Thin Layer Of Conducting Polymer Research Articles

Dielectric optical waveguide fabricated on a transparent substrate

Transparent glass substrates are routinely used in the fabrication of metasurfaces, augmented reality (AR), virtual reality (VR), and holographic devices. While readily compatible with photolithographic patterning methods, when electron beam (E-Beam) techniques are used, field distortion and stitching errors can result due to the buildup of charge. A common approach to overcome this issue is to deposit a thin conductive polymer layer (E-Spacer). However, if high-voltage E-Beam is used to achieve nano-features, the polymer conductivity is not sufficient. We have shown that by using chromium (Cr) as an overcoating conductive layer on the resist, we can achieve accurate and seamless patterning in multiple writing fields and used the method to fabricate on-chip Si3N4 waveguides on SiO2. This technique has the potential to enable the fabrication of large-scale integrated photonic systems on transparent or dielectric substrates.

Love wave propagation in piezoelectric structures bonded with conductive polymer films

In this study, we investigate analytically Love wave propagation in layered piezoelectric structures, where a thin conductive polymer layer is bonded to an unbounded piezoelectric substrate. The dispersive relation is derived and the effects of viscosity and conductivity on the phase velocity and attenuation of Love wave are analyzed and discussed. The results reveal that the effects of the viscosity and conductivity on the properties of Love wave are obvious. The phase velocity is affected by the viscosity and conductivity slightly, while the attenuation is remarkably changed with the varying frequency of the waves, viscosity and conductivity, respectively. The relationship between attenuation and frequency are not monotone increasing. The analytical solutions results are well-matched with the finite element results. The results in this work is useful for the design of acoustic wave device.

High-Performance Transparent and Conductive Films with Fully Enclosed Metal Mesh.

Metal mesh films as a kind of transparent conductive electrodes (TCEs) have shown high promise in various optoelectronic devices but are still challenged by a combination of high conductivity and transparency, mechanical robustness, and uniform electric field. Herein, we demonstrate a new concept of transparent and conductive films with a fully enclosed metal mesh, which is embedded in deep microcavities and is coated with a conductive polymer layer to combine these metrics. To ensure high conductivity and transparency, metal ink is filled into the fine (down to submicrometers) and deep mesh microcavities by electrowetting-assisted blading with low square resistances of 0.4 and 2.69 Ω sq-1 at typical transmittances of 76.9 and 87.4%, respectively. The covered thin conductive polymer layer improves the electric field uniformity of metal mesh films by at least three orders of magnitude. The fully enclosed metal mesh films exhibit excellent mechanical flexibility, indicated by the fact that the resistance is almost unchanged after 10,000 bending cycles at a bending radius of ∼5 mm. Based on the fully enclosed metal mesh films, the emission intensity of alternating current electroluminescent devices is improved by more than three times compared with that in the case of solely using common metal mesh films.

Imaging the Electrochemical Impedance of Single Cells via Conductive Polymer Thin Film.

Many fundamentally important biological phenomena involve the cells to establish and break down the adhesive interactions with the substrate. Here, we report a novel optical method that could directly image the electrochemical impedance of cell-substrate interactions at the single cell level with conventional microscopes and cameras. A thin conductive polymer layer on top of the ITO substrate (poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate), PEDOT:PSS) is used as the impedance imaging and sensing layer. A sinusoidal electrochemical potential is applied to the conductive polymer film, and the ion intercalation and transportation in the PEDOT:PSS layer will change the absorption spectrum of the polymer film. The attachment of the cells to the substrate will block and affect the ion doping and dedoping process, and therefore change the color of the polymer film. This process can be captured by any upright or inverted microscope with a simple camera. Utilizing this method, we have successfully imaged the impedance of single-cell attachment, observed the variations of cell-substrate interactions, and measured the impedance changes at different stages of the attachment process. This paper has proposed and successfully demonstrated a new strategy that translates the electrochemical impedance information to an optical signal that could be imaged and used to quantify the local responses. In addition, this method does not need any specially designed optical setup, which may lead to its broad applications in the clinics and biological research laboratories.

