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Optical Fiber Sensor Performance Evaluation in Soft Polyimide Film with Different Thickness Ratios
摘要： To meet the application requirements of curvature measurement for soft biomedical robotics and flexible morphing wings of aircraft, the optical fiber Bragg grating (FBG) shape sensor for soft robots and flexible morphing wing was implemented. This optical FBG is embedded in polyimide film and then fixed in the body of a soft robot and morphing wing. However, a lack of analysis on the embedded depth of FBG sensors in polyimide film and its sensitivity greatly limits their application potential. Herein, the relationship between the embedded depth of the FBG sensor in polyimide film and its sensitivity and stability are investigated. The sensing principle and structural design of the FBG sensor embedded in polyimide film are introduced; the bending curvatures of the FBG sensor and its wavelength shift in polyimide film are studied; and the relationship between the sensitivity, stability, and embedded depth of these sensors are verified experimentally. The results showed that wavelength shift and curvature have a linear relationship. With the sensor’s curvature ranging from 0 m?1 to 30 m?1, their maximum sensitivity is 50.65 pm/m?1, and their minimum sensitivity is 1.96 pm/m?1. The designed FBG sensor embedded in polyimide films shows good consistency in repeated experiments for soft actuator and morphing wing measurement; the FBG sensing method therefore has potential for real applications in shape monitoring in the fields of soft robotics and the flexible morphing wings of aircraft.
关键词： polyimide film,sensitivity,micro curvature sensor,soft robotics sensor,embedded depth
更新于2025-11-28 14:24:03
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Molecular dynamics simulation study on the structure and properties of polyimide/silica hybrid materials
摘要： A type of polyimide/silica (PI/SiO2) copolymer model was established through the dehydration of tetraethyl orthosilicate molecules (TEOS) and bonding to a silane coupling agent. The content of SiO2 was controlled by adjusting the number of molecules which bound to the TEOS. Finally, the silica was formed into a hybrid model (hybrid PI/SiO2) with a small molecule embedded in the PI. The model was optimized by geometric and molecular dynamics and the changes in the model structure, Young’s modulus, shear modulus, and glass-transition temperature (Tg) were analyzed. The results showed that the density and cohesive energy density of the composites could be improved by doping SiO2 in PI. Young’s modulus and shear modulus of PI/SiO2 hybrid materials were higher than undoped PI. The tensile strength reached 568.15 MPa when the doping content was 9%. Therefore, the structure design and content control of SiO2 was an effective way to improve the performance of a PI/SiO2 composite. The variation of Tg and tensile strength of PI/SiO2 hybrid composites is consistent with that of PI/SiO2 composite synthesized in real experiment, which will be a convenient method for new material design and performance prediction. ? 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 136, 47335.
关键词： molecular dynamics,shear modulus,Young’s modulus,polyimide/silica,glass-transition temperature
更新于2025-09-23 15:23:52
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Synthesis and characterization of optically transparent semi-aromatic polyimide films with low fluorine content
摘要： A series of novel semi-aromatic polyimides with low fluorine content were prepared from alicyclic dianhydrides, i.e. 1,2,4,5-cyclohexane-tetracarboxylic dianhydride (CHDA) and bicyclo[2.2.2]octa-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA), and three aromatic diamines containing ortho-substituted methyl and pendent phenyl groups, respectively. These polyimides exhibited excellent solubility even though their fluorine content lower than 10 wt.%. Chemical resistance to MEK and aqueous alkali of films was also satisfied for application as flexible substrates. The semi-aromatic polyimides showed outstanding heat resistance with Tg values up to 387 oC and good mechanical strength. These films had excellent optical transparency with cutoff wavelengths of 282-286 nm, transmittance >89% at 500 nm and yellowness indices <14.8. Especially, PIBF-3 and PIBF-6 were extremely transparent and very light color with thickness of 70 μm. Their improved optical transparency and elimination of coloration was mainly attributed to weakened electrophilicity of alicyclic dianhydrides, steric hindrance and distorted non-coplanar caused by ortho-substituted and bulky pendent groups.
关键词： Polyimide films,High transparency,Semi-aromatic.
