Polymer Film Thickness Research Articles

Fiber-Tip Fabry–Perot Cavity Pressure Sensor With UV-Curable Polymer Film Based on Suspension Curing Method

We investigate a novel and compact fiber-tip pressure sensor based on Fabry-Perot interferometer (FPI). The proposed device is fabricated by welding a Section of hollow silica tube (HST) on the end of single mode fiber (SMF) and then coating with ultraviolet (UV) curable polymer film at the tip of HST. A simple suspension curing method is introduced to control the formation of the UV curable polymer layer. Therefore, different thicknesses of the polymer film can be easily controlled. The pressure sensing mechanism is based on the cavity length change induced by ambient pressure. The sensor characteristics are studied theoretically and experimentally. The proposed fiber-tip pressure sensor with polymer film thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5.7\,\, \mu \text{m}$ </tex-math></inline-formula> exhibits a pressure sensitivity of 396 pm/kPa in the range of 0–30 kPa based on wavelength shift of the interference dip. Moreover, temperature crosstalk is measured, and the thermal-induced deformation of the polymer film is simulated using the Finite Element Analysis method. The proposed fiber-tip Fabry-Perot cavity pressure sensor has advantages of high sensitivity, fast response, excellent repeatability, compact size, cost effectiveness and easy fabrication, which makes it suitable for high sensitivity pressure detection in a limited space.

Uniform Contraction and High Force Output of Photoresponsive Shape‐Memory Polymer Actuators with Large Thickness Based on Vertical Distribution of Rare Earth Oxides

Front Cover: In article number 2100683 by Liang Fang, Chunhua Lu, and co-workers, three rare-earth oxides with selective photothermal effects toward different near-infrared light beams are assembled vertically in thick shape-memory polymer films. Simultaneous irradiation of three near-infrared light beams achieves a low temperature gradient along the film thickness. Uniform contraction, instead of folding or bending, is realized and high force output is generated.

Influence of Polymer Interfacial Protective Layer Thickness on the Stability of Lithium‐Metal Batteries

AbstractProtective layers formed of polymers with conjugated structures have been demonstrated to improve the cycling stability of lithium (Li)‐metal batteries by reducing Li dendrite growth. However, the influence of important film parameters, such as thickness and ionic conductivity, remains largely unexplored. The present work addresses this issue by investigating the influence of film thickness for electrochemically active polymethyl methacrylate (PMMA) protective layers on the growth of Li dendrites and the long‐term cycling stability of Li‐metal batteries. The results demonstrate that the cycling stability of cells employing PMMA/Cu electrodes attains a maximum value at an optimal polymer film thickness of 93 nm. The results of detailed analysis indicate that the optimal PMMA layer thickness improves the cycling stability of Li‐metal batteries by eliminating the uneven electric fields on the surface of the Cu electrode leading to Li dendrite growth, and by reducing the interfacial impedance due to the formation of intramolecular cyclopentanedione during the discharge/charge cycling. Accordingly, the results provide effective guidance in the future design of polymer protective layers by demonstrating that film thickness is a key factor influencing the cycling stability of Li‐metal batteries.

Influence of Various Technologies on the Quality of Ultra-Wideband Antenna on a Polymeric Substrate.

The design, simulation, realization, and measurement of an ultra-wideband (UWB) antenna on a polymeric substrate have been realized. The UWB antenna was prepared using conventional technology, such as copper etching; inkjet printing, which is regarded as a modern and progressive nano-technology; and polymer thick-film technology in the context of screen-printing technology. The thick-film technology-based UWB antenna has a bandwidth of 3.8 GHz, with a central frequency of 9 GHz, and a frequency range of 6.6 to 10.4 GHz. In addition to a comparison of the technologies described, the results show that the mesh of the screens has a significant impact on the quality of the UWB antenna when utilizing polymeric screen-printing pastes. Last but not least, the eco-friendly combination of polyimide substrate and graphene-based screen-printing paste is thoroughly detailed. From 5 to 9.42 GHz, the graphene-based UWB antenna achieved a bandwidth of 4.42 GHz. The designed and realized UWB antenna well exceeds the Federal Communications Commission’s (FCC) standards for UWB antenna definition. The modification of the energy surface of the polyimide substrate by plasma treatment is also explained in this paper, in addition to the many types of screen-printing pastes and technologies. According to the findings, plasma treatment improved the bandwidth of UWB antennas to 5.45 GHz, and the combination of plasma treatment with graphene provides a suitable replacement for traditional etching technologies. The characteristics of graphene-based pastes can also be altered by plasma treatment in terms of their usability on flexible substrates.

