metal or liquid metal microparticles (LMP) based conductive inks, though promising for fabrication of circuits for use in soft and stretchable electronics, are constrained by a few drawbacks such as need for encapsulation, need for sintering to induce conductivity, and smearing. To address these issues, herein, a stretchable conductive composite ink is developed by combining LMPs with carbon black (CB) in highly entangled polysiloxane elastomer. LMP‐dispersed elastomer lacks conductivity because of its non‐percolated network, however, the CB can interconnect LMPs to act as a bridge, thereby imparting conductivity to the elastomer. Due to presence of fluidic LMPs, the LMPs‐dispersed elastomer lies in soft regime with initial conductivity of 5.6 S m−1, aided by the presence of CB in the interstitial spaces between the LMPs. The highly entangled molecular network of the encapsulating elastomer endows the resulting composite with high stretchability (≈286%) and softness (0.648 MPa) and its long pot life enables rheological modulation of the ink to achieve pressure‐driven direct printed non‐smearing traces. The LMPs‐based conductive ink developed in this work is expected to be further utilized in the fabrication of soft robotics and electronic skin and integrated into electronic modules by facile direct 3D printing. [ABSTRACT FROM AUTHOR]

Liquid metal (LM) micro‐nano droplets show the superiority in reducing the high surface tension applicable in conductive inks for flexible electronics. However, the dynamic surface makes LM droplets susceptible to be oxidized, facing challenges in storage and applications. Herein, a bifunctional groups cross‐linking strategy is adopted to encapsulate LM droplets into a robust shell. During sonicating LM in carboxymethyl chitosan (CMCS) solution with bifunctional groups (i.e., carboxyl and amino groups), a robust interface shell is constructed by anchoring effect, thereby providing high chemical stability (>7d). When directionally freezing‐drying LM dispersions, aerogel with Janus architecture is produced driven by the gravity of LM droplets. Due to the unique heterogeneous structure, the resultant aerogel exhibits a selective multifunctional response toward directional bending. In addition, owing to the gradient distribution of CMCS within aerogel, moisture electricity generator can be built with a high output voltage of 460 mV. Thus, this bifunctional groups cross‐linking strategy not only improves the chemical stability of LM micro‐nano droplets, but also renders a new method for producing multifunctional aerogel with energy harvesting and selective directional recognition, and applicable in smart sensors and power supplying devices. [ABSTRACT FROM AUTHOR]

Vibration sensors are widely applied in the detection of faults and analysis of operational states in engineering machinery and equipment. However, commercial vibration sensors with a feature of high hardness hinder their usage in some practical applications where the measured objects have irregular surfaces that are difficult to install. Moreover, as the operating environments of machinery become increasingly complex, there is a growing demand for sensors capable of working in wet and humid conditions. Here, we present a flexible, superhydrophobic vibration sensor with parallel microcracks. The sensor is fabricated using a femtosecond laser direct writing ablation strategy to create the parallel cracks on a PDMS film, followed by spray-coating with a conductive ink composed of MWCNTs, CB, and PDMS. The results demonstrate that the developed flexible sensor exhibits a high-frequency response of up to 2000 Hz, a high acceleration response of up to 100 m/s2, a water contact angle as high as 159.61°, and a linearity of 0.9812 between the voltage signal and acceleration. The results indicate that the sensor can be employed for underwater vibration, sound recognition, and vibration monitoring in fields such as shield cutters, holding significant potential for mechanical equipment vibration monitoring and speech-based human–machine interaction. [ABSTRACT FROM AUTHOR]

The growing interest in flexible conductive materials and printed electronic components has spawned a series of new commercial applications, including smart devices, functional clothing, and intelligent packaging. This review summarizes the main preparation techniques for conductive ink fillers, while considering the influence of the source materials (metals, carbon nanoparticles and polymers) that affect the performance of the conductive inks. The preparation methods and related research advances in electronic components (flexible electrodes and sensors) based on inkjet printing and screen‐printing technology are summarized. In addition, the literature review reveals that the current research content rarely considers the influence of printing conditions on the quality of the printed electronic devices, thus indicating that numerous specific engineering challenges need to be overcome for the commercial application of printed electronics. [ABSTRACT FROM AUTHOR]

The relentless drive towards miniaturization and seamless integration of electronic components in wireless communications and wearable devices has significantly increased the demand for flexible, cost‐effective composites with high dielectric constants and low losses. This study presents a wideband, low‐profile, and flexible antenna with excellent on body radiation performance for wearable applications. The antenna is designed using a low‐loss composite film based on PMMA‐PVDF‐HFP‐PZT and silver‐based ink. The proposed flexible antenna exhibits a wide bandwidth of 132.16% with a voltage standing wave ratio (VSWR) of less than two. It achieves a peak gain of 2.76 dBi at 2.92 GHz and maintains a maximum radiation efficiency of 80% across the 1.26–6.17 GHz frequency range. These characteristics demonstrate that the antenna is an effective solution for achieving high data rates and reliable communication links. The antenna's suitability for wearable applications is assessed by testing it on a simulated human body and analyzing its behavior under physical deformation. The results under bending showed only a minimal frequency detuning, which is negligible given the antenna's wide operational bandwidth. The specific absorption rate (SAR) analysis shows values of approximately 1.88 W/kg at 3.5 GHz with an input power of 0.5 W, and 0.279 W/kg at 5.8 GHz with an input power of 0.45 W, which complies with established safety limits for exposure. Overall, these results suggest that the proposed antenna is a viable solution for integration into wearable medical devices, such as a doctor's chest badge, enabling noncontact interactions and reducing the risk of bacterial contamination. [ABSTRACT FROM AUTHOR]

