Poly Methyl Methacrylate Thin Films Research Articles

Combination of polyurethane and polymethyl methacrylate thin films as a microextraction sorbent for rapid adsorption and sensitive determination of neonicotinoid insecticides in fruit juice and tea by ultra high performance liquid chromatography with tandem mass spectrometry

An economical and effective thin film microextraction (TFME) for simultaneous analysis of ten neonicotinoid insecticides and metabolites in fruit juice and tea, was developed based on the combination of polyurethane (PU) and polymethyl methacrylate (PMMA) films as the sorbent followed by ultra high performance liquid chromatography with tandem mass spectrometry. The PU/PMMA composite was evidenced to possess rapid adsorption and strong accumulation towards neonicotinoids compared with the films used alone. A series of parameters were optimized, and the agitation mode, film size, ionic strength, desorption solvent and sample pH were found to dominate the microextraction process rather than the extraction temperature, agitation time and sample volume. The thin films are cost effective and efficient for single use analysis, but still can be reused at least 8 times with no significant loss in performance. The ten neonicotinoids were measured with good recoveries (81.1–107.9%), high enrichment factors (up to 135), low limits of detection (0.001–0.1 µg L−1), and wide linearity range (1–500 µg L−1, r2>0.9981) in fruit juice (apple, lemon, and pomegranate) and tea (green tea and black tea) samples. The proposed method was successfully applied to commercial fruit and tea drinks, and no samples were tested positive on target neonicotinoids. The PU/PMMA based TFME has shown great potential as an alternative to exhaustive extraction techniques for routine screening of trace neonicotinoids in fruit juice and tea by simplifying the analytical procedure, shortening the operation time, and lowering the material expense.

Polymer dewetting in solvent-non-solvent environment- new insights on dynamics and lithography-free patterning

HypothesisWe show that one may employ polymer dewetting in solvent-non-solvent environment to obtain lithography-free fabrication of well-defined nano- to micro- scale polymer droplets arrays from pre-patterned polymer films. The polymer droplet pattern may be converted to a series of hybrid organic–inorganic and inorganic well-defined nano-patterns by using sequential infiltration synthesis (SIS). In particular, we scrutinize the physical parameters which govern the dewetting of flat and striped polymer thin films, which is the key to obtaining our objective of lithography-free ordered nano-patterns. ExperimentsWe immerse polystyrene (PS) and polymethyl methacrylate (PMMA) thin films in water in the presence of chloroform vapors. We study the ensuing polymer dewetting dynamics and the pattern formation of nanospheres by employing in-situ light microscopy and scanning electron microscopy. We then investigate pattern formation by dewetting of polymer stripes, fabricated by directed solvent evaporation, and SIS of AlOx from vapor phase precursors, trimethyl aluminum (TMA) and H2O, within the nanosphere patterns. FindingsWe find that solvent- non-solvent environments render film dewetting rates, which are an order of magnitude faster than solvent vapor dewetting, and supports the formation of small solid polymer droplets, down to sub-100 nm droplet size, of large contact angles with the solid substrate. Pre-patterned polymer film stripes support the formation of highly ordered structures of polymer droplets, which are easily transformed to hybrid polymer-AlOx nanosphere patterns and templated AlOx nanosphere via SIS.

Nanoscale manipulation of materials patterning through thermomechanical nanolithography using atomic force microscopy

We conducted thermomechanical nanolithography to realize nanoscale manipulation of materials patterning on a polymethyl methacrylate thin film. We used atomic force microscopy with a heated tip make a single scratch on the film surface. The error in the machining force caused by the thermal expansion of the tip cantilever was corrected to guarantee the accuracy of machining force by calibrating the machining parameters, including the spring constant of the tip cantilever and the sensitivity coefficient of the optical lever for different tip temperatures. Three kinds of nanostructure including polymer nanowires, nanopit arrays, and nanogrooves were regulated via controlling scratching velocity and the heated temperature. Inspection of the nanopit arrays proved that fabrication of continuous bundles with desired dimensions can be realized by controlling the feed between adjacent scratching paths. The good agreement between the calculated stick–slip friction and observed machining outcomes demonstrated the feasibility of using stick–slip friction to predict the generation of nanopit structures.

