parylene-N Film Research Articles

Quantitative analysis of vitamin D using m/MALDI-TOF mass spectrometry based on a parylene matrix chip

Vitamin D deficiency is associated with various disorders and is diagnosed based on the concentration of 25-hydroxy vitamin D3 (25(OH)D3) in serum. The parylene matrix chip was fabricated to reduce the matrix background noise, and the homogenous distribution of the matrix was retained for the quantitative analysis of 25(OH)D3. The Amplex Red assay was performed to confirm that the sample-matrix mixing zone of the parylene matrix chip was formed below the surface of the parylene-N film. The homogeneous distribution of the matrix was verified from the fluorescence image. For effective analysis using a parylene matrix chip, 25(OH)D3 was modified through the nucleophilic addition of betaine aldehyde (BA) to form a hemiacetal salt. Such modified 25(OH)D3 with a positive charge from BA could be effectively analyzed using MALDI-TOF mass spectrometry. Serum 25(OH)D3 was extracted by liquid–liquid extraction (LLE) and quantified using MALDI-TOF mass spectrometry based on the parylene matrix chip. The intensity of the mass peak of 25(OH)D3 was linearly correlated (r2 = 0.992) with the concentration of 25(OH)D3 spiked in serum, and the LOD was 0.0056 pmol/μL. Energy drinks and vitamin D3 tablets were also employed for the real sample analysis. Finally, the results of the chemiluminescence binding assay and MALDI-TOF mass spectrometry were statistically analyzed to determine the applicability of the method using the Bland–Altman test and Passing–Bablok regression.

Modified parylene-N films as chemical microenvironments for differentiation and spheroid formation of osteoblast cells

In this work, the influence of parylene N film on the spheroid formation of osteoblast-like cells (MG-63) was determined and compared with that of high-hydrophilicity microenvironments, such as hydrophilic culture matrix and ultraviolet-treated parylene N film. To elucidate the change in cell properties due to the microenvironment of parylene N film, global gene expression profiles of MG-63 cells on parylene N film were analyzed. We confirmed the upregulated expression of osteoblast differentiation- and proliferation-related genes, such as Runx2, ALPL, and BGLAP and MKi67 and PCNA, respectively, using the real-time polymerase chain reaction. In addition, the differentiation and proliferation of osteoblast cells cultured on parylene N film were validated using immunostaining. Finally, the formation of spheroids and regulation of differentiation in human mesenchymal stem cells (MSCs) on parylene N film was demonstrated. The results of this study confirm that the microenvironment with the controlled hydrophobic property of parylene N film could effectively trigger the bone differentiation and maintains the proliferation of MSCs, similar to MG-63 cells without any scaffold structures or physical treatments.

UV-irradiated parylene surfaces for proliferation and differentiation of PC-12 cells.

PC-12 cells originate from neuroblastic cells, which have an ability to differentiate into neuronlike cells. In this work, the purpose was to estimate the influence of microenvironments on cell attachment and neuritogenesis capacity of PC-12 cells on parylene-N and parylene-C films with and without ultraviolet (UV) light treatment. The estimate of total cell number after incubation for 72h, the ratio of adherent to suspended cells, counting of neurite outgrowths on parylene-N or parylene-C films after UV exposure suggested that these films were suitable for proliferation as well as differentiation of PC-12 cells. The differences in surface properties of parylene-N and parylene-C films with and without UV exposure were analyzed by contact angle measurement, Fourier-transform infrared spectrometry, and X-ray photoelectron spectroscopy. According to these analyses, introduction of oxygen-related chemical functional groups was presumed to result in increased hydrophilicity and efficiency of protein immobilization on parylene-N and parylene-C films after UV treatment. According to fluorescent staining, western blotting, and cell cycle analysis, UV-treated parylene-C and parylene-N films appear to effectively facilitate simultaneous proliferation and differentiation of PC-12 cells with neurite outgrowth.

Fabrication of a thin plasmonic color sheet embedded with Al subwavelength gratings in parylene

In this study, we developed a thin plasmonic color sheet (TPCS) embedded with Al subwavelength gratings for use in flexible optical transmission filters, and experimentally demonstrated its transmission characteristics. Al subwavelength gratings were formed in a freestanding thin poly-para-xylylene (parylene-N) film less than 1-μm thick by using electron beam (EB) direct writing and sacrificial etching. The fabricated TPCS contained Al subwavelength gratings with periods ranging from 400nm to 600nm, and succeeded in shifting the transmission peak wavelength from 510nm to 650nm in the visible range. The freestanding thin parylene-N film deposited by room-temperature chemical vapor deposition provided enough flatness to the TPCS with a height difference of 900nm in a whole filter area, resulting in uniform transmission spectra. The experimentally obtained peak shift dependent on the grating period agreed well with theoretical calculation results.