[Display omitted] • Achieve high-precision DIW printing using conductive hydrogel ink. • Conductive hydrogel electrodes have remarkable stretchability and self-healing capabilities. • Develop a self-powered strain sensing system employing conductive hydrogel electrodes. • Construct a complex internal structure within the electrode. • Remote human motion detection based on hydrogel strain sensors. With rapid advancements in health and human–computer interaction, wearable electronic skins (e-skins) designed for application on the human body provide a platform for real-time detection of physiological signals. Wearable strain sensors, integral functional units within e-skins, can be integrated with Internet of Things (IoT) technology to broaden the applications for human body monitoring. A significant challenge lies in the reliance of most existing wearable strain sensors on rigid external power supplies, limiting their practical flexibility. In this study, we present an innovative strategy to fabricate glutaraldehyde (GA)-poly(vinyl alcohol) (PVA)/cellulose nanocrystals (CNC)/Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) conductive hydrogels through multiple hydrogen bonding systems. Combining the advantageous rheological properties of the precursor solution and the high specific surface area after freeze–thaw cycling, we have created a self-powered sensing system prepared by large-area printing using direct ink writing (DIW) printing. The resulting conductive hydrogel exhibits commendable mechanical properties (411 KPa), impressive stretchability (580 %), and robust self-healing capabilities (>98.3 %). The strain sensor, derived from the conductive hydrogel, demonstrates a gauge factor (GF) of 2.5 within a stretching range of 0–580 %. Additionally, the resultant supercapacitor displays a peak energy density of 0.131 mWh/cm3 at a power density of 3.6 mW/cm3. Benefiting from its elevated strain response and remarkable power density features, this self-powered strain sensing system enables the real-time monitoring of human joint motion. The incorporation of a 5G transmission module enhances its capabilities for remote data monitoring, thereby contributing to the progress of wireless tracking technologies for self-powered electronic skin. [ABSTRACT FROM AUTHOR]

Catechol (CT) is a phenolic compound widely used in various industrial sectors, but it is toxic; thus, there is a need for methods that aim to identify and quantify the existence of residues of this material in the environment. In this study a disposable printed electrochemical sensor was developed as an effective alternative for determining CT in water samples. The electrode, called SPEC, was manufactured using the screen-printing method using polyethylene terephthalate (PET) as a support, in which a conductive ink based on carbonaceous materials was used to print the working and auxiliary electrodes and a silver/silver chloride of ink on the reference electrode. The optimal ratio for the conductive ink was 6.25% carbon black, 35.42% graphite, and 58.33% nail polish. The ink obtained was characterized by scanning electron microscopy (SEM). The assessment of the effect of pH on the redox process showed Nernstian behavior (0.057 V pH−1), indicating that the process involves the same number of protons and electrons. Under optimized conditions, with 0.2 mol L−1 acetate buffer at pH 5.0, and by square wave voltammetry, the sensor presented sensitivity values of 0.31 μA L μmol−1, a detection limit of 5.96 μmol L−1, and a quantification limit of 19.87 μmol L−1. The sensor was applied to determine CT in tap water samples, and the results showed recoveries between 97.95 and 100.17%.

Fabricating high-conductive composites and constructing highly conductive networks are crucial for high-performance electrothermal film. In this study, an Ag nanowires/graphene (Ag/G) composite synthesized by liquid-phase exfoliation and in-situ photoreduction is mixed with carbon black (CB) to form a composite conductive ink, and a CB/Ag/G composite electrothermal film with a point-line-plane three-dimensional microstructure is obtained via blade coating process. Both the addition of Ag nanowires and a subsequent compression rolling treatment induce the establishment of the effective conductive network in the film, endowing it with an outstanding conductivity of 399.4 S cm−1. The film reaches a Ts of 204 °C with an input voltage of 3.0 V, and is successfully applied in water heating and de-icing, demonstrating its extraordinary electrothermal performance and vast potential for practical applications. The film is also used as an electromagnetic shielding film and heat dissipation substrate, showing exceptional electromagnetic shielding (42.5 dB) and heat dissipation properties. [ABSTRACT FROM AUTHOR]

AbstractEnhanced electrical conductivity and pressure sensing functionalities of phytic acid-doped polyaniline ink (PPhyA) incorporated with SnO2 (PPhyAS) and graphite flakes (PPhyAG) as reported in our previous article, encouraged us to explore the electrical conduction mechanism and associated optical properties. In order to realize the enhanced electrical conduction in the reported inks, detailed studies were carried out in our research described here in comparison with normal HCl-doped polyaniline (PANI). This can be attributed to the formation of a highly ordered molecular arrangement with high crystallinity, a change in the hopping pathway between two adjacent molecules and the hopping activation energy of the PANI chain in the phytic acid-doped ink systems. Optical parameters, such as absorption edge, Urbach energy, refractive index, extinction coefficient, optical conductivity and optical dielectric constants, were estimated from the result of UV-Vis spectroscopy. The results of these studies showed enhancement of the optical properties of the phytic acid-doped ink systems (PPhyA, PPhyAS and PPhyAG) in the low photon energy range as compared to HCl-doped PANI. Phytic acid-doped ink systems are paintable on a variety of flexible surfaces, such as paper and plastics. Hence, we suggest that the phytic acid-doped ink systems have a great potential for developing flexible and foldable circuitry for infrared optics and remote sensing. [ABSTRACT FROM AUTHOR]

