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The recent development in smart material-based actuators are composite structures of thin film integrated SMA/PI bimorph in the view of actuator cum sensing in electromechanical systems for medical, robotics, and aerospace application. The purpose of the present work on integrated SMA/PI bimorph is to reveal their ability to perform as actuators and sensors and study on control characteristics for soft robotic, positioning, and valve applications. Vide this research paper, the SMA bimorph actuator [thin film SMA (CuAlNi)/polyimide (Kapton) bimorph] is used as actuator cum sensor for position control. Proposed a Proportional Derivative combined Variable Structure Controller (PD-VSC) to control the displacement by Joule heating actuation in two ways, which are sensor-based control and self-sensing control. From the control characteristics in from of tracking and disturbance rejection, it is concluded that the integrated CuAlNi/Kapton bimorph can be successfully implemented for soft robotic, positioning, and valve applications. [ABSTRACT FROM AUTHOR]

To solve the non-uniformity of stress in space membrane structure and the lack of shear compliant border configuration design method, shear compliant borders are designed, optimized, and verified in terms of configuration. Firstly, an orthotropic model of the borders is built by combining Hill and Christensen-Lo composite material models. Secondly, a finite element form-finding method is put forward by establishing rectangular and cylindrical coordinates in different areas. The configuration of borders is obtained and the influence of the borders on the edge of the membrane is 0.23%, which means that the borders are compatible with the existing tensegrity systems, especially the tensioning components and the cable sleeves. Thirdly, simulation verifies that borders can cut the spread of shear stress and improve the stress uniformity in membrane structure. The maximum stress in the membrane effective area is decreased by 35.6% and the stress uniformity is improved by 30.5%. Finally, a membrane extension experiment is committed to compare the flatness of membrane surface under shear stress with and without shear compliant borders. The borders decrease the increment speed of flatness by 58.1%, which verifies the amelioration of stress uniformity. The shear compliant border configuration design method provides a reference for space membrane structure stress-uniform design. [ABSTRACT FROM AUTHOR]

The growing population of space debris in the near-Earth environment means there is an increased need for space-based detectors, capable of measuring and distinguishing natural space dust and anthropogenic orbital debris populations, to monitor and quantify the relative threat they pose. This has led to much research into the development of new detectors, including those based on time of flight (TOF) designs which can give impact speed and direction. Kapton's favourable properties (e.g. its low mass and ability to be manufactured as thin films) and tried and tested space applications, suggest it may be suitable for use in TOF detectors where impactor speed is measured by passage through several films with known separation. To test the measurement accuracy of such a detector, a prototype Kapton based TOF space dust and debris detector was constructed, and impacted at 2 and 4 km s−1. For a Kapton film thickness of 12.5 μ m and projectiles of 1 mm in size, within experimental uncertainties of ∼1%, there was no difference between incident projectile speed (as measured independently) and that measured by the TOF detector. This, confirms that Kapton based TOF detectors are capable of measuring particle speed to a high degree of accuracy, making them suitable for measuring the near-Earth particle environment. [ABSTRACT FROM AUTHOR]

The hydrolytic stability of polyimide films (PI) in a 0.9% sodium chloride solution in the temperature range of existing biological objects was studied. The kinetic parameters of hydrolysis of PI films were calculated. It was established that the hydrolysis rate constant of an adamantane-containing film was significantly lower than that of an industrial Kapton film. The dielectric constant after hydrolysis was determined. It was shown that the dielectric properties of the adamantane-containing polymer remained unchanged under the hydrolysis conditions. [ABSTRACT FROM AUTHOR]

Gadolia-doped Ceria-Barium Monoferrite (GDC-BaFe 2 O 4) thin films have been deposited on Kapton sheets using the DC sputtering method as electromagnetic (EM) wave-absorbing materials. The present study has examined the structural, magnetic, and microwave absorption properties of GDC-BaFe 2 O 4. The primary approaches used in this investigation included changing the surface form and applying EM wave-absorbing materials as surface coatings. X-ray diffraction research showed that the GDC-BaFe 2 O 4 thin films have an orthorhombic crystal structure. The bonding investigation revealed the existence of Fe-O, Ce-O, and Ba-O-Ba functional groups at 426.87, 517.42 and 1014.84 cm−1, respectively. Vibrating-sample magnetometry confirmed that saturation magnetization decreased with increasing sputtering time and revealed the ferromagnetic behavior of the GDC-BaFe 2 O 4 thin film. Ce, Gd, Ba, Fe, and O were evenly and similarly distributed over the Kapton surface of the GDC-BaFe 2 O 4 thin films, according to energy-dispersive X-ray spectroscopy and scanning electron microscopy. Based on the atomic force microscopy test, the root-mean-square roughness (R q) increased during the ion implantation procedure. With a 7.5-minute sputtering period, the microwave absorption ability reached a maximum reflection loss value of −39.6 dB (99.98 %) at 10 GHz. As a result of these findings, GDC-BaFe 2 O 4 appears to be a promising candidate for EM wave absorption. • DC sputtering was successfully used to generate Gadolia-doped Ceria-Barium Monoferrite thin films on Kapton substrates. • Ion implantation is used to modify the surface geometry of absorbent materials. • The GDC-BaFe 2 O 4 thin film has the ferromagnetic behavior. • The microwave absorption ability reaches a maximum reflection loss value of −39.66 dB (99.98 %) in the range of 10 GHz. • The GDC-BaFe 2 O 4 material was promising prospect for application as a microwave absorbing waves. [ABSTRACT FROM AUTHOR]

Advanced wireless communication technology claims miniaturized, reconfigurable, highly efficient, and flexible meta-devices for various applications, including conformal implementation, flexible antennas, wearable sensors, etc. Therefore, bearing these challenges in mind, a dual-band flexible metamaterial absorber (MMA) with frequency-reconfigurable characteristics is developed in this research. The geometry of the proposed MMA comprises a square patch surrounded by a square ring, which is mounted over a copper-backed flexible dielectric substrate. The top surface of the MMA is made of silver nanoparticle ink and a middle polyethylene terephthalate (PET) substrate backed by a copper groundsheet. The proposed MMA shows an absorption rate of above 99% at 24 and 35 GHz. In addition, the absorption features are also studied for different oblique incident angles, and it is found that the proposed MMA remains stable for θ = 10–50°. The frequency tunability characteristics are achieved by stimulating the capacitance of the varactor diode, which connects the inner patch with the outer ring. To justify the robustness and conformability of the presented MMA, the absorption features are also studied by bending the MMA over different radii of an arbitrary cylinder. Moreover, a multiple-reflection interference model is developed to justify the simulated and calculated absorption of the proposed MMA. It is found that the simulated and calculated results are in close agreement with each other. This kind of MMA could be useful for dual-band sensing and filtering operations. [ABSTRACT FROM AUTHOR]

