Poly Methyl Methacrylate Layer Research Articles

Development and Characterization of Passivation Methods for Microneedle-based Biosensors.

Microneedles (MN) are short, sharp structures that have the ability to painlessly pierce the stratum corneum, the outermost layer of the skin, and interface with the dermal interstitial fluid that lies beneath. Because the interstitial fluid is rich in biomarkers, microneedle-based biosensors have the potential to be used in a wide range of diagnostic applications. To act as an electrochemical sensor, the tip or the body of the MN must be functionalized, while the substrate areas are generally passivated to block any unwanted background interference that may occur outside of the skin. This work presents four different passivation techniques, based on the application of SiO2, polymethyl methacrylate (PMMA), an adhesive film, and varnish to the substrate areas. Optical, SEM and electrochemical measurements were performed to quantitatively assess the performance of each film. The data shows that whilst manual application of varnish provided the highest level of electrical isolation, the spin-coating of a 5 μm thick layer of PMMA is likely to provide the best combination of performance and manufacturability. Clinical Relevance- Substrate passivation techniques will improve the performance of microneedle-based non-invasive continuous monitoring systems.

Spin-casting of Micron-Scale Thick PMMA Films with Embedded Au Nanoparticles Formed by Laser Ablation in Liquid

Background: A Facile, scalable approach to fabrication of organic thin films with an embedded layer of nanoparticles in the ambient environment. The approach is based on step-bystep spin-coating of polymethylmethacrylate (PMMA) films and a nanoparticle layer. Objective: The goal of the present work is to fabricate a sandwich structure of the PMMA films for the top and bottom layers of a sandwich structure as well as a middle layer of nanoparticles formed in solution by the Laser Ablation in Liquid (LAL) method. Methods: First, a PMMA thin film was fabricated by spin-casting of PMMA solution in ethylacetate. Secondly, a solution of Au nanoparticles synthesized by laser ablation in ethanol was spin-cast on a prefabricated PMMA film. The distribution of Au nanoparticles and the morphology of the resulting film were analyzed using scanning electron microscopy (SEM), optical microscopy, and atomic microscopy (AFM). Finally, another PMMA layer was spin-cast on the nanoparticle-decorated film. Results: A hybrid organic film with the embedded layer of nanoparticles was fabricated using the spin-casting method for top and bottom layers as well as for the middle layer of Au nanoparticles fabricated by laser ablation in ethanol by a pulsed UV laser. Statistical and fractal analysis shows uniform distribution of nanoparticles on length scale above ten microns. Conclusion: Spin-cast-based layer-by-layer approach to fabrication of sandwich structures of organic films with embedded nanoparticlesis a facile and scalable method for hybrid organic - nanoparticle films. This approach can be extended for the fabrication of multi-layered hybrid structures.

Smart Error Sum Based on Hybrid Two-Trace Two-Dimensional (2T2D) Correlation Analysis.

Based on hybrid 2D correlation analysis, we recently derived and introduced a "smart error sum," a sophisticated loss function that can be used for solving nonlinear inverse problems like the determination of optical constants and oscillator parameters from a series of optical spectra in the infrared spectral region. The advantage of the smart error sum compared to the conventional sum of squared errors lies in its ability to marginalize multiplicative systematic errors such as, for example, reflectance values above unity in transflection spectra. This is enabled by a transformation, which allows fits to not exclusively focus on forcing fit spectra to agree with experimental spectra at every wavenumber point by all means, but also to take correlations such as spectral similarities and their changes with certain perturbations into account. In this work, we extend our approach to accommodate the treatment of individual spectra, instead of only series, based on hybrid two-trace two-dimensional (2T2D) correlation analysis. We evaluate and prove the value of our approach by individually analyzing experimental transflection spectra of polymethyl methacrylate (PMMA) layers on gold substrates. The comparison of the results with those obtained by the original smart error sum based on the whole set of spectra as well as those resulting from conventional fitting of series and individual spectra (using the conventional sum of squared errors) confirms the validity and soundness of the 2T2D smart error sum.