更新于2025-09-23 15:23:52
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A Novel Multilayer Sandwich Fabric-based Composite Material for Infrared Stealth and Super Thermal Insulation Protection
摘要： At present, infrared stealth materials for advanced detection and stealth technology is usually prepared with low emissivity coating on the surface, but there are very few efficient infrared stealth materials based on textiles with lightweight and flexible features. In this paper, we designed a carbon nanotube-doped aerogel (CNTAs) sandwich structure on polyimide (PI) fabric by hot pressing and then coated with a low emissivity Al-doped ZnO (ZAO) on the outer surface. The surface emissivity lower than 0.5 due to the existence of ZAO and the thermal conductivity of the intermediate interlayer aerogels as low as 0.013 W/(m?K). Additionally, through experiments, theoretical derivation and simulation analysis, we found the resultant composite demonstrated a high infrared stealth performance with super insulation effect, implying it will have a fine prospect in infrared stealth and thermal insulation protection fields with its unique structure and excellent properties.
关键词： Carbon Nanotube-doped Aerogel,Sandwich Structure,Infrared Stealth,Polyimide Fabric,Thermal Insulation,Al-doped ZnO
更新于2025-09-23 15:23:52
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Polyimide-TiO2 nanocomposites and their corresponding membranes: Synthesis, characterization, and gas separation applications
摘要： In this work at firstly a new class of polyimide/TiO2 (PI/TiO2) composites containing amino acid (Methionine) and benzimidazole fractions in the structure with chemical bonds between the polyimide and TiO2 network has been synthesized by the sol-gel reaction and characterized and then secondly carbon (C) membranes were prepared by carbonization of PI/TiO2 at different temperatures under vacuum and nitrogen flow. Carbonization temperature was critical in the modification of membrane structure. At the same temperature, the carbon membranes fabricated under nitrogen atmosphere had higher gas permeations than those fabricated under vacuum. With the introduction of the TiO2, there was no significant enhancement of the gas separation in the resulting PI/TiO2 composite membranes over the PI membrane, which still suffered a "trade-off" relationship between permeability and selectivity. However, the derived C/PI/TiO2 composite membranes exhibited better gas separation properties. The C/PI/TiO2 15% composite membrane produced the highest permeations of 650.47, 520.56, 187.92 and 115.22 GPU for He, CO2, O2 and N2, respectively. The bionanocomposites were analyzed for antibacterial activity against Gram-positive and Gram-negative bacteria. The results indicated that the synthesized bionanocomposites is effective against all of the studied bacteria, and its effectiveness is higher for Pseudomonas aeruginosa.
关键词： Polyimide,Composite membranes,Carbonization,TiO2,Gas permeations
更新于2025-09-23 15:23:52
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Effect of Different Inorganics on Polyimide-based Bragg Grating Humidity Sensor
摘要： Effect of activated carbon and lithium chloride on polyimide-based fiber Bragg Grating relative humidity sensor has been experimentally investigated. Through dip coating process, organic-inorganic hybrid coatings were deposited on fiber Bragg grating to form different relative humidity sensors. Experimental results show that the addition of activated carbon or lithium chloride alone could increase the humidity sensitivity (1.67 times and 1.61 times, respectively), but the structure which contains both lithium chloride and activated carbon increases the sensitivity most (3.9 times). In the 14-day stability test, the fluctuation of pure polyimide sensor is ± 6.5%, while the ones of activated carbon sensor, lithium chloride sensor, activated carbon and lithium chloride sensor are ± 3%, ± 8%, and ± 1.6%.
关键词： lithium chloride,fiber Bragg grating,activated carbon,polyimide,humidity sensor
更新于2025-09-23 15:22:29
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Dynamic operation of liquid crystal cell with inherently nanogroove-featured aligned carbon nanotube sheets
摘要： The use of a highly aligned carbon nanotube (CNT) sheet as a multifunctional constituent for liquid crystal (LC) displays and electro-optic LC applications is assessed. The CNT sheet can perform a dual function: one is an alignment layer for LCs, replacing the commonly used rubbed polyimide film, and the other is a transparent conductive layer, taking the place of indium tin oxide. The hydrophobic treatment improved the adhesion quality between aligned CNT bundles and the glass substrate, which helps to preserve the inherently aligned nanogroove morphology of transparent CNT sheets. The test LC display cells, comprising 4-cyano-4′-pentylbiphenyl molecules sandwiched between CNT-sheet-on-glass substrates, demonstrate the operation characteristics comparable to that of the conventional cell under temperature variation and ac electric field of 1 kHz. The results offer a possibility of deploying multifunctional CNT-sheet alignment layers in LC-based devices, especially in the future flexible display applications.
