Search Results (827)

We report the fabrication and electrochemical characterization of TiO₂-based impedimetric sensors for the analysis of artificial sweat compositions. Two-electrode topologies were patterned on indium tin oxide (ITO) substrates: an interdigitated electrode (IDE) configuration and a Hilbert fractal electrode (HFE) geometry. TiO₂ thin films with thickness up to 350 nm were deposited by dip-coating and evaluated as photoactive sensing layers. The impedimetric response of the sensors was investigated by electrochemical impedance spectroscopy in artificial sweat with composition varied in terms of ionic content (0–100 mM Na⁺) and organic content (2.5–30 mM lactic acid and 5–50 mM urea). Regardless of TiO₂ thickness, the high-frequency response is predominantly governed by electrode topology, with the HFE design exhibiting up to 2.5-fold higher modulation compared to the IDE configuration. Under UV illumination, a low-frequency, photo-assisted response emerges, influenced by the TiO₂ layer thickness and primarily sensitive to the organic components of the solution, particularly lactic acid. These results suggest that frequency-resolved impedance measurements in TiO₂|ITO structures may enable partial differentiation between ionic conductivity and organic contributions in sweat, providing a promising basis for multi-parameter sweat analysis. Full article

Indium Tin Oxide (ITO) is one of the most widely used ohmic materials for fabricating ohmic layers in thin-film solar cells. ITO thin layers have reached almost the maximum theoretical conductivity and the lowest practical resistivity. Along with indium’s toxic environmental impact and the high cost of materials, these are the reasons why new materials for efficient, cheaper thin-film transparent ohmic layers are being examined. One of those materials is copper-doped zinc oxide (ZnO:Cu). In this paper, we present a new approach to copper-doped zinc oxide fabrication methods, based on the modern authorial Physical Vapor Co-Deposition technique, which involves optimizing Cu concentration to fine-tune crystal structure, optical band gap, and electrical properties, creating n-type TCOs essential for efficient charge transport in next-generation thin films perovskite solar cells. Full article

Conducting polymer–metal nanocomposites are widely investigated as tunable photonic and optoelectronic media; however, reported property trends often remain empirical because electronic disorder at the absorption edge, refractive-index dispersion, free carrier dielectric response, and third-order nonlinearity are rarely quantified within a single, composition-controlled film series. This limitation is particularly relevant for electrochemically grown PANI coatings on transparent conductive substrates, where nanoparticle incorporation can simultaneously enhance polarization while introducing aggregation-driven heterogeneity. Here, Ag/PANI nanocomposite thin films were fabricated directly on indium tin oxide (ITO) by potentiostatic electrodeposition from an aniline/camphorsulfonic acid electrolyte containing controlled Ag nanoparticle loadings (5–15 wt.%). This study addresses the research gap by integrating complementary optical-disorder and dispersion formalisms with dielectric and nonlinear analyses to establish a composition structure optics map for device-relevant films. Ag incorporation narrows the indirect optical gap from 1.98 eV (PANI) to 1.81 eV (5 wt.%), 1.38 eV (10 wt.%), and 1.19 eV (15 wt.%), while markedly broadening the Urbach tail (0.377 eV → 1.28–1.64 eV at 5–10 wt.%). Wemple–DiDomenico modeling and Drude-type dielectric dispersion reveal strongly non-monotonic evolution of oscillator energetics and the carrier response, culminating in large bound-electron dielectric constants (ε_∞ up to 469.8) and plasma frequencies (ω_p up to 248 × 10¹² Hz) at 15 wt.% Ag. Third-order nonlinearity is substantially enhanced but composition-sensitive: χ³ increases from 6.73 × 10⁻⁹ esu (PANI) to ~7.6 × 10⁻⁸ esu at 5 and 15 wt.%, whereas the Kerr coefficient peaks at 25.91 × 10⁻⁷ esu for 5 wt.% and is suppressed at intermediate/high loading. These results demonstrate that the optimal nonlinear performance is governed by a disorder–dispersion balance and microstructure-dependent local-field effects rather than the Ag fraction alone. Full article

In this study, reactive radio frequency magnetron sputtering was used to deposit thin films. Gadolinium oxide was deposited on titanium nitride substrates at different deposition times and oxygen concentrations. Next, rapid thermal annealing and supercritical fluid treatment were performed. The three-dimensional profiler (alpha-step), X-ray diffractometer, and X-ray photoelectron spectroscopy were used to measure the thickness, surface morphology, crystal structure, and element analysis. Then, indium tin oxide was sputtered and deposited on the gadolinium oxide, which was covered with the metal mask to form a top electrode, thereby manufacturing a metal/insulator/metal resistive memory structure. Finally, a power meter was used to measure the characteristics of the resistive random access memory, including the current–voltage characteristics, and to explore the leakage current conduction mechanism and component durability. Full article