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 spin casting solvent on the self‐assembly of silicon‐containing block copolymer thin films via high temperature thermal treatment

AbstractThe present paper focuses on the influence of different solvents (toluene, mesitylene, acetone, tetrahydrofuran, propylene glycol monomethyl ether acetate (PGMEA) and ethyl acetate) on the self‐assembly behaviour of cylinder‐forming polystyrene‐block‐poly(dimethylsiloxane‐random‐vinylmethylsiloxane) diblock copolymer films deposited on thin brush layers of polystyrene (PS) or polymethylmethacrylate (PMMA) polymers grafted to a silicon substrate. The morphology and the key metrics for all samples were determined from the analysis of the SEM images and their evolution was investigated, as a function of the annealing time at 310 °C, for each solvent and for both PS and PMMA brushes. In general, shorter correlation lengths ξ are observed on PS brushes than on PMMA brushes. In addition, SEM data analysis reveals that tetrahydrofuran, PGMEA and ethyl acetate solvents promote a morphological change from fingerprint‐like parallel cylinders to a hexagonally packed dot pattern for annealing time tA > 30 s. Finally, the line edge roughness and linewidth roughness values are weakly dependent on both the casting solvent and the nature of the grafted brush. The reported data reveal that the choice of the polymer brush nature and of the solvent employed during the spin coating of the diblock copolymer film could substantially affect the self‐assembly process and requires accurate optimization due to their subtle interplay. © 2021 Society of Industrial Chemistry.

Термодеструкция полиметилметакрилата и его композита с фуллереном C-=SUB=-60-=/SUB=- после ультрафиолетового облучения

The analysis of the ultraviolet induced transformation of the thermal decomposition spectra of the monomer of the submicrometer layers of polymethylmethacrylate and its composite with fullerene C60 for different fullerene concentrations and irradiation doses has been carried out. Formation of the new decomposition stages in the spectra has been interpreted by the binding between C60 and side ester groups of polymethylmethacrylate.

Thermal decomposition of polymethylmethacrylate and its composite with fullerene C-=SUB=-60-=/SUB=- after ultraviolet irradiation

The analysis of the ultraviolet induced transformation of the thermal decomposition spectra of the monomer of the submicrometer layers of polymethylmethacrylate and its composite with fullerene C60 for different fullerene concentrations and irradiation doses has been carried out. Formation of the new decomposition stages in the spectra has been interpreted by the binding between C60 and side ester groups of polymethylmethacrylate. Keywords: polymethylmethacrylate, fullerene, ultraviolet irradiation, thermal decomposition, mass-spectrometry.

PMMA direct exfoliation for rapid and organic free transfer of centimeter-scale CVD graphene

Despite the various techniques developed for the transfer of large area graphene grown by chemical vapor deposition (CVD), the conventional polymethylmethacrylate (PMMA) transferring technique has been widely applied in laboratories due to its convenience and economical cost. However, the complete removal of PMMA on graphene surface has become a troublesome, and the PMMA residue could degrade the properties of graphene significantly. We report here a facile water assisted technique to directly peel off the PMMA layer over centimeter-sized CVD graphene film for the first time. No organic solvents are involved in the whole transfer process. The transferred graphene film is clean and intact over large area because of the cooperative effect of the capillary force and the van der Waals force which facilitates the conformal contact between graphene film and the substrate. Various types of graphene samples (i.e. monolayer, multilayer, and incomplete domains) can be easily transferred to diverse substrates including silicon wafer, sapphire, and quartz with good integrity. The transferred graphene film is of high cleanliness, and the graphene transistors show higher carrier mobility and lower level of p-type doping comparing to the conventional wet transfer technique.

Suppressing Interfacial Shunt Loss via Functional Polymer for Performance Improvement of Lead‐Free Cs2AgBiBr6 Double Perovskite Solar Cells

All‐inorganic lead‐free Cs2AgBiBr6 double perovskite solar cells (PSCs) have attracted growing attention owing to their eco‐friendly features and robust intrinsic stability. However, arising from the rapid crystal growth, the poor film quality always leads to substantial non‐radiative recombination and inferior performance improvement. Herein, high‐efficiency and stable Cs2AgBiBr6 PSCs are obtained by introducing a functional polymethyl methacrylate (PMMA) layer at the perovskite surface to avoid direct contact between carbon and the underlying charge transfer layer, as well as to passivate the defects. When assembling into solar cells, the non‐radiative charge recombination is suppressed and the interfacial charge extraction is accelerated. As a result, the carbon‐electrode‐based Cs2AgBiBr6 PSC yields an enhanced efficiency of 2.25% with a high open‐circuit voltage of 1.18 V. Moreover, the unencapsulated device exhibits superior long‐term stability owing to the protection of the PMMA layer from corrosion by the extraneous water and oxygen, retaining nearly 100% of the initial efficiency after storage in 25 °C, with 5% relative humidity (RH) for 80 days and high temperature of 85 °C, and 0% RH for 60 days, respectively. A simple method of polymer passivation for enhancing the performance and stability of Pb‐free Cs2AgBiBr6 PSCs is provided.