In this article, we report on the electrical performance of AlGaN/GaN high-electron mobility transistors (HEMTs) fabricated using gold (Au)-free process, after being transferred onto flexible Kapton tape. The transfer process followed in this work can be easily scaled-up to wafer level and involves a relatively simple process of epoxy bonding of the thin device layer onto the Kapton substrate. Electrical characteristics of the flexible HEMT indicate 5%–10% higher ON-current when bent with a radius of curvature of 2.1 cm (at low drain bias voltages), while the OFF-state performance remains unaffected. Initially, 2-DEG properties such as field-effect mobility and carrier concentration have been extracted. While FATFET measurements indicate negligible change in field-effect mobility, ${C}$ – ${V}$ measurements indicate $\sim 10$ % reduction in 2-DEG concentration after transfer. The comparison of the electrical characteristics of Au-free HEMTs indicates $\sim 50$ % reduction in the ON-current of the transferred devices. This is attributed to heating of the transistor channel caused due to low thermal conductivity of the polymer Kapton tape. Electrical characteristics of the flexible HEMT carried out under drain pulsing further support the above observation. This work is among one of the few reports on Au-free AlGaN/GaN HEMT operation on flexible Kapton tape. [ABSTRACT FROM AUTHOR]

Elastic peak electron spectroscopy (EPES) was employed to measure the inelastic mean free path (IMFP) for energies between 500 and 1600 eV for five insulating organic compounds: Kapton, polyethylene (PE), poly(methyl methacrylate) (PMMA), polystyrene (PS) and polytetrafluoroethylene (PTFE). A Ni and a Si sample were used as reference materials to avoid measurement of the elastic reflection coefficient in absolute units. Correction of experimental elastic peak intensities for surface excitations was performed which turned out to be essential. The results are compared with recent evaluations of optical constants to yield the IMFP in the literature giving satisfactory agreement, with deviations generally below 20%. Investigation of the kinematics in an electron reflection experiment shows that the dispersion coefficient used in REELS data analysis cannot be identified with the true plasmon dispersion. [ABSTRACT FROM AUTHOR]

Toxic gases are responsible for the loss of many human lives around the world, which is increasing every year. Toxicity can have various biological aspects on the human body. The exposure to its gases leads to harmful consequences for the organism, which leads to metabolic reactions and even death. For this purpose, the initial step is to detect these gases with miniature flexible structures and solid progressed estimation methods using a simulation software tool. The studied sensor is based on the frequency characterization of an RF Planar Resonant Structure, in which the active element is a patch of radiating graphene printed on a polyimide film (Kapton). The objective of this work is to use our Graphene-Kapton sensor for non-invasive testing applications. In our case, the device is tested to detect and recognize several dangerous and toxic gases such as Fluorine azide (F2N), Hydrogen Iodide (HI), Nitrogen (N2), Methane (CH4), and Carbon monoxide (CO). The simulation results indicate that the Graphene-Kapton flexible sensor exhibits an important sensing performance. The sensor is able to detect all the tested gases with a good sensitivity depending on each gas. As well as, the sensor shows a high sensitivity (0.1± 0.01)* 106 [ppm]-1 (0.1 [ppt]-1) of methane (CH4) gas with detection limit of (9±0.1) *10-6 ppm (9 ppt). [ABSTRACT FROM AUTHOR]

Reflection electron energy loss spectra (REELS) were measured for five insulating organic compounds: Kapton, polyethylene (PE), poly(methyl methacrylate) (PMMA), polystyrene (PS) and polytetrafluoroethylene (PTFE), as well as for Ni and Si, in the energy range between 200 and 1600 eV. The average number of surface excitations for a single surface crossing were determined from the experimental data and were found to be considerably smaller than for earlier studied materials, which mainly consisted of elemental metals [Surf. Sci. 486(2001)L461]. The surface excitation parameter, a material parameter used to quantify the relative intensity of surface losses in (photo)electron spectroscopy, was extracted from the data and compared with values found in the literature. The results indicate that surface excitations only have a minor influence on quantification of XPS spectra of polymers. On the other hand, a correction for surface excitations turns out to be essential for measurements of the electron inelastic mean free path of polymers when a metal is used as reference material. [ABSTRACT FROM AUTHOR]

The increasing usage of perovskite solar cells is being driven by their high efficiency and cost-effective manufacture. Polyethylene Terephthalate (PET) and Polyethylene Naphthalate (PEN) are flexible, transparent, and cost-effective. However, issues have been raised about their long-term stability, especially to the sensitivity of perovskite materials to environmental conditions like as moisture and heat, as well as the challenge of oxygen and moisture transmission across these substrates. Researchers are investigating Polyimide (PI), particularly colorless PI, for enhanced stability, but the techniques are costly. Kapton, a popular colored PI, provides excellent thermal and electrical insulation, but its reduced transparency provides optical issues. In this study, finite-difference-time-domain (FDTD) modeling and experimental analysis were utilized to investigate the optical properties and efficiency of perovskite solar cells on Kapton, PET, and glass substrates. According to the modeling, using Kapton instead of traditional substrates leads to a decrease of 16.6 % in the solar cells short circuit current (J SC). In laboratory experiments, by adding lithium (Li) as the dopant in the electron transport layer (ETL), the sheet resistance of the ETL was reduced from 214 to 2.4 kΩ/□. According to modeling, this enhancement resulted in a 3 % increase in the power conversion efficiency (PCE) of the solar cell, increasing to 17.4 % compared to 16.8 % on a PET substrate. Furthermore, using a Kapton substrate improves critical performance parameters like open circuit voltage (V OC) and fill factor (FF). • FDTD simulation for flexible perovskite solar cell structure. • Kapton substrate reduces absorption in perovskite layer compared to PET. • Deposited TiO 2 layer on Kapton has fine particle distribution and high coverage. • Li-doped TiO 2 enhances electron transport, V OC , and FF in solar cells. • Modified flexible solar cell on Kapton displayed 17.4 % efficiency. [ABSTRACT FROM AUTHOR]

