Ablation Of Polyimide Research Articles

Synthesis of Fe3O4 embedded LIG via laser ablation of PI/Fe(acac)3 film for enhanced electrocatalytic hydrogen evolution

Hydrogen production via electrocatalytic water splitting is generally considered as an efficient and eco-friendly strategy for energy storage. The exploration of novel electrocatalytic cathode material towards hydrogen evolution reaction (HER) has never ended. Laser induced graphene (LIG), as a cheap and porous material with large surface area, not only can be used as a carrier of active substances for collaborative catalysis towards hydrogen evolution, but also can be directly used as catalytic electrode via heteroatoms doping. We synthesized Fe3O4 embedded LIG via laser ablation of polyimide (PI)/Fe(acac)3 film and tested its HER electrocatalytic performance. An overpotential of 269 mV was obtained under the current density of 10 mA cm−2 with a slight current decay in the 10 h chronoamperometric examination in 1 M KOH electrolyte. This work provides an insight into methods of optimizing electrochemical properties and improving catalytic activity of LIG based materials. The performance of our Fe3O4 embedded LIG demonstrates the potential of LIG based materials as next generation HER electrocatalyst.

Shock compression experiments using the DiPOLE 100-X laser on the high energy density instrument at the European x-ray free electron laser: Quantitative structural analysis of liquid Sn

X-ray free electron laser (XFEL) sources coupled to high-power laser systems offer an avenue to study the structural dynamics of materials at extreme pressures and temperatures. The recent commissioning of the DiPOLE 100-X laser on the high energy density (HED) instrument at the European XFEL represents the state-of-the-art in combining x-ray diffraction with laser compression, allowing for compressed materials to be probed in unprecedented detail. Here, we report quantitative structural measurements of molten Sn compressed to 85(5) GPa and ∼3500 K. The capabilities of the HED instrument enable liquid density measurements with an uncertainty of ∼1% at conditions which are extremely challenging to reach via static compression methods. We discuss best practices for conducting liquid diffraction dynamic compression experiments and the necessary intensity corrections which allow for accurate quantitative analysis. We also provide a polyimide ablation pressure vs input laser energy for the DiPOLE 100-X drive laser which will serve future users of the HED instrument.

Femtosecond infra-red laser carbonization and ablation of polyimide for fabrication of Kirigami inspired strain sensor

Microfabrication of polyimide (PI) with femtosecond laser of wavelength 1030 nm is studied in two process conditions. Firstly, the low power-low scan speed regime is investigated for laser carbonization producing piezoresistive laser induced graphene (LIG). The heat accumulation model is modelled to find the temporal evolution of temperature at the laser focus for a single laser scan. Secondly, the high power-high scan speed regime is studied for laser ablation where clean ablation was observed due to multiphoton absorption. To demonstrate the application of this process, a two-dimensional (2D) LIG based strain sensor is drawn on a Kapton PI sheet using laser carbonization and transformed into a three-dimensional (3D) conformal sensor by cutting into a Kirigami design using laser ablation. The strain in the sensor is calculated from finite element analysis and the gauge factor is 88.58 ± 0.16. This laser process enables the transformation of any 2D PI sheet into a 3D conformal sensor using femtosecond laser, which is useful for wearable sensors and health-monitoring applications. The fabricated sensor is demonstrated used on a knee-joint to monitor real-time tracking of bending and twisting knee movements.

Ultrathin, Graphene‐in‐Polyimide Strain Sensor via Laser‐Induced Interfacial Ablation of Polyimide

AbstractLaser‐induced graphene sensors have attracted considerable interest in various fields; however, the low sensitivity and conformability limit their further applications in measuring soft, large deformable structures. Here, an innovative method of interface ablation is presented to convert the interfacial polyimide into graphene by nanosecond ultraviolet laser (308 nm). Significantly different from the traditional laser surface ablation, interface ablation demonstrates its unique capacity to produce high‐quality graphene with limited ablation depth, which benefits from the combined effect of highly concentrated temperature distribution, the confinement of reaction product, and a unique ablation mode dominated by heat conduction. Using this method, an ultrathin (8 µm), graphene‐in‐polyimide (GiP) strain sensor is obtained, which is six times thinner than that prepared by the traditional surface ablation. The ultrathin GiP sensors exhibit excellent conformability (small bending radius of 400 µm), high strain sensitivity (24.8), and high force sensitivity (4.2 N−1). Demonstrations of this GiP strain sensor in the deformation measurement of the morphing aircraft (e.g., bending, twisting, and impact) illustrate its powerful abilities in the health monitoring of equipment, thus providing engineering opportunities for smart devices requiring accurate deformation measurement.

