Polyimide Thin Films Research Articles

Suppression of Secondary Electron Emissions on the Graphene-Coated Polyimide Materials Prepared by Chemical Vapor Deposition

Polyimide thin-film materials are widely used in aerospace and particle gas pedals, etc., but the phenomenon of secondary electron emission occurred under vacuum conditions. The graphene-coated polyimide materials were prepared for this phenomenon to suppress secondary electron emissions. The graphene coating was prepared on the polyimide surface through chemical vapor deposition (CVD). Scanning electron microscope images (SEM), X-ray photoelectron spectrometer images (XPS), Raman spectroscopy, atomic force microscopy (AFM), and other analytical methods were used to characterize the properties of the prepared materials. The C1s XPS fine spectra and Raman curve analyses showed that the material has an abundant sp2 hybridized structure, and the sp2 structure can reduce secondary electron emissions. The C, O, and N contents in the tested samples were 65.85, 20.47, and 13.68 at.%, respectively. It was examined that the graphene coating had an inhibitory effect on the secondary electron emissions of polyimide materials, and the secondary electron emission yield (SEY) was significantly reduced. The results of secondary electron tests showed that the maximum SEY (δmax) of the polyimide material decreased from 1.72 to 1.52 after the preparation of the graphene coating. The mechanism of using a graphene coating to reduce the SEY of polyimide was analyzed from experimental and theoretical perspectives. The results of this study can provide research ideas for polyimide thin film materials in aerospace, particle gas pedals, and other applications.

Flexible and gradually bonded metal organic framework coatings for atomic oxygen protection of polyimide films

Rapid development of coatings with atomic oxygen (AO) resistance, which benefit long-duration exploration mission in low earth orbit (LEO), poses a challenging requirement on flexible coatings with excellent bonding property. Metal organic framework (MOF) has abundant sites and organic–inorganic hybrid chemical composition, which displays potential in increasing AO resistance, flexibility and bonding property simultaneously. Here, we combined surface modification and spin-coating to prepare MIL-53(Al) (a kind of materials of Lavashir skeleton) coated polyimide (PI) thin film exhibiting excellent flexibility, bonding property and AO resistance, which had no cracks after bending 1000 times, had no peeling off and had only 12% erosion yield compared with pristine PI, verified by the bend test, cross-cut tape test and AO exposure experiment respectively. Also, the mechanism of homogeneous film formation was explained, in which MIL-53(Al) seed layer provided binding force between coating and substrate, and the microstructural transformation caused by breathing effect and negative linear compressibility (NLC) prevented the occurrence of coating cracking. This work extends the application range of MIL-53(Al), optimizes the application of MOFs film formation, and offers a new idea to protect the spacecrafts in LEO.

Fabrication of Large‐Area Organic Thin Film Transistor Array with Highly Uniform Water‐Borne Polyimide Gate Dielectric via Green Solvent‐Engineered Bar‐Coating Process

AbstractHere, the utilization of a highly uniform water‐borne polyimide (W‐PI) thin film as a gate dielectric layer for large‐scale organic thin film transistors (OTFTs) exceeding 100 cm2 is presented, employing the bar‐coating technique. The W‐PI thin films are obtained uniformly over a large area by systematically manipulating the surface tension of the water‐soluble poly(amic acid) salts (W‐PAAS) solution using alcohol as a co‐solvent in a “Green” process. The thickness of the W‐PI thin film is precisely controlled within the range of tens to hundreds of nanometers by adjusting key parameters, including the concentration of the W‐PAAS solution, wire diameter, and bar‐coating speed. As a result, 500 pentacene‐based OTFTs are successfully fabricated on a 10 × 10 cm2 substrate, utilizing a 280 nm thick W‐PI gate dielectric film. These devices exhibit excellent uniformity, with field‐effect mobility of 0.20 ± 0.02 cm2 V−1 s−1. Furthermore, the fabrication of electronic devices using an environmental‐friendly bar‐coating method on large‐area flexible substrates is demonstrated. This study highlights the considerable potential of eco‐friendly W‐PI thin films as dielectric materials, offering advantages such as cost‐effectiveness and high efficiency for reliable industrial applications.

