Cyclo-olefin Polymer Surface Research Articles

B-037 Zeon original coating technology COP microplates for cell imaging

Abstract Background Zeon has developed high quality microplate made of Cyclo Olefin Polymer (COP) and special coat reagent for cell culture for Aurora microplates. The new 96 well-microplates have best-in-class properties for analysis of cultured cells can reduce the background of fluorescence images absolutely and excellent bottom flatness for observation of target. This enables to obtain high-precision data for cell analysis. Also, we developed Zeon original coating (ZOC) reagent specialized for COP surface. It is suitable for various cells including neurons derived from human induced pluripotent stem cells (iPSC), primary cells, general cell lines, and so on. ZOC coated COP microplates (ZOC plates) are fully-precoated and ready-to-use. Methods We evaluated the following points regarding ZOC plates. The cells used were derived from human iPSC. [1. Storage stability] ZOC plates were stored at room temperature for a long time. After that, cardiomyocyte cells were cultured for 3 days on the plates. The cell adhesion and beat rate were evaluated. [2. Neurite extension] Dopaminergic neurons were cultured for 14 days, then the neurite extension was evaluated. For comparison, a conventional poly-D-lysine* (PDL) coating was used. [3. Lot-to-lot variation] COP microplates coated with different lots of ZOC reagents were prepared. Glutamatergic neurons were cultured for 14 days on those plates, then the neurite extension and cell morphology were evaluated. *The typical coating reagent applied for neuronal culture. Results [1.] ZOC plates stored over 12 months at room temperature showed excellent cell adhesion, and the beat rate was equivalent to prepared just before use. [2.] ZOC plates tended to extend neurites more than PDL coated plates. [3.] No variation between lots was observed on ZOC plates regarding the neurite extension and cell morphology. Conclusions We suggest applying the combination of high accuracy for cell imaging using COP microplates and high performance for cell culture using ZOC can provide high precision data at bioassay research. This would be a significant value for development of drug screening processes at pharmaceutical company.

Comparison of vacuum ultraviolet irradiation and oxygen plasma treatment as pretreatment for copper seed layer on cycloolefin polymer

This study explores the factors governing the peel strength characteristics between a cycloolefin polymer (COP) film and a copper plating layer with a copper seed layer, for applying to antenna circuits in 6 G communications. The peel strength depended on the surface modification methods as pretreatment for copper seed layer formation: vacuum ultraviolet (VUV) irradiation and oxygen plasma treatment. VUV irradiation induced a modified layer with brittleness on the COP surface, leading to substrate failure. Conversely, oxygen plasma treatment formed a quite thin modified layer and facilitated Cu2O formation by bonding functional groups on the topmost COP surface with copper in the seed layer at the interface between the COP film and the copper plating layer, resulting in interface failure rather than substrate failure. Therefore, enhancing peel strength involves preventing the formation of a modified layer on the surface and generating a significant quantity of functional groups on the topmost surface.

Crystallinity improvement of room-temperature PLD-deposited ZnO thin films on cyclo-olefin polymer substrates subject to surface-pretreatment with vacuum-UV-light irradiation

The effect of the surface-pretreatment of cyclo-olefin polymer (COP) substrates with vacuum-ultraviolet (VUV) light irradiation on the crystal growth of ZnO thin films deposited by room-temperature pulsed laser deposition (PLD) was investigated for development of flexible optical devices. 172-nm-excimer light irradiation with durations of 60 to 600 s in air was found to make the COP surface more hydrophilic and smooth. It was verified from measurements of X-ray diffraction, atomic force microscope and high-resolution transmission electron microscope that the ZnO thin films grown on the VUV-light-pretreated COP substrates exhibited enhanced (0001) orientation growth and increased crystallinity compared with the samples grown on substrates not subject to the pretreatment; the samples on the pretreated substrates also showed a smooth surface and atomically sharp interface between the thin film and the substrate. The electrical resistivity of the ZnO thin film grown on the VUV-light-pretreated COP substrate was estimated to be 2.3 × 10−3 Ωcm, which was 40% lower than that of the film grown on the untreated substrate.

