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Oil and gas resources are becoming increasingly difficult to extract owing to long-term exploitation. Therefore, hydraulic pressure technologies, such as fracturing proppants, are needed to stimulate production. In this study, the strength and corrosion resistance of quartz were increased by modifying quartz sand and preparing high-performance coated-sand-based oil-fracturing proppants. Although many resins play crucial roles in the process of preparing fracturing proppants, their performances differ considerably. Chemical structural compositions and microstructures were investigated through infrared spectroscopy and scanning electron microscopy. The modification mechanism of quartz sand and the bonding mechanism between quartz sand and different types of resin proppants were analyzed by systematically investigating the flexural strength, corrosion resistance of the proppants as a function of resin contents, and curing temperature. The results show that the performance of the coated proppants is superior to those of conventional quartz sand and ceramic proppants. The flexural strength of modified quartz sand improved by 5.3%. The best performance was obtained using an 8% polyimide resin film and a curing temperature of 180 °C, achieving a coated sand proppant with a breakage ratio of 2.89% under 55.2 MPa. [ABSTRACT FROM AUTHOR]

Flexible thermoelectric generators (TEGs) with pn-junction single-walled carbon nanotube (SWCNT) films on a polyimide substrate have attracted considerable attention for energy harvesting. This is because they generate electricity through the photo-thermoelectric effect by self-generated temperature gradient under uniform sunlight irradiation. To increase the performance and durability of the pn-junction TEGs, n-type films need to be improved as a priority. In this study, bismuth telluride (Bi2Te3) nanoplates synthesized by the solvothermal method were added to the n-type SWCNT films, including a cationic surfactant to form the nanocomposite films because Bi2Te3 has high n-type thermoelectric properties and high durability. The performances of the pn-junction TEGs were investigated by varying the heat treatment times. When the artificial sunlight was uniformly irradiated to the pn-junction TEGs, a stable output voltage of 0.47 mV was observed in the TEG with nanocomposite films heat-treated at 1 h. The output voltage decreased with increasing heat treatment time due to the decrease in the p-type region. The output voltage of TEG at 1 h is higher than that of the TEGs without Bi2Te3 nanoplates under the same conditions. Therefore, the addition of Bi2Te3 nanoplates was found to improve the performance of the pn-junction TEGs. These findings may aid in the development of facile and flexible optical devices, including photodetectors and hybrid devices integrating solar cells. [ABSTRACT FROM AUTHOR]

The exponential demand for real-time monitoring applications has altered the course of sensor development, from sensor electronics miniaturization, e.g., resorting to printing techniques, to low-cost, flexible and functional wearable materials. Humidity sensing has been used in the prevention and diagnosis of medical conditions, as well as in the assessment of physical comfort. This paper presents a resistive flexible humidity sensor composed of silver interdigitated electrodes (IDTs) screen printed onto polyimide film and an active layer of multiwall carbon nanotubes (MWCNT) dispersed in a water-soluble polymer, polyvinyl alcohol (PVA). Different MWCNT/PVA sensor sizes and MWCNT percentages are tested to study their effect on the initial electrical resistance (Ri) values and sensor response at different humidity percentages. The results show that the Ri values decrease with the increase in % MWCNT. The sensor size did not influence the sensor response, while the % MWCNT affected the sensor behavior upon relative humidity (RH) increments. The 1% MWCNT/PVA sensor showed the best response, reaching a relative electrical resistance, ΔR/R0, of 509% at 99% RH. Comparable with other reported sensors, the produced MWCNT/PVA flexible sensor is simpler, greener and shows a good sensitivity to humidity, being easily incorporated in wearable monitoring applications, from sports to medical fields. [ABSTRACT FROM AUTHOR]

Hydrogen sensors are important in a hydrogen‐driven society to prevent explosions caused by hydrogen leaks into the atmosphere. In previous studies, resistive hydrogen sensors on polymer films have metal oxide nanostructures decorated with novel metals that enable good responses at room temperature. However, the in situ growth process of sensing nanostructures has the disadvantage of ineffective fabrication, particularly when preparing a thick catalyst layer to produce reliable readouts from the catalytic hydrogen combustion. This work presents a catalytic combustion hydrogen sensor with a thick catalyst layer anchored in a UV resin layer on polyimide film. Catalyst anchoring channels are made by UV imprinting with a glass mold. The sensor consists of a sensing electrode and a microheater, both made of Au within an area of 1.2 mm diameter. UV imprinting produces a UV resin layer of 27 µm thick and catalyst anchoring channels of 14 µm deep and 20–30 µm wide, which are filled with Pt/TiO2 as a catalyst. The sensing response is 7.9% for 1% H2 under ambient conditions, and the detection range is 0.1–3% H2. The UV‐resin microstructures can effectively retain a thick catalyst layer to enhance sensitivity, and their low thermal conductivity reduces heat loss. [ABSTRACT FROM AUTHOR]

Transparent and light films with high electrical conductivity are preferred for flexible electronic applications. Here, a film exhibiting high transparency, electrical conductivity, and flexibility is produced using a polyimide (PI) substrate and multiwalled carbon nanotubes (MWCNTs) through spray coating. Cost‐effective MWCNTs are used instead of other electrically conductive materials, including silver nanowire ink, single‐walled carbon nanotubes (SWCNTs), and other carbon materials. The average sheet resistance of the prepared MWCNT–PI film is 520.2 Ω □−1 (infinite for the bare PI film), which is lower than the sheet resistances of the SWCNT–PI film reported by another group. This can be attributed to the increase in electrical conductivity of the highly transparent PI film due to the use of MWCNTs. The transparency of the MWCNT–PI film is 71.834% at 550 nm. When MWCNTs and PI are combined, MWCNTs protrude from the surface of the PI film, creating networks and increasing electrical conductivity. Atomic force microscopy analysis reveals that MWCNT networks form on the surface of the MWCNT–PI film. This study suggests the possibility that MWCNTs can also be used as carbon materials for flexible and highly transparent films. [ABSTRACT FROM AUTHOR]

Polyimides (PIs) have been extensively used in thin film and micro-electromechanical system (MEMS) processes based on their excellent thermal and mechanical stability and high glass transition temperature. This research explores the development of a novel multilayer and multifunctional polymer composite electro-piezomagnetic device that can function as an energy harvester or sensor for current-carrying wires or magnetic field sensing. The devices consist of four layers of composite materials with a polyimide matrix. The composites have various nanoparticles to alter the functionality of each layer. Nanoparticles of Ag were used to increase the electrical conductivity of polyimide and act as electrodes; lead zirconate titanate was used to make the piezoelectric composite layer; and either neodymium iron boron (NdFeB) or Terfenol-D was used to make the magnetic and magnetostrictive composite layer, which was used as the proof mass. A novel all-polymer multifunctional polyimide composite cantilever was developed to operate at low frequencies. This paper compares the performance of the different magnetic masses, shapes, and concentrations, as well as the development of an all-magnetostrictive device to detect voltage or current changes when coupled to the magnetic field from a current-carrying wire. The PI/PZT cantilever with the PI/NdFeB proof mass demonstrated higher voltage output compared to the PI/Terfenol-D proof mass device. However, the magnetostrictive composite film could be operated without a piezoelectric film based on the Villari effect, which consisted of a single PI-Terfenol-D film. The paper illustrates the potential to develop an all-polymer composite MEMS device capable of acting as a magnetic field or current sensor. [ABSTRACT FROM AUTHOR]

