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Laser-induced photothermal generation of flexible and salt-resistant monolithic bilayer membranes for efficient solar desalination
摘要： Harvesting solar energy and generating steam through solar thermal energy are viable approaches with diverse applications such as power generation, desalination, and water purification. Particularly, for efficient and stable solar desalination, hierarchically porous materials are desired to enable the required multiple functionalities. However, high thermal/chemical energy required and time consumed remain roadblocks. In this study, a facile, fast, and scalable laser-induced photothermal method to achieve flexible monolithic bilayer sheets (MBS) of hierarchically porous graphitic carbon (HPGC) and polymeric foam for use in salt-resistant and flexible solar steam generators is reported. The MBS-based self-floating solar steam generator shows outstanding solar desalination performance with a solar thermal efficiency of 83.2% (1-sun) and a high salt-rejection ratio (99.9%). Efficient solar thermal energy transformation is achieved by the versatile multi-functionalities of the MBS, including broad-spectrum solar light absorption, heat localization, and capillary action. Anisotropic wetting properties of hydrophobic HPGC and hydrophilic polyimide (PI) foam effectively prevent salt accumulation on the HPGC surface. The salt-resistant MBS enable long-term stability for solar desalination with actual seawater. Our laser-based photothermal method has potential in the development of high-performance solar thermal systems with substantial cost reduction by scalable production of multiscale hierarchically structured materials from micro-structured polymers.
关键词： monolithic bilayer structures,solar evaporation,porous polyimide,salt-resistant solar steam generators,self-floating,flexibility,laser-induced graphene
更新于2025-09-19 17:13:59
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Flexible and Highly Sensitive Strain Sensor Based on Laser-Induced Graphene Pattern Fabricated by 355 nm Pulsed Laser
摘要： A laser-induced-graphene (LIG) pattern fabricated using a 355 nm pulsed laser was applied to a strain sensor. Structural analysis and functional evaluation of the LIG strain sensor were performed by Raman spectroscopy, scanning electron microscopy (SEM) imaging, and electrical–mechanical coupled testing. The electrical characteristics of the sensor with respect to laser fluence and focal length were evaluated. The sensor responded sensitively to small deformations, had a high gauge factor of ~160, and underwent mechanical fracture at 30% tensile strain. In addition, we have applied the LIG sensor, which has high sensitivity, a simple manufacturing process, and good durability, to human finger motion monitoring.
关键词： polydimethylsiloxane (PDMS),355 nm pulsed laser,strain sensor,laser-induced graphene (LIG),polyimide
更新于2025-09-16 10:30:52
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Distributed Fiberoptic Sensor for Simultaneous Humidity and Temperature Monitoring Based on Polyimide-Coated Optical Fibers
摘要： Along temperature, humidity is one of the principal environmental factors that plays an important role in various application areas. Presented work investigates possibility of distributed fiberoptic humidity monitoring based on humidity-induced strain measurement in polyimide (PI)-coated optical fibers. Characterization of relative humidity (RH) and temperature response of four different commercial PI- and one acrylate-coated fiber was performed using optical backscattering reflectometry (OBR). The study addresses issues of temperature-humidity cross-sensitivity, fiber response stability, repeatability, and the influence of annealing. Acrylate-coated fiber exhibited rather unfavorable nonlinear RH response with strong temperature dependence, which makes it unsuitable for humidity sensing applications. On the other hand, humidity response of PI-coated fibers showed good linearity with fiber sensitivity slightly decreasing at rising temperatures. In the tested range, temperature sensitivity of the fibers remained humidity independent. Thermal annealing was shown to considerably improve and stabilize fiber RH response. Based on performed analysis, a 20 m sensor using the optimal PI-coated fibers was proposed and constructed. The sensor uses dual sensing fiber configuration for mutual decoupling and simultaneous measurement of temperature and RH variations. Using OBR, distributed dual temperature-RH monitoring with cm spatial resolution was demonstrated for the first time.