Facile In-Tube-Center Packaging of Flexible Airflow Rate Microsensor for Simultaneous Respiration and Heartbeat Measurement

Respiration and heartbeat are among the important vital signs of living beings. Taking advantage of the physical attachment of the lung and heart, measurements of both can be performed simultaneously using airflow rate microsensors to measure the respiration airflow. For such airflow rate sensors, the packaging is crucial to define and encapsulate the airflow region. In this study, we propose a facile packaging technique for flexible airflow rate microsensors. The thermal calorimetric sensing structure was fabricated through a standard microfabrication technology on a thin polyimide (PI) film. The film was packaged at the center of a resin tube utilizing its buckling. We also proposed an approach to improve the time response by limiting the thermal capacity around the sensing structure through the implementation of a thin substrate for the sensing structure supported by a thicker film. The strategy successfully improved both the time response and sensitivity of the airflow rate sensor. Finally, the utilization of the sensor for simultaneous respiration and heartbeat measurement was demonstrated through an animal experiment using a small animal, namely rats.

Vertically aligned polyimide films prepared from lyotropic liquid-crystalline smectic precursors

Vertically aligned (VA), fully aromatic polyimide (PI) thin films were successfully prepared from a lyotropic smectic liquid-crystalline precursor of poly(amic ester) (PAE) containing perfluorooctyl (Rf) terminal groups using a “push-coating” method. Because the repeating units of PAE form the smectic layer, the main chains of PAE are oriented perpendicular to the layer. A homeotropically aligned smectic structure is induced by the step-by-step stacking growth of the layer from the monolayer of the Rf groups self-organized on the hydrophobic interfaces (interfaces between the PAE solution and air or a surface-modified substrate), leading to a vertically aligned PAE. By optimizing the preparation conditions, the values of the orientational order parameter (S) of the push-coated PAE film exceeded 0.7. The homeotropically aligned PAE films were imidized by heating to 300 °C, and the high S values were maintained in the subsequent imidization to give VA PI films. Despite the large standard deviation in the temperature variation of the optical path length of the VA PI films, the small and reversible variations in S confirmed that the vertical orientation of the PI films was thermodynamically stable.

The sensory and photo-catalytic properties of graphene oxide and polyimide thin films implanted by 1500 keV Cu ions

Thin films of polyimide (PI) and graphene oxide (GO) were exposed to the accelerated Cu-ions with an energy of 1500 keV at different ion fluences (3.75 × 1012; 3.75 × 1014; 1 × 1016) cm−2. The reason for Cu-ion irradiation lies in the modification of thin PI and GO layers and their subsequent use in electronics, photo-catalysis and humidity sensing. It was expected that three ways would primarily carry out modification: i) interaction of the accelerated ions with atoms and electrons of the irradiated films, ii) implantation of Cu ions inside the matrices and their attachment to the structures in the form of CuO, and iii) formation of C and Cu aggregates and Cu nanoparticles in the subsurface layer to form an electrically conductive network. The effects of the interactions of energetic Cu-ions on the PI and GO matrices, including the prediction of the depth of Cu ion penetration, were simulated by SRIM software. Elemental changes, including the depth profiles of implanted Cu-ions, were investigated by Rutherford backscattering spectrometry (RBS) and Elastic recoil detection analysis (ERDA). Changes in the chemical bonding on the PI and GO surfaces were studied by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The effect of energetic Cu-ions on the surface morphology was analyzed by Atomic force microscopy (AFM). For the possible application of PI and GO composites in electronics and sensory, the sheet resistivity were measured by the two- point method and the effect of air humidity on electrical properties was studied. Furthermore, the degradation of Rhodamine B solution in the presence of prepared composites under UV-light irradiation was measured for possible use in photo-catalysis. It was found that the interaction of Cu- ions with the matrix leads to the release of oxygen and hydrogen, resulting in an increase in carbon concentration. The increase in carbon concentration leads to an increase in the electrical conductivity of both materials. The irradiation with Cu ion fluence of 1 × 1016 cm−2 probably formed in PI a subsurface conducting network that reduced the sheet resistivity by almost eleven orders of magnitude. The ion irradiation by Cu ion with fluences below 1 × 1016 cm−2 enhances the photo- catalytic properties of both used materials and the best result was achieved in the case of PI irradiated by the ion fluence of 3.75 × 1014 cm−2.