In response to the significant challenges posed by the rapid progress of multi-spectral detection technologies to traditional stealth techniques, this paper presents a flexible transparent metasurface structure that is compatible with radar and infrared stealth. It consists of multi-layer functional patterned indium tin oxide (ITO) films and a flexible polydimethylsiloxane (PDMS) substrate. The metasurface uses a high-duty-cycle multi-scale circular ring to achieve a microwave absorption bandwidth of 30 GHz and low infrared emissivity of 0.33 in an optimized ultra-thin 2.65 mm thickness system. The simulation results show that the metasurface achieves absorption exceeding 90% in the frequency range of 10.8–40.8 GHz, which covers common radar bands like X, Ku, K, and Ka. Furthermore, the structure exhibits polarization insensitivity and sustains stable absorption in a wide range of 60 degrees of transverse magnetic (TM) fields. Meanwhile, it decreases the radar cross-section (RCS) by more than 10 dB over a wide angular range even when bent. This study presents a feasible metasurface with ultra-thin, flexible, transparent, and multi-spectral compatibility for the next generation of stealth systems. Full article

Terahertz (THz)-based metasurface biosensors have garnered considerable interest owing to their strong electromagnetic (EM) resonance-based sensing methods. Nonetheless, the majority of published designs exhibit constrained optical transparency and angular sensitivity, hence limiting their integration with optoelectronic systems and reducing sensing reliability at oblique angles. This study introduces a graphene-based optically transparent terahertz metasurface that demonstrates wide-angle stability for biosensing applications to address these challenges. The proposed metasurface utilizes a patterned graphene resonator integrated with an optically transparent silicon dioxide (SiO₂) dielectric substrate and a conductive indium–tin–oxide (ITO) ground configuration, enabling efficient THz absorption at the resonant frequency while maintaining optical transparency. Due to its structural symmetry, the suggested structure exhibits polarization insensitivity and angular stability up to 60° for both transverse electric (TE) and transverse magnetic (TM) modes. Furthermore, the comprehensive operating mechanism is explained by impedance matching theory, surface current distribution, and analysis of electric field distributions. A thorough numerical analysis of the proposed metasurface was conducted by incorporating analytes with varying refractive indices using CST Microwave Studio, demonstrating its effective sensing capabilities, with a sensitivity of 0.69 THz/RIU and a quality factor of 24.67. A comparative examination with existing designs reveals that the proposed device, due to its optical transparency, angular stability, and high sensitivity, demonstrates significant potential for terahertz biosensing applications. Full article

The blood-brain barrier (BBB) is one of the most selective physiological interfaces in the human body. Transendothelial electrical resistance (TEER) has become a widely adopted quantitative metric for assessing its in vitro structural and functional integrity. Although TEER measurements are routinely incorporated into BBB-on-chips, the absence of harmonized electrode architectures, measurement settings, and reporting standards continues to undermine reproducibility and translational reliability among laboratories. This systematic review provides the first comprehensive classification and critical comparison of electrode configurations used for TEER assessment, specifically within BBB-on-chip systems. Eligible studies were analyzed and categorized according to electrode design, fabrication method, integration strategy, and operational constraints. We critically evaluated six principal electrode architectures, highlighting their performance trade-offs in terms of uniformity of current distribution, long-term stability, scalability, and compatibility with dynamic shear conditions. Furthermore, we propose a bioinspired TEER reporting framework that consolidates essential metadata, including electrode specification, temperature control, viscosity effects, and blank resistance correction. Our analysis proposes screen-printed and hybrid silver-indium tin oxide (ITO) electrodes as promising candidates for next-generation BBB platforms. Moreover, our review provides a structured roadmap for standardizing TEER electrode design and reporting practices to facilitate interlaboratory consistency and accelerate the adoption of BBB-on-chip systems as truly biomimetic platforms for predictive neuropharmacological workflows. Full article

Magnetron sputtering serves as a key method for fabricating functional thin films used in transparent film heaters. However, as heater designs become more intricate, achieving uniform film deposition on nonrectangular areas induces localized overheating owing to current density crowding, compromising long-term reliability of the device. To address this limitation, a simulation-assisted design and fabrication strategy is presented to realize a uniform temperature profile through the precise regulation of the sheet resistance distribution of the film. Initially, an electrothermal-coupled finite element model was established using COMSOL Multiphysics to inversely determine the spatial gradient of sheet resistance required for achieving a uniform thermal distribution. Subsequently, a custom-designed mesh shadow mask was used to locally adjust the flux of indium tin oxide (ITO) sputtered particles, enabling the establishment of a relationship between the mask’s aperture geometry and the resulting particle deposition profile. The magnetic field and plasma simulations were integrated to model particle transport and design a specialized gradient aperture-based shadow mask, enabling the deposition of an ITO film with a controlled sheet resistance gradient in a single magnetron sputtering step. Experimental results demonstrated that the proposed method decreased the maximum temperature variation by 8.25 °C and reduced the standard deviation of the surface temperature by 82.1% at an average temperature of 45 °C within a defined nonrectangular heating region, demonstrating a substantial improvement in temperature uniformity relative to conventional uniform coating processes. Full article