A low dielectric polyimide/polyimide microsphere (PI/PM) composite film was constructed by thermal imidization of polyamic acid from pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA) in the presence of porous PM. The PM particles with particle size of about 2 μm were prepared via the solvothermal method using 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) and ODA as monomers through thermal imidization. Due to the favorable compatibility between the porous PM and PI matrix, the mechanical properties, thermal stability, and dielectric properties of the obtained composite films were significantly improved. The PI/PM composite films had a tensile strength of 44.18–64.32 MPa, and the corresponding elongation at break of 6.21%–11.7%. Furthermore, the thermogravimetric temperatures of T5% were 538.9–563.7°C. The dielectric constants of the composite films at 1 MHz were 2.59–3.68, and the corresponding dielectric loss were only 0.0119–0.00405. Thus, the combination of excellent mechanical properties, high thermal stability, extremely low dielectric constant, and dielectric loss make the composite films ideal for deployment as high‐performance materials for 5G applications. Highlights: Low dielectric polyimide composite film was prepared by thermal imidization of polyamic acid in the presence of porous polyimide microspheres.Porous polyimide microspheres were prepared by thermal using the imidization solvothermal method.Low dielectric polyimide composite film with good comprehensive properties. [ABSTRACT FROM AUTHOR]

To improve the thermodynamic and mechanical properties of asymmetric polyimide (PI), a method to enhance the linearity of PI by using a structural reorganization approach was designed. First, two novel diamines containing benzimidazole and benzoxazole groups, namely PADBZ and PDBOA, were constructed and synthesized. Thereafter, two new kinds of PI films (PADBZ‐PMDA and PDBOA‐PMDA) were prepared and polymerized with 1,2,4,5‐benzenetetracarboxylic anhydride (PMDA). Based on structural reorganization, PADBZ‐PMDA and PDBOA‐PMDA had repeating units of the same chemical composition and different linearity with PABZ‐BPDA and BOA‐BPDA, respectively. Comparing PADBZ‐PMDA and PABZ‐BPDA, due to the transfer in the position of benzene, PADBZ‐PMDA with high linearity showed the improved heat resistance (Tg up to 448°C), dimensional stability (CTE down to 2.3 ppm/K) and mechanical properties. PDBOA‐PMDA and BOA‐BPDA had the same situation. This study provided a unique solution to enhance the performances of PI by increasing the linearity using a structural reorganization approach. [ABSTRACT FROM AUTHOR]

Polyimide (PI) surfaces coated with and without boron nitride nanotubes (BNNTs) were treated using an atmospheric‐pressure cold plasma in open air. This treatment increased the surface wettability of the PI, measured by a decrease in water contact angle from 68° to 16°, resulting in a more uniform BNNT coating and improved surface adhesion. The plasma treatment of the BNNT‐coated PI surfaces also effectively removed residual polymer surfactants used for BNNT dispersion in water, without causing any thermal damage due to the low plasma and PI's surface temperatures of 350 and 300 K, respectively. The reactive oxygen species in the plasma, such as hydroxyl molecules and oxygen atoms, played an important role in these processes. Atmospheric‐pressure plasma can be employed in various applications in which thermally weak polymer‐based substrates are coated with BNNTs. [ABSTRACT FROM AUTHOR]

In this study, a compound filler consisting of zinc sulfide (ZnS) nanoparticles and reduced graphene oxide (RGO) was synthesized using the hydrothermal method and utilized to enhance the tribological properties of the polyimide (PI) film. The ZnS@RGO/PI composites displayed the lowest wear rate of 3.89 × 10−8 mm3 N−1 m−1 at a load of 200 N, which were significantly lower than that of both pure PI and RGO/PI films. Furthermore, the microstructure and chemical composition of the compound were characterized and analyzed, revealing that the ZnS nanoparticles were effectively attached to the surface of RGO through the chemical bonding between them. Finally, finite element analysis shows that the chemical bonding between ZnS and RGO have the effect to stop the crack expanding under pressure, and a wear mechanism is also given to demonstrate this 'Ball-on-plane' compound's enhancement to the tribological properties. [ABSTRACT FROM AUTHOR]

This study reports a micromachined parylene-C-coated integrated electrode (IDE) sensor fabricated on a polyimide film. Glucose and uric acid within the human sweat concentration range were tested using hydrothermally grown ZnO nanoparticles (NPs) immobilized on the IDE regions of sensors and modified with urate oxidase and glucose oxidase enzymes. Four important sensing parameters, including capacitance, impedance, resistance, and phase, were simultaneously investigated during the dynamic test. The sensor fabrication and characterization of ZnO NPs and ZnO NP formed sensing film were described in detail. The experimental results show that the amount of capacitance change and phase change vs. the concentration variation of glucose and uric acid exhibits an excellent linear regression relationship. On the other hand, the amount of impedance change vs. concentration variation of glucose and uric acid exhibits a power regression relationship. Sensitivities of uric acid and glucose detection based on capacitance changes were 0.1131 pF/µM and 0.7875 pF/µM, respectively. Limits of detection of uric acid and glucose were 1.23 µM and 0.311 µM, respectively. Thus, the developed sensor can be applied to wearable devices for the quantitative analysis of sweat composition in the future. [ABSTRACT FROM AUTHOR]

As triboelectric nanogenerator (TENG) technology continue to evolve, its application in harsh environments has increasingly captivated the interest of researchers. However, the current research on heat-resistant triboelectric materials remains predominantly focused on the development of tribo-negative materials, with scant attention given to their equally crucial tribo-positive counterparts. In this study, the tribo-positive polyimide (PI) material with enhanced tribo-positivity is developed by integrating amide groups with electron-donating effects into the molecular chain. Furthermore, the TENG devices based on this series of tribo-positive PI materials have demonstrated an open-circuit voltage (VOC) of 242 V, a short-circuit current (ISC) of 8.13 μA, and a transferred charge (QSC) of 117 nC. Notably, these devices also demonstrate the capability to efficiently generate electricity even under elevated temperature conditions. This work not only proposes a potential molecular design strategy for developing high-performance tribo-positive PI materials applicable in TENGs, but also markedly propels the advancement of robust energy-harvesting devices engineered for operation at elevated temperatures. [ABSTRACT FROM AUTHOR]