关键词： Indium-tin oxide transparent conductor,Aligned carbon nanotube sheets,Liquid crystal cells,Polyimide alignment layer for liquid crystal display
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Saint Petersburg, Russia (2018.10.22-2018.10.23)] 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Features of Space Charge Relaxation in a Polyimide Printed Circuit Board
摘要： Polyimide films are widely used as substrates for printed circuit boards. The process of space charge accumulating in dielectric substrates is not highly desirable, since space charge distorted the parameters of the electrical circuits. This work is devoted to the study of the accumulation and relaxation of charge in films of thermoplastic polyimide R-BAPB with different degrees of crystallinity, in order to reduce the accumulated charge and the time of its relaxation. Relaxation mechanisms are analyzed and methods for reducing the relaxation time of the space charge are determined.
关键词： PCB,conductivity,electret,homocharge,relaxation,corona discharge,space charge,crystallinity,polyimide
更新于2025-09-23 15:22:29
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Biomimetic Polyimide-Supported Cuprous Oxide Photocatalytic Film with Tunable Hydrophobicity, Improved Thermal Stability, and Photocatalytic Activity toward CO <sub/>2</sub> Reduction
摘要： Flexible and thermally stable polyimide (PI) ?lms containing a hierarchical surface structure were synthesized as substrates to support visible-light active cuprous oxide for photocatalytic reduction of carbon dioxide for the ?rst time. With the nanocasting technique, the surface structure on the leaves of Xanthosoma sagittifolium was successfully duplicated on PI ?lms. Followed by the ion-exchange process and adequate thermal treatment, cuprous oxide nanoparticles were successfully immobilized on the arti?cial PI leaves and exhibited the capability to photoreduce carbon dioxide into carbon monoxide under visible-light illumination. With the selection of biomimetic structures and adjustment of fabrication parameters, the hydrophobicity and optical absorption edge of the photocatalytic ?lm were tunable. An increase in hydrophobicity improved the yield of carbon monoxide. The introduction of a hierarchical structure on the surface and cuprous oxide within the matrix dramatically enhanced the thermal stability of the PI ?lm. The ?exible photocatalytic ?lm is a promising material for the applications requiring high mechanical and thermal stability, such as industrial ?ue-gas treatments.
关键词： Thermal Stability,CO2 Reduction,Hydrophobicity,Polyimide,Photocatalytic,Biomimetic,Cuprous Oxide
更新于2025-09-23 15:22:29
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Effects of triethylamine on the imidization temperature and properties of PI adhesive
摘要： To make clear the effects of triethylamine(TEA) on the imidization temperature and properties of polyimide(PI) adhesive,precursors poly(amic acid) salt(PAAS) synthesized via 4,4-Diaminodiphenylmethane(MDA),2,2-Bis[4-(4-aminophenoxy)phenyl]propane(BAPP),3,3',4,4'-Benzophenonetetracrboxylic dianhydride(BTDA) and TEA in N-Methyl pyrrolidone (NMP) were prepared and used to obtain PI adhesive. The chemical structure of PAAS and PI films were confirmed by 1H NMR and FTIR spectroscopy. It was found that PI-2 adhesive obtained from PAAS-2( the mole ratio of TEA/repeating unite of PAA=2/1) had the best property. TGA showed that the temperature for 5% weight loss of PI-2 could achieve 497 ℃ and tensile test showed PI-2 had superior bonding strength of 14.83 MPa. In addition,the damping performance of PI-2 had a great improvement compared with PI obtained from PAA. Moreover,through the study of imidization temperature,the results suggested that PI adhesive obtained from PAAS could complete the imidization reaction at 280 ℃,which had great significance for saving energy. And PI-300 ℃(the maximum imidization temperature of which was 300 ℃) had superior thermal stability,bonding strength and damping performance simultaneously.
关键词： Imidization temperature,Bonding strength,Polyimide,Poly(amic acid) salt
更新于2025-09-23 15:21:21