This paper presents a novel broadband circularly polarized optically transparent monopole antenna using indium tin oxide (ITO) and PMMA. The proposed design successfully integrates ultra-wideband circular polarization characteristics with exceptional optical transparency. The antenna, constructed with a three-layer configuration utilizing ITO films as both the radiating patch and ground plane, along with transparent PMMA serving as the substrate, features compact dimensions of 40 × 40 × 1 mm³. By leveraging a co-optimized design incorporating a slotted hexagonal-ring radiating patch, triangular perturbation ground plane, and stepped-impedance feeding structure, the antenna achieves a circularly polarized operating bandwidth of 2.8–6.6 GHz (fractional bandwidth of 77.9%), with an axial ratio < 3 dB and return loss < −15 dB. The experimental findings exhibit strong consistency with the simulations, illustrating a high level of visible-light transmittance and radiation patterns characterized by right-hand circular polarization in the positive z-axis direction (+z) and left-hand circular polarization in the negative z-axis direction (−z). This innovative antenna shows great potential for applications in smart windows, display integration, and 5G communication systems. Full article

Aniline (ANI) was electropolymerized on ITO substrates with different surface resistivities. The process was performed by cyclic voltammetry from an aqueous, homogeneous solution containing sulfuric acid and the aniline monomer using various numbers of cycles and scan rates. The resulting polymer films (PANI) were characterized by ATR-IR spectroscopy, spectroscopic ellipsometry and atomic force microscopy. The influence of ITO surface resistivity on the electropolymerization process, the quality of the obtained PANI layers, and their optical properties was evaluated. Homogeneous PANI films were produced on ITO substrates with surface resistivities of 15–25 Ω/sq, encompassing both emeraldine salt and emeraldine base forms. Although the film’s growth was rapid, it also led to adhesion issues. In contrast, for ITO substrates with surface resistivities of 70–100 Ω/sq and 80–100 Ω/sq, the resulting films showed improved adhesion but were less homogeneous. Nevertheless, the conductive emeraldine salt form of polyaniline was successfully obtained. The conductive form of polyaniline was obtained without any additional modifications to the electropolymerization procedure. Notably, the literature provides no systematic analysis of electropolymerization on ITO substrates with different surface resistivities, which opens up new research opportunities and provides a basis for the rational design and optimization of PANI-based electro-optical coatings for advanced sensing applications. Full article

Conductive polymers (CPs), such as polypyrrole (PPy), have shown promising properties for use as electro-responsive bioactive scaffolds for tissue regeneration. PPy can be synthesized by chemical electrosynthesis and doped with biomolecules such as hyaluronic acid (HA). Taking advantage of the electrochemical synthesis versatility, nanofibers for surface-modified indium tin oxide (ITO) electrodes can be used as templates to produce tridimensional HA-doped PPy scaffolds. In this study, polyvinyl alcohol/chitosan (PVA/CTS) electrospun nanofibers deposited on ITO electrodes were used as a 3D template for the in situ electrosynthesis of HA-doped PPy to produce a bioactive scaffold for tissue engineering. The final material gathers the advantages of each biopolymer, the porous morphology of the nanofiber, and the conductivity of the electrosynthetized polymer. Furthermore, the biological activity of the NF-PVA/CTS@PPy:HA composite was evaluated in NIH-3T3 fibroblasts by MTT, resulting in a cell viability of 146 ± 40% and wound-healing capacity of 97 ± 1.9% at 24 h of culture. Full article

In this study, we investigated the effect of annealing ultrathin silver (Ag) films of varying thicknesses (1–6 nm) on both their optical absorption and the performance of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) organic solar cells (OSCs). The Ag films were deposited on indium tin oxide (ITO) anodes and annealed at 300 °C for 1–2 h to modify the anodic interface. The optical and electrical properties of the resulting devices were systematically characterized and optimized. The results revealed that a 1 nm AgO layer annealed for 2 h significantly enhanced the device performance, yielding a 6% increase in power conversion efficiency compared to the standard configuration. This improvement is attributed to two main factors: (i) a 25% increase in light absorption of the AgO/P3HT:PCBM film due to localized surface plasmon resonance of Ag nanoparticles and (ii) an 11% reduction in series resistance resulting from the favorable alignment of the Ag work function with the ITO anode and the polymer HOMO, which facilitates efficient hole extraction. These findings highlight the potential of ultrathin, annealed Ag/AgO interfacial layers as an effective strategy to enhance light absorption and charge transport in OSCs. Full article