Erratum: “Ultraviolet nanosecond laser ablation of polyimide with thermal and nonthermal effects near threshold fluence” [J. Laser Appl. 34, 032004 (2022)

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Measurement of shock roughness due to phase plate speckle imprinting relevant for x-ray diffraction experiments on 3rd and 4th generation light sources

Laser-shock compression experiments at 3rd and 4th generation light sources generally employ phase plates, which are inserted into the beamline to achieve a repeatable intensity distribution at the focal plane. Here, the laser intensity profile is characterized by a high-contrast, high-frequency laser speckle. Without sufficient smoothing, these laser non-uniformities can translate to a significant pressure distribution within the sample layer and can affect data interpretation in x-ray diffraction experiments. Here, we use a combination of one- and two-dimensional velocity interferometry to directly measure the extent to which spatial frequencies within the laser focal spot intensity pattern are smoothed out during propagation within the laser plasma and a polyimide ablator. We find that the use of thicker polyimide layers results in spatially smoother shock fronts, with the greatest degree of smoothing associated with the highest spatial frequencies. Focal spots with the smallest initial speckle separation produce the most rapid smoothing. Laser systems that employ smoothing by spectral dispersion techniques to rapidly modulate the focal plane intensity distribution are shown to be the most effective ones in producing a spatially smooth shock front. We show that a simple transport model combined with the known polyimide Hugoniot adequately describes the extent of shock smoothness as a function of polyimide thickness. Our results provide a description of spatial structure smoothing across a shock front, which can be used to design targets on x-ray free electron laser facilities.

Direct-write formation of integrated bottom contacts to laser-induced graphene-like carbon

We report a simple, scalable two-step method for direct-write laser fabrication of 3D, porous graphene-like carbon electrodes from polyimide films with integrated contact plugs to underlying metal layers (Au or Ni). Irradiation at high average CO2 laser power (30 W) and low scan speed (∼18 mm s)−1 leads to formation of ‘keyhole’ contact plugs through local ablation of polyimide (initial thickness 17 μm) and graphitization of the plug perimeter wall. Top-surface laser-induced graphene (LIG) electrodes are then formed and connected to the plug by raster patterning at lower laser power (3.7 W) and higher scan speed (200 mm s)−1. Sheet resistance data (71 ± 15 Ω sq.)−1 indicates formation of high-quality surface LIG, consistent with Raman data which yield sharp first- and second-order peaks. We have also demonstrated that high-quality LIG requires a minimum initial polyimide thickness. Capacitance data measured between surface LIG electrodes and the buried metal film indicate a polyimide layer of thickness ∼7 μm remaining following laser processing. By contrast, laser graphitization of polyimide of initial thickness ∼8 μm yielded devices with large sheet resistance (>1 kΩ sq.)−1. Raman data also indicated significant disorder. Plug contact resistance values were calculated from analysis of transfer line measurement data for single- and multi-plug test structures. Contacts to buried nickel layers yielded lower plug resistances (1-plug: 158 ± 7 Ω , 4-plug: 31 ± 14 Ω) compared to contacts to buried gold (1-plug: 346 ± 37 Ω , 4-plug: 52 ± 3 Ω). Further reductions are expected for multi-plug structures with increased areal density. Proof-of-concept mm-scale LIG electrochemical devices with local contact plugs yielded rapid electron transfer kinetics (rate constant k 0 ∼ 0.017 cm s−1), comparable to values measured for exposed Au films (k 0 ∼0.023 cm s)−1. Our results highlight the potential for integration of LIG-based sensor electrodes with semiconductor or roll-to-roll manufacturing.

