A KrF excimer laser was used at 248 nm wavelength to fabricate support membranes and the final PNIPAM pore-filled thermally responsive PET membranes of four different thicknesses (50, 75, 100, ...125 μm). The surface and cross-sectional morphologies of the ablated support membranes were elucidated using optical microscopy and micro-CT. Proper combinations of laser operational parameters (energy fluence, number of pulses, pulse frequency) and mesh size were determined for each thickness membrane based on energy required for perforation, average pore size and morphological observations.
Temperature responsive poly(N-isopropylacrylamide) (PNIPAM) hydrogel was grafted in membrane pores through pulsed laser polymerization (PLP) at 3 progressive grafting density values. Four thicknesses membranes of 4 grafting conditions (1 ungrafted and 3 grafted) were characterized using water permeation test. Permeation behavior and thermal response were found for all 4 thicknesses of membranes at grafted state, and the permeation results displayed a decreasing trend in permeability coefficient with increasing thickness, while thermal response displayed an increasing trend with increasing thickness at higher grafting density state. Scanning Electron Microscopy (SEM) was utilized to characterize the surface and pore grafting phenomena on membranes of different thicknesses under different grafting conditions. Our results indicate that the film thickness has little or no effect on kinetics of PLP for given laser operation parameters. Thus, our results reveal that similar crosslink structure is obtained in PNIPAM grafted in the pores of different thickness support membranes when using the same PLP conditions.
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•Four different thickness polyethylene terephthalate (PET) membranes were perforated by KrF excimer laser for porosity.•Temperature responsive hydrogel, poly(N-isopropylacrylamide), grafted in membrane pores by Pulsed Laser Polymerization (PLP).•Membrane thickness had little impact on PLP kinetics.•Membrane water permeability decreased as membrane thickness increased at certain grafting density.•Thermo-responsiveness of membrane increased by increasing its thickness at higher number grafting laser pulses (P = 900).
In this letter, we report the KrF excimer laser annealing for achieving high-performance ferroelectric Hf 0.5 Zr 0.5 O 2 (HZO). The laser anneals the target device layer effectively with a high ...heating/cooling rate without overheating under-layer deep structures. The impact of laser fluence, number of pulses, and pulse duration on the ferroelectricity in HZO was carefully studied through numerical simulation and experiment. The remnant polarization 2 P r of 22 μC/cm 2 , a coercive field of ~1 MV/cm, and a cycling endurance of > 10 8 were achieved in the 8 nm ferroelectric HZO thin film annealed by the laser with an ultra-low laser fluence of ~ 84 mJ/cm 2 and 20 pulses. Benefiting from the large beam size of KrF excimer laser, the laser annealing is practical for obtaining stable wafer-scale ferroelectric HZO within a short time.
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•UD CFRP was treated by KrF laser in atmosphere, argon and underwater environments.•Argon environment treatment resulted in the porosity around exposed fibres.•Two step underwater ...laser treatment developed flakes-like-surface-structure.•Adhesive bonding strength of 35.8 MPa was achieved after underwater treatment.•Bonding strengths of normal atmosphere and argon treatments were 31.7 and 31.9 MPa.
Unidirectional CFRP was treated by KrF laser in normal atmosphere, argon and underwater environments, before adhesive bonding. KrF laser removed the top resin layer and exposed the carbon fibres. Porosity and holes were generated around exposed carbon fibres after argon environment treatments and flakes-like-surface-structure was generated after underwater treatments with two-step method. KrF laser treatments increased Sq and Sdr values. Sdr was more influential for adhesive joint shear strength. These laser treatments in all environments transformed secondary and tertiary aliphatic amines to primary and secondary aliphatic amines, respectively. SLSS study confirmed that the highest shear strength of 35.78 MPa which was 45% higher than the untreated joint, was achieved after underwater treatment. Normal atmosphere and argon environment treatments resulted in 31.74 and 31.95 MPa, respectively. Adhesive failure which occurred after argon environment treatments, reduced after normal atmosphere treatments. Underwater treatments resulted in cohesive failure and thin layer cohesive failure.
pH-responsive smart gating membranes were developed using a two-step fabricating process. In the first step, a porous polyimide (PI) support membrane with ordered, regular, and well-defined pores was ...obtained with a 248 nm KrF excimer laser using a lithography technique. The porous membranes were then grafted with poly(acrylic acid) (PAAc) hydrogel by free radical polymerization using the same excimer laser. The number of pulses and frequency could be varied to obtain a range of water permeabilities. Permeability of membrane changed significantly due to swelling and deswelling of PAAc inside the pores at pH 7 and pH 3, respectively. These hydrogel networks were firmly grafted inside pores and remained mechanically intact even after using high pressure during permeability studies. PAAc grafting was confirmed using ATR-FTIR. PAAc hydrogel distribution inside membrane pores was analyzed using SEM and fluorescence microscopy. To quantify the amount of polymer grafted, TGA studies were carried out. Diffusion studies were also carried out using caffeine as a drug molecule to evaluate the application of membrane in drug delivery devices. The linear drug release profile obtained from the study confirmed the potential application of membrane for drug delivery purposes. Results obtained also suggest that the fabrication method developed is fast, efficient, solvent-free, and economical.