Although lead is a very good radiation shielding material, its toxicity has led researchers to find alternative materials instead of it. Moreover, as the use of Kapton polyimide (PI) film in nuclear power plants and space exploration increases, the need to reveal the radiation degradation properties of this material has come along. In this regard, in the present study, it is aimed to determine the mass and linear attenuation coefficients, half value layer, tenth value layer, mean free path and radiation protection efficiency attenuation parameters for this material, experimentally and theoretically, by using the gammas of the 133Ba radioisotope. Experimental gamma attenuation measurements were made by a spectrometer using a Hamamatsu multi pixel photon counter device with a silicon photomultiplier sensor. The constant fraction discrimination timing method was used to reduce the electronic noise of the spectrometer. The attenuation parameters determined experimentally by following two ways were compared with the theoretical ones obtained from the XCOM program. [ABSTRACT FROM AUTHOR]

To study the initiation and development of interfacial electrical damage in multi-layer dielectrics, an aging test of 3-layer polyimide films was conducted under pulsed voltage with a repetitive frequency of 500 Hz and a maximal amplitude of 30 kV. The variation in the damage morphology with the number of applied pulses was analyzed by a statistical method. The circuit current and partial discharge at different aging stages was measured, and the Fourier transform infrared spectrum analysis results of the aged and unaged sample regions were compared. The results demonstrate that the partial discharge in the dielectric interface gap, which is unavoidable in manufacturing, is the main cause of damage. It initiates from the interface and grows into the interior of the dielectric with the application of pulses. When there are no macroscopic defects on dielectric films, damage presents a punctiform morphology. The damage process can be divided into the following three stages: surface roughening damage, steady growth stage of damage points, and pre-breakdown stage. Differing from dielectrics without macroscopic defects, dielectrics with original void defects present transverse dendritic damage channels that initiate from the edge of the defect. [ABSTRACT FROM AUTHOR]

A spiral‐artificial basilar membrane (S‐ABM) sensor is reported that mimics the basilar membrane (BM) of the human cochlea and can detect sound by separating it into 24 sensing channels based on the frequency band. For this, an analytical function is proposed to design the width of the BM so that the frequency bands are linearly located along the length of the BM. To fabricate the S‐ABM sensor, a spiral‐shaped polyimide film is used as a vibrating membrane, with maximum displacement at locations corresponding to specific frequency bands of sound, and attach piezoelectric sensor modules made of poly(vinylidene fluoride‐trifluoroethylene) film on top of the polyimide film to measure the vibration amplitude at each channel location. As the result, the S‐ABM sensor implements a characteristic frequency band of 96‐12,821 Hz and 24‐independent critical bands. Using real‐time signals from discriminate channels, it is demonstrated that the sensor can rapidly identify the operational noises from equipment processes as well as vehicle sounds from environmental noises on the road. The sensor can be used in a variety of applications, including speech recognition, dangerous situation recognition, hearing aids, and cochlear implants, and more. [ABSTRACT FROM AUTHOR]

Polyimide (PI) films are well recognized for their outstanding chemical resistance, radiation resistance, thermal properties, and mechanical strength, rendering them highly valuable in advanced fields such as aerospace, sophisticated electronic components, and semiconductors. However, improving their optical transparency while maintaining excellent thermal properties remains a significant challenge. This review systematically checks over recent advancements in enhancing the optical and thermal performance of PI films, focusing on various strategies through molecular design. These strategies include optimizing the main chain, side chain, non-coplanar structures, and endcap groups. Rigid and flexible structural characteristics in the proper combination can contribute to the balance thermal stability and optical transparency. Introducing fluorinated substituents and bulky side groups significantly reduces the formation of charge transfer complexes, enhancing both transparency and thermal properties. Non-coplanar structures, such as spiro and cardo configurations, further improve the optical properties while maintaining thermal stability. Future research trends include nanoparticle doping, intrinsic microporous PI polymers, photosensitive polyimides, machine learning-assisted molecular design, and metal coating techniques, which are expected to further enhance the comprehensive optical and thermal performance of PI films and expand their applications in flexible displays, solar cells, and high-performance electronic devices. Overall, systematic molecular design and optimization have significantly improved the optical and thermal performance of PI films, showing broad application prospects. This review aims to provide researchers with valuable references, stimulate more innovative research and applications, and promote the deep integration of PI films into modern technology and industry. [ABSTRACT FROM AUTHOR]

The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions. An important challenge to be solved urgently is the reduction of imidization temperature. In this work, twelve kinds of polyimide films with different chain rigidity were prepared at low temperature of 200 °C, in the absence or presence of imidazole used as the catalyst. The molecular rigidity and free volume were theoretically calculated, and relationship between structure and properties were systematically studied. The results show that imidization reaction under low temperatures is significantly affected by the rigidity of molecular chains. The rigid structure of polyimide is not conducive to the low-temperature imidization, but this adverse effect can be eliminated by adding catalyst, resulting the notably increased imidization degree. The optical and thermal properties can be improved to a certain extent for the chemically catalyzed system, resulting in relatively higher heat resistance and thermal stability. While the mechanical performance could be determined by complicating factors, greatly different from polyimide films prepared by high temperature method. To investigate aggregation structures of films, the effect of chain rigidity and catalyst on the stacking or orientation of molecular chains was further elaborated. This work can contribute to the understanding of chemically catalyzed imidization that is rarely reported in the existing research, and will provide guidance for the low-temperature preparation of high-performance polyimides. [ABSTRACT FROM AUTHOR]

A novel fluorinated diamine monomer (FPMDA ) was synthesized from p-fluorobenzaldehyde and 2, 6-dimethylaniline, and then reacted with pyromellitic anhydride to obtain a fluorinated polyimide (FPI). The structures of the synthesized FPMDA diamine monomer and polyimide were characterized by FTIR, nuclear magnetic hydrogen spectroscopy, and mass spectrometry (MS) ;the thermal properties of the polyimide film were characterized using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results showed that FPI has excellent solubility in solvents such as DMF, NMP, and THF. FPI also shows good thermal stability, under nitrogen environment, with thermal decomposition temperature Td5% of 550 °C, Td10% of 580 °C, and char yield of 58.7% at 1 000 °C, its glass transition temperature is greater than 400 °C . [ABSTRACT FROM AUTHOR]

Planar microwave bow-tie diodes on bases of selectively doped semiconductor structures are successfully used in the detection and imaging of electromagnetic radiation in millimeter and submillimeter wavelength ranges. Although the signal formation mechanism in these high-frequency diodes is said to be based on charge-carrier heating in a semiconductor in a strong electric field, the nature of the electrical signal across the bow-tie diodes is not yet properly identified. In this research paper, we present a comprehensive study of a series of various planar bow-tie diodes, starting with a simple asymmetrically shaped submicrometer-thick n-GaAs layer and finishing with bow-tie diodes based on selectively doped GaAs/AlGaAs structures of different electrical conductivity. The planar bow-tie diodes were fabricated on two different types of high-resistivity substrates: bulky semi-insulating GaAs substrate and elastic dielectric polyimide film of micrometer thickness. The microwave diodes were investigated using DC and high-frequency probe stations, which allowed us to examine a sufficient number of diodes and collect a large amount of data to perform a statistical analysis of the electrical parameters of these diodes. The use of probe stations made it possible to analyze the properties of the bow-tie diodes and clarify the nature of the detected voltage in the dark and under white-light illumination. The investigation revealed that the properties of various bow-tie diodes are largely determined by the energy states residing in semiconductor bulk, surface, and interfaces. It is most likely that these energy states are responsible for the slow relaxation processes observed in the studied bow-tie diodes. [ABSTRACT FROM AUTHOR]