Simple and scalable production of micro-supercapacitors (MSCs) is crucial to address the energy requirements of miniature electronics. Although significant advancements have been achieved in fabricating MSCs through solution-based printing techniques, the realization of high-performance MSCs remains a challenge. In this paper, graphene-based MSCs with a high power density were prepared through screen printing of aqueous conductive inks with appropriate rheological properties. High electrical conductivity (2.04 × 104 S∙m−1) and low equivalent series resistance (46.7 Ω) benefiting from the dense conductive network consisting of the mesoporous structure formed by graphene with carbon black dispersed as linkers, as well as the narrow finger width and interspace (200 µm) originating from the excellent printability, prompted the fully printed MSCs to deliver high capacitance (9.15 mF∙cm−2), energy density (1.30 µWh∙cm−2) and ultrahigh power density (89.9 mW∙cm−2). Notably, the resulting MSCs can effectively operate at scan rates up to 200 V∙s−1, which surpasses conventional supercapacitors by two orders of magnitude. In addition, the MSCs demonstrate excellent cycling stability (91.6% capacity retention and ~100% Coulombic efficiency after 10,000 cycles) and extraordinary mechanical properties (92.2% capacity retention after 5000 bending cycles), indicating their broad application prospects in flexible wearable/portable electronic systems. [ABSTRACT FROM AUTHOR]

Biocompatible, sustainable, and conductive inks are of special interest and are highly valued in the printable bioelectronics. However, the conventional inks, which increase electrical conductivity by mixing metal particles or graphene, can cause long‐term damage when applied to the body and environment. Herein, a method for creating a stable matrix based on a UV‐cross‐linkable polymer to which a conductive polymer can be grafted is investigated to solve the above problems by recycling biomass. Through this, it is possible to achieve high conductivity using only biocompatible and sustainable polymers. Here, conductive inks for printable bioelectronics are developed by grafting polypyrrole on methacrylate‐modified sericin and poly(ethylene glycol) diacrylate (PEGDA). The highest electrical conductivity is achieved by adjusting the ratio of the pyrrole monomers polymerized on each polymer until the conductivity is optimized. Owing to the photoreactive nature of PEGDA, the prepared conductive inks are cross‐linked by UV light, thus giving them easy‐printing properties. The biodegradability, biocompatibility, and electrical properties of the printed patterns are systematically analyzed. This study has significant implications in the field of sustainable and printable bioelectronics as it has developed of a conductive ink with the biocompatibility, biodegradability, and high conductivity that is safer and simpler than conventional methods. [ABSTRACT FROM AUTHOR]

This study presents the development of a low‐cost, easy‐to‐prepare carbon‐based ink for printed electrodes using polyethylene terephthalate (PET) as the support material. The ink was composed of graphite and cellulose acetate (80 : 20%) mixed with acetone and cyclohexanone as solvents. The screen‐printing technique, a versatile and economical method that allows the printing of high‐thickness films, was used to produce the sensor. The developed sensor was characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM), demonstrating good electrochemical behavior with a well‐defined peak corresponding to the redox probe and a low background current. The optimization process focused on analyzing and discussing the ink manufacturing process and characterizing the materials used. The performance of the fabricated printed electrode was evaluated using a potassium ferrocyanide probe as a model redox system. The proposed sensor has the potential for use in electroanalytical determinations and can be produced at a low cost of US$ 0.897 per unit. This study aims to contribute to the development of printed sensors that can be produced on a large scale, are disposable, and can be used to determine different analytes. [ABSTRACT FROM AUTHOR]

Flexible electronics have revolutionized the field by overcoming the rigid limitations of traditional devices, offering superior flexibility and adaptability. Conductive ink performance is crucial, directly impacting the stability of flexible electronics. While metal filler-based inks exhibit excellent conductivity, they often lack mechanical stability. To address this challenge, we present a novel conductive ink utilizing a ternary composite filler system: liquid metal and two micron-sized silver morphologies (particles and flakes). We systematically investigated the influence of filler type, mass ratio, and sintering process parameters on the composite ink's conductivity and mechanical stability. Our results demonstrate that flexible wires fabricated with the liquid metal/micron silver particle/micron silver flake composite filler exhibit remarkable conductivity and exceptional bending stability. Interestingly, increasing the liquid metal content results in a trade-off, compromising conductivity while enhancing mechanical performance. After enduring 5000 bending cycles, the resistance change in wires formulated with a 4:1 mass ratio of micron silver particles to flakes is only half that of wires with a 1:1 ratio. This study further investigates the mechanism governing resistance variations during flexible wire bending. Additionally, we observed a positive correlation between sintering temperature and pressure with the conductivity of flexible wires. The significance of the sintering parameters on conductivity follows a descending order: sintering temperature, sintering pressure, and sintering time. Finally, we demonstrate the practical application of this technology by integrating the composite ink-based flexible wires with conductive polymer-based strain sensors. This combination successfully achieved the detection of human movements, including finger and wrist bending. [ABSTRACT FROM AUTHOR]