Experimental study of current-voltage (I-V) characteristics and frequency dependences of impedance in copper-Kaptoncopper structures in the temperature range 240 - 300 K were carried out. Concentration and mobility of charge carriers thermally excited from traps with exponential distribution by energy in Kapton bulk and metal-Kapton interface and injected from copper electrodes into Kapton were estimated from the fitting of experimental I-V curves within the frame of the model of the space charge limited current (SCLC). Concentration and the width of energy of localized states, arising from the disorder of the Kapton structure, are additionally estimated from the I-V characteristics. [ABSTRACT FROM AUTHOR]

• Hypervelocity impact flash is reported on thin Kapton films at speeds up to 5 km s −1. • The flashes from two layers of film provide a time of flight and hence projectile speed. • The accuracy of the speed is good to 1%. The impact flash from hypervelocity impact on thin (12.5 µm) Kapton film was observed. The projectile sizes ranged from 0.1 to 1 mm, with speeds from 2 to 5 km s−1 and penetrated the Kapton intact, leaving holes the same size as the projectile (to within measurement errors). The flash intensity (normalised to impactor mass) scaled with impact speed to the power 5.5. However, the data also suggest that at constant speed the intensity scales with the area of the hole in the Kapton and not the projectile mass (i.e. with some property of the target and not as a function of the projectile energy or momentum). Using two layers of Kapton, it was possible to construct a Time of Flight (TOF) system, which used the time of the onset of the flash in each layer to produce flight speeds accurate to within typically 1%. When compared to the projectile speed pre-impact, there was no indication of projectile deceleration during passage through the Kapton film. In addition, when PVDF acoustic sensors were placed on the Kapton film, they exhibited an electromagnetic "pick-up" signal from the impact of projectile on the Kapton, confirming suspicions of signal interference from past work with acoustic sensors. The ability of the light flash to provide accurate impact timing signals suggests the TOF system would be suitable for use as a cosmic dust or debris impact detector in space (e.g. Low Earth Orbit). [ABSTRACT FROM AUTHOR]

This study investigates the properties and performance of bismuth ferrite thin films on Kapton sheets as electromagnetic (EM) wave-absorbing materials. The main techniques employed in this study involved modifying the surface geometry and using electromagnetic wave-absorbing materials as surface coatings. X-ray diffraction analysis revealed a cubic crystal structure of the bismuth ferrite thin films. The bonding analysis showed the presence of Bi–O and Fe–O functional groups at 432.26 and 519.48 cm−1, respectively. Vibrating-sample magnetometry revealed the ferromagnetic behavior of the bismuth ferrite thin film, confirming that saturation magnetization decreased with increasing sputtering time. Moreover, the calcination temperature affected the coercive field; the higher the calcination temperature, the higher the coercivity of the BiFeO 3 (BFO) thin film layer. Scanning electron microscopy with energy-dispersive X-ray spectroscopy of the bismuth ferrite thin films revealed the presence of Bi, Fe, and O—evenly and homogeneously distributed on the Kapton surface. After the ion implantation process, the atomic force microscopy test results showed an increased root-mean-square roughness (R q). The root-mean-square roughness value for Kapton before the process was approximately 7.5 nm, while the root-mean-square roughness values for BFO 10 min and BFO 12.5 min were approximately 18.8 nm and 25.3 nm, respectively. The microwave absorption ability reached a maximum reflection loss value of − 40.4 dB (99.9 %) in the range of 9.98 GHz with a sputtering duration of 10 min. Therefore, these results suggest bismuth ferrite is a potential candidate as an EM wave absorber. [ABSTRACT FROM AUTHOR]

Degradation in Kapton foil after gamma irradiation at low fluence is presented. These foils are irradiated for doses ranging from 10 to 500 kGy. The irradiated (10–50 kGy) Kapton foils show an uniform increase in visible absorption from 500 to 800 nm that decreases for further irradiation up to 500 kGy. FTIR spectra show first decrease in the absorption for all the peaks from 10 to 50 kGy and then increase from 50 to 500 kGy irradiation. Absorption of water moisture has also been observed at low fluence (∼10 kGy) that decreases at higher doses of irradiation. Difference spectra of Kapton before and after irradiation show chain scission at low fluence. This chain scission creates various types of defects, radicals and color centers. The reorganization/cross-linking of bonds is found at higher doses (>50 kGy) of irradiation, where the moisture absorbed at low doses of irradiation plays an important role. The Kapton foil shows opposite nature in terms of chain scission and cross-linking in comparison to the Poly (methyl methacrylate) irradiated in similar conditions. [ABSTRACT FROM AUTHOR]

PEPITES is a new type of transparent beam profiler (<10 µm water-equivalent thickness (WET)) under development that will equip the beam line of the ARRONAX cyclotron. Segmented electrodes consisting of nanometric thick gold strips deposited on a thin polymer membrane make the active part. In order to characterize the damages induced in the polymer, UV–Vis spectroscopy and scanning electron microscope have been used on 8 μm thick Kapton polyimide membranes irradiated with 68 MeV proton beams up to 7 × 1015 H+/cm2. Dynamic and permanent damage was observed only at a high fluence level, thus ensuring long-term operation of the PEPITES detector in its nominal working environment. [ABSTRACT FROM AUTHOR]

Indirect recoil implantation following a nuclear reaction is a technique used to activate the surface of materials that cannot be directly activated by a charged particle beam. This research focuses on the indirect activation of Kapton® foils, which serves as a model of plastic or plastic coated surface activation. The alpha particle primary beam, produced by a cyclotron accelerator hits a stack of titanium and Kapton® interlaced foils. The implanted activity in the Kapton® foils is presented as a function of the primary beam energy for two separate implanted radioisotopes 51Cr and 48V, having suitable nuclear parameters for tracing in engineering experiments. [ABSTRACT FROM AUTHOR]