Transparent radiative cooling films containing poly(methylmethacrylate), silica, and silver

Window is the least energy-efficient part of buildings or cars; however radiative cooling, as an efficient energy-zero technology, is rarely used in window films of buildings or cars. Therefore, we in this work fabricated a transparent dual-layer film for daytime radiative cooling, which contained a layer of polymethyl methacrylate (PMMA) uniformly mixed with modified silica nanoparticles (SiO2 NPs) and a layer of silver. The dispersion of the modified SiO2 NPs in PMMA was notably improved through in-site grafting PMMA, which resulted in a high transparency of the radiative cooling film even at a high filling fraction of SiO2 (20 wt%). Owing to the strong broadband IR absorbance/emittance (εAW = 94.3%) and high sunlight reflectance (ρ ≈ 50%), the dual-layer film possessed a high cooling capacity and could achieve an average temperature drop of 1.4 °C than pure PMMA film in the daytime outdoor cooling measurement. In the simulated automotive cooling test, the dual-layer film cooled the interior space up to 6 °C below ambient temperature during peak solar hours. The excellent optical property and cooling capability exhibit a promising application of building and car windows for cooling their interior spaces.

Whispering Gallery Mode Resonator Temperature Compensation and Refractive Index Sensing in Glucose Droplets.

Among the different types of photonic sensor devices, optical whispering gallery mode resonators (WGMRs) have attracted interest due to their high level of sensitivity, small size, and ability to perform real-time temperature measurements. Here we demonstrate the applicability of temperature measurements using WGMR in both air and liquid environments. We also show that WGMR allowed measurements of the refractive index variations in an evaporating glucose–water solution droplet. The thermal tuning of WGMR can be reduced by coating WGMRs with a thin layer of polymethyl methacrylate (PMMA). Dip-coating the silica microsphere multiple times significantly reduced the resonance shift, partially compensating for the positive thermo-optical coefficient of silica. The shift direction changed the sign eventually.

Controllable refractive index sensing and multi-functional detecting based on the spin Hall effect of light.

In this work, based on the spin Hall effect of light (SHEL), by considering the surface plasmon resonance (SPR) effect, a multi-functional detecting and controllable refractive index (RI) sensing structure containing sodium is theoretically established. The results reveal that the sodium layer has great influence on transverse shift (TS) of SHEL, while the polymethyl methacrylate (PMMA) layer has a large impact on the resonance angle. In the symmetrical distribution of TS, sodium has obvious advantages over gold and silver in the TS and sensitivity. The quantitative relationship between the TS and the RI of the sensing medium is established. Fermi energy, thicknesses of PMMA and sodium can be adjusted to measure the RI of three different orders. Remarkably, the sensitivity can be controlled by changing the thickness of sodium. The structure can also be used to measure the resonance angle and Fermi energy. Therefore, besides the advantages of sodium, this work realizes controllable sensing of RI and the functions of resonance angle and Fermi energy detecting. These studies may open avenues for the application of optical RI sensors and the precision measurement of other physical quantities.

Enhanced One-Photon and Two-Photon Amplified Spontaneous Emissions of CsPbBr3 Thin Films by Insulating Polymer Coating

Lead halide perovskite is an attractive candidate for fabricating low-cost one-photon and two-photon-pumped lasers. However, the presence of vast trap sites and the leakage of electric fields limit the efficient amplified spontaneous emission (ASE) performances. Herein, we show that incorporating an insulating polymethylmethacrylate layer with a proper thickness onto perovskite films can play an important role in not only reducing both one-photon and two-photon ASE thresholds but also improving the light exposure stability remarkably. By means of spectroscopic investigation and optical simulation, the enhancement was ascribed to the trap passivation and electric field restraint and improved light outcoupling due to the dielectric confinement by the formation of symmetric waveguides structure. This work indicates the possibility of simple and effective approaches to realize efficient ASE and lasing.

Characterizing and Optimizing Piezoelectric Response of ZnO Nanowire/PMMA Composite-Based Sensor.