Laser-induced graphene (LIG) provides a three-dimensional porous structure of graphene, which is suitable for application to energy storage devices and flexible electronics. Controlling the morphology and structure of LIG and understanding its underlying principle are important for enhancing the performance of LIG-based devices. Here, we investigated the effects of graphene interfacing with a precursor material on the LIG formation. A CO2 laser with different powers and scan rates was irradiated on a polyimide film covered with mono-, bi-, and trilayer graphene to fabricate in situ LIG contacts. As the number of graphene layers increases, the threshold energy required for the LIG formation decreases. In addition, the interfacing graphene causes spreading and smoothing of the LIG electrodes in the in-plane direction. A numerical study on the effect of the interfacing graphene on heat transfer was also conducted. The simulation results showed that the graphene layer enhances thermal diffusion to facilitate the LIG formation; this was also observed in the experimental results. Our study on the interfacial effects of a nanomaterial on the LIG formation provides design guidelines for considering heat transfer in LIG electronics fabricated with heterogeneous materials and structures. [ABSTRACT FROM AUTHOR]

Two organo‐soluble polyimide (PI) resins were prepared from a tricyclic fluoro‐containing dianhydride 9,9‐bis(trifluoromethyl)xanthene‐2,3,6,7‐tetracarboxylic dianhydride (6FCDA) and aromatic diamine of 2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane (BDAF) for PI‐IIa and 1,3‐bis(3‐aminophenoxy)benzene (133APB) for PI‐IIb, respectively. For comparison, two analogous PIs were prepared from 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and the same diamines to afford PI‐Ia (6FDA‐BDAF) and PI‐Ib (6FDA‐133APB), respectively. Incorporation of the rigid and planar xanthene units in the 6FCDA‐PIs obviously decreased the solubility of the resins in organic solvents. Flexible and tough PI films were fabricated from the PI solutions in N,N‐dimethylacetamide (DMAc). The PI films derived from the rigid and planar 6FCDA dianhydride exhibited obviously enhance thermal stability, and high‐temperature dimensional stability. For example, PI‐IIa (6FCDA‐BDAF) showed the glass transition temperature (Tg) and coefficient of linear thermal expansion (CTE) values of 311.5°C and 50.5 × 10−6/K, respectively, which were all superior to those of the PI‐Ia counterpart (Tg = 264.6°C; CTE = 55.4 × 10−6/K). In addition, the 6FCDA‐PI films maintained the intrinsically excellent optical transparency of the fluoro‐containing PI films and showed the comparable optical properties to those of the 6FDA‐PI films. As for the properties highly related to the space applications, all the PI films exhibited low solar absorptivity (α) values of 0.18–0.20 and the good thermal emissivity (ε) values in the range of 0.68–0.70. PI‐Ia (6FDA‐BDAF) and PI‐IIa (6FCDA‐BDAF) films showed the similar atomic oxygen erosion behaviors with the standard Kapton® type of PI film derived from pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA). [ABSTRACT FROM AUTHOR]

The proposed paper presents the design of a leaky‐wave antenna inspired by holographic metasurfaces employing thin film. Leveraging the holographic principle, this metasurface showcases its transformative capacity by converting an omnidirectionally radiating monopole into a highly directional antenna emitting leaky waves. The holographic metasurface is constructed using a thin film of polyimide (PI) (Df = 0.008; Dk = 3.5), measuring 50 μm in thickness. The antenna structure comprises multiple layers, commencing with the top PI layer, succeeded by a 40 μm thick adhesive layer (Df = 0.004; Dk = 6). Subsequent layer includes the Rogers RT/duroid 5880 substrate (Df = 0.0009; Dk = 2.20), grounded at the bottom and has a thickness of 1.6 mm. The meticulously tailored design of the proposed antenna ensures optimal performance at 15 GHz, facilitating directional radiation and precise beam steering at 10 degrees (ϴ = 10°). This innovative design, incorporating the holographic metasurface on thin film, significantly enhances the antenna's performance, increasing gain from 1.5 dBi to 13.8 dBi. [ABSTRACT FROM AUTHOR]

Interfacial solar steam generation can produce clean water in an environmentally friendly and efficient way. The evaporator employing graphene as a photothermal conversion material represents an excellent paradigm within the realm of interfacial evaporators. However, existing graphene materials exhibit a certain degree of hydrophobicity and are associated with intricate manufacturing processes. Hence, the study proposes a hydrophilic composite graphene‐based material incorporating CuO, which is fabricated through a straightforward laser‐induced graphene synthesis method directly onto a polyimide film coated with CuCl2. Due to the fast capillary performance endowed by the enhanced hydrophilicity and hierarchical structural morphology, the assembled laser‐induced‐graphene evaporator achieves an evaporation rate of 2.54 kg m−2 h−1 under 1 sun irradiation with an evaporation efficiency of 91.1%, while also demonstrating excellent desalination capabilities. The as‐prepared graphene‐based evaporator has significant potential for desalination and wastewater treatment applications, offering an effective solution to address clean water challenges in remote areas. [ABSTRACT FROM AUTHOR]

Patterns on polymers usually have different mechanical properties as those of the substrates, causing deformation or distortion and even detachment of the patterns from the polymer substrates. Herein, we present a wrinkling strategy, which utilizes photolithography to define the area of stress distribution by light-induced physical crosslinking of polymers and controls diffusion of residual solvent to redistribute the stress and then offers the same material for patterns as substrate by thermal polymerization, providing uniform wrinkles without worrying about force relaxation. The strategy allows the recording and hiding of up to eight switchable images in one place that can be read by the naked eye without crosstalk, applying the wrinkled polymer for optical anti-counterfeiting. The wrinkled polyimide film was also utilized to act as a substrate for the creation of fine copper circuit by a full-additive process. It generates flexible integrated circuit (IC) carrier board with copper wire density of 400% higher than that of the state-of-the-art in industry while fulfilling the standards for industrialization. Current wrinkling processes for pattern formation cannot be easily controlled, resulting in deformation or detachment of patterns from substrates. Here, Zhong et al. report a wrinkling strategy for creating patterned structures with long-range order and resistant to force relaxation. [ABSTRACT FROM AUTHOR]