Contact electrification is a direct triboelectrification method for producing current through charge transfer when two different differentiated materials have brought into contact. For the first time, we developed a simple triboelectric nanogenerator (TENG) where the electronic charges were realized through contact separation mode between sand-polished Kapton (SPK) and Al surface. Here, we demonstrated the energetic interfacial contact between these surfaces and observed satisfactory output performance. The novel SPK-TENG produced 40 V and 2.8 µA, of open-circuit voltages (Voc) and short-circuit currents (Isc) at 4 Hz, respectively. Mainly, the SPK-TENG was dramatically increased up the performance of TENG, up to 40% of Voc and 42% of Isc, with respect to the Kapton film because the mobility of electrons is very high on the device surface compared to the other pristine Kapton film. The fabricated SPK-TENGs were good candidates for satisfying the need for alternative contact separation mode TENGs. [ABSTRACT FROM AUTHOR]

We aim to determine the detection threshold of Kapton as an Etched Track Detector irradiated with 345 MeV/u U ion, as well as other several heavy ions of Al, Si, Ar, Kr and Xe. The heavier ions are found to have higher detection threshold in the stopping power. At the same stopping power, the track registration sensitivity decreases with increasing the nuclear charge of ions. U ion has the lowest sensitivity as S = 0.04 at the detection threshold of 3400 keV/μm. We have updated the conventional radial dose distribution theory using a relatively new experimentally supported formula for the effective charge up to U ion. The local doses at a track radius of 0.8 nm, which is half of the length of a repeat unit of Kapton, is useful to understand the relation between the sensitivity of heavy ions and the stopping power at each detection threshold. [ABSTRACT FROM AUTHOR]

Purpose: We developed a new class of aerogel‐based thin‐film self‐powered radiation sensors employing high‐energy electron current (HEC) in periodic multilayer (high‐Z | polyimide aerogel (PA) | low‐Z) electrode microstructures. Materials: Low‐Z (Al) and high‐Z (Ta) electrodes were deposited on 50 μm‐thick PA films to obtain sensors with Al‐PA‐Ta‐PA‐Al structures. Sensors were tested with x rays in the 40–120 kVp range and with 2.5 MV, 6 MV, and 6 MV‐FFF linac beams (TrueBeam, Varian). Performance of PA‐HEC sensors was compared to commercial A12 Farmer ionization chamber as well as to radiation transport simulations using CEPXS/ONEDANT with nanometer‐to‐micrometer spatial resolution. The computations included periodic and single‐element structures N x (Al‐PA‐Ta‐PA‐Al) with variable layer thicknesses. Results: Signal from PA‐HEC sensors was proportional to the simulated net leakage electron current (averaged over the PA thickness). Experimental response was linear with dose and independent of dose rate. Detector responses to different x‐ray sources show higher signals for kVp photon energies, as expected, though a strong signal was obtained for MV energies as well. The signal scaled with total effective area inside the multielemental structures; for example, the yield of a multielement sensor made with 20 Ta layers compared to a single‐element structure with 1 Ta layer of the same total thickness of Ta was 10 times greater for 6 MV beam and 23 times greater for 120 kVp. Beam attenuation per element in the detector was 0.5%, 1%, 3%, and 46%, respectively for 6 MV, 6 MV FFF, 2.5 MV, and 120 kVp. Conclusion: We demonstrated the feasibility of aerogel‐based multilayer HEC radiation detector and its application for flux/dose monitoring of kVp and radiotherapy MV beams with small beam attenuation. [ABSTRACT FROM AUTHOR]

Abstract Large, thin, prestressed membranes known as 'gossamer' structures have many applications in space, including light reflection and electromagnetic signal collection. The prestress forces applied to these structures usually causes some wrinkling of the membrane to occur, and the degree of wrinkling affects the reflective performance of the structure. The primary aim was to assess whether solar radiation pressure could affect the wrinkle pattern of gossamer structures, with a particular focus on solar sails. Several prestressed rectangular membranes with dimensions and material properties representative of current and future solar sails, a class of membrane structures typically made of Kapton, were modelled to investigate the effects of pressure on the wrinkle pattern. It was shown that increasing the pressure applied normal to the membrane surface increased the amplitude and decreased the wavelength of the wrinkles. However, no significant change in the wrinkle pattern was found to occur until the magnitude of the applied pressure was much greater than that likely to be experienced by gossamer structures due to solar radiation pressure. Therefore it was concluded that the effects of solar pressure will have no significant impact on the future development of larger and thinner gossamer structures than exist at present. [ABSTRACT FROM AUTHOR]

[Display omitted] • The cleavage of polyimide upon impact by atomic oxygen can be divided into three stages. • Under the impact of atomic oxygen, the protective coating protects the substrate much better than the mixed filler material. • The protective effect of the SiO 2 protective coating is superior to that of graphene due to its serrated structure. • Sio 2 absorbs and stores incident atomic oxygen and reacts with subsequent incident atomic oxygen. KAPTON-type polyimide (PI) is a crucial polymer that is often used in the aerospace industry, but the high levels of atomic oxygen (AO) in low-earth orbit (LEO) can cause the polymer to deteriorate and peel, so it is especially important to protect PI from AO. Incorporating nano-reinforcements into PI and applying a protective coating to the surface of PI are the two basic strategies for shielding PI from AO impact. Herein, to investigate the effect and mechanism of different protection methods, molecular models of PI reinforced with graphene (Gr) and carbon nanotubes (CNTs) as well as covered by silica (SiO 2) and Gr, respectively, are constructed. Reactive molecular dynamics simulations are then performed to explore the degradation mechanisms of PI under AO impact. Results indicated that the addition of CNT and Gr can improve the resistance of PI to AO erosion, and their protective effect is mainly by burying in the PI substrate to prevent the penetration of AO downward. Additionally, the protective effect of covering the PI surface with a protective layer is significantly better than that of mixing nanomaterials into the PI substrate. Meanwhile, the protective effect of the Gr protective layer is weaker than that of SiO 2 due to its smooth surface, which tends to slip when AO is incident, and it plays a protective effect mainly by bouncing the incident AO. By comparison, the SiO 2 protective layer can be embedded into the substrate due to its serrated structure, which better protects the substrate, and it protects the substrate mainly by absorbing the incident AO. This study provides useful guidance for the identification of promising candidate materials for LEO applications, as well as for the development of molecular design for AO-resistant polymeric materials. [ABSTRACT FROM AUTHOR]