Publisher’s Note: “Ultraviolet nanosecond laser ablation of polyimide with thermal and nonthermal effects near threshold fluence” [J. Laser Appl. 34, 032004 (2022)

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Ultraviolet nanosecond laser ablation of polyimide with thermal and nonthermal effects near threshold fluence

Typically, a 355 nm laser is not sufficient for inducing photochemical ablation and leads to photothermal effects such as melting and recasting. Consequently, most previous studies on the irradiation of polyimide (PI) with such lasers have focused on temperature distribution on the surface and variations in the absorption properties of PI depending on the temperature and time. Herein, the authors demonstrate ablation without thermal effects on the surface of PI using a 355 nm pulse nanosecond laser near the threshold fluence. For ablation without thermal effects, the ablated and nonablated areas can be clearly distinguished in the area exposed to the laser. The interface between these areas, that is, the ablation shape, became wider with increasing laser fluence, even when the spot size remained unchanged; also, the shape of the ablated area was related to the laser intensity distribution. Ablation with thermal effects began to appear in the nonablated areas at higher laser fluence. This study shows that PI, which is physically stable and relatively inexpensive, can be used to develop cation exchange membranes, which can be applied to organic flow cells as well as microbial fuel cells.

Comparing Structure and Sorption Characteristics of Laser-Induced Graphene (LIG) from Various Polymeric Substrates

Laser-induced graphene (LIG) has recently gained significant attention for its potential application in various fields. Here, we show that the laser ablation of Kevlar fabric, polyimide (PI), and poly(ether)sulfone (PES) substrates results in the formation of a highly porous graphene with different physicochemical features. LIG powder was used as an adsorbent for the dye removal. The LIG materials obtained from each substrate exhibited a different macroporous structure and demonstrated relatively high efficiency in the adsorptive removal of cationic dye. The generation of graphene from each polymeric substrate was confirmed by characterizing the LIGs. We found that the laser power had a large influence on the formation and quality of the LIG; higher laser power increased the degree of graphitization and resulted in a more porous graphene structure, which eventually led to an increase in the adsorption capacity. The LIG’s adsorption capability is hypothesized to be primarily due to the highly porous structure of LIG, while π–π and hydrophobic interactions were found to have a marginal influence on the adsorbent–adsorbate interactions. LIG derived from PI displayed the highest sorption capacity among different polymeric substrates tested. The maximum equilibrium methylene blue adsorption capacity was found to be 153.3 mg/g using the Langmuir model.

Probing the lattice structure of dynamically compressed and released single crystal iron through the alpha to epsilon phase transition

Experiments using broadband Laue x-ray diffraction (XRD) were used to examine the lattice structure of dynamically compressed [100]-oriented single crystal iron samples at the Dynamic Compression Sector at the Advanced Photon Source. These experiments used 1 μm thick iron single crystal samples sandwiched between a polyimide ablator and a polycarbonate window. A 100 J, 10 ns duration laser pulse incident on the polyimide ablator was used to shock compress the iron samples to initial stresses greater than 25 GPa, exceeding the ∼13 GPa alpha (body-centered-cubic or bcc structure) to epsilon (hexagonal-close-packed or hcp structure) phase transition stress. XRD measurements were performed at various times relative to the shock wave entering the iron sample: early times, <∼150 ps while the initial shock waves propagated through the iron; intermediate times, after the iron equilibrated with the ablator and window reaching a plateau stress state (12 or 17 GPa) lasting several nanoseconds; and late times, during uniaxial strain release. The early time measurements show that in <∼150 ps, the high-pressure hcp phase is relaxed with a c/a ratio of 1.61, contrary to previous laser shock experiments where a c/a ratio of 1.7 was inferred. In the plateau stress state and partially released states, XRD measurements showed that the hcp structure retained a c/a ratio of 1.61 with no observable changes in the microstructure. Upon stress release at ∼1 GPa/ns release rate, the reverse phase transition (hcp to bcc) to the original single crystal orientation (implying a transformation memory effect) was observed to reach completion somewhere between 13 and 11 GPa, indicating little stress hysteresis under rapid uniaxial strain release. A similar memory effect for the reverse hcp to bcc transformation has been previously observed under hydrostatic compression. However, the bcc/hcp orientation relationships differ somewhat between dynamic and static compression experiments, implying that the transformation pathway under uniaxial dynamic strain differs from the Burgers mechanism.