Applications of graphene transistor optimized fabrication process in monolithic integrated driving gallium nitride micro-light-emitting diode

In the information display field, micro-light-emitting diodes (micro-LEDs) possess high potentials and they are expected to lead the direction of developing the next-generation new display technologies. Their display performances are superior to those produced by the currently prevailing liquid crystal and organic light-emitting diode based technologies. However, the micro-LED pixels and their driving circuits are often fabricated on different wafers, which implies that the so-called mass transfer seems to be inevitable, thus facing an obvious bottleneck. In this paper, the emerging graphene field effect transistors are used as the driving elements and integrated onto the GaN micro-LEDs, which is because the pixels and drivers are prepared directly on the same wafer, the technical problem of mass transfer is fundamentally bypassed. Furthermore, in traditional lithographic process, the ultraviolet photoresist directly contacts the graphene, which introduces severe carrier doping, thereby leading to deteriorated graphene transistor properties. This, not surprisingly, further translates into lower performances of the integrated devices. In the present work, proposed is a technique in which the polymethyl methacrylate (PMMA) thin films act as both the protection layers and the interlayers when optimizing the graphene field effect transistor processing. The PMMA layers are sandwiched between the graphene and the ultraviolet photoresist, which is a brand new device fabrication process. First, the new process is tested in discrete graphene field effect transistors. Compared with those devices that are processed without the PMMA protection thin films, the graphene devices fabricated with the new technology typically show their Dirac point at a gate voltage (<i>V</i><sub>g</sub>) deviation from <i>V</i><sub>g</sub> = 0, that is, 22 V lower than their counterparts. In addition, an increase in the carrier mobility of 32% is also observed. Finally, after applying the newly developed fabrication process to the pixel-and-driver integrated devices, it is found that their performances are improved significantly. With this new technique, the ultraviolet photoresist no longer directly contacts the sensitive graphene channel because of the PMMA protection. The doping effect and the performance dropping are dramatically reduced. The technique is facile and cheap, and it is also applicable to two-dimensional materials besides graphene, such as MoS<sub>2</sub> and h-BN. It is hoped that it is of some value for device engineers working in this field.

Quantitative measurement of nanofriction between PMMA thin films and various AFM probes

This study reports the quantitative, precise and accurate results of nanoscale friction measurements with the use of an Atomic Force Microscope calibrated with a precise nanoforce sensor. For this purpose, three samples of spin-coated thin Polymethylmethacrylate (PMMA) films were prepared with the following thicknesses: 235, 343, and 513 nm. Three different AFM probes were used for the friction measurements: with diamond-like carbon (DLC) tip with a small (15 nm) or big (2 µm) tip radius, and a reference silicon tip with a small (8 nm) radius. The results show that in all of the studied cases, the coefficient of friction strongly depends on the applied load, being much higher for a lower load. Furthermore, a strong relation of the friction force on the cantilever’s geometry, the scanning velocity, and the film thickness was observed.

Optical Characterization of Chalcone‐Doped PMMA Thin Films for Photonic Applications Using Spectroscopic Technique of Drop Casting Method

AbstractThin films of PMMA (polymethyl methacrylate) and chalcone prepared via drop casting method is reported here. The newly synthesized chalcone derivative namely 1‐(3‐methoxy‐phenyl)‐3‐(4‐nitro‐phenyl)‐propanone (C2) is used to dope the films with different concentrations. The prepared films are transparent so they are studied for applications in photonics. Optical characterization of the samples is done through different spectroscopy techniques. Absorption spectra of the samples is obtained using UV–vis spectrophotometer. Other significant optical parameters such as refractive index, extinction coefficient, and band gap energies are calculated from the absorption spectra. The doping effect is observed on emission spectra that is obtained using fluorescence spectrophotometer. Also, FTIR spectra of the doped films is obtained and compared with the pure compound to notice changes in the peak values and intensity of the peaks. The present work is done to study the effect of doping on optical properties and figure out the application of samples in photonics.

Luminescent Solar Concentrators from Waterborne Polymer Coatings

This study reports for the first time the use of waterborne polymers as host matrices for luminescent solar concentrators (LSCs). Notably, three types of waterborne polymer dispersions based either on acrylic acid esters and styrene (Polidisp® 7602), acrylic and methacrylic acid esters (Polidisp® 7788) or aliphatic polyester-based polyurethane (Tecfin P40) were selected as amorphous coatings over glass substrates. Water soluble Basic Yellow 40 (BY40) and Disperse Red 277 (DR277) were utilized as fluorophores and the derived thin polymer films (100 μm) were found homogeneous within the dye range of concentration investigated (0.3–2 wt.%). The optical efficiency determination (ηopt) evidenced LSCs performances close to those collected from benchmark polymethylmethacrylate (PMMA) thin films and Lumogen Red F350 (LR) with the same experimental setup. Noteworthy, maximum ηopt of 9.5 ± 0.2 were recorded for the Polidisp® 7602 matrix containing BY40, thus definitely supporting the waterborne polymer matrices for the development of high performance and cost-effective LSCs.