Initial Clinical Experience with Thin-Film Polyimide Subdural Electrodes for Seizure Monitoring (P2-1.005)

<h3>Objective:</h3> NA <h3>Background:</h3> Subdural grid-and-strips are used routinely in pre-surgical evaluations for people with drug-resistant epilepsy (DRE). Thin-film polyimide electrodes (NeuroOne Evo, 0.08mm) which have been approved for clinical use, are thinner and better conform to brain convolutions than current market grids. <h3>Design/Methods:</h3> We present two patients with DRE who underwent intracranial EEG (iEEG) monitoring with thin-film polyimide subdural electrode grid- and-strip electrodes as well as traditional EEG for pre-surgical evaluation. Patient 1 had a prior left mesial temporal lobe ablation with seizure recurrence. They underwent left temporal craniotomy with implantation of two subdural grids, three strips and additional depth electrodes. IEEG demonstrated two habitual seizures arising from anterior temporal subdural strips. Functional mapping identified the basal-temporal and Wernicke’s speech areas. Left anterior temporal lobectomy was performed and he remains seizure free 9 months post-resection. Patient 2 underwent bilateral stereoEEG electrode placement with coverage in the frontal/temporal/insular regions and subdural strip electrodes. IEEG demonstrated seizure onset from the left hippocampus and right hippocampal spikes. Given bilateral findings, they underwent Responsive Neurostimulation System implantation. <h3>Results:</h3> The two patients underwent subdural electrode placements without complications. IEEG recordings were comparable between NeuroOne Evo and traditional electrodes in terms of integrity, artifactual content and signal recording characteristics. The thinner profile of the Evo grid tail facilitated dura closure and reduced mass effect compared to traditional grids. By trimming material from the tip of the subdural strip, the electrode was placed through a burr hole without difficulty. Recording from these grids contributed to presurgical evaluation and led to surgical interventions. <h3>Conclusions:</h3> Our initial experience suggests that thin-film electrodes are a viable option for subdural iEEG that could safely minimize intracranial mass effect/brain shift and improve surgical ease of use. <b>Disclosure:</b> Dr. Reina has nothing to disclose. Dr. Song has received personal compensation in the range of $0-$499 for serving as a Consultant for Clearpoint Neuro. The institution of Dr. Song has received research support from NIH. Dr. Culler has nothing to disclose. Dr. Aronson has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Medtronic.

Fullerene-doped polyimide materials treated via the vacuum ultraviolet irradiation: Novel possible approach to create the structured relief

&lt;p&gt;Among the various surface reliefs obtained by the modification of the nanostructured materials used for the orientation of the liquid crystal molecules or applied as the possible way to extend the optical limiting mechanisms, the vacuum ultraviolet irradiation can provoke the novel approach with the varied contact angle and can be recommended for use in the development of the light- and electro-addressable liquid crystal spatial light modulators, switchers, and limiters. The main accent in the current paper is connected with the study of an impact of the vacuum ultraviolet irradiation with the different wavelength and power densities on the fullerene-structured polyimide thin films. To support the proposed idea, the spectral measurements were carried out, the contact wetting angles of the structured surface were determined, and an atomic force microscopic analysis was performed. Based on the data obtained, it is proposed to effectively use such relief formed by the vacuum ultraviolet irradiation for the design of the modulators and converters of the laser radiation, some biomedicine devices and the solar cells as well where a liquid crystal mesophase is actively used as an electro-optical modulating layer. Some ideology of the current article is aimed that the polyimide materials, when irradiated in the vacuum ultraviolet, can perform a dual role, as a photo layer and as an orienting layer as well.&lt;/p&gt;

Influence of the Ammonia Concentration in Chemical Bath Deposition and Selenourea Concentration in Hydrothermal Process on the Properties of CdS and Sb2S3−ySey Thin Films and the Photovoltaic Performance of the Corresponding Solar Cells

To explore the feasibility of the flexible Sb2S3−ySey thin‐film solar cell fabrication using polyimide thin films as substrates, CdS thin films are prepared on SnO2:F conducting glass (FTO) substrates by decreasing the ammonia concentration of chemical bath deposition, and Sb2S3−ySey thin films are grown on the FTO/CdS substrate by changing the selenourea concentration of hydrothermal process. The influence of the ammonia and selenourea concentration on properties of CdS and Sb2S3−ySey is systematically investigated and solar cells with the architecture of FTO/CdS/Sb2S3−ySey/spiro‐OMeTAD/Au are fabricated. For CdS thin films on FTO substrate, the thickness decreases and roughness increases with the decrease of ammonia concentration in chemical bath deposition. The compact and full‐coverage CdS thin films with thickness of 50 ± 6 nm are successfully obtained using the low ammonia concentration (0.59 m). For Sb2S3−ySey thin films on FTO/CdS substrate, the Se:S:Sb atomic ratio and thickness increases with the increase of selenourea concentration in hydrothermal process. The optimal selenourea concentration is 6 mM. The solar cells with the 50 ± 6 nm thick CdS thin film and Sb2S2.10Se0.56 thin film achieve photoelectric conversion efficiency of 8.07%. The results can provide an efficient support for further applying polyimide thin films to fabricate flexible Sb2S3−ySey thin film solar cells.