Band-type microelectrodes for amperometric immunoassays

A band-type microelectrode was made using a parylene-N film as a passivation layer. A circular-type, mm-scale electrode with the same diameter as the band-type microelectrode was also made with an electrode area that was 5000 times larger than the band-type microelectrode. By comparing the amperometric signals of 3,5,3′,5′-tetramethylbenzidine (TMB) samples at different optical density (OD) values, the band-type microelectrode was determined to be 9 times more sensitive than the circular-type electrode. The properties of the circular-type and the band-type electrodes (e.g., the shape of their cyclic voltammograms, the type of diffusion layer used, and the diffusion layer thickness per unit electrode area) were characterized according to their electrode area using the COMSOL Multiphysics software. From these simulations, the band-type electrode was estimated to have the conventional microelectrode properties, even when the electrode area was 100 times larger than a conventional circular-type electrode. These results show that both the geometry and the area of an electrode can influence the properties of the electrode. Finally, amperometric analysis based on a band-type electrode was applied to commercial ELISA kits to analyze human hepatitis B surface antigen (hHBsAg) and human immunodeficiency virus (HIV) antibodies.

Surface modification of parylene-N films for the culture of osteoblast-like cells (MG-63)

The influence of microenvironments on the culture of osteoblast-like cells (MG-63) has been investigated using parylene films with different surfaces, such as parylene-N film, UV-modified parylene-N film, functional parylene film with amine groups (parylene-A), and UV-modified parylene-A film. In this work, parylene-N film was found to induce dramatic changes in cell adhesion and cell viability before and after UV-treatment with respect to the culture of osteoblast-like cells (MG-63). The influences of such a chemical environment on cell culture were investigated in relation to the cell proliferation (viability and proliferation rate) and the cell physiology (cell cycle, protein synthesis, and differentiation) of cells grown on parylene-N film, UV-modified parylene-N film, parylene-A film, and UV-modified parylene-A film in comparison with cells grown on a polystyrene surface.

Development of a sensitive SPR biosensor for C-reactive protein (CRP) using plasma-treated parylene-N film

Parylene-N film has high protein immobilization property after plasma-treatment. In this work, the optimum conditions for plasma-treatment of parylene-N films were investigated to develop a highly sensitive SPR biosensor. The effects of the plasma power and plasma-treatment time on the surface of parylene-N films were analyzed by measuring film contact angle and roughness from atomic force microscopy images. The plasma power was applied at a range of 0–100W for different treatment times. The influence of plasma-treatment was also analyzed using the depth profiles from X-ray photospectroscopy. From this analysis, chemical functional groups (those related to oxygen) were introduced and were estimated to penetrate up to 4nm and 8nm from the top surface of the parylene-N film due to treatment with plasma powers of 50W and 100W, respectively, for 1min. Based on the optimum plasma-treatment conditions for the plasma power and the plasma-treatment time, an SPR biosensor was developed for the detection of the human C-reactive protein.

Molecular beam deposition and polymerization of parylene-N ultrathin films: Effective buffers in organic light emitting diodes

Abstract Ultrathin Parylene-N (PPXN) films were prepared by using a home-made Knudsen Cell (KC). The PPXN films were identified by infrared (IR) spectra. The morphology and insulativity of PPXN films were measured by atomic force microscope (AFM) and current density versus voltage ( j – V ) characteristics. Well controlled 1-nm-thick PPXN thin films were inserted at different locations in the N′-bis(naphthalene-1-yl)-N, N′-bis(phenyl) benzidine (NPB) layers of organic light emitting diodes (OLEDs) with the structure of ITO/NPB/tris (8-hydroxyquinolato) aluminum (Alq 3 )/LiF/Al. For an optimized PPXN inserted structure, current efficiency of 6.27 cd/A was achieved, 11% higher than the 5.64 cd/A of the control one with 1-nm-thick PPXN buffer inserted at the anode interface. The device current efficiency improvement is due to the electron blocking of PPXN buffers, and the current density variation of devices under operation was explained by tunneling barrier reduction.