Anisotropic conductive adhesives (ACAs) are the preferred interconnection technology for applications that employ large dies, flexible substrates, and ultra fine‐pitch interconnects. Conventional ACAs require relatively high bonding pressures and temperatures, and ultra fine‐pitch applications challenge the trade‐off between low interconnect resistance and risk of short circuits. This study introduces an ACA‐like interconnection technology that addresses these limitations, allowing for low‐pressure, low‐temperature assembly processes with enhanced particle control at the interconnects. Conductive particles are deposited onto a patterned carrier and subsequently transferred to electrical pads using either non‐conductive film or Ag sintering. The Ag sintering process is performed at a low temperature (140 °C) and low bonding pressure (1 N for a 10 × 10 mm2 chip). The capability of controlling the position and number of conductive particles within individual interconnects is demonstrated. This presents possibilities for achieving ultra‐fine pitch interconnects with negligible risk of short circuits, without compromising electrical resistance. It is demonstrated that interconnect resistance can be tuned by varying the number of conductive particles (achieving a resistance as low as 33 mΩ with 25 particles per interconnect). This approach is applicable to scenarios where the bonding force and temperature must remain low due to the nature of substrate materials. [ABSTRACT FROM AUTHOR]

Over the past several years, atomically thin two‐dimensional carbides, nitrides, and carbonitrides, otherwise known as MXenes, have been expanded into over fifty material candidates that are experimentally produced, and over one hundred fifty more candidates that have been theoretically predicted. They have demonstrated transformative properties such as metallic‐type electrical conductivities, optical properties such as plasmonics and optical nonlinearity, and key surface properties such as hydrophilicity, and unique surface chemistry. In terms of their applications, they are poised to transform technological areas such as energy storage, electromagnetic shielding, electronics, photonics, optoelectronics, sensing, and bioelectronics. One of the most promising aspects of MXene's future application in all the above areas of interest, we believe, is reliably developing their flexible and bendable electronics and optoelectronics by printing methods (henceforth, termed as printed flexible MXetronics). Designing and manipulating MXene conductive inks according to the application requirements will therefore be a transformative goal for future printed flexible MXetronics. MXene's combined property of high electrical conductivity and water‐friendly nature to easily disperse its micro/nano‐flakes in an aqueous medium without any binder paves the way for designing additive‐free highly conductive MXene ink. However, the chemical and/or structural and hence functional stability of water based MXene inks over time is not reliable, opening research avenues for further development of stable and conductive MXene inks. Such priorities will enable applications requiring high‐resolution and highly reliable printed MXene electronics using state‐of‐the art printing methods. Engineering MXene structural and surface functional properties while tuning MXene ink rheology in benign solvents of choice will be a key for ink developments. This review article summarizes the present status and prospects of MXene inks and their use in inkjet‐printed (IJP) technology for future flexible and bendable MXetronics. [ABSTRACT FROM AUTHOR]

Copper-based conductive ink has received attention to fabricate thin, flexible, and lightweight devices through printing techniques. In particular, the copper formate based conductive inks, called metal organic decomposition (MOD) inks, which are fabricated by using amine ligand coordinated copper formate have been well studied because of higher oxidative resistant against air than that of metallic copper before thermal annealing. The copper formate moiety of amine ligand coordinated copper formate complexes varies by changing the coordinated amine species, however, for the thermal decomposition temperature of such ink is not well understand. Here, we analyzed the influence of the amine ligand on the thermal decomposition temperature drop of copper formate moiety. Amine-copper formate complexes bearing several amine ligands containing primary amine, pyridine, and imidazole groups were fabricated. The relationship between the evaluated decomposition temperature and the differences between the wavenumbers of symmetric and antisymmetric vibration mode peaks in Fourier transform infrared (FTIR) spectra was found to be nearly linear. This finding demonstrates that the thermal decomposition temperature is governed by the structural modification of formate ions by the coordination of amine groups. Based on this finding, the order of thermal decomposition temperature of the copper moiety is predictable by using FTIR measurement. [ABSTRACT FROM AUTHOR]

Miniaturization and flexibility are becoming the trend in the development of electronic products. These key features are driving new methods in the manufacturing of such products. Printed electronics technology is a novel additive manufacturing technique that uses active inks to print onto a diverse set of substrates, realizing large-area, low-cost, flexible and green manufacturing of electronic products. These advantageous properties make it extremely compatible with flexible electronics fabrication and extend as far as offering revolutionary methods in the production of flexible electronic devices. In this paper, the details of a printing process system are introduced, including the materials that can be employed as inks, common substrates, and the most recently reported printing strategies. An assessment on future setbacks and developments of printed flexible electronics is also presented. [ABSTRACT FROM AUTHOR]

Hyperplastic scars, especially keloids, have posed a significant clinical challenge due to their high recurrence rate. Compression therapy, a cost‐effective treatment, has demonstrated efficacy in reducing scarring and preventing recurrence. However, the compression methods exhibit limitations in adapting to the complex contours and accurately adjusting the treatment pressure, resulting in unsatisfactory treatment effects. In this study, silicone is chosen as the substrate layer ink, while the conductive ink is developed by incorporating nano‐carbon black into the polymer composite. These are printed alternately within the supported gels to construct an integrated orthotic device with precise pressure control capabilities and complex structures. Results demonstrated the printed orthosis displayed excellent mechanical properties, durability and biocompatibility. It can successfully detect various stress changes with short response times. The utilization of finite element analysis aided in the design of personalized orthosis to achieve optimal pressure for scar treatment. Finally, orthosis‐mediated pressure treatment is performed on rat tail scar models. By monitoring resistance value, it can be inferred whether the treatment pressure applied by orthosis fell within an optimal range. Overall, personalized piezoresistive anti‐scar orthoses offer an accurate and effective treatment method for scar. This innovative approach presents a novel strategy in the realm of personalized scar management. [ABSTRACT FROM AUTHOR]