Enhancing the Output Performance of a Triboelectric Nanogenerator Based on Modified Polyimide and Sandwich-Structured Nanocomposite Film

Recently, scientists have been facing major obstacles in terms of improving the performances of dielectric materials for triboelectric nanogenerators. The triboelectric nanogenerator (TENG) is one of the first green energy technologies that can convert random mechanical kinetic energy into electricity. The surface charge density of TENGs is a critical factor speeding up their commercialization, so it is important to explore unique methods to increase the surface charge density. The key to obtaining a high-performance TENG is the preparation of dielectric materials with good mechanical properties, thermal stability and output performance. To solve the problem of the low output performance of PI-based triboelectric nanogenerators, we modified PI films by introducing nanomaterials and designed a new type of sandwich-shaped nanocomposite film. Herein, we used polyimide (PI) with ideal mechanical properties, excellent heat resistance and flexibility as the dielectric material, prepared an A-B-A sandwich structure with PI in the outer layer and modified a copper calcium titanate/polyimide (CCTO/PI) storage layer in the middle to improve the output of a TENG electrode. The doping amount of the CCTO was tailored. The results showed that at 8 wt% CCTO content, the electrical output performance was the highest, and the open-circuit voltage of CCTO/PI was 42 V. In the TENG, the open-circuit voltage, short-circuit current and transfer charge of the prepared sandwich-structured film were increased by 607%, 629% and 672% compared to the TENG with the PI thin film, respectively. This study presents a novel strategy of optimizing dielectric materials for triboelectric nano-generators and has great potential for the future development of high output-performance TENGs.

Flexible Nanoarchitectonics for Biosensing and Physiological Monitoring Applications (Small 9/2023)

Flexible Mesoporous Electronics In article number 2204946, Hoang-Phuong Phan, Yusuke Yamauchi, Tuan-Khoa Nguyen, Mostafa Kamal Masud, and co-workers develop flexible mesoporous architectures using selective electrochemical deposition. Soft metallic nanopores formed on thin polyimide films offer excellent mechanical bendability, high sensitivity for glucose sensing, and low impedance that facilitates detection of neural activities. These features suggest the promise of soft mesoporous material systems for biomedical applications.

Lyotropic Liquid Crystalline Property and Organized Structure in High Proton-Conductive Sulfonated Semialicyclic Oligoimide Thin Films.

Fully aromatic sulfonated polyimides with a rigid backbone can form lamellar structures under humidified conditions, thereby facilitating the transmission of protons in ionomers. Herein, we synthesized a new sulfonated semialicyclic oligoimide composed of 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA) and 3,3'-bis-(sulfopropoxy)-4,4'-diaminobiphenyl to investigate the influence of molecular organized structure and proton conductivity with lower molecular weight. The weight-average molecular weight (M w) determined by gel permeation chromatography was 9300. Humidity-controlled grazing incidence X-ray scattering revealed that one scattering was observed in the out-of-plane direction and showed that the scattering position shifted to a lower angle as the humidity increased. A loosely packed lamellar structure was formed by lyotropic liquid crystalline properties. Although the ch-pack aggregation of the present oligomer was reduced by substitution to the semialicyclic CPDA from the aromatic backbone, the formation of a distinct organized structure in the oligomeric form was observed because of the linear conformational backbone. This report is the first-time observation of the lamellar structure in such a low-molecular-weight oligoimide thin film. The thin film exhibited a high conductivity of 0.2 (±0.01) S cm-1 under 298 K and 95% relative humidity, which is the highest value compared to the other reported sulfonated polyimide thin films with comparable molecular weight.