Measurement of Quantum Yields of Monolayer TMDs Using Dye-Dispersed PMMA Thin Films.

In general, the quantum yields (QYs) of monolayer transition metal dichalcogenides (1L-TMDs) are low, typically less than 1% in their pristine state, significantly limiting their photonic applications. Many methods have been reported to increase the QYs of 1L-TMDs; however, the technical difficulties involved in the reliable estimation of these QYs have prevented the general assessment of these methods. Herein, we demonstrate the estimation of the QYs of 1L-TMDs using a poly methyl methacrylate (PMMA) thin film embedded with rhodamine 6G (R6G) as a reference specimen for measuring the QYs of 1L-TMDs. The PMMA/R6G composite films with thicknesses of 80 and 300 nm demonstrated spatially homogeneous emissions with the incorporation of well-dispersed R6G molecules, and may, therefore, be used as ideal reference specimens for the QY measurement of 1L-TMDs. Using our reference specimens, for which the QY ranged from 5.4% to 22.2% depending on the film thickness and R6G concentrations, we measured the QYs of the exfoliated or chemical vapor deposition (CVD)-grown 1L-WS2, -MoSe2, -MoS2, and -WSe2 TMDs. The convenient procedure proposed in this study for preparing the thin reference films and the simple protocol for the QY estimation of 1L-TMDs may enable accurate comparisons of the absolute QYs between the 1L-TMD samples, thereby enabling the development of a method to improve the QY of 1L-TMDs.

Enhancement of side‐coupled surface plasmon resonance sensitivity by application of polymethylmethacrylate thin polymer films

Here the theoretical and experimental investigation for enhancing surface plasmon resonance (SPR) sensitivity in a side-coupled excitation system by the application of polymethylmethacrylate (PMMA) polymer thin films is presented. Proper selection of film materials, gold layer thicknesses d Au and SPR incident angle ( θ SPR ) resulted in the increased effective refractive index of the sensing region, and hence of the device sensitivity, and the dynamic detection range. This work demonstrates, by first-order approximations, a characterisation scheme of SPR chips with unknown gold layer thickness d Au and uncertainty in SPR incident angle. The scheme utilised fitting theoretical calculations to measured SPR responses while varying d Au and θ SPR in equations. Device sensitivity nearly doubled following application of thin PMMA thin films on gold surfaces when sensing water-chloroform mixtures as opposed to untreated surfaces that lacked a PMMA layer. The proposed work demonstrates a facilitative balance between theoretical expectations and experimental data to develop sensors for future applications.

PREPARATION OF MESOSCOPIC STRUCTURE POLY METHYL METHACRYLATE THIN FILMS FOR AFM DATA STORAGE DEVICES.

Poly methyl methacrylate (PMMA) thin films were prepared by dip coating method. Benzene was used as a solvent to prepare PMMA thin films for the time periods ranging from 1 min. to 1 h. The thickness of the films deposited was measured by using an electronic thickness measuring instrument (Tesatronic-TTD-20). Fourier Transform Infrared spectrum was used to identify the above said films. X-ray diffraction spectra indicated the predominantly amorphous nature of the films. Surface morphology of the coated films studied by using scanning electron microscope (SEM) indicated the absence of any pits, cracks and pin holes in the surface. Both as grown and annealed films showed smooth and amorphous structures. The closer SEM inspection revealed the presence of self assembled mesoscopic cells. The mesoscopic structure PMMA thin films could be used as an AFM-based data storage which is promising alternative to conventional magnetic data storage because it offers great potential for considerable storage density improvements.

Hand-held soil moisture meter using polymer coated sensor

An appropriate proportion of water content in the soil is critical for plant growth [1]. The use of capacitive soil moisture sensor exploits the very property of soil that the dielectric value of soil varies with the amount of water content [2], [3]. Use of a capacitive sensor for soil moisture measurement provides some advantages such as better accuracy after soil-specific calibration, high sensitivity, flexibility in probe design, easy installation and cost-effectiveness. A copper cladded epoxy material, coated with a thin film of polymethyl methacrylate (PMMA) polymer, is an established procedure to fabricate the sensor [3], [4], which has been used here for soil moisture sensing. This paper describes the development of a rechargeable battery-operated hand-held meter for fieldwork by using this PMMA coated sensor along with a suitable signal conditioning circuit. The thermo-gravimetric method has been utilized to obtain the actual moisture content of soil [5] and calibrate it with respect to the voltage output of the meter. Moreover, with the moisture content, surrounding temperature and humidity are also useful atmospheric parameters used by weather stations [6]. For this, a DHT12 sensor has been integrated with this hand-held meter. IoT extension of measured data is implemented by a SIM900A GPRS/GSM modem to make the meter smart.