Due to the outstanding coupling between piezoelectric and semiconducting properties of zinc oxide nanowires, ZnO NW-based structures have been demonstrating promising potential with respect to their applicability in piezoelectric, piezotronic and piezo-phototronic devices. Particularly considering their biocompatibility and biosafety for applications regarding implantable medical detection, this paper proposed a new concept of piezoelectric composite, i.e., one consisting of vertically aligned ZnO NW arrays and an insulating polymer matrix. First, the finite element method (FEM) was employed to drive optimization strategies through adjustment of the key parameters such as Young’s modules and the dielectric constant of the dielectric constituents, together with the density and dimension of nanowire (NW) itself. Second, to investigate the functionality of each individual layer of composite, different designed structures were fabricated and characterized in terms of electrical and piezoelectric properties. Next, experimental and simulation tests were performed, indicating that the decreasing thickness of the top poly(methyl methacrylate) layer (PMMA) can substantially enhance the piezoelectric sensitivity of the ZnO NW composite. Besides the further benefit of no polarization being needed, our material has a comparable charge coefficient (d33) with respect to other lead-free alternatives (e.g., BaTiO3), confirming the high sensing abilities of the developed structure based on vertically aligned ZnO NW arrays. Finally, a time-varying model combining piezoelectricity and electric circuit modules was investigated in detail, giving rise to an estimation of the d33 coefficient for ZnO NWs. Based on this study, the developed material is revealed to be highly promising in medical applications, particularly regarding the FFR technique, where coronary pressure can be measured through a piezoelectric sensor.

PMMA sacrificial layer based reliable debonding of ultra-thin chips after lapping

Ultra-thin chips (UTCs) are needed to meet the performance and packaging related requirements of flexible electronics and 3D integrated circuits (ICs). However, handling of UTCs (<50 μm thick), particularly after thinning, is a challenging task as the excessive mechanical stresses could lead to cracking. Such damages could be prevented by restricting the stresses to acceptable levels. Herein, we present a new reliable and cost-effective method based on a polymethylmethacrylate (PMMA) sacrificial layer (20 μm-thick). The PMMA layer results in 4 order of magnitude lower stress on UTCs and, as a result, the reliable removal or debonding of UTCs (35 μm-thick) from the glass substrate has been achieved. The distinctive features of the presented method are high reliability and cost-effectiveness (an order of magnitude cheaper) with respect to conventional methods that use UV curable tapes. The UTCs with metal-oxide-semiconductor capacitors (MOSCAPs) devices were also obtained using this approach and were evaluated under different bending conditions. The stable and uniform performance (134 pF) observed under bending conditions demonstrates that the presented technique could be useful for integration of high-performance flexible UTCs on flexible printed circuit boards for various practical application.

Characterization of Inkjet-Printed Digital Microfluidics Devices.

Digital microfluidics (DMF) devices enable precise manipulation of small liquid volumes in point-of-care testing. A printed circuit board (PCB) substrate is commonly utilized to build DMF devices. However, inkjet printing can be used to fabricate DMF circuits, providing a less expensive alternative to PCB-based DMF designs while enabling more rapid design iteration cycles. We demonstrate the cleanroom-free fabrication process of a low-cost inkjet-printed DMF circuit. We compare Kapton and polymethyl methacrylate (PMMA) as dielectric coatings by measuring the minimal droplet actuation voltage for a range of actuation frequencies. A minimum actuation voltage of 5.6 V was required for droplet movement with the PMMA layer thickness of 0.2 μm and a hydrophobic layer of 0.17 μm. Significant issues with PMMA dielectric breakdown were observed at actuation voltages above 10 V. In comparison, devices that utilized Kapton were found to be more robust, even at an actuation voltage up to 100 V.

Highly efficient exosome purification from human plasma by tangential flow filtration based microfluidic chip

Abstract Exosomes play an important role in microenvironmental regulation, cellular communication, tumor progression/metastasis and prognosis. A key challenge in the study of exosomes is the isolation and purification of exosomes from contaminants. In this study, we develop a size-dependent microfluidic chip to isolate and purify exosomes from human blood by tangential flow filtration. The microfluidic chip combines symmetrically two polymethyl methacrylate (PMMA) layers with serpentine channels and a nanoporous polycarbonate track etched (PCTE) membrane in between. Due to the uniform pore size (∼100 nm in diameter) of the nanoporous PCTE membrane, protein contaminants can be cleaned with high efficiency (> 97 %), and exosomes trapped in the microfluidic chip can be collected by reverse elution with high recovery (> 80 %). The collected exosomes are subjected to matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) analysis. Based on the fingerprint peaks of exosomes, it is demonstrated that plasma proteins are largely cleaned and only exosome proteins dominate the mass spectra. Compared to ultracentrifugation (UC) that is considered as the “gold standard” for exosome isolation and purification, the size-dependent microfluidic chip-based protocol shows higher protein cleaning efficiency and exosome recovery rate. The whole process takes

Semiempirical, parameterized spectrum estimation for x-ray computed tomography.