In situ synthesis of fluorescent silicon nanodots for determination of total carbohydrates in a paper microfluidic device combined with laser prepared graphene heater

We report a simple, rapid, low-resource and one-step method for formation of fluorescent silicon nanodots (SNDs) in a microfluidic paper-based analytical device (μPAD) incorporated in a reusable, portable and flexible heater for determination of total carbohydrates. The synthesis of SNDs is based on the redox reaction between (3-aminopropyl) triethoxysilane (APTS) reagent and carbohydrates, which act as a reducer. The graphene-based heater was fabricated by laser ablation of Kapton polyimide. Thereby, the developed system heat the μPAD during the synthesis of SNDs at 80 °C for 30 min. The blue emitting SNDs formed have an emission peak wavelength at 475 nm. We used a digital camera and smartphone for the quantitative analysis of total carbohydrates expressed such as index of glucose or fructose with grey scale value as the analytical parameter. Under the optimal conditions, the method has a low detection limit (0.80 μM for glucose and 0.51 μM for fructose, respectively), and a linear response (10–200 μM for glucose and 10–100 μM for fructose). The method has been applied to the determination of glucose in biological fluids (serum and urine samples). In addition, determination of total carbohydrates in commercial juices and teas have been carried out.

Novel method to reduce the transverse sensitivity of granular thin film strain gauges by modification of strain transfer

Abstract. Strain gauges based on polyimide carrier foils and piezoresistive granular thin films are highly sensitive to strain. Unlike conventional metal foil, granular film strain gauges also have a pronounced sensitivity to strain acting in the transverse direction. A novel method that allows for the modification of the strain transfer is proposed and proven experimentally. The method is based on the creation of stand-alone polyimide paths, on top of which the piezoresistive thin film is located. In this way, the granular film hardly receives any transverse strain; hence, the transverse sensitivity is drastically reduced. A picosecond laser system can be used for both patterning of the thin film and for controlled ablation of polyimide in order to generate well-defined high path structures. The working principle of the method is demonstrated by simulation, followed by an experimental verification using measurements of the transverse gauge factor. Furthermore, the output signal of force transducers may be increased using granular thin film strain gauges of reduced transverse sensitivity.

Femtosecond pulsed laser ablation of polyimide at oblique angles for medical applications

We report the ablation results for surface modification of polyimide Kapton HN foils using ultrashort femtosecond laser pulses. The modification threshold fluences for 75μm thick films of polyimide were determined at different incident angles (0°, 20°, 30°, 45°, and 50°) for vertical and horizontal diameters. Ablation at oblique angles was investigated as such interactions are found during laser procedures with the eye that require scanning of the beam and are very important to know for the treatment of various eye diseases. Polyimide, in this study, was considered as a model for corneal sculpting. Use of ultrashort femtosecond laser pulses for high-precision patterning of the sample, without thermal damage to the surroundings, has been investigated. The relationship between the incidence angle with ablation threshold fluence, threshold energy, and beam radius are described. Also, threshold energies and threshold fluences for different thicknesses of polyimide were investigated.

Inferring the electron temperature and density of shocked liquid deuterium using inelastic X-ray scattering

An experiment designed to launch laser-ablation-driven shock waves (10 to 70 Mbar) in a planar liquid-deuterium target on the OMEGA Laser System and to diagnose the shocked conditions using inelastic x-ray scattering is described. The electron temperature (Te) is inferred from the Doppler-broadened Compton-downshifted peak of the noncollective (αs = 1kλD > 1) x-ray scattering for Te > TFermi. The electron density (ne) is inferred from the downshifted plasmon peak of the collective (αscatter > 1) x-ray scattering. A cylindrical layer of liquid deuterium is formed in a cryogenic cell with 8-μm-thick polyimide windows. The polyimide ablator is irradiated with peak intensities in the range of 1013 to 1015 W/cm2 and shock waves are launched. Predictions from a 1-D hydrodynamics code show the shocked deuterium has a thickness of ∼0.1 mm with spatially uniform conditions. For the drive intensities under consideration, electron density up to ∼5 × 1023 cm−3 and electron temperature in the range of 10 to 25 eV are predicted. A laser-irradiated saran foil produces Cl Lyαemission. The spectrally resolved x-ray scattering is recorded at 90° for the noncollective scattering and at 40° for the collective scattering with a highly oriented pyrolytic graphite (HOPG) crystal spectrometer and an x-ray framing camera.