It is a challenge to simultaneously achieve a high selectivity and permeance for the glassy polymeric membranes. Herein, the asymmetric Kapton membrane fabricated by pyromellitic dianhydride and 4,4′-oxydiphenylenediamine was prepared by the phase inversion method and characterized by rheometer, SEM, TGA, FT-IR and tensile testing. The aim of this work is to enhance gas separation performance of the membrane and its application value via optimizing the concentration of acetone additive, coagulation bath composition and evaporation time. After optimizing, results showed that the transition from the instantaneous coagulation to the delayed coagulation, and the inner membrane structure is gradually transferred from the finger-like shape to the sponge-like shape. The optimized gas separation performance of the resulting Kapton membrane has the permeance of 2.49 GPU and 1.10 GPU for H 2 and CO 2 , respectively, as well as selectivity of 57.07 and 25.27 for H 2 /CH 4 and CO 2 /CH 4 , respectively. [Display omitted] • A facile phase inversion method for the fabrication of a high-performance asymmetric Kapton membrane. • A defect-free membrane structure was prepared by the optimization of a series of operation parameters. • A high permeance of 2.49 GPU and 1.10 GPU for H 2 and CO 2 , respectively. • A high selectivity of 57.07 and 25.27 for H 2 /CH 4 and CO 2 /CH 4 , respectively. [ABSTRACT FROM AUTHOR]

Abstract: In this study, polystyrene‐ and poly(methyl methacrylate)‐grafted polyimide films were prepared successfully using click chemistry and the ATRP technique. Firstly, kapton films were prepared from stepwise thermal imidization of polyamic acid. Surface modification of kapton films was then achieved by chloromethylation followed by the azide decoration process. For surface grafting of kapton films, polystyrene and poly(methyl methacrylate) as alkyne functional polymers were prepared with alkyne and bromine double functionality using propargyl‐2‐bromopropionate as an initiator. A coupling reaction with azide‐decorated PI surface and alkyne functional polymers was achieved via the Huisgen‐1,3‐dipolar cycloaddition reaction. FTIR spectroscopy, contact angle measurement, thermogravimetry (TG) and differential scanning calorimetry (DSC), energy dispersive X‐ray analysis (EDX) and GPC techniques were used to characterize the grafted polyimides. According to the TG analysis, kapton film was modified at the rate of 8% and 10% with PS and PMMA, respectively. [ABSTRACT FROM AUTHOR]

A continuous and uniform AZ31 magnesium alloy coating was deposited by magnetron sputtering to protect flexible polyimide substrate (Kapton HN) from atomic oxygen (AO) erosion-corrosion in low earth orbit. The AO erosion yield of the coated Kapton was determined to be 8.87 × 10 −26 cm 3 atom −1 after exposure to AO fluence of 1.47 × 10 21 atoms cm −2 , about 34 times lower than that of blank Kapton. XPS analysis results showed that an oxide layer of MgO formed on the surface of the coating after AO exposure, which is the main reason for the enhanced AO erosion-corrosion resistance of the AZ31 Mg-alloy coating. [ABSTRACT FROM AUTHOR]

The effect on aircraft materials in the near space environment is a key part of air-and-space integration research. Ozone and aerodynamic fluids are important organizational factors in the near space environment and both have significant influences on the performance of aircraft materials. In the present paper a simulated ozone environment was used to test polyimide material that was rotated at the approximate velocity of 150–250 m/s to form an aerodynamic fluid field. The goal was to evaluate the performance evolution of materials under a comprehensive environment of ozone molecular corrosion and aerodynamic fluids. The research results show that corrosion and sputtering by ozone molecules results in Kapton films exhibiting a rugged “carpet-like” morphology exhibits an increase in surface roughness. The morphology after ozone exposure led to higher surface roughness and an increase in surface optical diffuse reflection, which is expressed by the lower optical transmittance and the gradual transition from light orange to brown. The mass loss test, XPS, and FTIR analysis show that the molecular chains on the surface of the Kapton film are destroyed resulting in C C bond breaking to form small volatile molecules such as CO 2 or CO, which are responsible for a linear increase in mass loss per unit area. The C N and C O structures exhibit weakening tendency under ozone exposure. The present paper explores the evaluation method for Kapton’s adaptability under the ozone exposure test in the near space environment, and elucidates the corrosion mechanism and damage mode of the polyimide material under the combined action of ozone corrosion and the aerodynamic fluid. This work provides a methodology for studying materials in the near-space environment. [ABSTRACT FROM AUTHOR]

An optical strain sensor was developed for use in stretchable electronics. It consists of a diffraction grating formed directly on the examined surface illuminated by a laser beam which creates interference pattern. This pattern can then be used to determine axial and lateral strains for a uniaxial stress states. Direct laser interference patterning was employed as a fast processing tool for the preparation of micro- and sub-microgratings. Two coherent beams of Nd:YAG laser with 532 nm wavelength and pulse duration of 10 ns were used to selectively remove material from the irradiated sample surface. This technique creates periodic pattern on the metallized surface of polymeric substrates. New sensors formed by direct laser interference patterning method were able to resolve higher order diffraction maxima, which would be of benefit for strain measurement application. Experimental setup for tensile tests was composed of laser probe, the sensor element, and CCD camera. To extract strain values, we analysed acquired interference pattern images in real time software, developed with LabVIEW environment. This kind of contactless strain sensor is suitable for examination of stretchable electronics component for which conventional tensile tests are either not acceptable or can interfere with its normal operation. [ABSTRACT FROM AUTHOR]

In the past few years, the Aerospace Corporation and other labs have been exploring how electrostatic discharges propagate over the surface of a positively charged dielectric surfaces, like solar arrays, on a spacecraft. One goal of these explorations is ultimately to aid in the extrapolation of transient currents measured on coupons in the laboratory to currents expected on full-scale spacecraft assemblies. In the popular plasma bubble model, the electrostatic discharge plasma is expected to expand radially from a single arc initiation point at the ion sound velocity, which depends on the composition of the conductor at that initiation point. In this paper, we examine how changing the conductor material at the arc initiation site affects propagation on a positively charged Kapton surface. By measuring current flowing into a series of concentric electrodes beneath this Kapton surface, we can monitor surface neutralization as a function of time and radial distance from the arc site. Results will be presented for a selection of cathode materials, and implications for existing and future models will be discussed. [ABSTRACT FROM AUTHOR]