关键词： fiberoptic sensors,distributed humidity sensing,polyimide-coated optical fibers,optical frequency-domain reflectometry,dual sensing
更新于2025-09-16 10:30:52
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[IEEE 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Berlin, Germany (2019.6.23-2019.6.27)] 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - A Microassembled Triangular-Prism-Shape Three-Dimensional Electric Field Sensor
摘要： This paper, for the first time, presents a microassembled three-dimensional (3D) electric field sensor (EFS), which is a chip-level compact triangular-prism-shape sensor consisting of X-, Y- and Z-axis electric field (EF) sensing chips. The proposed 3D EFS is fabricated on a silicon-on-insulator (SOI) die, introducing photosensitive polyimide (PSPI) into its micromachining process to produce flexible micro-hinges and make separate components into a foldable integrative structure. Interlocking latches are employed to ensure the orthogonality of the three sensing axes. Structures of each EF sensing chip are symmetrically designed for reducing cross-axis coupling interference, and good performances have been demonstrated by experiments.
关键词： microassembly,Electric field sensor,triangular-prism-shape,three-dimensional,photosensitive polyimide
更新于2025-09-16 10:30:52
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Remarkable Improvement in Foldability of Polya??Si Thina??Film Transistor on Polyimide Substrate Using Blue Laser Crystallization of Amorphous Si and Comparison with Conventional Polya??Si Thina??Film Transistor Used for Foldable Displays
摘要： Highly robust poly-Si thin-film transistor (TFT) on polyimide (PI) substrate using blue laser annealing (BLA) of amorphous silicon (a-Si) for lateral crystallization is demonstrated. Its foldability is compared with the conventional excimer laser annealing (ELA) poly-Si TFT on PI used for foldable displays exhibiting field-effect mobility of 85 cm2 (V s)-1. The BLA poly-Si TFT on PI exhibits the field-effect mobility, threshold voltage (VTH), and subthreshold swing of 153 cm2 (V s)-1, -2.7 V, and 0.2 V dec-1, respectively. Most important finding is the excellent foldability of BLA TFT compared with the ELA poly-Si TFTs on PI substrates. The VTH shift of BLA poly-Si TFT is ±0.1 V, which is much smaller than that (±2 V) of ELA TFT on PI upon 30 000 cycle folding. The defects are generated at the grain boundary region of ELA poly-Si during folding. However, BLA poly-Si has no protrusion in the poly-Si channel and thus no defect generation during folding. This leads to excellent foldability of BLA poly-Si on PI substrate.
关键词： grain boundary,polyimide substrates,protrusions,flexible low-temperature poly-Si thin-film transistors,blue laser annealing
更新于2025-09-16 10:30:52
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Highly enhanced Raman scattering with good reproducibility observed on a flexible PI nanofabric substrate decorated by silver nanoparticles with controlled size
摘要： Surface-enhanced Raman scattering (SERS) spectroscopy is considered as a highly powerful analytical tool for environmental contaminants monitoring, detection of bio/chemical warfare agents, explosive detection and biological sensing. In this study, silver nanoparticles (Ag NPs) decorated polyimide (PI) nanofabric was successfully prepared as an active flexible substrate for SERS. Without any surface modification and activation, this Ag@PI nanofabric SERS substrate was prepared via an integrated process of electrospinning and ion exchange-in situ reduction. ATR-FTIR, ICP, XRD, SEM, and TGA were used to investigate the influencing factors during preparation. p-Aminothiophenol (p-ATP) was used as the probe molecule to characterize the SERS performance of Ag@PI nanofabric substrate. As a result, this Ag@PI nanofabric exhibits remarkable enhancement effect (EF = 9.0 × 103), good reproducibility, ultra-low detection limit (10?14 mol/L), and a good linear relationship between the concentration of p-ATP and intensity of its characteristic peak, making it a desirable candidate as the SERS substrate.