Aromatic polyimide films are widely used in high-tech fields due to their excellent combination of thermal, mechanical, and electrical properties. These films serve as precursors for the preparation of high thermal conductivity graphite films, with carbon content up to 70%, exhibits exceptional thermal and electrical conductivity, making it a promising precursor for polymer-based graphite films. This study focuses on the reserch of graphitization using commercial DuPont Kapton polyimide film. The polyimide film was rapped around a cylindrical mold and heat-treated at various temperatures. The impact of the process system on graphitization was thoroughly investigated, along with the evolution of polyimide's structure and properties during heat treatment. Results demonstrated that the size of the prepared films initially increased and then decreased with the increase in graphitization temperature. Additionally, the color of the prepared films transitioned from yellow-brown to black and eventually gray matte. The brittleness of the prepared films followed a similar pattern of initially increasing and then decreasing. When the temperature was below 2200 °C, the surface of the graphite films was smooth and defectless. However, at 2200 °C, small holes appeared on the surface, and at 2300 °C, the surface began to exhibit a "foaming" phenomenon, which intensified with temperature. XRD and Raman spectra analysis revealed that the degree of graphitization, crystallinity, and order of the prepared films increased with temperature. At 2800 °C, the sample achieved a theoretical degree of graphitization of 95.35% and a thermal conductivity of 1246.36 W/(m·K). [ABSTRACT FROM AUTHOR]

Laser-inscribed graphene (LIG) is an emerging material for micro-electronic applications and is being used to develop supercapacitors, soft actuators, triboelectric generators, and sensors. The fabrication technique is simple, yet the batch-to-batch variation of LIG quality is not well documented in the literature. In this study, we conduct experiments to characterize batch-to-batch variation in the manufacturing of LIG electrodes for applications in electrochemical sensing. Numerous batches of 36 LIG electrodes were synthesized using a CO2 laser system on polyimide film. The LIG material was characterized using goniometry, stereomicroscopy, open circuit potentiometry, and cyclic voltammetry. Hydrophobicity and electrochemical screening (cyclic voltammetry) indicate that LIG electrode batch-to-batch variation is less than 5% when using a commercial reference and counter electrode. Metallization of LIG led to a significant increase in peak current and specific capacitance (area between anodic/cathodic curve). However, batch-to-batch variation increased to approximately 30%. Two different platinum electrodeposition techniques were studied, including galvanostatic and frequency-modulated electrodeposition. The study shows that formation of metallized LIG electrodes with high specific capacitance and peak current may come at the expense of high batch variability. This design tradeoff has not been discussed in the literature and is an important consideration if scaling sensor designs for mass use is desired. This study provides important insight into the variation of LIG material properties for scalable development of LIG sensors. Additional studies are needed to understand the underlying mechanism(s) of this variability so that strategies to improve the repeatability may be developed for improving quality control. The dataset from this study is available via an open access repository. [ABSTRACT FROM AUTHOR]

Mechanical damage to the surface of polyimide during manufacture and utilization may act as critical determinants of the properties and longevity of the material. In order to address this issue, this study prepared thermoplastic polyimide (TPI) films through the copolymerization of isocyanate and acid anhydride, which possesses superior self‐healing ability after being mechanical damaged. Moreover, polyimide films still retain its exceptional tensile strength (>90 MPa) with Young's modulus (E) (>3 GPa), high thermal stability (glass transition temperature (Tg) >220°C), and excellent insulation performance (breakdown strength (Eb) >180 kV/mm) after self‐healing. Introducing cross‐linked structures and flexible groups into the thermoplastic resin matrix appropriately not only imparts self‐healing capabilities to the material but also retains its excellent mechanical properties. The combination of straightforward copolymerization and distinctive self‐healing prowess renders it an appropriate strategy for confronting self‐healing challenges. [ABSTRACT FROM AUTHOR]

Fractal‐like geometries applied to biosignal‐electrodes design show great potential for enhancing the signal acquisition of sensing systems. This study reports a novel approach for flexible, silver‐free, and dry fractal‐like electrodes based on Laser‐Induced Graphene (LIG) obtained through laser photothermal processing of a commercial polyimide film. This one‐step mask‐less manufacturing process enables the simple fabrication of natural and optimized fractal‐like shapes inspired by actual snowflake patterns. To ensure a reliable and standardized connection to the measurement unit, the electrodes are equipped with a snap terminal. The electrodes are structurally characterized using various techniques including Scanning Electron Microscopy (SEM), Raman spectroscopy, and X‐ray Photoelectron Spectroscopy (XPS). By benchmarking the performance of these electrodes against Ag/AgCl wet commercial electrodes and LIG electrodes shaped as commercial ones, a heart rate‐monitoring accuracy of over 96.8% is achieved, with high specificity, positive prediction, and sensitivity, surpassing the 95.8% achieved by conventional commercial electrodes. These results demonstrate the efficacy of fractal‐based designs in combination with LIG‐based transduction, offering flexible and cost‐effective electrocardiogram (ECG) electrodes with improved performance compared to traditional wet electrodes. [ABSTRACT FROM AUTHOR]

Titanium oxide (TiO2) coated polyimide has broad application prospects under extreme conditions. In order to obtain a high-quality ultra-thin TiO2 coating on polyimide by atomic layer deposition (ALD), the polyimide was activated by in situ oxygen plasma. It was found that a large number of polar oxygen functional groups, such as carboxyl, were generated on the surface of the activated polyimide, which can significantly promote the preparation of TiO2 coating by ALD. The nucleation and growth of TiO2 were studied by x-ray photoelectron spectroscopy monitoring and scanning electron microscopy observation. On the polyimide activated by oxygen plasma, the size of TiO2 nuclei decreased and the quantity of TiO2 nuclei increased, resulting in the growth of a highly uniform and dense TiO2 coating. This coating exhibited excellent resistance to atomic oxygen. When exposed to 3.5 × 1021 atom cm−2 atomic oxygen flux, the erosion yield of the polyimide coated with 100 ALD cycles of TiO2 was as low as 3.0 × 10−25 cm3/atom, which is one order less than that of the standard POLYIMIDE-ref Kapton® film. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) is a wide-band gap semiconductor that exceeds other semiconducting materials (except diamond) in electrical, mechanical, chemical, and radiation stability. In this paper, we report a novel approach to fabrication of SiC nano films on a Si substrate, which is based on the endotaxial growth of a SiC crystalline phase in a graphite-like carbon (GLC) matrix. GLC films were formed by carbonization of rigid rod polyimide (PI) Langmuir–Blodgett (LB) films on a Si substrate at 1000 °C in vacuum. After rapid thermal annealing of GLC films at 1100 °C and 1200 °C, new types of heterostructures SiC(10 nm)/GLC(20 nm)/Si(111) and SiC(20 nm)/GLC(15 nm)/SiC(10 nm)/Si(111) were obtained. The SiC top layer was formed due to the Si-containing gas phase present above the surface of GLC film. An advantage of the proposed method of endotaxy is that the SiC crystalline phase is formed within the volume of the GLC film of a thickness predetermined by using PI LB films with different numbers of monolayers for carbonization. This approach allows growing SiC layers close to the 2D state, which is promising for optoelectronics, photovoltaics, spintronics. [ABSTRACT FROM AUTHOR]