A statistical design of experiments (DoE) was used to evaluate the effects of CF 4 O 2 plasma on Kapton films in which the duration of treatment, volume ratio of plasma gases, and microwave power were selected as effective experimental factors for systematic investigation of surface modification. Static water contact angle ( θ W ), polar component of surface free energy ( γ S p ) and surface O/C atomic ratio were analyzed as response variables. A significant enhancement in wettability and polarity of the treated films compared to untreated Kapton films was observed; depending on the experimental conditions, θ W very significantly decreased, showing full wettability, and γ S p rose dramatically, up to ten times. Within the DoE the conditions of plasma treatment were identified that resulted in selected optimal values of θ W , γ S p and O/C responses. Surface chemical changes were detected by XPS and ATR-IR investigations that evidenced both the introduction of fluorinated groups and the opening of the imide ring in the plasma-treated films. [ABSTRACT FROM AUTHOR]

Due to a smooth hydrophobic surface of Kapton film, it is very difficult to coat an inorganic oxide coating on its surface. In this study, the surface of Kapton was treated by NH3·H2O and silicon coupling agent to improve the polymer surface wettability. Changes in surface hydrophilicity were studied by contact angle measurement. The samples were irradiated by atomic oxygen (AO) in a ground-based simulation system. TiO2/SiO2 multi-layer coatings were prepared on the surface of Kapton by sol-gel method to resist AO erosion. The optical transmittance and surface morphology of samples were investigated by UV-vis spectroscopy and scanning electronic microscope. The results indicated that the TiO2/SiO2 sol could easily form a uniform thin coating on the surface of pretreated Kapton. After AO exposure, the coatings became more compact, without peeling off. The AO erosion yield value of coated Kapton was sharply down, and the samples had good optical transparency. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Interaction of high energy electrons with spacecraft materials, such as polyimide (PI, Kapton®), is known to cause their physical degradation. In this paper, we investigated chemical and optical changes in Kapton® during and after irradiation with high energy (90 keV) electrons. Several complimentary characterization techniques were utilized to qualify and quantify radiation induced property changes in the material, including directional-hemispherical reflectance (DHR) coupled with Fourier transform infrared (FTIR) spectroscopy, electron paramagnetic resonance (EPR), and the surface potential decay method. It was found that the conductivity of radiation-damaged PI is significantly increased compared to that of the pristine material. This change is attributed to the creation of radicals during irradiation, which could play a critical role in the transport of electrons through the bulk of the damaged material. Excessive radicals are likely originating from a radiation-induced breakage of phenyl rings and/or ether bridges forming a metastable carbonyl. [ABSTRACT FROM AUTHOR]

This letter presents the design of a flexible highly efficient antenna for Wireless Energy Transfer (WET) at 13.56 MHz. The proposed antenna uses very thin kapton, with a thickness of 25 µm as a substrate, and an 18 µm layer of copper as the conductive material. The 40 mm x 40 mm 6 loop antenna produces almost 90% ETE (energy transfer efficiency) and a bandwidth (BW) of almost 4 MHz for inductive wireless communications. This flexible antenna is suitable for use in small mobile devices, for wireless charging and communication purposes at the NFC operating frequency. In addition, kapton offers very high durability, high mechanical strength, and unique distortional resistance to harsh environments and corrosive aqueous etchants, in this way increasing the reliability of the antenna. [ABSTRACT FROM AUTHOR]

Kapton film, which is a typical aromatic polyimide (PI) film, exhibits excellent thermal stability and flexibility. Therefore, it is used widely for flexible printed circuit boards in combination with other resins and metals. However, this makes it difficult to recycle it. In this work, we focused on the steam pyrolysis technique, which is a method of depolymerizing condensation polymers without solvents, catalysts, or high pressure, as a way of overcoming this issue. The steam pyrolysis of Kapton film was carried out using a thermogravimetric (TG) analyzer equipped with a steam generator. In addition, the TG results were evaluated further using model fitting techniques. It was found that steam enhanced the hydrolysis of the imide ring, which occurred on the surface of the PI film. The hydrolysis selectivity was as high as 89% at 528 °C. However, steam did not significantly enhance the Kapton decomposition rate, owing to rapid carbonization, which took place because of the simultaneous occurrence of pyrolysis. Thus, the obtained results implied that high-yield monomer recovery can be achieved by lowering the temperature to prevent pyrolysis and by improving the steam contact efficiency to enhance hydrolysis within the material. [ABSTRACT FROM AUTHOR]

The focus of this study is the preparation of carbon-based materials that satisfy the requirements of developing quasi-optic controllable absorbers for terahertz technology. These materials have been obtained from a commercially available organic polymer, Kapton ® HN polyimide, through a pyrolysis process conducted in an inert atmosphere at different temperatures. The pyrolysis of Kapton film up to 1200 °C left a black residue principally composed of graphitic-carbon with a yield of about 55%. The D.C. conductivity of materials measured at 295 K increases with increasing pyrolysis temperature. The starting organic polymer is turned from an insulator to conductor material when heat-treated at over 700 °C. Moreover, in the frequency range 220–500 GHz, the pyrolyzed materials show distinct optical properties, which have variant degrees of terahertz absorption. Kapton ® HN polyimide that is thermally converted into carbon-based materials may be used for the realization of calibrated terahertz absorbers, particularly for thermal transducers. [ABSTRACT FROM AUTHOR]

In this communication, a fully organic dual-band antenna is presented. It consists of a coplanar waveguide coupled to an elliptical monopole antenna designed on a kapton substrate. This antenna is fabricated from a process, based on the use of a conductive polymer (Polyaniline) doped with multiwall carbon nanotubes, that has been optimized for this application. The flexibility of both kapton substrate and doped conductive polymer gives the antenna the ability to be freely crumpled paving the way to body-worn high data rate communications at microwave frequencies. Applications in wireless networks can also be addressed by using this kind of antennas. In this study, a comparison between the performance of an antenna under bending conditions (using a three-dimensional support) and its uncrumpled version is presented. We evaluate the crumpling effect on the resonant frequency, the bandwidth and the radiation patterns. A good agreement is observed between measurements and simulations data, even when the antenna is crumpled. [ABSTRACT FROM PUBLISHER]