Combining Electrospinning and Vapor-Phase Polymerization for the Production of Polyacrylonitrile/ Polypyrrole Core-Shell Nanofibers and Glucose Biosensor Application.

In this work, polyacrylonitrile (PAN) nanofiber mats coated with conductive polypyrrole layers were produced at the surface of gold electrodes by a two-step approach combining electrospinning and vapor phase polymerization. In the first step, smooth and uniform PAN fibers exhibiting an average diameter of 650 ± 10 nm were generated through electrospinning of 12 wt% PAN solutions. The electrospun PAN fibers were impregnated with iron(III)tosylate (FeTos), annealed at 70°C and used as a robust and stable template for the growth of a thin layer of conductive polymer by co-polymerizing pyrrole (Py) and pyrrole-3-carboyxylic acid (Py3COOH) vapors under nitrogen atmosphere. The carboxyl groups introduced in polypyrrole coatings enabled further covalent binding of a model enzyme, glucose oxidase. The effect of different parameters (concentration of FeTos into the immersion solution, time of polymerization, Py/Py3COOH molar ratio) on the PAN/PPy/PPy3COOH/GOx impedimetric biosensor response was investigated. In the best conditions tested (immersion of the PAN fibers into 20 wt% FeTos solution, polymerization time: 30 min, 1:2 Py/Py3COOH ratio), the biosensor response was linear in a wide range of glucose concentration (20 nM−2μM) and selective toward ascorbic and uric acids. A very low limit of detection (2 nM) compared to those already reported in the literature was achieved. This value enables the determination of glucose in human serum after a large dilution of the sample (normal concentrations: 3.6 mM−6.1 mM range).

Development of two-dimensional interdigitated center of pressure sensor

This paper presents the development of a two-dimensional (2D) flexible patch sensor to detect and monitor the center of pressure (CoP) location and the total magnitude of a spatially distributed pressure to the specific surface areas of engineering structures. The CoP sensor with the contact mode induced by a pressure distribution was formulated by force sensitive resistor technology and was mainly composed of a thin conductive polymer layer, adhesive spacers, and two interdigitated patterned electrode films with unique sensing aperture shadings. By properly mapping the interdigitated electrode patterns to the top and bottom surfaces of the conductive polymer, the proposed sensor ideally enables to measure an overall applied pressure level and its centroid location within a predetermined sensing region in real-time. The CoP sensor containing 36 sensing sections within a dimension of around 3 × 3 inches was prototyped and experimentally investigated to verify its capability to identify the CoP location and magnitude due to the presence of a permanent magnet-based local pressure distribution. Only five electric wires connected to the CoP sensor to inspect the pressure-sensing positions of 36 segments. The evaluation results of the measured sensor data demonstrate good agreements with the actual test parameters such as the total pressure and its centroid position with about 5% locational error. However, to provide accurate information on the overall pressure range, the compensation factors must be determined and applied to the individual sensing sections of the sensor.

Synthesis of Manganese Oxide Microspheres by Ultrasonic Spray Pyrolysis and Their Application as Supercapacitors

Manganese oxide (MnO2) microspheres are prepared using an ultrasonic spray pyrolysis (USP) process. A mixed solution of potassium permanganate and hydrochloric acid is nebulized into microsized droplets, which are then carried by air flow through a furnace tube. Each microdroplet serves as one microreactor and produces one microsphere. Upon heating, KMnO4 is decomposed into MnO2 microspheres; this synthetic process can easily be scaled up. Characterization of the MnO2 microspheres by scanning electron microscopy, transmission electron microscopy, powder X‐ray diffraction, Raman spectroscopy, and X‐ray photoelectron spectra is described. Different morphologies of MnO2 microspheres can be controlled by tuning the precursor concentrations (and ratios) and furnace temperatures. Microspheres synthesized at 150 °C give amorphous MnO2 while synthesis at 500 °C yields crystalline α‐MnO2. The electrochemical properties investigated by cyclic voltammetry give specific capacitance as high as 320 F g−1, demonstrating promising properties as supercapacitors. In addition, these microspheres can be directly sprayed on conductive substrates, such as carbon fiber paper, and may have useful applications as a supercapacitor electrode coating. The supercapacitive properties of MnO2 microspheres at higher charge and discharge rates can be improved by increasing the surface area coverage or coating them with a thin layer of conductive polymer.