Polyethylene oxide composite electrolytes are widely used in lithium‐ion batteries because of their excellent moldability, good flexibility, and favorable chemical compatibility. However, they still suffer from low ionic conductivity and weak mechanical strength. Herein, a 3D nanofiber‐reinforced dual‐salt composite solid electrolyte (PI@PCB) is synthesized. Benefiting from the support of the porous polyimide films and the addition of lithium bis(oxalate)borate, the obtained PI@PCB electrolyte exhibits high mechanical strength, good thermal stability, excellent electrochemical stability, and a high lithium ion transference number (0.70). In addition, the assembled Li/PI@PCB/Li cell shows the lowest overpotential of 200 mV at the initial cycling stage and increases to 246 mV slightly after 1500 h. The capacity retention rate of Li/PI@PCB/LFP battery is about 88.3% after 500 cycles at 60 °C. [ABSTRACT FROM AUTHOR]

Polymers with a low dielectric constant (Dk) are promising materials for high-speed communication networks, which demand exceptional thermal stability, ultralow Dk and dissipation factor, and minimum moisture absorption. In this paper, we prepared a series of novel low-Dk polyimide films containing an MCM-41-type amino-functionalized mesoporous silica (AMS) via in situ polymerization and subsequent thermal imidization and investigated their morphologies, thermal properties, frequency-dependent dielectric behaviors, and water permeabilities. Incorporating 6 wt.% AMS reduced the Dk at 1 MHz from 2.91 of the pristine fluorinated polyimide (FPI) to 2.67 of the AMS-grafted FPI (FPI-g-AMS), attributed to the free volume and low polarizability of fluorine moieties in the backbone and the incorporation of air voids within the mesoporous AMS particles. The FPI-g-AMS films presented a stable dissipation factor across a wide frequency range. Introducing a silane coupling agent increased the hydrophobicity of AMS surfaces, which inhibited the approaching of the water molecules, avoiding the hydrolysis of Si–O–Si bonds of the AMS pore walls. The increased tortuosity caused by the AMS particles also reduced water permeability. All the FPI-g-AMS films displayed excellent thermooxidative/thermomechanical stability, including a high 5% weight loss temperature (>531 °C), char residue at 800 °C (>51%), and glass transition temperature (>300 °C). [ABSTRACT FROM AUTHOR]

Orientation film is a key material in liquid crystal displays, and the technology of inducing liquid crystal molecular orientation through polyimide photoorientation film is widely studied. In this work, polyimide is a random copolymer synthesized from a mixture of cyclobutanetetracarboxylic dianhydride and pyromellitic dianhydride, 4,4' ‐ diaminodiphenylmethane, 3,3', 5,5'‐ tetramethylbenzidine, and Methanone, bis (4‐aminophenyl) ‐, homopolymer. In this study, we investigated the pre‐inclination of a series of photo‐crosslinked diamine structures for the polymerization of RM monomers by PSVA (Polymer Stabilized Vertical Alignment) technology, and mainly investigated the pre‐inclination of a series of light‐oriented films with different molar fraction reaction monomers polymerized on the backbone. The results show that the polymerization of 2‐(methacrylate)ethyl ester 3,5‐diaminobenzoic acid reaction monomer with 6.3% molar fraction of polyimide photooriented film achieves high pre‐tilt adjustment under low light accumulation conditions, and successfully achieves excellent optical & reliability performance. [ABSTRACT FROM AUTHOR]

The irreversible threshold voltage (Vth) shift by polyimide (PI) charging is experimentally demonstrated. The Vth of device without PI electrode is positively moved during the release. Interestingly, the shifted Vth is not recovered to initial value up to one month. The mechanism for the irreversibility is suggested. [ABSTRACT FROM AUTHOR]

Polyimide (PI) films equipped on the surface of spacecraft are susceptible to ultraviolet damage. Herein, the performance of two kinds of polyimide films i.e. 3,3′,4,4′-biphenyl dianhydride-p-phenylenediamine (BPDA-PDA) and pyromellitic dianhydride-4,4′-oxydianiline (PMDA-ODA) under vacuum ultraviolet (VUV, 172 nm) irradiation was studied. The failure behavior of the PI films was studied by tensile tests, thermogravimetry (TGA), thermomechanical analysis (TMA), electric breakdown, UV–visible transmittance and scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to analyze the molecular structure. The results indicated that the tensile strength of BPDA-PDA PI and PMDA-ODA PI films decreased by 10.4 and 7.4% under VUV irradiation, respectively; the breakdown strength and UV-transmittance also deteriorated. Besides, the surface morphology of the PI films showed a large number of microcracks after VUV irradiation, which we ascribe to the breakage of imide rings (C-N-C) and ether bonds (C-O-C) of the PI films. However, the thermal stability (residual weight) of both PI films remained constant compared to the initial level; this can be explained by the combined effect of bond breaking and cross-linking of the polyimide films. [ABSTRACT FROM AUTHOR]

Polyimides externally deployed in spacecraft or satellites extensively have various aerospace hazards, including atomic oxygen (AO) erosion, irradiation degradation, and electrostatic charge/discharge (ESC/ESD). To cope with these challenges, we fabricate a ZnO/CuNi‐polyimide composite film with augmented permanence. Using spectroscopy and microscopy techniques, we have shown that the combination of chelation and cross‐linking in the interfacial architecture leads to enhanced interfacial compatibility and mechanical robustness. Besides, due to the positive AO diffusion barrier ability of the wurtzite ZnO, our composite film shows remarkable AO resistance and a very small Ey value of 6.88 × 10−26 cm3/atom, which is merely 2.29% of that of pristine polyimide. Moreover, the well‐defined nanocrystalline state with minimal lattice swelling (0.3%–0.7%) of the Fe+‐irradiated ZnO/CuNi‐polyimide at a damaging dose of 353.4 dpa demonstrates its excellent irradiation resistance. Finally, the ZnO/CuNi‐polyimide also shows sufficient electrostatic dissipation capacity to cope with the ESC/ESD events. Our fabrication approach for composite films based on multi‐technology integration shows potential for aerospace applications and deployment. [ABSTRACT FROM AUTHOR]

The excellent electrical properties of graphene have received widespread attention. However, the difficulty of electron transfer between layers still restricts the application of graphene composite materials to a large extent. Therefore, in this study, graphene/polyimide films were subjected to a Joule heating treatment to improve the electrical conductivity of the film by ~76.85%. After multiple Joule thermal cycle treatments, the conductivity of the graphene/polyimide film still gradually increased, but the increase in amplitude tended to slow down. Finally, after eight Joule heat treatments, the conductivity of the graphene/polyimide film was improved by ~93.94%. The Joule heating treatment caused the polyimide to undergo atomic rearrangement near the interface bonded to the graphene, forming a new crystalline phase favourable for electron transport with graphene as a template. Accordingly, a model of the bilayer capacitive microstructure of graphene/polyimide was proposed. The experiment suggests that the Joule heating treatment can effectively reduce the distance between graphene electrode plates in the bilayer capacitive micro-nanostructures of graphene/polyimide and greatly increases the number of charge carriers on the electrode plates. The TEM and WAXS characterisation results imply atomic structure changes at the graphene/polyimide bonding interface. [ABSTRACT FROM AUTHOR]