The leak rate of helium gas through thin Kapton HN foils was measured for various temperatures between 310 and 150 K and gas pressures ranging from 10 to 300 mbar. From these measurements the permeability constant P ( T ) and its temperature dependence were determined. At room temperature the permeability constant for Kapton HN is P ( T =296 K ) = ( 2.56 ± 0.31 ) barrer. The temperature dependence of P ( T ) was verified to drop exponentially with decreasing temperature, causing a change in the permeability by more than two orders of magnitude in the range between 310 and 150 K. [ABSTRACT FROM AUTHOR]

An increasing body of research has been dedicated to determining the magnitude and scaling of spurious electrostatic discharge current transients on solar arrays and other spacecraft dielectrics under inverted gradient charging conditions. A flashover propagation velocity is typically determined, and assumed to be a single constant number that characterizes the collection of events. The complexity of flight-like test articles and diversity of methods used for deriving this velocity from laboratory data have led to apparently conflicting results. In this paper, we attempt to clarify the radial dynamics of electrostatic discharge (ESD) plasmas on a positively charged surface via the use of a simple test article, composed of eight concentric annular electrodes covered with Kapton. Time-resolved induced ESD currents, recorded as a function of electrode radial distance from the inception point, were used to derive empirical velocity distributions. These distributions lead to a number of effects, such as \sim 1/r^2 scaling with distance at the beginning of a discharge. Implications for ESD propagation and comparison with previous studies are discussed. [ABSTRACT FROM PUBLISHER]

We have studied the energy shift introduced by surface charging during the course of ion beam analysis of an insulating material (a Kapton thin film) using Rutherford Backscattering Spectrometry (RBS). The potential that develops was found to be proportional to both the incident ion energy and the sample thickness. This correlation suggests a conductance mechanism that is based on the ion beam induced carriers that are generated in the material. A simple relationship between the mobility of the induced carriers and the built-up surface potential has been derived. It provides a semi-quantitative explanation for the observed spectral offset. This relationship also provides important insight into the electrical characteristics of the insulating material being irradiated. In the specific case of Kapton, we observed a split of the high energy edge in the RBS spectra, which we suggest is most likely a reflection of the presence of both amorphous and crystalline forms of Kapton. Some contribution from partial discharge of the surface potential to the surrounding is also considered. [ABSTRACT FROM AUTHOR]

Purpose: Flexible microcoils integrated with ablation catheters can improve the temperature accuracy during local MR-thermometry in Nd:YAG laser interstitial thermal therapies. Here, the authors are concerned with obtaining a preliminary confirmation of the clinical utility of the modified catheter. They investigate whether the thin-film substrate and copper tracks of the printed coil inductor affect the symmetry of the thermal profile, and hence of the lesion produced. Methods: Transmission spectroscopy in the near infrared was performed to test for the attenuation at 1064 nm through the 25 jum thick Kapton substrate of the microcoil. The radial transmission profile of an infrared high-power, light emitting diode with >80% normalized power at 1064 nm was measured through a cross section of the modified applicator to assess the impact of the copper inductor on the optical profile. The measurements were performed in air, as well as with the applicator surrounded by two types of scattering media; crystals of NaCl and a layer of liver-mimicking gel phantom. A numerical model based on Huygens-Fresnel principle and finite element simulations, using a commercially available package (COMSOL Multiphysics), were employed to compare with the optical measurements. The impact of the modified optical profile on the thermal symmetry was assessed by examining the high resolution microcoil derived thermal maps from a Nd:YAG laser ablation performed on a liver-mimicking gel phantom. Results: Less than 30% attenuation through the Kapton film was verified. Shadowing behind the copper tracks was observed in air and the measured radial irradiation correlated well with the diffraction pattern calculated numerically using the Huygens-Fresnel principle. Both optical experiments and simulations, demonstrate that shadowing is mitigated by the scattering properties of a turbid medium. The microcoil derived thermal maps at the end of a Nd:YAG laser ablation performed on a gel phantom in a 3 T scanner confirm that the modified irradiation pattern does not disrupt the thermal symmetry, even though, unlike tissue, the gel is minimally scattering. Conclusions: The results from this initial assessment indicate that microcoils can be safely integrated with ablation catheters and ensure that the complete necrosis of the liver tumor can still be achieved. [ABSTRACT FROM AUTHOR]

Indium tin oxide (ITO) has been widely used as the electrode material in touch-screen displays and solar cells attributing to its combined high electrical conductivity and optical transparency. Moving forward from wafer based electronics to flexible/stretchable electronics, brittle electronic materials like ITO are significantly hindering the deformability of the integrated systems. To minimize strains in inorganic materials when subjected to stretch, thin metallic and ceramic films can be patterned into serpentine shapes. Although metallic serpentines have received extensive studies, experimental investigations on ceramic serpentines have not been reported. We perform uniaxial tension tests on Kapton-supported ITO serpentine thin films with in situ electrical resistance measurements. It is found that the narrower serpentine ribbons are more stretchable than their wider counterparts. We propose a generic empirical equation to predict the stretchability using three dimensionless geometric parameters. Conclusions reached for Kapton-supported ITO serpentine films are generally applicable to gold, silicon, and other stiff serpentine films bonded to stiff polymer substrates such as Kapton and polyethylene terephthalate. [ABSTRACT FROM AUTHOR]

We present measurements of the thermal conductivity between 0.05 and 1 K, and radioactive contamination levels, for some thermally isolating materials. TIMET Ti 15-3-3-3, Mersen grade 2020 graphite, Vespel SP-1, Vespel SP-22, Vespel SCP-5000, Vespel SCP-5050, Graphlite CFRP, and a Kapton/epoxy composite are all investigated. Thermal conductivities were measured using a single-heater longitudinal heat flow method. Material radioactivity was determined for the materials at a low background counting facility using a high-purity gamma detector and GEANT4 Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