关键词： Nanofiber,Polyimide,Substrate,SERS,Silver nanoparticle
更新于2025-09-16 10:30:52
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Flexible ITO-free sky-blue polymer light-emitting diodes and printed polymer solar cells based on AgNW/PI transparent conductive electrode
摘要： In this work, transparent and conductive as well as flexible silver nanowire/polyimide (AgNW/PI) composite film with an average figure of merit as high as 111.3, which is the ratio of electronic conductivity to optical conductivity, is produced by a simple peel-off method without any post treatments. When employing the AgNW/PI composite film as the flexible transparent conductive anode in blue polymer light-emitting diodes (PLEDs), the device shows a high external quantum efficiency of 3.42% which is comparable to the rigid ITO-based control device with an efficiency of 3.96%. Moreover, for the flexible printed polymer solar cell (PSCs) with AgNW/PI as the transparent conductive anode, a high power conversion efficiency of 4.01% is achieved, which is also comparable to that of the rigid ITO-based PSC. This work systematically demonstrates that AgNW/PI composite film has a promising prospect for application in all kinds of flexible optoelectronic devices, such as light-emitting diodes, solar cells, flat panel displays, and so on.
关键词： Printing,ITO-free,Flexible Ag nanowire/polyimide,Polymer solar cells,Polymer light-emitting diodes
更新于2025-09-12 10:27:22
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Surface structuring of Kapton polyimide with femtosecond and picosecond IR laser pulses
摘要： Pulsed laser ablation is one of the most efficient and clean methods for high-precision processing and modification of polymers and biomaterials. Polymer ablation has been extensively investigated with ultraviolet lasers while little attention has been given to the infrared (IR) region, which becomes particularly interesting with the recent advances in ultrashort laser technologies. Here, we report the results of a comparative study on 1030-nm ultrashort laser structuring of Kapton polyimide, a polymer important in a variety of applications, with direct comparison of 247-fs and 7-ps laser pulses. The laser-induced damage thresholds for both pulse durations have been determined and the femtosecond laser threshold has been found to be considerably lower than that for picosecond pulses (by a factor of ～ 3.5). Both femtosecond and picosecond laser–produced craters have been thoroughly investigated as a function of pulse energy and focusing conditions. It has been demonstrated that femtosecond laser pulses enable accurate polyimide structuring while picosecond irradiation regimes result in a number of undesired effects such as re-deposition of the ablation debris, surface swelling, and the formation of high rims around the ablation craters. The mechanisms of polyimide ablation with femtosecond and picosecond IR laser pulses are discussed.
关键词： crater profile,swelling,laser ablation,damage threshold,laser processing,ultrashort laser pulses,multiphoton absorption,polymers,polyimide
更新于2025-09-12 10:27:22
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Laser-Patternable Graphene Field Emitters for Plasma Displays
摘要： This paper presents a plasma display device (PDD) based on laser-induced graphene nanoribbons (LIGNs), which were directly fabricated on polyimide sheets. Superior field electron emission (FEE) characteristics, viz. a low turn-on field of 0.44 V/μm and a large field enhancement factor of 4578, were achieved for the LIGNs. Utilizing LIGNs as a cathode in a PDD showed excellent plasma illumination characteristics with a prolonged plasma lifetime stability. Moreover, the LIGN cathodes were directly laser-patternable. Such superior plasma illumination performance of LIGN-based PDDs has the potential to make a significant impact on display technology.
关键词： plasma illumination,polyimide,field electron emission,laser-induced graphene
更新于2025-09-11 14:15:04
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Effect of Below-Freezing Temperature on Optical Loss of Polyimide-Coated Optical Fibers
摘要： An increase in the optical loss in polyimide-coated optical fibers, caused by microbendings is detected at temperatures below –25 ?C. It is shown that the observed increase in the optical loss is due to the presence of a residual N-methyl-2-pyrrolidone solvent in the polyimide coating.
关键词： polyimide varnish,protective–strengthening coating,optical fiber
更新于2025-09-11 14:15:04