KrF excimer laser (λ = 248 nm) has been employed to anneal nanocrystalline Tin oxide (SnO2) films deposited at 200 °C using spray pyrolysis. With the increase of irradiation laser fluence, the film ...crystallinity has been improved while the matrix stress decreased along all the crystal planes except (110) and (301), for an energy density of 150 mJ/cm2 as compared to non-irradiated films. The maximum liquid petroleum gas (LPG) response observed for a fluence 150 mJ/cm2 is 92.6% at 350 °C whereas a response is 4% at the onset sensing temperature of 100 °C. Moreover, the response and recovery times have also improved by the laser processing and the cross sensitivity for NH3 and NO2 gases are in a desirable range. FESEM images of irradiated films show polygonal shaped distributions of aggregated nanocrystalline particle-clusters with grain boundaries and nanovoids. XPS shows oxygen deficient lattice besides surface and/or pore-bound oxygen contributions. Raman analyses confirm the sub-stoichiometric SnO2-x phases and a high concentration of defects such as oxygen vacancies (OVs) on surface sites. Based on these observations, the gas sensing mechanism is discussed in brief.
•Gas response of pyrolysis deposited, excimer laser annealed, SnO2 films studied.•150 mJ/cm2 fluence gives rapid response and recovery times of 10 s and 20 s respectively.•The LPG sensitivity for concentration range 200–500 ppm is around 0.02/ppm at 350 °C.•The LPG response at an operating temperature of 150 °C is 20% for 1000 ppm.•OVs along with sub-stoichiometric states contribute to the enhanced gas response.
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•Adhesive strength of KrF laser treated UD, 4HSW and PW CFRP were investigated.•KrF laser ablated the top layer matrix and exposed carbon fibres without damage.•KrF laser affected the ...C-N bonds and de-polymerized the matrix polymer.•Laser treated UD, 4HSW and PW CFRP showed 32.8, 23.9 and 35.2 MPa bonding strength.•AF reduced largely and CF, TLCF, FTF were prevalent after KrF laser pre-treatment.
Several types of carbon fibre reinforced polymers (CFRP) are available based on the appearance of the carbon fibre laminates. In this study, three distinct types of CFRPs, namely, unidirectional (UD CFRP), 4-Harness Satin weaved (4HSW CFRP) and plain weaved (PW CFRP) were selected to compare the bonding strength performance of specific CFRP/CFRP adhesive joints after KrF laser pre-treatment. KrF excimer laser with top hat beam profile was utilized. This treatment increased the Sq and Sdr values significantly for all three CFRP types. KrF laser affected the matrix polymer C-N bonds and converted the tertiary and secondary aliphatic amines to secondary and primary amines, respectively, after de-polymerization. Single lap shear stress (SLSS) test revealed that the average adhesive bonding strength achieved respectively for UD CFRP, 4HSW CFRP and PW CFRP after KrF laser pre-treatment were 32.80, 23.97 and 35.21 MPa which were 104.34%, 47.24% and 39.72% higher than their pristine counterparts. Repeatability of the SLSS results were more for weaved pattern CFRPs. Adhesive failure reduced drastically and presence of cohesive failure, thin layer cohesive failure and fibre tear failure were prevalent in SLSS for all considered CFRPs. Comparison of all results showed that the best performance was obtained for PW CFRP.
Due to the increasing importance of microfluidic chips in medical, nuclear, and chemical industries, we focused on improving various parameters in manufacturing their components, most importantly ...microchannels. Channels with a length of several hundred microns are constructed based on two crucial factors: substrates and the procedure. Numerous substrates can be employed, amongst which PMMA polymer has been chosen due to its transparency, flexibility, and cheapness with respect to glass. As for the procedure, laser ablation is commonly used for manufacturing microchannels. Nanosecond KrF laser is used to advantage from not only its high absorption of polymeric material in ultra-violet wavelengths but also its higher accessibility and cost-effectiveness. In this paper, irradiation parameters are optimized including the scanning speed of the laser, laser fluence, and repetition rate of the laser pulse in the fabrication of microchannels on PMMA polymer. The fluidic properties of the fabricated channels such as hydraulic diameter, Reynolds number, and the regime of water flow are also investigated. Results confirm the domination of the laminar regime for water flow in these microchannels.
•Numerical simulation of KrF laser treatment of UD, 4HSW and PW CFRP has been done.•Simplified geometric model of each mentioned CFRPs has been proposed.•Differential thermal conductivity method has ...been used for each modelling.•The heat flow patterns with time within carbon fibre layers have been shown.•Best resemblance with experimental results have been obtained for weaved CFRPs.
Carbon fibre reinforced polymers or plastics (CFRP) are being used in the aerospace and automotive industry as the structural material. In this study, numerical simulation of KrF excimer laser treatment of three different CFRPs namely unidirectional CFRP (UD CFRP), plain weaved CFRP (PW CFRP) and 4-Harness Satin weaved CFRP (4HSW CFRP) has been done. Simplified geometric model of each considered CFRP has been proposed utilizing differential thermal conductivity method. Individual parameter combinations those have resulted in the rise of the temperature of the resin layer near or more than the glass transition temperature of the same are selected exclusively for each CFRP type. KrF laser treatment experiments have been performed for each mentioned CFRPs with those individually selected parameter combinations. Excellent match of the results from the proposed numerical study has been observed with the experimental findings and the best resemblance has been obtained in case of weaved pattern CFRPs. The heat flow patterns with time within the carbon fibre layers have been also demonstrated for both PW CFRP and 4HSW CFRP.
It has been reported that the good correlation in sensitivity and resolution between EUV exposure and EB exposure because of the similar mechanism of the photochemical-reaction in photoresists during ...exposure. However, in the early stages of EUV resist development, there are problems on the points of the cost and time-consuming to evaluate all EUV resist materials by EB exposure. Therefore, we investigated the possibility of using KrF exposure as the initial screening of EUV resists. In former report, we evaluated the correlation of sensitivity between KrF and EUV exposure, KrF and EB exposure, EB and EUV exposure respectively by using various type of resists. Then we could find there is some correlation between each exposure. In this report, we formulated some types of KrF resist and investigated whether there is a correlation of sensitivity between KrF and EUV exposures.
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