Accurate monitoring of gas mixture transport kinetics through polymeric membranes

• Membrane permeation of CO 2 – rich gas mixture with many gaseous components. • Procedure to monitor mixture transport kinetics by quadrupole mass spectrometer (QMS). • Procedure to resolve the permeation flux of components with overlapping QMS signal. • High accuracy in the measure of penetrant diffusivity and permeability values. • Evidence of plasticization and competitive sorption processes. The accurate assessment of the membrane gas separation properties requires improved metrologies when the feed gases are mixtures rich of components such as biogases, flue gases and mixtures produced by CO 2 reforming. We present an original mass spectroscopy- based approach that permits to monitor the permeation kinetics of gas mixtures formed by components with overlapping mass signals. In the instrumental setup, sample-holder and quadrupole mass spectrometer are hosted in an Ultra High Vacuum chamber which is kept under dynamic pumping conditions during the experimental run. This setup permits to measure, as a function of time, the permeation flux of each mixture component, monitoring kinetics with transient lasting down to the ~ 1 s order. The flux detection limit is 10 -6 cm 3 (STP) m −2 s −1 for species with unambiguously attributable mass signal and no worse than 10 -5 cm 3 (STP) m −2 s −1 for species with overlapping mass signal. Tests were carried out at room temperature with ~ 50 μm thick polymer films exposed to CO 2 - rich gas mixtures at total pressure below 10 5 Pa. The analysis of permeation flux kinetics allows the evaluation of the diffusion constant of migrating species with ~ 4 % indetermination. In steady-state conditions the permeation flux through a poly(lactic acid) film is measured with accuracy better than ~ 3 % for components with unambiguously attributable mass signal ( CO 2 , O 2 ) and no worse than ~ 6 % for those with overlapping mass signal ( N 2 , CO ).

Development of a Sensor Based on Poly(1,2‐diaminoanthraquinone) for Individual and Simultaneous Determination of Mercury (II) and Bismuth (III)

AbstractContamination of natural water by mercury (Hg2+) and bismuth (Bi3+) metal ions have been extensively studied due to their toxic effects. A validated square‐wave anodic stripping voltammetry (SW‐ASV) method for determining Bi3+ and Hg2+ ions individually and simultaneously is described. A new electrochemical sensor was constructed using a gold (Au) electrode that has been modified with poly(1,2‐diaminoanthraquinone) (p‐1,2‐DAAQ). Scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy were used to characterize the p‐1,2‐DAAQ/Au modified electrode. Factors such as the polymer film thickness, electrolyte, square wave parameters and preconcentration conditions were optimized to improve the performance of the modified Au electrode. Good linear responses were achieved in the concentration ranges of 1–200 μg L−1 and 1–50 μg L−1 forBi3+ and Hg2+, respectively, and the limits of detection were 0.27 μg L−1 (Bi3+) and 0.29 μg L−1 (Hg2+). The interference study results illustrated the high selectivity of the modified electrode for detection of Bi3+ and Hg2+. The proposed SW‐ASV method was successfully applied for Bi3+ and Hg2+analyses in different real water samples.

Study of UV-initiated polymerization and UV crosslinking of acrylic monomers mixture for the production of solvent-free pressure-sensitive adhesive films

UV-polymerizable and UV-crosslinkable pressure-sensitive adhesive acrylic compositions are widely applied for high-quality carrier-free films, one-sided or double-sided self-adhesive tapes. Comprehensive studies of the properties of novel acrylic PSAs for carrier-free films or adhesive tapes were carried out. Solvent-free acrylic pressure-sensitive adhesive layers were UV-crosslinked using various photoreactive crosslinking agents. Polymer content during UV-polymerization, prepolymers viscosity, temperature changes of prepolymer during UV-initiated polymerization process were investigated. The chemical structure of prepolymer and polymerized acrylic film were examined using FTIR spectroscopy. Prepolymer mixtures were transferred on the transparent carriers to form 1 mm thick polymer films, and then UV-crosslinked after the addition of the selected acrylic crosslinker. Final adhesive films were then tested to evaluate their functional properties as the tack, peel adhesion, and shear strength at 20 °C and 70 °C. From the results reveal that both concentrations of acrylic acid in the prepolymer, and cross-linking agent in the final polymer layer, have a significant influence on the functional properties of the produced PSA films.