Exocytosis involving the fusion of intracellular vesicles with cell membrane, is thought to be modulated by the mechanical cues in the microenvironment. Single‐cell electrochemistry can offer unique information about the quantification and kinetics of exocytotic events; however, the effects of mechanical force on vesicular release have been poorly explored. Herein, we developed a stretchable microelectrode with excellent electrochemical stability under mechanical deformation by microfabrication of functionalized poly(3,4‐ethylenedioxythiophene) conductive ink, which achieved real‐time quantitation of strain‐induced vesicular exocytosis from a single cell for the first time. We found that mechanical strain could cause calcium influx via the activation of Piezo1 channels in chromaffin cell, initiating the vesicular exocytosis process. Interestingly, mechanical strain increases the amount of catecholamines released by accelerating the opening and prolonging the closing of fusion pore during exocytosis. This work is expected to provide revealing insights into the regulatory effects of mechanical stimuli on vesicular exocytosis. [ABSTRACT FROM AUTHOR]

In this research, a novel electrochemical biosensor is proposed based on inducing graphene formation on polyimide substrate via laser engraving. Graphene polyaniline (G-PANI) conductive ink was synthesized by planetary mixing and applied to the working zone of the developed sensor to effectively enhance the electrical signals. The laser-induced graphene (LIG) sensor was used to detect alpha-fetoprotein (AFP) and 17β-Estradiol (E2) in the phosphate buffer saline (PBS) buffer and human serum. The electrochemical performance of the biosensor in determining these biomarkers was investigated by differential pulse voltammetry (DPV) and chronoamperometry (CA). In a buffer environment, alpha-fetoprotein (AFP) and 17β-Estradiol detection range were 4–400 ng/mL and 20–400 pg/mL respectively. The experimental results showed a limit of detection (LOD) of 1.15 ng/mL and 0.96 pg/mL for AFP and estrogen, respectively, with an excellent linear range (R2 = 0.98 and 0.99). In addition, the designed sensor was able to detect these two types of biomarkers in human serum successfully. The proposed sensor exhibited excellent reproducibility, repeatability, and good stability (relative standard deviation, RSD = 0.96%, 1.12%, 2.92%, respectively). The electrochemical biosensor proposed herein is easy to prepare and can be successfully used for low-cost, rapid detection of AFP and E2. This approach provides a promising platform for clinical detection and is advantageous to healthcare applications. [ABSTRACT FROM AUTHOR]

The printed electronics (PEs) market has witnessed substantial growth, reaching a valuation of USD 10.47 billion in the previous year. Driven by its extensive use in a multitude of applications, this growth trend is expected to continue with a projected compound annual growth rate of 22.3% from 2022 to 2032. Compared to screen printing, the adoption of inkjet printing (IJP) technology to manufacture PEs has been limited to laboratory‐scale research only. The fact that IJP's inability to maintain consistent high‐resolution quality over large printing areas has made transitioning IJP for commercial production arduous. Most of the previous literatures have focused on holistic discussion on material design for IJP, but this review provides insight into key aspects in material processing up to printing optimization to realize high‐resolution PEs. This review also highlights the challenges in controlling the functional ink properties and their interaction with the substrate as well as printing parameters to deliver the desired quality of the droplets and final prints. Imminent application of IJP in PEs and future perspectives are also included in this review. [ABSTRACT FROM AUTHOR]

Purpose: To introduce alternating current‐controlled, conductive ink‐printed marker that could be implemented with both custom and commercial interventional devices for device tracking under MRI using gradient echo, balanced SSFP, and turbo spin‐echo sequences. Methods: Tracking markers were designed as solenoid coils and printed on heat shrink tubes using conductive ink. These markers were then placed on three MR‐compatible test samples that are typically challenging to visualize during MRI scans. MRI visibility of markers was tested by applying alternating and direct current to the markers, and the effects of applied current parameters (amplitude, frequency) on marker artifacts were tested for three sequences (gradient echo, turbo spin echo, and balanced SSFP) in a gel phantom, using 0.55T and 1.5T MRI scanners. Furthermore, an MR‐compatible current supply circuit was designed, and the performance of the current‐controlled markers was tested in one postmortem animal experiment using the current supply circuit. Results: Direction and parameters of the applied current were determined to provide the highest conspicuity for all three sequences. Marker artifact size was controlled by adjusting the current amplitude, successfully. Visibility of a custom‐designed, 20‐gauge nitinol needle was increased in both in vitro and postmortem animal experiments using the current supply circuit. Conclusion: Current‐controlled conductive ink‐printed markers can be placed on custom or commercial MR‐compatible interventional tools and can provide an easy and effective solution to device tracking under MRI for three sequences by adjusting the applied current parameters with respect to pulse sequence parameters using the current supply circuit. [ABSTRACT FROM AUTHOR]