Internal Stresses in Plasma Deposited Polymer Film Coatings

A technique for measuring the internal stresses in polymer films deposited on a glass substrate in gas discharge plasma is developed. Using this technique, the dependence of internal stress in thin films of polymethylmethacrylate and polystyrene on the deposition time and the current density of the barrier discharge at atmospheric pressure is studied. It is found that, when forming thin polymer coatings from monomers with high polymerization efficiency, the average value of internal stresses is higher than that for coatings obtained from monomers having low polymerization efficiency in barrier discharge plasma at atmospheric pressure. This can be explained by an increase in the specific number of cross-links in the first type of films under the action of ultraviolet radiation from the plasma. The quasi-optimal deposition time of the polymer film coating from styrene is found in which the value of the internal stress is minimal at a film thickness acceptable for a number of practical applications.

Flexible Hydrogen Sensor Using Ni-Zr Alloy Thin Film

A triple-layered PMMA/Ni64Zr36/PDMS hydrogen gas sensor using hydrogen permeable alloy and flexible polymer layers is fabricated through spin coating and DC-magnetron sputtering. PDMS(polydimethylsiloxane) is used as a flexible substrate and PMMA(polymethylmethacrylate) thin film is deposited onto the Ni64Zr36 alloy layer to give a high hydrogenselectivity to the sensor. The measured hydrogen sensing ability and response time of the fabricated sensor at high hydrogen concentration of 99.9 % show a 20 % change in electrical resistance, which is superior to conventional Pd-based hydrogen sensors, which are difficult to use in high hydrogen concentration environments. At a hydrogen concentration of 5 %, the resistance of electricity is about 1.4 %, which is an electrical resistance similar to that of the Pd77Ag23 sensor. Despite using low cost Ni64Zr36 alloy as the main sensing element, performance similar to that of existing Pd sensors is obtained in a highly concentrated hydrogen atmosphere. By improving the sensitivity of the hydrogen detection through optimization including of the thickness of each layer and the composition of Ni-Zr alloy thin film, the proposed Ni-Zr-based hydrogen sensor can replace Pd-based hydrogen sensors.

Comparison of AFM Nanoindentation and Gold Nanoparticle Embedding Techniques for Measuring the Properties of Polymer Thin Films.

The surfaces of polymer and interfaces between polymer and inorganic particles are of particular importance for the properties of polymers and composites. However, the determination of the properties of surfaces and interfaces poses many challenges due to their extremely small dimensions. Herein, polystyrene and polymethyl methacrylate thin film on silicon wafer was used as a model system for the measurement of the properties of the polymer near free surface and at the polymer-solid interface. Two different methods, i.e., nanoindentation using atomic force microscopy (AFM) and the gold nanoparticle embedding technique, were used for these measurements. The results showed the elastic modulus of PS near the free surface determined by nanoindentation was lower than the bulk value. Based on contact mechanics analysis, nanoparticle embedding also revealed the existence of a lower-modulus, non-glassy layer near the free surface at temperatures below the bulk glass transition temperature (Tg). However, near the polymer-solid interface, the AFM nanoindentation method is not applicable due to the geometry confinement effect. On the other hand, the nanoparticle embedding technique can still correctly reflect the interactions between the polymer and the substrate when compared to the ellipsometry results.

Thermally cross-linked polyvinyl alcohol as gate dielectrics for solution processing organic field-effect transistors

Poly(vinyl alcohol) (PVA) thin-films were cross-linked by N,N’-methylene bisacrylamide (MBA) in a thermal induced radical process at 100℃. The cross-link improved the dielectric properties of PVA thin-films. The effect of surface passivation by cross-linked polymethyl methacrylate (PMMA) thin-films on the electrical properties and the surface characteristics of the PVA gate dielectrics were also investigated. The surface passivation layer significantly reduced surface hydrophilicity and improved the morphology of semiconductor layers. The bilayer dielectrics were applied in solution processed OFET devices with a bottom-gate bottom-contact structure.

Fabrication of Nanopatterns on Silicon Surface by Combining AFM-Based Scratching and RIE Methods

This study presents an atomic force microscope (AFM)-based scratching combined with reactive ion etching (RIE) method to fabricate nanopatterns on the silicon surface. All AFM-based scratching processes are performed on the polymethylmethacrylate (PMMA) film to create features in order to protect the AFM tip from wearing and enlarge its life time. Two types of resist films are selected for the RIE process. One is only PMMA thin-film resist, and the other one contains two-layer thin-film resist which are PMMA and aluminum thin films. The nanopatterns on the silicon after etching using RIE with these two types of resist film are compared. Results show that when using PMMA film, the width of the nanopattern on silicon is larger than on the PMMA film, and the material pile-ups formed during the scratching process cannot be considered as a resist. On the contrary, the aluminum thin films can improve the quality of the transfer. It indicates that the thin-film resist with bilayers can guarantee the transfer accuracy of the features, which can expand the application of the AFM tip-based scratching technique.