Computer modelling of the laser ablation of polymers

Laser ablation of polymers has been the subject of extensive studies for nearly three decades. Results of these investigations have shown that thermal effects play an important role during frequency tripled nanosecond Nd:YAG laser ablation of polyimide. Despite of the studies, effect of these processes has not been satisfactorily clarified. Thermal effects, photochemical and other phenomena still exist and so the thermal modelling of laser ablation is a very specialised problem. The investigation in this paper deals with special conditions in thermal models, which highly differ from more common conditions. Although there are numerous excellent thermal modelling software available, mainly in the field of electronics technology, these are not suitable or ready for handling special conditions, for example the removing of material from the domain under investigation, which is one of the most important areas. Hence we decided to develop a special thermal modelling tool. The model designing aspects which define the development process are presented in this paper.

KrF pulsed laser ablation of polyimide

In the present paper, polyimide surfaces were processed with pulsed KrF laser radiation at fluences near the ablation threshold. The morphology of the processed surfaces was studied by scanning electron microscopy and chemical analyses performed by electron dispersive spectroscopy. The formation of conical structures was observed for radiation fluences lower than 0.5 J/cm2. The areal density of cones increases with the number of pulses and decreases with the radiation fluence. At low fluences (<150 J/cm2), cones are formed due to shadowing by calcium phosphate impurities while for higher fluences the main mechanism of cones formation is believed to be radiation hardening.

Theoretical and experimental investigations into laser ablation of polyimide and copper films with 355-nm Nd:YVO4 laser

Abstract The micromachining of thin films multi-layered with metal and polymer is of great interest due to the superior flexibility and high conductivity of these films. Laser ablation of these laminated materials is a combination of the photochemical evaporation and the photothermal melt expulsion. In the ablation of metal, the photothermal effect is dominant, while in the ablation of polymer the photochemical effect is more intense. In this paper, in order to predict the etching depth the laser ablation of polyimide (PI) and copper (Cu) films, we adopted a theoretical model, called the Srinivasan–Smrtic–Babu (SSB) model, which considers both the photothermal and photochemical effects. The model parameters were obtained by fitting the experimental data from sources in the relevant literature. We used a 355-nm DPSS Nd:YVO4 laser to carry out a laser ablation of PI and Cu films. In experiments, we examined the effects of laser fluence on the quality of the ablated surfaces. Experimental results showed that at laser fluence lower than the threshold energy, high-quality surfaces with no burr or deformation were achieved.

Thermal simulation of UV laser ablation of polyimide

The aim of our research is to provide a simulation tool for manufacturing processes that takes the influence of temperature distribution thus the underlying copper pattern and pulse repetition frequency into account. To establish such simulation software, a finite element model was set up which is able to describe the thermal processes and ablation induced by laser irradiation of polymers. The etch rate description usually applied for excimer lasers was slightly altered to be adequate for Gaussian lasers by writing pulse energy instead of fluence. This theoretical consideration was proved by experiments. The experiments also revealed the temperature dependence of etch rate and the influence of pulse repetition frequency on the amount of ablated material. The experimental, analytical and simulation results are in good agreement.

Preparation of Polyimide Ablator Coatings Using an Improved Solvent Vapor Smoothing Process

We completed the development of a method for preparing smooth vapor-deposited polyimide ablators up to 160 m thick for NIF target capsules. The process consists of two steps. The first step is vacuum chemical vapor deposition of monomer species, pyromellitic dianhydride and 4,4′-oxidianiline, onto the surface of a spherical shell mandrel where they may react to form polyamic acid. In the second step dimethyl sulfoxide (DMSO) vapor exposure in a gas-levitation smoothing apparatus swells and fluidizes the outer surface. Roughness in the outer fluid layer is reduced by surface-tension-driven flow. The shells are cured in the final smoothing step by heating to 300°C, converting the polyamic acid to polyimide. Recent experiments using X-ray radiography have allowed us to determine the depth of solvent penetration and the solvent concentration over a range of solvent exposure conditions. We found that the rate of penetration is a function of the solvent partial pressure in the flowing vapor stream. The concentration of solvent in the swollen layer is ∼0.43 g/cm3 and is independent of exposure conditions. Using the penetration information we were able to improve the smoothing process by increasing the solvent partial pressure. The optimized vapor smoothing process allowed us to consistently meet the surface smoothness specifications of NIF capsules.