Transparent conductive oxides (TCOs), such as indium tin oxide (ITO), are essential for flexible electronics; however, conventional vacuum-based deposition is costly and thermally aggressive for polymers. This study investigated the surface functionalization of PET substrates with ITO thin film-based forced hydrolysis as a low-cost, reproducible alternative. $\mathrm{S}\mathrm{n}{\mathrm{O}}_2$ nanoparticles were synthesized by forced hydrolysis at 180 °C for 3 h and 6 h, yielding crystalline nanoparticles with a cassiterite phase and an average crystallite size of 20.34 nm. The process showed high reproducibility, enabling consistent structural properties without complex equipment or high-temperature treatments. The $\mathrm{S}\mathrm{n}{\mathrm{O}}_2$ sample obtained at 3 h was incorporated into commercial ${\mathrm{I}\mathrm{n}}_2{\mathrm{O}}_3$ to form a mixed In–Sn–O oxide, which was subsequently deposited onto PET substrates by spin coating onto UV-activated PET. The resulting 1.1 µm ITO films demonstrated good adhesion (4B according to ASTM D3359), a low resistivity of 1.27 × 10⁻⁶ Ω·m, and an average optical transmittance of 80% in the visible range. Although their resistivity is higher than vacuum-processed films, this route provides a superior balance of mechanical robustness, featuring a hardness of (H) of 3.8 GPa and an elastic modulus (E) of 110 GPa. These results highlight forced hydrolysis as a reproducible route for producing ITO/PET thin films. The thickness was strategically optimized to act as a structural buffer, preventing crack propagation during bending. Forced hydrolysis-driven PET sheet functionalization is an effective route for producing durable ITO/PET electrodes that are suitable for flexible sensors and solar cells. Full article

This study proposes design and fabrication methods for an electromagnetic metasurface absorber (MA) that absorbs electromagnetic waves using a metasticker attached on a dielectric substrate blocked by a copper sheet. To guarantee a high design freedom as well as make the absorption bandwidth (BW) as broad as possible, a square-fractal ring is chosen as the metapattern, and its design is optimized using a genetic algorithm. To fabricate the square-fractal rings in a simple manner, an indium-tin-oxide film is cut by using a laser-cutting machine. Then, the metasticker is fabricated by assembling the metapatterns on a double-sided adhesive film which could be attached on the dielectric substrate using the opposite side of the film. From measured results of the finalized MA of which damaged regions caused by the laser-cutting process are compensated in the design process, a broad $-10$ dB reflectance BW is confirmed from 4.39 to 7.51 GHz of which the fractional BW is 52.44% for the normal incidence. Moreover, a fractional BW of 4.35% is measured in a wide incident angle range from $0°$ to $60°$ for both the transverse electric and the transverse magnetic polarizations simultaneously. Full article

As a core candidate material for indium-free transparent conductive oxides, tin dioxide (SnO₂) thin films are gradually replacing indium tin oxide (ITO) and becoming a research focus in the field of optoelectronic devices, thanks to their excellent physicochemical stability, wide bandgap characteristics, and abundant tin resource reserves. This review focuses on SnO₂ thin films. Firstly, it elaborates on the tetragonal rutile crystal structure characteristics of SnO₂ and the transparent conductive mechanism based on oxygen vacancies and doping elements to regulate free electron concentration, while clarifying the key parameters for evaluating their transparent conductive properties. Subsequently, it systematically summarizes the research progress in preparing SnO₂ transparent conductive thin films via physical methods and chemical methods in recent years. It compares the microstructure and transparent conductive properties of thin films prepared by different methods, and analyzes the regulatory laws of preparation processes, doping types, and film thickness on their optoelectronic properties. Furthermore, this work supplements the current application status of SnO₂ thin films in devices. Meanwhile, the core performance differences between indium-free tin-based thin film devices and ITO-based devices are compared. Finally, we have summarized the advantages and challenges of physical and chemical methods in the preparation of SnO₂ thin films. It also forecasts the application potential of interdisciplinary integration of physical–chemical methods and the development of new doping systems in the preparation of high-performance SnO₂ transparent conductive thin films. This review aims to provide theoretical guidance and technical references for the selection and process optimization of SnO₂ transparent conductive thin films in fields such as photovoltaic devices and flexible optoelectronic equipment. Full article