This document is an editorial for a special issue of the journal Micromachines on the topic of micro and nanosensors. The editorial highlights the growing interest in making electrochemical sensors smaller while maintaining their sensitivity and selectivity. It explains that micro and nanosensors are used for highly sensitive measurements of various parameters such as pressure, humidity, concentration, and temperature, and have wide applications in fields like electronics, medicine, automotive, and industry. The special issue includes eight papers that cover topics such as laser-inscribed graphene electrodes, glucose sensors, tunnel magnetoresistance current sensors, quartz resonant pressure sensors, MEMS fluxgate sensors, metamaterial structures, micro 4D imaging sensors, and the electrochemical usage of microscale sensors for the determination of antidiabetic drugs. The editorial expresses gratitude to the authors and reviewers for their contributions to the special issue. [Extracted from the article]

Despite the remarkable progress of perovskite solar cells (PSCs), challenges remain in terms of finding effective and viable strategies to enhance their long‐term stability while maintaining high efficiency. In this study, a new insulating and hydrophobic fluorinated polyimide (FPI: 6FDA‐6FAPB) was used as the interface layer between the perovskite layer and the hole transport layer (HTL) in PSCs. The functional groups of FPI play a pivotal role in passivating interface defects within the device. Due to its high work function, FPI demonstrates field‐effect passivation (FEP) capabilities as an interface layer, effectively mitigating non‐radiative recombination at the interface. Notably, the FPI insulating interface layer does not impede carrier transmission at the interface, which is attributed to the presence of hole tunneling effects. The optimized PSCs achieve an outstanding power conversion efficiency (PCE) of 24.61 % and demonstrate excellent stability, showcasing the efficacy of FPI in enhancing device performance and reliability. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) silver nanoplates are chemically synthesized in the presence of guar gum – a naturally occurring biopolymer. The polymer directs anisotropic growth of silver nuclei into high aspect ratio nanoplates spanning 4500 ± 500 nm lateral length with thickness as small as 40 ± 10 nm. After a thorough investigation of the reaction parameters (temperature, precursor to reductant ratio, and polymer quantity) on the morphology of the product, a scalable synthetic protocol to achieve good yields (95%–98%) of highly pure (~100%) 2D silver nanoplates (AgNPls) in a facile, inexpensive, room temperature, aqueous phase chemical reaction of only about 5 min is devised. The optimized AgNPls induce appreciable conductivity of 5.5 ± 0.38 S/cm in polyimide at only 12 wt% loading. Consequently, the resulting polymer nanocomposite (containing 12 wt% AgNPls), at only 130 ± 15 μm thickness and 0.45 g/cm3 density, effectively blocks electromagnetic radiation in X‐band with a total shield effectiveness of about 10 dB resulting in substantially high specific shielding effectiveness and absolute shielding effectiveness of 22.48 and 1729.23 dB cm3 g−1, respectively. Additionally, the nanocomposites remain thermally stable up to 500°C in oxidative environment and possess an appreciably high storage modulus of 3.113 GPa at 50°C. These low‐density conductive polyimide films, therefore, present great prospects in shielding against electromagnetic interference under extreme conditions. [ABSTRACT FROM AUTHOR]

Sticking between the thermoplastic polymer and metal tool is a crucial issue, as it determines whether the manufactured part can be ejected from the metal mold. Polyimide (PI) release films have been widely used in the processing of fiber‐reinforced thermoplastic polymer composites. Compared with other release mediums such as release agents, PI release film has a higher release efficiency. However, the underlying release mechanism is still not well understood which is essential to improve their performance further and reduce the cost. In this paper, poly(ether ketone ketone) (PEKK) polymer was melted and cooled down between two PI films. The surface morphologies and chemical compositions of the PI film and PEKK were characterized both before and after release using atomic force microscope, x‐ray photoelectron spectroscopy, contact angle measurements, and confocal microscopy. It showed that a thin PI layer was transferred from the PI release film to the PEKK surface during the release process. Based on these experimental results, a modified boundary layer mechanism is proposed as a hypothesis to describe the release mechanism of PI films. Our results give a fundamental understanding of how PI film works for the release of thermoplastics with high processing temperatures and may help to improve the performance and reduce the costs of existing PI films and may give guidance to the design of new release media. [ABSTRACT FROM AUTHOR]

Despite the remarkable progress of perovskite solar cells (PSCs), challenges remain in terms of finding effective and viable strategies to enhance their long‐term stability while maintaining high efficiency. In this study, a new insulating and hydrophobic fluorinated polyimide (FPI: 6FDA‐6FAPB) was used as the interface layer between the perovskite layer and the hole transport layer (HTL) in PSCs. The functional groups of FPI play a pivotal role in passivating interface defects within the device. Due to its high work function, FPI demonstrates field‐effect passivation (FEP) capabilities as an interface layer, effectively mitigating non‐radiative recombination at the interface. Notably, the FPI insulating interface layer does not impede carrier transmission at the interface, which is attributed to the presence of hole tunneling effects. The optimized PSCs achieve an outstanding power conversion efficiency (PCE) of 24.61 % and demonstrate excellent stability, showcasing the efficacy of FPI in enhancing device performance and reliability. [ABSTRACT FROM AUTHOR]

Considering the ongoing evolution of flexible printed circuit boards and the importance of safeguarding the intellectual property of circuit designs, there exists an imperative demand for the development of a black film exhibiting exceptional electrical properties and remarkable light‐shielding capabilities. Consequently, this work employs a straightforward strategy to enhance the opacity of polyimide films by incorporating carbon black (CB) and manganese dioxide (MnO2) as black fillers using an in situ doping method. Rigorous tests are conducted, analyzing properties such as dielectric constant, dielectric loss, breakdown field strength, current density, and ferroelectric energy storage. The optimal ratio of CB to MnO2 (mass fraction) is determined as 1:5, with a total powder doping amount of 6 wt%, providing the best ratio relative to the matrix resin. This ratio ensures an optimal powder dispersion state, resulting in an outstanding breakdown field of 147.4 kV/mm and ultralow dielectric constants, measuring less than 3.78 at 103 Hz. This composite film is anticipated to find applications as a cutting‐edge material for electronic devices and the semiconductor industry. [ABSTRACT FROM AUTHOR]

Graphene oxide/polyimide nanocomposites, expect that these properties increase. That's why by the incorporation of modified graphene oxide into polyimides, graphene oxide polyimide nanocomposite can be achieved with excellent properties as compared to the parent material and may perform better than polyimide in different applications like in batteries and nano-platelet fillers etc. The aim of this research project is to enhance the thermal conductivity of graphene oxide (GO)/PI nanocomposite films. These polyimide nanocomposite films will be analyzed and characterized using X-rays diffractions (XRD), Fourier transform infrared spectroscopy (FTIR). We will measure the thermal stability of polyimide nanocomposites films by using gravimetric analysis (TGA). [ABSTRACT FROM AUTHOR]