Development of SPR biosensor for the detection of human hepatitis B virus using plasma-treated parylene-N film

A plasma-treated parylene-N film was presented for the immobilization of proteins through physical adsorption. The changes in surface properties of the parylene-N film after plasma-treatment were analyzed using contact angle microscopy and AFM. To demonstrate the high protein-immobilization efficiency of the plasma-treated parylene-N film, the immobilization efficiencies of differently modified surfaces were compared using model proteins with different surface charges, such as streptavidin (pI=5, negatively charged at pH 7), horseradish peroxidase (pI=6.6, nearly neutral at pH 7), and avidin (pI=10, positively charged at pH 7). The application of the plasma-treated parylene-N film as an SPR biosensor was also tested by immobilizing model proteins. An SPR biosensor based on the plasma-treated parylene-N film was developed for the detection of the human hepatitis virus surface antigen (HBsAg), and the plasma-treated parylene-N film was estimated to improve the sensitivity of SPR biosensor as much as 1000-fold by enhancing immobilization of receptor antibodies.

Parylene‐matrix chip for small molecule analysis using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

In matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS), analyte molecules are known to be ionized by mixing with organic matrix molecules. As the organic matrix molecules are ionized, they generate unreproducible mass peaks such that MALDI-TOF MS is nearly impossible in the low mass-to-charge (m/z) range (<1000). In this work, we aimed to develop a parylene-matrix chip for the detection of small molecules in the low m/z range by using MALDI-TOF MS. The parylene-matrix chip was fabricated by the deposition of a partially porous parylene-N thin film on a dried organic matrix array. The properties of the parylene thin film were analyzed by atomic force microscopy (AFM) and cyclic voltammetry (CV). Mass spectrometry was performed by using a parylene-matrix chip with eight amino acids as model analytes. The surface roughness and the electric conductivity of the parylene-N film were analyzed by AFM and CV analysis to determine its suitability for a parylene-matrix chip. The ionization of samples on the parylene-matrix chip was optimized by adjusting the laser intensity. The feasibility of applying a parylene-matrix chip for small molecule analysis was tested by using eight kinds of amino acids as model analytes and the simultaneous detection of multiple analytes from the amino acid mixture was also demonstrated. The parylene-matrix chip can be applied for the detection of multiple analytes in the m/z ratio range of small molecules (<1000) using MALDI-TOF MS.

Towards flexible organic thin film transistors (OTFTs) for biosensing.

We have studied parylene-N and parylene-C for their use as substrates and gate dielectrics in OTFTs. Parylene-N films with a thickness of 300 nm show the required dielectric properties, as verified by breakthrough-voltage measurements. The surface roughness measured for 300 nm thick parylene-N films is 4-5 nm. However, initial growth of parylene depends on the subjacent surface. This results in different thicknesses on Au electrodes and substrate materials for thin films. Capping of micro-patterned Au-electrodes with a thin Al layer via lift-off results in homogenous parylene film thickness on the whole sample surface. OTFTs are fabricated on glass with parylene-N as a gate dielectric and pentacene as a semiconductor. The electrodes are patterned by photolithography enabling micrometer sized features. The contact resistance is extracted by variation of the channel length. Modification of the parylene dielectric layer surface by plasma treatment with oxygen after deposition allows shifting of the threshold voltage to more positive values, however at the cost of increasing hysteresis. OTFTs fabricated on thin parylene-C films can be peeled off and could result in flexible devices employing parylene-C foil as a substrate. For a foil thickness of 3-4 μm, operational devices can be bent down to radii less than 1 mm, e.g. in the range of cannulas. Operation of such OTFTs with parylene-C as a gate dielectric in liquids is demonstrated. The OTFT current can be modulated by the potential in the electrolyte as well as by the bottom gate potential. This allows for application of such OTFTs as sensors in medical devices.

Insertion of parylene-N films in electron transport layer: An effective approach for efficiency improvement of organic light emitting diodes

Efficiency of tris (8-hydroxyquinolato) aluminum (Alq3) based organic light emitting diodes has been obviously improved by inserting a parylene-N (PPXN) buffer layer with proper thickness and location in the Alq3 layer. For an optimized PPXN inserted structure, current efficiency of 6.89 cd/A and luminous power efficiency of 1.85 lm/W were achieved; both are 42% higher than the 4.84 cd/A and 1.30 lm/W of the buffer free structure, respectively. The light emitting spectra of 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) doped Alq3 (Alq3:DCM) strips showed the electron current enhancement resulted in the observed efficiency improvement of PPXN inserted devices. The device current evolutions were explained by nonuniform potential distribution in the organic layer and the tunneling barrier reduction.