Evaluation of analysis volume in total reflection X‐ray fluorescence analysis

AbstractTotal reflection X‐ray fluorescence (TXRF) is widely used for trace elemental analysis, wherein a thin monochromatic X‐ray beam is typically applied at glancing angles. The actual volume of the sample measured by the instrument (analysis volume) depends on the dimensions of the X‐ray beam and glancing angle, and it is a key feature in sample preparation for TXRF analysis. Herein, the analysis volume, including the analysis region and analysis height, was experimentally evaluated. A thin Au layer approximately 5 nm thick and 1 mm in diameter was prepared at a specific position on a flat glass substrate using a vacuum evaporation device. The position of this Au layer was controlled by manipulating a mask plate with a small hole. Nine samples were prepared at different Au layer positions and analyzed at 8 azimuth angles using a tabletop TXRF instrument. Finally, the Au XRF intensity distribution was visualized on a glass substrate. It was found that the XRF emitted over a diameter of approximately 5 mm was effectively detected using the tabletop TXRF instrument. The analysis height was experimentally evaluated using a thin Au layer deposited on a polyimide film 5 mm in diameter and 5 nm thick. The Au layer height was adjusted by inserting polyimide thin films between the Au layer and the glass substrate. The Au XRF intensity drastically decreased with increasing Au layer height, suggesting that the XRF emitted from the sample is effectively detected at heights of &lt;10 μm by using the described setup.

Electrochemical Testing of a New Polyimide Thin Film Electrode for Stimulation, Recording, and Monitoring of Brain Activity.

Subdural electrode arrays are used for monitoring cortical activity and functional brain mapping in patients with seizures. Until recently, the only commercially available arrays were silicone-based, whose thickness and lack of conformability could impact their performance. We designed, characterized, manufactured, and obtained FDA clearance for 29-day clinical use (510(k) K192764) of a new thin-film polyimide-based electrode array. This study describes the electrochemical characterization undertaken to evaluate the quality and reliability of electrical signal recordings and stimulation of these new arrays. Two testing paradigms were performed: a short-term active soak with electrical stimulation and a 29-day passive soak. Before and after each testing paradigm, the arrays were evaluated for their electrical performance using Electrochemical Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV) and Voltage Transients (VT). In all tests, the impedance remained within an acceptable range across all frequencies. The different CV curves showed no significant changes in shape or area, which is indicative of stable electrode material. The electrode polarization remained within appropriate limits to avoid hydrolysis.

Development of MEMS Flow and Pressure Sensor Device for Detection of Extravasation at an Early Stage

We developed a flow and pressure measurement device for detection of extravasation by intravenous injection of anticancer drugs at an early stage. Intravenous injection of a drug solution using a syringe pump enables a low‐speed and highly accurate drug‐administration rate. However, because the syringe pump forcibly delivers the drug solution, the drug solution is administrated at a constant administration rate regardless of the leakage of the drug solution to the outside of the blood vessel (extravasation) due to the indwelling needle coming out of the blood vessel. The proposed device is integrated into a flow‐channel structure consisting of a PDMS layer in which a MEMS thermal‐flow sensor formed on thin polyimide film and a pressure sensor are stacked on a plastic plate as a substrate. Therefore, it is possible to measure both the drug‐administration rate and injection pressure. Early detection of extravasation can be achieved by identifying the state of needle‐puncture based on changes in injection pressure. Then, the amount of leaked drug after leak occurs can be accurately measured with a flow sensor. We evaluated the flow and pressure detection function of the proposed device and confirmed that it is possible to detect extravasation early through an experiment involving a piece of raw chicken simulating human skin and flesh. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

A space deployable antenna model based on shape memory alloy composite with folding‐deploying two‐way behavior

AbstractIn this study, a flexible space deployable antenna model with good self‐folding and deploying two‐way shape memory effect is proposed and prepared based on shape memory alloy composite strips and polyimide thin film. The thickness and cyclic properties of the shape memory alloy strip were considered for the two‐way shape memory effect. Good self‐folding at 110°C and self‐deploying at 20°C for 10 min were demonstrated. Moreover, the Joule heating method was applied to improve the folding speed within 90 s. The two‐way shape memory effect with reversible self‐folding and deploying behavior of the space deployable antennas is aimed at improving avoidance of space debris in future applications.