Polymer materials with a low dielectric constant and low dielectric loss have the potential to be applied to high-frequency signal transmissions, such as mobile phone antennas and millimeter wave radars. Two types of diamines, 4,4′-diamino-p-tetraphenyl (DPT) and crown ether diamine (CED), were prepared for ternary copolymerization with BPDA in this study. Cross-links with molecular chains were formed, increasing molecular chain distance by utilizing rings of CED. The MPI films exhibit a good thermal performance with the increase in CED addition, with Tg > 380 °C and CTE from −4 × 10−6 K−1 to 5 × 10−6 K−1. The Young's modulus can reach 8.6 GPa, and the tensile strength is above 200 MPa when 5% and 7% CED are introduced. These MPI films exhibit good mechanical performances. The dielectric constant of PI−10% film can go as low as 3.17. Meanwhile, the relationship between dielectric properties and molecular structure has been demonstrated by Molecular Simulation (MS). PI molecules are separated by low dielectric groups, resulting in a decrease in the dielectric constant. [ABSTRACT FROM AUTHOR]

To synthesize colorless superheat‐resistant polyimide films, one of the valid approaches is the incorporation of the asymmetric and warped structures in the main chain. Applying this approach on 5(6)‐amino‐2‐(4‐aminobenzene)benzimidazole (PABZ) and changing its linearity, 6, 5′‐diamine‐2′‐methyl‐1‐methyl‐2‐phenylbenzimidazole (5a) and 6, 3′‐diamine‐2′‐methyl‐1‐methyl‐2‐phenylbenzimidazole (5b) were devised and synthesized successfully, then polymerized with 1,2,4,5‐cyclohexanetetracarboxylic dianhydride (HPMDA). The prepared poly(benzimidazole imide)s (PBIIs) with the rigid main chain and loose packing had the excellent heat‐resistant level (Tg > 400°C) and optical properties (T400 > 80%). Besides, the alterations resulting from various linearities were discussed comprehensively. This research is beneficial to the application of optical field, providing a promising candidate of heat‐resistant colorless materials. [ABSTRACT FROM AUTHOR]

Attenuated total internal reflection (ATR) spectra of polyimide PI-2610 films deposited on single-crystal silicon wafers by centrifugation were studied after irradiation with 5-MeV electrons in a linear accelerator at doses of 1∙1014–2∙1015 cm–2. The strongest bands in the spectrum of the PI-2610 polyimide films were attributed to vibrations of the imide ring C–N–Cst (1349 cm–1) and aromatic ring (1517 cm–1), stretching vibrations of the imide ring C=Ostr (1700 cm–1) and CO–Cst-group C–C bonds (1074 cm-1), and bending vibrations of C–H bonds with maxima at 734 and 828 cm–1. The spectral shape and intensities of bands with maxima at 1700 and 1349 cm–1 due to C=O and C=N–Cstr vibrations were observed to change at an initial dose of 1∙1014 cm–2. It was assumed that this was due to relaxation of metastable states of these groups. The intensities of bands corresponding to asymmetric and symmetric stretching vibrations of C–H2 bonds decreased at a dose of 2∙1015 cm–2. The intensities of ATR bands due to vibrations of C=O and C–N bonds and aromatic and imide rings practically did not change. [ABSTRACT FROM AUTHOR]

Developing new heating techniques is crucial for manufacturing carbon fiber-reinforced polymer (CFRP) composite parts, as these kinds of components usually need to be chemically cured or physically consolidated under specific temperature fields. Recently, great attention has been paid to differentiated heating methods since they can exert a uniform temperature field on the component and its tooling which always have uneven thermal mass distributions. Moreover, they also offer the possibility of improving the curing or consolidation quality through customized temperature fields. In this paper, we report a differentiated microwave heating method based on pre-designed electromagnetic resonators which has the advantages of wireless connections, quick response, and precise temperature control. To verify the idea, four kinds of resonators with rectangular copper patterns on polyimide films of different thicknesses were first designed and fabricated, making the CFRP laminate have an absorbance of 28%, 47%, 70%, and 81% at different locations. Then, a differentiated heating performance was validated under a fixed microwave power of 1200 W where the temperature of those locations was stabilized at 52.8 °C, 69.1 °C, 86.2 °C, and 93.8 °C, respectively. On this basis, a simulation model with a prediction accuracy of more than 90% was established to model the relationship between the structural parameters of the resonator and the required microwave heating performance. Finally, as a potential application, the proposed method was used to achieve a uniform heating process of a variable-thickness structure. Compared with the overall heating method, the temperature difference was reduced by 82%. [ABSTRACT FROM AUTHOR]

Communication with hand gestures plays a significant role in human‐computer interaction by providing an intuitive and natural way for humans to communicate with machines. Ultrasound‐based devices have shown promising results in contactless hand gesture recognition without requiring physical contact. However, it is challenging to fabricate a densely packed wearable ultrasound array. Here, a stretchable ultrasound array is demonstrated with closely packed transducer elements fabricated using surface charge engineering between pre‐charged 1–3 Lead Zirconate Titanate (PZT) composite and thin polyimide film without using a microscope. The array exhibits excellent ultrasound properties with a wide bandwidth (≈57.1%) and high electromechanical coefficient (≈0.75). The ultrasound array can decipher gestures up to 10 cm in distance by using a contactless triboelectric module and identify materials from the time constant of the exponentially decaying impedance based on their triboelectric properties by utilizing the electrostatic induction phase. The newly proposed metric of the areal‐time constant is material‐specific and decreases monotonically from a highly positive human body (1.13 m2 s) to negatively charged polydimethylsiloxane (PDMS) (0.02 m2 s) in the triboelectric series. The capability of the closely packed ultrasound array to detect material along with hand gesture interpretation provides an additional dimension in the next‐generation human‐robot interaction. [ABSTRACT FROM AUTHOR]

Flexible organic light-emitting diode display devices fabricated on polyimide (PI) substrates have more obvious residual image problems due to the abnormal threshold-voltage (Vth) shifts of a thin film transistor (TFT). In this paper, the Vth shift of TFT fabricated on a PI substrate was analyzed. We explained the worse bias stability and worse recovery of TFT with a PI substrate compared with TFT with a glass substrate, by an interlayer charging effect (Maxwell–Wagner effect) and a technology computer-aided design (Silvaco). When bias stress was applied for a long time, the interface between the PI substrate and the buffer layer will have a charging effect under the action of an electric field, and the charging charge will react on the channel and hinder the formation of the channel. We found that there are differences in the scale of charge under different voltage stress conditions, and this will result in different Vth shifts of driving TFTs for displays units. [ABSTRACT FROM AUTHOR]