This paper presents an innovative method for fabricating reflectarray antennas using inkjet printing technology on flexible substrates, markedly enhancing integration and manufacturability compared to traditional PCB methods. The technique employs inkjet printing to deposit conductive inks directly onto a flexible polyethylene naphthalate (PEN) substrate, seamlessly integrating feed and reflectarray components without complex assembly processes. This streamlined approach not only reduces manufacturing complexity and costs but also improves mechanical flexibility, making it ideal for applications requiring deployable antennas. The design process includes an origami-inspired folding of the substrate to achieve the desired three-dimensional antenna structures, optimizing the focal length to dimension ratio (F/D) to ensure maximum efficiency and performance. The feed and the reflectarray geometry are optimized for an F/D of 0.6, which achieves high gain and aperture efficiency, demonstrated through detailed simulations and measurements. For normal incidence, the configuration achieves a peak gain of 9.3 dBi and 48% radiation efficiency at 10 GHz; for oblique incidence, it achieves 7.3 dBi and 40% efficiency. The study underscores the significant potential of inkjet-printed antennas in terms of cost-efficiency, precision, and versatility, paving the way for new advancements in antenna technology with a substantial impact on future communication systems. [ABSTRACT FROM AUTHOR]

Self‐charging power systems (SCPSs) are envisioned as promising solutions for emerging electronics to mitigate the increasing global concern about battery waste. However, present SCPSs suffer from large form factors, unscalable fabrication, and material complexity. Herein, a type of highly stable, eco‐friendly conductive inks based on poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are developed for direct ink writing of multiple components in the SCPSs, including electrodes for miniaturized spacer‐free triboelectric nanogenerators (TENGs) and microsupercapacitors (MSCs), and interconnects. The principle of "one ink, multiple functions" enables to almost fully print the entire SCPSs on the same paper substrate in a monolithic manner without post‐integration. The monolithic fabrication significantly improves the upscaling capability for manufacturing and reduces the form factor of the entire SCPSs (a small footprint area of ≈2 cm × 3 cm and thickness of ≈1 mm). After pressing/releasing the TENGs for ≈79000 cycles, the 3‐cell series‐connected MSC array can be charged to 1.6 V while the 6‐cell array to 3.0 V. On‐paper SCPSs are promising to serve as lightweight, thin, sustainable, and low‐cost power supplies. [ABSTRACT FROM AUTHOR]

Conductive ink is an important component to fabricate printed electronics, such as flexible, stretchable, and wearable electronics. Solvents are essential for fabrication of conductive inks, but most of the organic solvents are expensive, toxic, and not environmentally friendly. In this review, stability, wettability, and electrical conductivity of different types of solvent- and water-based metal and carbon-based conductive inks are discussed. Further, the utilization of surfactants to facilitate aqueous homogeneous dispersion and stability of metal and carbon nanomaterial-based conductive material is discussed. Particularly, the solvent- and water-based surfactant-assisted conductive inks on the stability and electrical properties of metal- and carbon-based conductive materials are highlighted. In addition, the different characterization methods for assessing the dispersion and stability of conductive inks, such as zeta potential, UV–Visible, long-term stability, and wettability properties, were discussed in this review. [ABSTRACT FROM AUTHOR]

Silver-based metal–organic decomposition inks composed of silver salts, complexing agents and volatile solvents are now the subject of much research due to the simplicity and variability of their preparation, their high stability and their relatively low sintering temperature. The use of this type of ink in inkjet printing allows for improved cost-effective and environmentally friendly technology for the production of electrical devices, including flexible electronics. An approach to producing a silver salt-based reactive ink for jet printing has been developed. The test images were printed with an inkjet printer onto polyimide substrates, and two-stage thermal sintering was carried out at temperatures of 60 °C and 100–180 °C. The structure and electrical properties of the obtained conductive lines were investigated. As a result, under optimal conditions an electrically conductive film with low surface resistance of approximately 3 Ω/square can be formed. [ABSTRACT FROM AUTHOR]

Additive manufacturing of ceramics has attracted large interest due to its unique ability to rapidly prototype, low cost, and increased geometric complexity. Material extrusion technique is often considered for processing and shaping fine and dense ceramic structures because of the high solid loading in ink. In this work, 8 mol.% yttria-stabilized zirconia ink with 70 wt% ceramic loadings was prepared to print zirconia samples in horizontal and vertical directions, following two different filament orientations: 0/90° and ±45°. The study's main objective was to evaluate printing design influences on mechanical properties. This was assessed through flexural testing and digital image correlation analysis. Experimental findings showed that samples printed horizontally with ±45° filament orientation displayed the highest strength. A detailed inspection of fracture surfaces revealed that printing defects were the critical failure location sites formed after sintering and intimately related to printing design issues. After that, a conductive sensor was integrated into the surfaces of 3D-printed specimens by screen-printing silver-based conductive ink to analyze the structural health of zirconia samples. The sensing capabilities of printed conductive patterns were investigated using the four-point bending tests. The results demonstrated that the electrical resistance of the printed silver patterns increased as the applied load on zirconia substrates rose. It indicates that hybrid material extrusion and screen printing techniques are favored ways to manufacture sensors for structural detection of advanced 3D-printed ceramics. [ABSTRACT FROM AUTHOR]

Temperature sensors are critical components in many industrial and research applications, particularly in harsh environments where high temperatures, corrosion and mechanical stress are prevalent. In this paper, we investigate the use of plasma spray technique as a versatile and simple method to print multipoint thermocouples and resistance temperature detectors (RTDs) based on NiCr-NiAl coatings on steel and ceramic substrates using stencil masking and laser scribing. The thickness of alumina the dielectric layer was optimized using metal-insulator-metal test. The thermoelectric properties of the printed thermocouples were investigated up to 1000 °C. The thermal independency of printed thermocouples and the capability of multilocation measurement at the surface on the same substrate was demonstrated. The thermoelectric properties of the printed RTD were investigated up to 850 °C. The electrical resistance of the RTD sensor is linear with the temperature variation from room temperature to 500 °C. The oxidation effect of the printed sensor metallic layers at high temperature was investigated and discussed. [ABSTRACT FROM AUTHOR]