Biofabricated silver nanoparticles incorporated polymethyl methacrylate as a dental adhesive material with antibacterial and antibiofilm activity against Streptococcus mutans.

In this study, polymethyl methacrylate (PMMA) thin films incorporated with biofabricated silver nanoparticles were used to evaluate the in vitro antimicrobial and antibiofilm activity against the cariogenic bacterium Streptococcus mutans. For this, silver nanoparticles (AgNPs) were generated using Bacillus amyloliquefaciens SJ14 culture (MAgNPs) and extract from Curcuma aromatica rhizome (CAgNPs). The AgNPs were further characterized by UV-Vis spectroscopy and high-resolution transmission electron microscopy. The minimum inhibitory concentration, minimum bactericidal concentration and antibiofilm activity of AgNPs against S. mutans were also assessed. Here, MAgNPs were found to have superior antimicrobial activity when compared to CAgNPs. TheMAgNPs and CAgNPs also demonstrated 99% and 94% inhibition of biofilm formation of S. mutans at concentrations of 3µg/mL and 50µg/mL, respectively. The AgNPs were further incorporated into PMMAthin films using solvent casting method. The thin films were also characterized by scanning electron microscopy and UV-Vis spectroscopy. Subsequently, both PMMA/MAgNPs and PMMA/CAgNPs nanocomposite thin films were subjected to antimicrobial and antibiofilm analysis. Themicrobicidal activity wasfound to be higher for the PMMA/MAgNPs thin film, which highlights the potency of microbially synthesized AgNPs as excellent agents to inhibitcariogenic bacteria from colonisingdental restorative material.

A multiple-band perfect absorber for SEIRA applications

Recently perfect absorbers (PAs) have received significant interest due to their characteristics of complex electric permittivity (ε) and magnetic permeability (μ). By rationally designing these artificial structures, the impedance of the perfect absorber can be matched to free space with an independent adjustment in the electric and magnetic resonances, where this structure leads to strong absorption from mid- to near-IR wavelength. In this article, we proposed a multiband PA platform, which simultaneously operates with a near unity absorption at different resonances that could be an ideal candidate for multiple sensing of molecular fingerprints. We numerically analyzed the dependence of the optical response of the PA platform through finite-difference time domain (FDTD) simulations for a fine-tuning mechanism of the PA platform. We theoretically demonstrated the surface enhanced infrared absorption (SEIRA) capability of our PA platform by studying its optical response with a thin protein bilayer and a polymethyl-methacrylate (PMMA) film. As an initial step we experimentally showed the vibrational modes of a thin PMMA film. We believe, our findings could open new avenues for reliable SERIA platforms through providing multiple vibrational finger print information compared to its conventional counterparts relying only on a single sensing data.

Memory effect and electrical hysteresis in CdS nanorods embedded polymer thin films

Herein, we report the memory characteristics and hysteresis behavior of the cadmium sulphide (CdS) embedded poly-methyl methacrylate (PMMA) thin films in a sandwich cell configuration. The devices were fabricated by depositing different concentrations of CdS-PMMA nanocomposites onto indium tin oxide (ITO) coated glass substrates by spin coating technique. Aluminum (Al) was deposited through thermal evaporation technique and was used as top electrode. Structural analysis of the synthesized CdS were performed by using X-ray diffraction (XRD) and field emission scanning electron microscopy (Fe-SEM). UV-Visible absorption spectroscopy and photoluminescence (PL) spectroscopy were performed for optical analysis and optical energy gap was estimated. The current-voltage characteristics of the fabricated devices were studied which displays anti clockwise hysteresis behavior. The area within the hysteresis loop increases with increasing the concentration of CdS within the PMMA thin films.

Preparation of poly methyl methacrylate thin film by solution casting method to study its ultrasonic velocity

Polymers are long chain giant organic molecules are assembled from many smaller molecules called monomers. The work reflects the preparation of poly methyl methacrylate thin film by solution casting method. The XRD of PMMA/ZrO2 polymer is taken to confirm the structure and nature of material. Furthermore, it is characterized by finding the ultrasonic velocity at different concentration of ZrO2 and at different temperature keeping the frequency same.