To develop a tool to produce accurate, well-validated x-ray spectra for standalone use or for use in an open-access x-ray/CT simulation tool. Spectrum models will be developed for tube voltages in the range of 80kVp through 140kVp and for anode takeoff angles in the range of 5° to 9°. Spectra were initialized based on physics models, then refined using empirical measurements, as follows. A new spectrum-parameterization method was developed, including 13 spline knots to represent the bremsstrahlung component and 4 values to represent characteristic lines. Initial spectra at 80, 100, 120, and 140kVp and at takeoff angles from 5° to 9° were produced using physics-based spectrum estimation tools XSPECT and SpekPy. Empirical experiments were systematically designed with careful selection of attenuator materials and thicknesses, and by reducing measurement contamination from scatter to <1%. Measurements were made on a 64-row CT scanner using the scanner's detector and using multiple layers of polymethylmethacrylate (PMMA), aluminum, titanium, tin, and neodymium. Measurements were made at 80, 100, 120, and 140kVp and covering the entire 64-row detector (takeoff angles from 5° to 9°); a total of 6,144 unique measurements were made. After accounting for the detector's energy response, parameterized representations of the initial spectra were refined for best agreement with measurements using two proposed optimization schemes: based on modulation and based on gradient descent. X-ray transmission errors were computed for measurements vs calculations using the nonoptimized and optimized spectra. Half-value, tenth-value, and hundredth-value layers for PMMA, Al, and Ti were calculated. Spectra before and after parameterization were in excellent agreement (e.g., R2 values of 0.995 and 0.997). Empirical measurements produced smoothly varying curves with x-ray transmission covering a range of up to 3.5 orders of magnitude. Spectra from the two optimization schemes, compared with the unoptimized physic-based spectra, each improved agreement with measurements by twofold through tenfold, for both postlog transmission data and for fractional value layers. The resulting well-validated spectra are appropriate for use in the open-access x-ray/CT simulator under development, the x-ray-based Cancer Imaging Toolkit (XCIST), or for standalone use. These spectra can be readily interpolated to produce spectra at arbitrary kVps over the range of 80 to 140kVp and arbitrary takeoff angles over the range of 5° to 9°. Furthermore, interpolated spectra over these ranges can be obtained by applying the standalone Matlab function available at https://github.com/xcist/documentation/blob/master/XCISTspectrum.m.

A simple and low-cost approach for irreversible bonding of polymethylmethacrylate and polydimethylsiloxane at room temperature for high-pressure hybrid microfluidics

Microfluidic devices have been used progressively in biomedical research due to the advantages they offer, such as relatively low-cost, rapid and precise processing, and an ability to support highly automated analyses. Polydimethylsiloxane (PDMS) and polymethylmethacrylate (PMMA) are both biocompatible materials widely used in microfluidics due to their desirable characteristics. It is recognized that combining these two particular materials in a single microfluidic device would enable the development of an increasingly in-demand array of new applications, including those requiring high flow rates and elevated pressures. Whereas complicated and time-consuming efforts have been reported for bonding these two materials, the robust adhesion of PDMS and PMMA has not yet been accomplished, and remains a challenge. In this study, a new, simple, efficient, and low-cost method has been developed to mediate a strong bond between PMMA and PDMS layers at room temperature in less than 5 min using biocompatible adhesive tape and oxygen plasma treatment. The PDMS–PMMA bond was hydrolytically stable, and could tolerate a high influx of fluid without any leakage. This study addresses the limitations of existing approaches to bond these materials, and will enable the development of highly sought high-pressure and high-throughput biomedical applications.

High-Performance PVDF-HFP Based Gel Polymer Electrolyte Modified by Core-Shell SiO2-PMMA for Electrochromic Devices

The aim of the study was to determine the effect of inorganic core-shell SiO2 nanoparticles modified with polymethyl methacrylate (PMMA) layer, on the optical and electrochemical properties of poly vinylidenefluoride-co-hexafluoropropylene (PVDF-HFP) gel polymer electrolyte (GPE). The core-shell SiO2 nanoparticles were first modified with PMMA to improve its dispersibility and compatibility in the polymer matrix. The morphology and structural properties of the core-shell SiO2 nanoparticles before and after modification were characterized by XRD, FTIR and SEM analysis. Then the modified SiO2 nanoparticles were used to prepare the composite GPE, composed of chemically modified core-shell structured SiO2-PMMA and PVDF-HFP polymer matrix. The transformation of nano-silica to SiO2-PMMA nanoparticles shows the better compatibility of PMMA and PVDF-HFP that favours the silica to be well dispersed in the organic matrix and significantly improve the doping effect. Various concentrations of modified SiO2-PMMA were used to dope PVDF-HFP GPEs. The results indicate that the 10% doping shows the highest ionic conductivity i.e. 2.22 × 10−3 s cm−1. In addition, the composite GPEs show the high transmittance and good thermal stability; therefore it can add important insight into developing high-performance materials for electrochromic devices.