In this work, a chemical grafting polymerization method was employed to synthesize EHPMC-g-PANI self-supporting films. Polyaniline (PANI) was grafted onto hydroxypropyl methylcellulose (HPMC) modified with epichlorohydrin (EPHMC) to obtain an EHPMC-g-PANI aqueous dispersion, which was subsequently dried to form the self-supporting films. The introduction of HPMC, with its excellent film-forming ability and mechanical strength, successfully addressed the poor film-forming ability and mechanical properties intrinsic to PANI. Compared to in situ polymerized HPMC/PANI, the EHPMC-g-PANI exhibited significantly improved storage stability. Moreover, the fabricated EHPMC-g-PANI films displayed a more uniform and smoother morphology. The conductivity of all the films ranged from 10−2 to 10−1 S/cm, and their tensile strength reached up to 36.1 MPa. These results demonstrate that the prepared EHPMC-g-PANI holds promising potential for applications in various fields, including conductive paper, sensors, and conductive inks. [ABSTRACT FROM AUTHOR]

Catechol (CT) is a phenolic compound widely used in various industrial sectors, but it is toxic; thus, there is a need for methods that aim to identify and quantify the existence of residues of this material in the environment. In this study a disposable printed electrochemical sensor was developed as an effective alternative for determining CT in water samples. The electrode, called SPEC, was manufactured using the screen-printing method using polyethylene terephthalate (PET) as a support, in which a conductive ink based on carbonaceous materials was used to print the working and auxiliary electrodes and a silver/silver chloride of ink on the reference electrode. The optimal ratio for the conductive ink was 6.25% carbon black, 35.42% graphite, and 58.33% nail polish. The ink obtained was characterized by scanning electron microscopy (SEM). The assessment of the effect of pH on the redox process showed Nernstian behavior (0.057 V pH−1), indicating that the process involves the same number of protons and electrons. Under optimized conditions, with 0.2 mol L−1 acetate buffer at pH 5.0, and by square wave voltammetry, the sensor presented sensitivity values of 0.31 μA L μmol−1, a detection limit of 5.96 μmol L−1, and a quantification limit of 19.87 μmol L−1. The sensor was applied to determine CT in tap water samples, and the results showed recoveries between 97.95 and 100.17%. [ABSTRACT FROM AUTHOR]

Silver nanoparticles are widely utilized in printed electronics for forming conductive lines due to their exceptional electrical conductivity, resistance to oxidation, and mechanical reliability. Molecular dynamics simulations are employed to monitor real-time sintering behavior at the atomic scale. This feat is challenging to achieve through experimental means. Thermal properties, including melting points and sintering behaviors, are theoretically characterized across a range of particle sizes (from 3 nm to 20 nm). This study analyzes the melting behavior of multi-sized silver nanoparticles and simulates the structural evolution and morphology changes during the sintering process. The simulations reveal noteworthy phenomena, such as variations in melting points, gyration radii, and mean square displacements based on different particle sizes. Additionally, an optimal sintering temperature is determined through shrinkage coefficient calculations. These simulation outcomes shed light on phenomena at the atomic level, presenting a theoretical foundation for optimizing conductive ink formulation and refining sintering conditions. [ABSTRACT FROM AUTHOR]

In the era of wearable electronic devices, which are quite popular nowadays, our research is focused on flexible as well as stretchable strain sensors, which are gaining humongous popularity because of recent advances in nanocomposites and their microstructures. Sensors that are stretchable and flexible based on graphene can be a prospective 'gateway' over the considerable biomedical speciality. The scientific community still faces a great problem in developing versatile and user-friendly graphene-based wearable strain sensors that satisfy the prerequisites of susceptible, ample range of sensing, and recoverable structural deformations. In this paper, we report the fabrication, development, detailed experimental analysis and electronic interfacing of a robust but simple PDMS/graphene/PDMS (PGP) multilayer strain sensor by drop casting conductive graphene ink as the sensing material onto a PDMS substrate. Electrochemical exfoliation of graphite leads to the production of abundant, fast and economical graphene. The PGP sensor selective to strain has a broad strain range of ⁓60%, with a maximum gauge factor of 850, detection of human physiological motion and personalized health monitoring, and the versatility to detect stretching with great sensitivity, recovery and repeatability. Additionally, recoverable structural deformation is demonstrated by the PGP strain sensors, and the sensor response is quite rapid for various ranges of frequency disturbances. The structural designation of graphene's overlap and crack structure is responsible for the resistance variations that give rise to the remarkable strain detection properties of this sensor. The comprehensive detection of resistance change resulting from different human body joints and physiological movements demonstrates that the PGP strain sensor is an effective choice for advanced biomedical and therapeutic electronic device utility. [ABSTRACT FROM AUTHOR]