Soft x-ray measurement of the toroidal pinch experiment RX reversed field pinch plasma using transition edge sensor calorimeter

A superconductive transition edge sensor (TES) calorimeter is for the first time applied for the diagnostics of the reversed field pinch plasma produced in the toroidal pinch experiment RX (TPE-RX), and the instrumental system is fully described. The first result from the soft x-ray spectroscopy in 0.2–3keV with an energy resolution ∼50eV are also presented. The TES calorimeter is made of a thin bilayer film of titanium and gold with a transition temperature of 151mK and its best energy resolution at our laboratory is 6.4eV, while it was significantly degraded by about a factor of eight during the plasma operation. The TES microcalorimeter was installed in a portable adiabatic demagnetization refrigerator (ADR), which is originally designed for a rocket experiment. The detector box is carefully designed to shield the strong magnetic field produced by the ADR and TPE-RX. The ADR was directly connected to TPE-RX with a vacuum duct in the sideway configuration, and cooled down to 125mK stabilized with an accuracy of 10μK rms using an improved proportional, integral, and derivative (PID) control method. Thin aluminized Toray Lumirror or Parylene-N films were used for the IR to UV blocking filters of the incident x-ray window to allow soft x-rays coming into the detector with good efficiency. TPE-RX was operated with the plasma current of Ip=220kA, and the wave forms of the TES output for every plasma shot lasting ∼80ms were obtained with a digital oscilloscope. The wave forms were analyzed with the optimal filtering method, and x-ray signals were extracted. A total of 3472 counts of x-ray signals were detected for 210 plasma shots during the flat-top phase of t=35–70ms. Combined with the data measured with a lithium drifted silicon detector in the 1.3–8keV range, spectral features are investigated using a spectral fitting package XSPEC. The obtained spectrum is well explained by thermal plasma emission, although an impurity iron-L line emissions at variously ionized states are dominant around 0.7–1.2keV. At least three different temperature components ranging T=350–900eV are required to account for the spectral shape, while the average temperature is consistent with the ruby laser Thomson scattering measurement.

Formation of body-centered-cubic tantalum via sputtering on low-κ dielectrics at low temperatures

Sputtered Ta films (60 nm) were deposited at room temperature onto selected substrates, including silicon, SiO2, porous methyl silsesquioxane (porous MSQ), parylene-N (Pa-N) caulked porous MSQ, benzocyclobutene (BCB), and SiLK layers. It was observed that the Ta structure after deposition mainly depends on the underlayer surface chemistry. β-Ta with a resistivity of ∼130–160μΩcm and an average grain size of ∼20nm was observed after sputter depositing 60-nm-thick Ta films onto the oxygen-rich materials of native oxide of Si, SiO2, and porous MSQ. α-Ta with a much lower resistivity (∼35μΩcm) and an average grain size of ∼16nm was observed after sputter deposition of Ta onto a substrate with a 4-nm-thick hydrocarbon Pa-N film on porous MSQ. α-Ta was also formed when sputter depositing on the hydrocarbon BCB and SiLK low-κ dielectrics. The lattice constants of the α-Ta films were slightly larger (3.310–3.351 Å) than those of the bulk Ta (3.305 Å).

Evaluation of the IR–UV blocking filters for ADR with a TES microcalorimeter

IR to UV blocking filters are indispensable for refrigerators of space missions, hence material and design of the filters determine overall X-ray detection efficiency. We have tested Toray–Lumirror ( C 10 H 8 O 4 ) and Parylene-N ( C 8 H 8 ) films with thin Al coating, installed in a portable ADR system with a TES microcalorimeter. Aperture cone structures are attached surrounding the films to protect them from adhesion of contaminants. The system was connected to the Manson X-ray generator with a vacuum duct, and the X-ray spectrum from the electron beam target was obtained by cooling down to 100 mK. We observed bremsstrahlung continuum and fluorescence lines from the electron target modified with C- and O-edges of the filters and strong C-/O-K α lines. We fitted the depth of each edge and determined the quantities of both elements in line of sight. The fit result is consistent with the expected values for C and Al, while suggesting 1.3 ± 0.3 μ m build-up of ice for O. We may need to contrive a way to avoid contaminant, e.g., introducing heaters.