Evaluation of detatchable board-to-board interconnects on screen printed electronic structures

Hybrid printed electronics (HPE) combines advantages of conventional electronics manufacturing technologies such as surface mount technology with those of printed electronics in order to realize more complex electronic systems. To realize the final product, such HPE subassemblies have to be connected to higher-level assemblies. So far interconnection techniques for the so-called level 3 interconnection between printed subsystems and standard electronics have not yet been considered adequately in scientific research. In this paper, alternative detachable level 3 interconnection technologies, i.e. spring loaded contact pins, zero insertion force (ZIF) as well as Non-ZIF connectors are investigated systematically regarding their electrical behaviour against the background of printed electronics. Screen-printed silver filled polymer thick film paste is used to realize printed conductor patterns on flexible polymer substrates, which are connected later on with the alternatives mentioned above. Transition resistance is measured using the four wire method as produced, after repeated mating cycles as well as after accelerated aging tests. The various electrical contacts are subjected to thermal stress in temperature cycling testing and during aging at a constant high temperature. As a result it can be stated, that the sping-loaded contact pins used in this investigation show superior behavior compared with the selected connectors in terms of resistance increase after mating cycles. Concerning long-term behavior after thermal cyling and high temperature storage, all investigated alternaives reveal convincing results.

Gas-sensing performance enhancement in ZnS/polymer films by homogenous morphology surface

The ZnS/polymer films have been successfully prepared by casting technique with different thickness (10,12,13.5 and 14 ) and to carry out a comprehensive study of their gas detection performance. All the different ZnS polymer films thickness demonstrates excellent selectivity and accuracy and stability. ZnS- doped PMMA films show higher sensitivity to ethanol vapors. Further, the films show fast response and recovery to methanol and methanol vapors at higher operating temperatures. The methanol-ethanol sensing mechanism of the film has been explained.

Accuracy of Swanepoel Method in Calculation of Polymer Film Thicknesses

Accuracy of Swanepoel Method in Calculation of Polymer Film Thicknesses

Simultaneous Determination of Refractive Index and Thickness of Submicron Optical Polymer Films from Transmission Spectra.

High-transparency polymers, called optical polymers (OPs), are used in many thin-film devices, for which the knowledge of film thickness (h) and refractive index (n) is generally required. Spectrophotometry is a cost-effective, simple and fast non-destructive method often used to determine these parameters simultaneously, but its application is limited to films where h > 500 nm. Here, a simple spectrophotometric method is reported to obtain simultaneously the n and h of a sub-micron OP film (down to values of a few tenths of a nm) from its transmission spectrum. The method is valid for any OP where the n dispersion curve follows a two-coefficient Cauchy function and complies with a certain equation involving n at two different wavelengths. Remarkably, such an equation is determined through the analysis of n data for a wide set of commercial OPs, and its general validity is demonstrated. Films of various OPs (pristine or doped with fluorescent compounds), typically used in applications such as thin-film organic lasers, are prepared, and n and h are simultaneously determined with the proposed procedure. The success of the method is confirmed with variable-angle spectroscopic ellipsometry.

ZnO Polymeric Composite Films for n-Decane Removal from Air Streams in a Continuous Flow NETmix Photoreactor under UVA Light.

Polymeric composite films have been explored for many photocatalytic applications, from water treatment to self-cleaning devices. Their properties, namely, thickness and porosity, are controlled mainly by the preparation conditions. However, little has been discussed on the effect of thickness and porosity of polymeric composite films for photocatalytic processes, especially in gas phase. In the present study, different preparation treatments of ZnO-based polymeric composite films and their effects on its performance and stability were investigated. The polymeric composites were prepared by solution mixing followed by non-solvent induced phase separation (NIPS), using poly(vinylidene fluoride) (PVDF) as the matrix and ZnO-based photocatalysts. Different wet thickness, photocatalyst mass, and treatments (e.g., using or not pore-forming agent and compatibilizer) were assessed. A low ZnO/PVDF ratio and higher wet thickness, together with the use of pore-forming agent and compatibilizer, proved to be a good strategy for increasing photocatalytic efficiency given the low agglomerate formation and high polymer transmittance. Nonetheless, the composites exhibited deactivation after several minutes of exposure. Characterization by XRD, FTIR-ATR, and SEM were carried out to further investigate the polymeric film treatments and stability. ZnO film was most likely deactivated due to zinc carbonate formation intensified by the polymer presence.