A comparison study of high thermal stable and resistant polyimides

Polyimide thin films with high thermal stability and resistance will contribute to the development of flexible energy devices, which could be compatible with their high temperature fabrication process. Thus, we have prepared poly(amic acid) solutions with bisbenzimidazole and bisbenzoxazole based diamines and finally fabricated polyimide thin films. After comparing with commercial type polyimides, the polyimides containing bisbenzimidazole and bisbenzoxazole segments showed excellent thermal decomposition temperatures (of 581 and 584 °C, respectively), outstanding mechanical properties (with a tensile strength of 218 and 192 MPa, respectively), and relatively low water absorption percentages (of 0.68% and 0.63%, respectively). The superior properties should be ascribed to the rigid molecular chain skeleton, strong inter- and intra-molecular-chain forces, and hydrogen bonds.

VO2 films on flexible thin polyimide films: Fabrication and characterization of electrical and optical properties in insulator-metal transition

We report on the realization of thin polyimide films on which phase transition vanadium dioxide (VO2) films grow. Biased reactive sputtering achieved b-axis-oriented growth of VO2 films on ZnO-buffered polyimide films with a thickness of 8.5 μm. By peeling off the polyimide films from a quartz substrate, stand-alone VO2/ZnO/polyimide layered films that exhibited insulator-metal transition (IMT) with nearly three orders of resistivity change were fabricated. Dependence of IMT on a mechanical curvature was investigated for demonstrating the high flexibility. Temperature-dependent optical transmittance at 1.45 μm showed a high switching ratio for infrared light in VO2/ZnO/polyimide layered films. The proposed structure can be utilized for active metasurfaces that control terahertz waves with quite low reflection loss due to its small thickness.

First Food and Drug Administration Cleared Thin-Film Electrode for Intracranial Stimulation, Recording, and Monitoring of Brain Activity-Part 1: Biocompatibility Testing.

Subdural strip and grid invasive electroencephalography electrodes are routinely used for surgical evaluation of patients with drug-resistant epilepsy (DRE). Although these electrodes have been in the United States market for decades (first FDA clearance 1985), their fabrication, materials, and properties have hardly changed. Existing commercially available electrodes are made of silicone, are thick (>0.5 mm), and do not optimally conform to brain convolutions. New thin-film polyimide electrodes (0.08 mm) have been manufactured to address these issues. While different thin-film electrodes are available for research use, to date, only one electrode is cleared by Food and Drug Administration (FDA) for use in clinical practice. This study describes the biocompatibility tests that led to this clearance. Biocompatibility was tested using standard methods according to International Organization for Standardization (ISO) 10993. Electrodes and appropriate control materials were bent, folded, and placed in the appropriate extraction vehicles, or implanted. The extracts were used for in vitro and in vivo tests, to assess the effects of any potential extractable and leachable materials that may be toxic to the body. In vitro studies included cytotoxicity tested in L929 cell line, genotoxicity tested using mouse lymphoma assay (MLA) and Ames assay, and hemolysis tested in rabbit whole blood samples. The results indicated that the electrodes were non-cytotoxic, non-mutagenic, non-clastogenic, and non-hemolytic. In vivo studies included sensitization tested in guinea pigs, irritation tested in rabbits, acute systemic toxicity testing in mice, pyrogenicity tested in rabbits, and a prolonged 28-day subdural implant in sheep. The results indicated that the electrodes induced no sensitization and irritation, no weight loss, and no temperature increase. Histological examination of the sheep brain tissue showed no or minimal immune cell accumulation, necrosis, neovascularization, fibrosis, and astrocyte infiltration, with no differences from the control material. In summary, biocompatibility studies indicated that these new thin-film electrodes are appropriate for human use. As a result, the electrodes were cleared by the FDA for use in clinical practice [510(k) K192764], making it the first thin-film subdural electrode to progress from research to clinic. Its readiness as a commercial product ensures availability to all patients undergoing surgical evaluation for DRE.

Optical and electrochromic properties of thin films of ambipolar polyimides with pendant groups based on thioxanthenone derivatives

The optical and electrochromic properties of thin films obtained by centrifugation from solutions containing ambipolar polyimides with pendant groups based on 9H-thioxanthene-9-one and its S-dioxide derivative are studied using spectral ellipsometry, spectrophotometry, and spectroelectrochemistry. It is shown that the spectral dependences of the refractive index n(E) and the absorption coefficient α(E) as well as the electrochromic properties of polyimide thin films under electrochemical reduction and oxidation conditions strongly depend on the type of the pendant group. Based on the estimates of the band gap Eg a conclusion is made about the possible promising use of thin films of polyimides as working layers in memristors of a new type. Keywords: memristors, dielectric films, ambipolar polyimides, ellipsometry, electrochromism.