In this work, a quasi-stationary procedure has been applied to analyze the heat flux from copper samples to liquid nitrogen (\LN2). The purpose is to quantify the influence of the surface treatment on the heat flux. Copper samples with different surface roughness as well as copper samples whose surface had been previously laminated with commercially available Kapton (lamination or self-adhesive tape) have been tested. The experimental procedure consisted in cooling down the copper samples in a liquid nitrogen bath from room temperature to 77.3 K (boiling temperature of \LN2 at atmospheric pressure). During the cool-down, the temperature has been measured and recorded. From the measured temperature data, the heat flux and the boiling curve were calculated for each copper sample. According to the experimental results, the surface roughness does not have a general influence on the cooling behavior. Regarding the laminated samples, results show a significant change in the boiling curve. In this case the cooling capability in \LN2 is therefore enhanced. This behavior is due to the low thermal-conductivity of the lamination material. Indeed, that leads to a small temperature difference between the lamination and the coolant. [ABSTRACT FROM PUBLISHER]

This work presents a promising ultrasound wearable technology based on a piezoelectric transducer, realized on flexible highly oriented Aluminum Nitride, with significant mechanical displacement in spite of being attached on a rigid support. Circular membranes with different radius sizes, based on 1-μm-thick AlN thin film as the active piezoelectric layer, are designed, fabricated, and characterized. The AlN is deposited on kapton HN substrate with a low sputtering deposition temperature that allows the integration and the compatibility with flexible electronics. Mechanical and thermal stability of kapton makes this polyimide based sheet a potential substrate for flexible piezoelectric thin film technology. The actuation at low voltage (1-10 V) of the AlN membranes is studied in air in the range of ultrasound frequencies, from 0 Hz up to 2 MHz; the voltage amplitude, the shape and displacement of the flexure mode (0, 1) is studied by a Laser Doppler Vibrometer to characterize the mechanical properties of the device. [ABSTRACT FROM AUTHOR]

Highlights: [•] Simulation of piezoelectric materials to choose best material for manufacturing. [•] Manufacturing of a nanogenerator on two different substrates. [•] Flexible nanogenerator has a higher output voltage compared to Si nanogenerator. [•] The bending degree of nanowires greatly affects the measured output voltage of nanogenerator. [•] The contact resistance between nanowires and electrode affects output voltage in nanogenerators. [ABSTRACT FROM AUTHOR]

Abstract: Transparent, uniform and adherent ZnO thin films were obtained using radio frequency magnetron sputtering. These films were deposited onto kapton substrates with various thicknesses. Following deposition, some of the ZnO thin films were annealed at different temperatures in air. The morphological structure of ZnO thin films, annealed and as-deposited, was studied using modern methods such as: X-ray photoelectron spectroscopy, X-ray diffraction (XRD) and atomic force microscopy. It was noticed that structural and optical properties of these films depend both on the deposition conditions, annealing temperature and the nature of the used substrate. Therefore, XRD studies showed a polycrystalline structure and a hexagonal symmetry for the obtained thin films. The crystalline structure of the annealed ZnO films exhibited strong orientation along the c axis, with the (002) plane parallel to the kapton substrate. The electrical conductivity of these films, before annealing, has a value between 1.63 and 2.48×10−4 Ω−1 cm−1.The optical analyses were investigated by measuring the transmittance curves that were used to find the optical bandgap energy. Post-deposition annealing of the ZnO/kapton samples led to an increase in the optical bandgap from 3.19 to 3.24eV, emphasizing that annealing and nature of the substrate influence the characteristics of the thin film. [Copyright &y& Elsevier]

Abstract: Carbon nanofibres decorated with metal nanoparticles were deposited over kapton, a polyimide flexible substrate, onto which array interdigitated electrodes in one side and a common heater in the backside were printed using inkjet printing technique. The control over metal type (as-grown, Au, Pd) and the decoration percentage gave us the possibility to improve the sensors response, and also enhance the selectivity by taking advantage of the different interaction behaviors of tested target gas molecules with different hybrid materials that occur at room temperature. [Copyright &y& Elsevier]

A microelectromechanical system (MEMS) device might function perfectly well in the controlled environment in which it has been created. However, the device can be a real viable product only after it has been fabricated with proven performance in a package. As such, the assembly yield of a MEMS package is often a challenging target to meet. The design and fabrication of a free-floating membrane on a flexible substrate to enable easy and cost-effective packaging of MEMS devices is examined. Since standard MEMS fabrication processes are designed for rigid substrates, several process modifications were required to handle flexible substrates. The adaptation of each fabrication process has been documented. Furthermore, detailed information regarding the selection of compatible materials, as well as incompatibilities that were encoun tered, has been presented to aid future researchers in developing processes for flexible substrates. [ABSTRACT FROM AUTHOR]

Abstract: Due to a smooth hydrophobic surface of Kapton, it is very difficult for other materials to bond to it. In this study, using solvothermal method to modify the surface of Kapton substrates, the adhesion between silica film and Kapton substrate was greatly improved. Silica films were prepared on Kapton substrate via sol–gel method and the samples were irradiated by atomic oxygen (AO) in a ground-based simulation system. The AO erosion yield values of the samples after AO irradiation were tested. The surface morphology and the structure of silica films were investigated by scanning electronic microscope (SEM) and Fourier transformed infrared spectroscopy (FTIR). The results indicated that a uniform thin film was easily formed on the surface of Kapton. After AO exposure, the silica films become smoother and more uniform, without peeling off, and the AO erosion yield of coated Kapton was sharply down, equivalent to only 4.7% of pristine Kapton. [Copyright &y& Elsevier]

Abstract: By using surface sol–gel method with perhydropolysilazane (PHPS) as a precursor, a silica coating was prepared on a Kapton substrate as an atomic oxygen (AO) protective coating. The AO exposure tests were conducted in a ground-based simulator. It is found that the erosion yield of Kapton decreases by about three orders of magnitude after the superficial application of the coating. After AO exposure, the surface of the coating is smooth and uniform, no surface shrinkage induced cracks or undercutting erosion are observed. This is because that during AO exposure the PHPS is oxidized directly to form SiO2 without through intermediate reaction processes, the surface shrinkage and cracking tendency are prohibited. Meanwhile, this PHPS derived silica coating also presents self-healing effect due to the oxidation of free Si. Compared with other kinds of silica or organic polymer coatings, this PHPS derived silica coating exhibits a superior AO erosion resistance. [Copyright &y& Elsevier]