Kinetics of Photocrosslinking and Surface Attachment of Thick Polymer Films

Kinetics of Photocrosslinking and Surface Attachment of Thick Polymer Films

Unraveling Depth-Specific Ionic Conduction and Stiffness Behavior across Ionomer Thin Films and Bulk Membranes

Interfacial behavior of submicron thick polymer films critically controls the performance of electrochemical devices. We developed a robust, everyday-accessible, fluorescence confocal laser scanning microscopy (CLSM)-based strategy that can probe the distribution of mobility, ion conduction, and other properties across ionomer samples. When fluorescent photoacid probe 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) was incorporated into <1 μm thick Nafion films on substrates, the depth-profile images showed thickness- and interface-dependent proton conduction behavior. In these films, proton conduction was weak over a region next to substrate interface, then gradually increased until air interface at 88% RH. Conversely, consistently high proton conduction with no interface dependence was observed across 35-50 μm thick bulk, free-standing Nafion membranes. A hump-like mobility/stiffness distribution was observed across Nafion films containing mobility-sensitive probe (9-(2-carboxy-2-cyanovinyl)julolidine) (CCVJ). The proton conduction and mobility distribution were rationalized as a combinatorial effect of interfacial interaction, ionomer chain orientation, chain density, and ionic domain characteristics.

A Novel Cobalt Metallopolymer with Redox-Matched Conjugated Organic Backbone via Electropolymerization of a Readily Available N4 Cobalt Complex.

Fast and reversible cobalt-centered redox reactions in metallopolymers are the key to using these materials in energy storage, electrocatalytic, and sensing applications. Metal-centered electrochemical activity can be enhanced via redox matching of the conjugated organic backbone and cobalt centers. In this study, we present a novel approach to redox matching via modification of the cobalt coordination site: a conductive electrochemically active polymer was electro-synthesized from [Co(Amben)] complex (Amben = N,N′-bis(o-aminobenzylidene)ethylenediamine) for the first time. The poly-[Co(Amben)] films were investigated by cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM), in situ UV-vis-NIR spectroelectrochemistry, and in situ conductance measurements between −0.9 and 1.3 V vs. Ag/Ag+. The polymer displayed multistep redox processes involving reversible transfer of the total of 1.25 electrons per repeat unit. The findings indicate consecutive formation of three redox states during reversible electrochemical oxidation of the polymer film, which were identified as benzidine radical cations, Co(III) ions, and benzidine di-cations. The Co(II)/Co(III) redox switching is retained in the thick polymer films because it occurs at potentials of high polymer conductivity due to the optimum redox matching of the Co(II)/Co(III) redox pair with the organic conjugated backbone. It makes poly-[Co(Amben)] suitable for various practical applications based on cobalt-mediated redox reactions.

Gas‐phase chemistry and reactive‐ion etching kinetics for silicon‐based materials in C4F8 + O2 + Ar plasma

AbstractIn this study, we investigated the effects of C4F8/O2 and Ar/O2 component ratios in C4F8 + O2 + Ar gas system on plasma parameters, gas‐phase chemistry, and etching kinetics for Si, SiO2, and Si3N4 under the condition of inductively coupled radiofrequency (13.56 MHz) plasma. The use of plasma diagnostics by Langmuir probes, together with the zero‐dimensional plasma modeling, allowed one to compare two different gas mixing regimes in respect to (a) electrons‐ and ions‐related plasma parameters; (b) steady‐state densities of plasma active species; and (c) formation and decay kinetics for F atoms and polymerizing radicals. It was shown that variations in both C4F8/O2 and Ar/O2 mixing ratios result in nonmonotonic (with maximums at ∼10% to 15% O2) Si, SiO2, and Si3N4 etching rates as well as in opposite changes in corresponding effective reaction probabilities. The model‐based analysis of etching mechanisms allowed one to suggest that the net effect from all heterogeneous (i.e., appeared on the etched surface) interaction pathways may be controlled either by the fluorocarbon radical flux (in the case of Ar/O2 mixing ratios at constant fraction of C4F8) through the polymer film thickness or by the O atom flux (in the case of C4F8/O2 mixing ratios at constant fraction of Ar) through the balance of adsorption sites.

Dynamic Reversible Evolution of Wrinkles on Floating Polymer Films under Magnetic Control

In this paper, we present a simple and versatile method to dynamically and reversibly tailor surface wrinkles on a floating polymer film by combining a magnetic droplet and neodymium magnet. The magnetic force from the attraction of the neodymium magnet to the magnetic droplet is the main reason for surface instabilities of floating polymer films, which can induce radial stress in the radial direction, and further, compressive stress in the circumferential direction. This compressive stress can trigger not only floating film wrinkling but also a wrinkle-fold transition. Surface morphologies on the floating polymer film have been systematically studied, by varying the distance between the magnetic droplet and neodymium magnet, polymer film thickness, and magnetic droplet volume. With the decrease in the distance between a magnetic droplet and a neodymium magnet, the decrease in polymer film thickness, and the increase in the magnetic droplet volume, the wrinkle numbers increase and even a wrinkle-fold transition happens. Additionally, the coupling effect of multiple magnetic droplets on the floating film has also been used to achieve novel surface wrinkle patterns, which greatly widens the applications of surface wrinkling.