Hindered Copper Ion Penetration in Parylene-N Films

Recently, it has been suggested that the existence of certain oxygen-containing chemical groups at copper/polymer interfaces aids copper ionization and its subsequent diffusion into these polymers. In the present study, poly(paraxylylene-N) or Parylene-N was selected for copper diffusion studies. It was demonstrated that no copper ion penetration was detected in the Parylene-N films under bias temperature stressing conditions of 150°C and 0.5 MV/cm. The present finding suggests that one may control copper penetration by employing dielectrics or passivation layers devoid of oxygen in the multilevel interconnect metallization scheme. © 2003 The Electrochemical Society. All rights reserved.

Tera Tool [terahertz time-domain spectroscopy

The terahertz differential time-domain spectroscopic method is applied to characterize the dielectric and optical properties of a variety of thin films at terahertz frequency. The results of several samples including silicon dioxide, parylene-n polymer film, tantalum oxide film, and protein thin layer samples were presented. The dielectric property of silicon dioxide thin film is well fitted to that of a bulk. The dielectric properties of parylene-n thin films show good agreement with the result measured by the goniometric terahertz time-domain spectroscopy. The dielectric and optical properties of the tantalum oxide show reasonable data with previously available data. Some properties in thin films are slightly different from the bulk materials. The origin of this discrepancy is considered due to fine grain formation, mechanical stresses, formation of interfacial layers, or rough interfaces during thin-film deposition process. The terahertz differential time-domain spectroscopy may be applied to the measurement of the dielectric and optical properties of thin films (nanometer to micrometer) of several materials, which cannot be done by any other method.

Novel Parylene-N films deposited at liquid nitrogen temperatures

Vapor deposition polymerization of Parylene-N films at −196°C produces optically opaque, highly porous films. Film density averaged 0.195 g/cm 3, more than five times less than that of conventional non-porous Parylene-N films deposited near room temperature, which have densities of 1.11 g/cm 3. Deposition rates, measured as the change in film thickness per unit time, averaged 8.3 μm/min. This rate is more than two orders of magnitude greater than the deposition rates of nonporous films near room temperature, at otherwise fixed conditions of monomer delivery rate and deposition chamber pressure. On a mass deposition rate basis, the new low temperature film deposition rate is more than an order of magnitude faster than the corresponding rate at room temperature.

Chemical Vapor Deposition (CVD) of Parylene Films using Liquid Source Delivery

AbstractParylene-N films were formed on silicon substrates at a substrate temperature of −20 °C and pressures from 4 - 7 torr via liquid source precursor delivery. [2.2 ] Paracyclophane, the precursor of parylene-N, was dissolved in an organic solvent and delivered into a vaporizer / pyrolysis unit. The solution was vaporized at ∼ 200 °C and its vapor was cracked at ∼ 700 °C to generate the reactive morromeric species. Films were grown by condensation and polymerization, and analyzed by infrared (FTIR), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) analysis. These analyses indicated the formation of parylene-N films without detectable solvent contamination or incorporation into the polymeric films.

Improved growth and thermal stability of Parylene films

Experimental results for the deposition of low dielectric constant Parylene-N and Parylene-F films are explained by a mechanism based on bulk phase diffusion reaction in the film. The deposition rate of Parylene-F decreases significantly as time increases and ultimately achieves steady state. Very favorable agreement with experiments at a substrate temperature of −10 °C is obtained for parylene-F with a rate constant of kf=5×10−5/s, and a diffusion coefficient Df=1.3×10−8 cm2/s. In contrast, the much higher rate constant at room temperature for Parylene-N films is kf=0.16/s and the predicted deposition rate is constant after a very small period of time (tss&amp;lt;4/kf=25 s). This prediction is confirmed by the experiments. The model predicts correctly that low deposition temperatures improve both the deposition rate and thermal stability of Parylene films. Our experiments confirm this prediction and one obtains both high growth rates and high molecular weight films at lower deposition temperatures. Furthermore, experiments show that the longer chains formed at low temperatures significantly improve the thermal stability of the films. The deposition rate also can be improved by using higher reactor pressures. However, the pressure that can be employed is limited to about 100 mTorr to maintain high quality films. At liquid nitrogen temperature (77 K), the deposition rate is three orders of magnitude larger than the film deposition rate at room temperature. The increased monomer concentration on the substrate due to higher condensation leads to this increased deposition rate.