Liquid single crystal elastomer/conducting polymer bilayer composite actuator: modelling and experiments

In order to integrate electroconductive properties in a Liquid Single Crystal Elastomer (LSCE) and to test direct actuation of the LSCE by Joule heating, we present a new bi-layered all-organic composite actuator based on the coupling of a nematic LSCE with a conductive polymer. The bending actuator is fabricated by depositing a thin conductive polymer layer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) over the surface of a polysiloxane-based monodomain nematic LSCE film. Mechanical properties of PEDOT:PSS, better matched with LSCE ones compared with metals or inorganic nanoparticles used in other approaches, allowed us to develop an all-organic reliable millimetre-scale actuating composite. The thermally induced elongation/compression of the LSCE over 30% is exploited for the fabrication of bending actuators with curvature up to κ = 0.64 mm−1. The LSCE and the composite material are characterized as regards their thermo-mechanical and electrical properties. A model is introduced to describe bending of the composite as a function of the thermo-mechanical properties of the LSCE, and the model is assessed by comparing the model results with the experimental findings. Bending actuation via direct Joule heating of the composite is also assessed by supplying the necessary current (50 mA at 1.3 V) through wires connected to the composite. These results open new possibilities for the application of LCEs in the micro and soft robotics fields, as well as in the biomedical field.

Polythiophene-based charge dissipation layer for electron beam lithography of zinc oxide and gallium nitride

The ability of thin polythiophene layers to dissipate accumulated charge in the electron beam lithography (EBL) of wide bandgap semiconductors, such as zinc oxide and gallium nitride, is demonstrated. A quick and inexpensive processing method is demonstrated for EBL exposure of dense and high-resolution patterns in a hydrogen silsesquioxane (HSQ) negative-tone resist deposited on bulk ZnO samples and with GaN/AlN on sapphire substrates. For the former, experimental results are given for three different cases: where no charge dissipation layer was used as well as cases where 40-nm-thick Al and 100-nm-thick conductive polymer layers were used on the top of the HSQ resist. For the latter material, EBL exposure was investigated for pure HSQ and for HSQ with a thin conductive polymer layer on top. Based on the scanning electron microscope observations of the resulting photonic crystal (PhC) pattern, conventional Al and the proposed polymer approach were compared. Good agreement between these results is reported, while the new method considerably simplifies sample processing. Spin-coatable conducting polymer may be easily removed due to its solubility in water, which makes it a perfect solution for the processing of amphoteric oxide samples, i.e., zinc oxide. Gallium nitride processing also benefits from polymer dissipation layer usage due to extended exposure range and the avoidance of dense pattern overexposure in HSQ.

Metal grid/conducting polymer hybrid transparent electrode for inverted polymer solar cells

A simple method was developed using metal grid/conducting polymer hybrid transparent electrode to replace indium tin oxide (ITO) for the fabrication of inverted structure polymer solar cells. The performance of the devices could be tuned easily by varying the width and separation of the metal grids. By combining the appropriate metal grid geometry with a thin conductive polymer layer, substrates with comparable transparency and sheet resistance to those of ITO could be achieved. Polymer solar cells fabricated using this hybrid electrode show efficiencies as high as ∼3.2%. This method provides a feasible way for fabricating low-cost, large-area organic solar cells.