Aerosol Jet Direct Writing Polymer-Thick-Film Resistors for Printed Electronics

To improve performance and reduce size of printed-circuit board (PCB) in electronics industry, embedding discrete components within a board substrate has been an effective approach by reducing solder joints and their associated impedance mismatching, inductive reactance, etc. With its unique capabilities for non-contact precision material deposition, the Aerosol Jet® direct-write technology has been enabling additive manufacturing of fine-feature electronics conformally onto flexible substrates of complicated shapes. The CAD/CAM controlled relative motions between substrate and print head allows convenient adjustment of the pattern and pile height of deposited material at a given ink volumetric deposition rate. To date in the printed electronics industry, additively printing embedded polymer-thick-film (PTF) resistors has mostly been done with screen printing using carbon-based paste inks. Here we demonstrate results of Aerosol Jet® printed PTF resistors of resistance values ranging from ~50 W to &gt; 1 kW, adjustable (among several variable parameters) by the number of stacked layers (or print passes with each pass depositing a fixed amount of ink) between contact pads of around 1 mm apart with footprint line typically &lt; 0.3 mm. In principle, any ink material that can be atomized into fine droplets of 1 to 5 microns can be printed with the Aerosol Jet® system. However, the print quality such as line edge cleanliness can significantly influenced by ink rheology which involves solvent volatility, solids loading, and so on. Our atomizable carbon ink was made by simply diluting a screen printing paste with a compatible solvent of reasonable volatility, which can be cured at temperatures below 200 oC. We show that Aerosol Jet® printed overlapping lines can be stacked to large pile height (to reduce the resistance value) without significant increase of line width, which enables fabricating embedded resistors with adjustable resistance values in a limited footprint space.

On Relationships between Gas-Phase Chemistry and Reactive Ion Etching Kinetics for Silicon-Based Thin Films (SiC, SiO2 and SixNy) in Multi-Component Fluorocarbon Gas Mixtures.

This work summarizes the results of our previous studies related to investigations of reactive ion etching kinetics and mechanisms for widely used silicon-based materials (SiC, SiO2, and SixNy) as well as for the silicon itself in multi-component fluorocarbon gas mixtures. The main subjects were the three-component systems composed either by one fluorocarbon component (CF4, C4F8, CHF3) with Ar and O2 or by two fluorocarbon components with one additive gas. The investigation scheme included plasma diagnostics by Langmuir probes and model-based analysis of plasma chemistry and heterogeneous reaction kinetics. The combination of these methods allowed one (a) to figure out key processes which determine the steady-state plasma parameters and densities of active species; (b) to understand relationships between processing conditions and basic heterogeneous process kinetics; (c) to analyze etching mechanisms in terms of process-condition-dependent effective reaction probability and etching yield; and (d) to suggest the set gas-phase-related parameters (fluxes and flux-to-flux ratios) to control the thickness of the fluorocarbon polymer film and the change in the etching/polymerization balance. It was shown that non-monotonic etching rates as functions of gas mixing ratios may result from monotonic but opposite changes in F atoms flux and effective reaction probability. The latter depends either on the fluorocarbon film thickness (in high-polymerizing and oxygen-less gas systems) or on heterogeneous processes with a participation of O atoms (in oxygen-containing plasmas). It was suggested that an increase in O2 fraction in a feed gas may suppress the effective reaction probability through decreasing amounts of free adsorption sites and oxidation of surface atoms.

Coherent perfect absorption in resonant materials

Coherent perfect absorption (CPA) is an interferometric effect that guarantees full absorption in a lossy layer independently of its intrinsic losses. To date, it has been observed only at a single wavelength or over narrow bandwidths, whereupon wavelength-dependent absorption can be ignored. Here we produce CPA over a bandwidth of ∼60 nm in a 2 µm thick polymer film with a low-doping concentration of an organic laser dye. A planar cavity is designed with a spectral ‘dip’ to accommodate the dye resonant linewidth, and CPA is thus achieved even at its absorption edges. This approach allows realizing strong absorption in laser dyes—and resonant materials in general—independently of the intrinsic absorption levels, with a flat spectral profile and without suffering absorption quenching due to high doping levels.