Energy‐harvesting technologies offer a sustainable, maintenance‐free alternative to conventional energy‐storage solutions in distributed low‐power applications. Flexible thermoelectric generators (TEGs) can generate electric power from a temperature gradient, even on complex surfaces. Organic materials are ideal candidates for flexible TEGs due to their good solution‐processability, natural abundance, low weight, and flexibility. Electronic and thermoelectric properties of organic materials have steadily progressed, while device architectures leveraging their advantages are largely missing. Here, a design and fabrication method are proposed for producing fully screen‐printed, flexible monolithic organic TEGs scalable up to m2, compatible with any screen‐printable ink. This approach is validated, along with its scalability, by printing TEGs composed of two different active inks, in three configurations, with up to 800 thermoelements, with performances well matching simulations based on materials parameters. It is demonstrated that by using an additive‐free graphene ink, a remarkable power density of 15 nW cm−2 at ΔT = 29.5 K can be achieved, with an estimated weight‐normalized power output of 1 µW g−1, highlighting a strong potential in portability. Owing to such power density, only limited areas are required to generate microwatts, sufficient for operating low‐power electronic devices such as sensors, and wearables. [ABSTRACT FROM AUTHOR]

We developed a novel method to minimize the bezel of flexible displays through backside bonding of a chip on film, resulting in the bezel width of less than 500 μm as compared to 1000 μm of conventional displays. The metal embedded in polyimide (MEP) layer is placed between the first and second polyimide (PI) substrates and connected to the metal lines of the backplane via the MEP contact (M‐CNT) hole. Subsequently, the nonconductive film (NCF) bonding and intense pulsed light sintering are performed using conductive ink. Conductive ink as the interconnect material capable of low‐temperature sintering is applied to avert thermal degradation and crack. At a high temperature (65 ℃) and humidity (90% relative humidity), the contact resistance was a drivable level for the display after 240 h. The normalized strain in the M‐CNT hole and MEP area were less than 0.4, indicating the absence of cracks during the NCF bonding. These results demonstrated that the backside bonding method was suitable for extremely narrow bezels of the nextgeneration flexible displays. [ABSTRACT FROM AUTHOR]

Conductive ink is the key to the development of flexible printed electronics. However, at present, the sintering temperature of conductive ink is still high, which restricts its use in some flexible substrates. This paper reported a kind of non-granular silver conductive ink which can be sintered at low temperature. The particle-free silver conductive ink was prepared from silver acetate using ammonia as the complexing agent, ethanol as an auxiliary agent and formic acid as a reducing agent. The obtained conductive ink droplets were coated on PET substrate and then sintered into film in an oven. The conductive ink and film were characterized by means of X-ray diffractometer (XRD), scanning electron microscope (SEM), Fourier infrared spectrometer (FTIR) and other methods. The effects of formic acid and ethanol on the properties of the conductive ink and film were systematically investigated. The results show that the conductive ink has good stability. After sintered at 90 °C for 60 min, its resistivity is 11.83 µΩ cm. By adjusting the ink formula, the roughness and uniformity of silver film can be improved significantly and the film will exhibit good bending performance. [ABSTRACT FROM AUTHOR]

The functionalization of conductive inks has been carried out through the decomposition of hydrogen peroxide (H2O2) onto the surface of silver nanoparticles (AgNPs). The ink prepared using this eco-friendly chemical reagent has been characterized structurally, chemically, and morphologically, showing the presence of stable AgNPs with suitable properties as well as the absence of residual contamination. The electrical conductivity of such a solution-processable ink is evidenced for patterns designed on flexible photographic paper substrates, using a refillable fountain pen that is implemented as a printing mechanism for the fabrication of simple printed circuit boards (PCBs). The functionality and durability of the tested systems are demonstrated under various mechanical constraints, aiming to basically reproduce the normal operation conditions of flexible electronic devices. The obtained results indicate that the implementation of these AgNP-based inks is relevant for direct applications in inkjet printing technology, thus paving the way for the use of greener chemicals in ink preparation. [ABSTRACT FROM AUTHOR]

In this work, a new and convenient fabrication process for screen-printed reduced graphene oxide-molybdenum disulfide electrode (SPrGO-MoS2E) was proposed. Reduced graphene oxide-molybdenum disulfide (rGO-MoS2) composite was hydrothermally synthesized and then dispersed in deionized water and ethanol with a ratio of 2:3 (v/v) to form a conductive suspension. The suspension was then blended with carbon paste at a ratio of 0.1:9.9 (g/g) to obtain a screen-printable rGO-MoS2 conductive ink. An electrochemical sensing electrode was formed by screening this conductive ink onto a polyethylene terephthalate substrate. The characteristics of this electrode were investigated by scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffractometry, Raman spectroscopy, and electrochemical impedance spectroscopy. Overall, the conductive suspension comprising the rGO-MoS2 composite showed higher electrochemical sensing performance compared with electrodes containing only rGO or MoS2. Cyclic voltammetry revealed that the SPrGO-MoS2 electrode exhibited excellent electrochemical sensing performance toward several electroactive species, namely, potassium hexacyanoferrate (III) ([Fe(CN6)]3−/4−), nicotinamide adenine dinucleotide (NAD+/NADH), and hydrogen peroxide (H2O2) dissolved in 0.1 M PBS (pH 7.4). The limits of detection for [Fe(CN6)]3−/4−, NAD+/NADH, and H2O2 were 0.34, 0.25, and 1.36 μM, respectively. In addition, the reproducibility, repeatability, and stability determined from the relative standard deviations (RSDs, n = 7) of these analytes were less than 12.1 %, 8.6 %, and 7.4 %, respectively. Therefore, the ready-to-use SPrGO-MoS2E could be an alternative material for advanced chemical and biological sensing applications.