Influence of Protein Adsorption on Aggregation in Prefilled Syringes.

Protein aggregate formation in prefilled syringes (PFSs) can be influenced by protein adsorption and desorption at the solid-liquid interface. Although inhibition of protein adsorption on the PFS surface can lead to a decrease in the amount of aggregation, the mechanism underlying protein adsorption-mediated aggregation in PFSs is unclear. This study investigated protein aggregation caused by protein adsorption on silicone oil-free PFS surfaces [borosilicate glass (GLS) and cycloolefin polymer (COP)] and the factors affecting the protein adsorption on the PFS surfaces. The adsorbed proteins formed multilayered structures that consisted of two distinct types of layers: proteins adsorbed on the surface of the material and proteins adsorbed on top of the proteins on the surface. A pH-dependent electrostatic interaction was the dominant force for protein adsorption on the GLS surface, while hydrophobic effects were dominant for protein adsorption on the COP surface. When the repulsion force between proteins was weak, protein adsorption on the adsorbed protein layer was increased for both materials and as a result, protein aggregation increased. Therefore, a formulation with high colloidal stability can minimize protein adsorption on the COP surface, leading to reduced protein aggregation.

Culturing Chinese hamster ovary cells on cyclo olefin polymer triggers epithelial-mesenchymal transition and spheroid formation, which increases the foreign gene expression driven by the Moloney murine leukemia virus long terminal repeat promoter.

Chinese hamster ovary (CHO) cells are frequently used for recombinant protein production (RPP) as a host. While the RPP has been proven successful, there is still a compelling need for further improvement. Cyclo olefin polymer (COP) is a plastic material widely utilized due to its properties including its low protein absorption. We applied this as a raw material for RPP cell culture to see if the COP is suitable. A recombinant CHO cell line expressing the human erythropoietin (hEPO) gene under the control of the Moloney murine leukemia virus-long terminal repeat (MMLV-LTR) was established. When the cells were cultured in a dish made from COP, the cells attached to the bottom, and then started to float and form spheroids. RNASeq data analysis suggested the epithelial-mesenchymal transition (EMT) was triggered with receptor tyrosine kinase activation shortly after cultivation. It coincided with the hEPO transcription increase. After the cell floating, though EMT marker gene expression subsided, a hEPO expression increase sustained. When fibronectin was applied to COP dish surface, the cell floating was suppressed and hEPO expression decreased. We then treated cells with MβCD, a drug that destroys the lipid raft, eliminating molecules in the raft. This facilitated cell floating and spheroid formation coincided with hEPO expression enhancement. These results suggest interactions between a cell and COP surface might trigger the EMT and the subsequent event, both of which activated the MMLV-LTR promoter. Thus, employing COP for culturing cells, a potent RPP system could be established with its advantage for efficient protein purification.

Microstructured SiOx/COP Stamps for Patterning TiO2 on Polymer Substrates via Microcontact Printing.

Microcontact printing (μCP) techniques have sparked a surge of interests in microfabrication since they help produce arrays on a wide range of target substrates in a facile and efficient manner. Polydimethylsiloxane (PDMS), as a well-established material for stamps, has constraints resulting from its hydrophobicity and softness, and the replication of PDMS stamps usually requires rigid masters or processes using a photoresist. Herein, a novel μCP stamp based on cyclo-olefin polymer (COP) is produced through vacuum ultraviolet (VUV) lithography. 2,4,6,8-Tetramethylcyclotetrasiloxane is selectively deposited at the affinity-patterns on the COP surface, and these patterned siloxane films are converted into SiOx meanwhile protecting the COP beneath them from the VUV photoetching. By this means, a patterned relief is fabricated on the COP plates, resulting in a hydrophilic SiOx/COP μCP stamp with punch heights of ∼180 nm. The novelty arises from the simplicity of the master- and photoresist-free microstructuring, and the higher stiffness of SiOx/COP stamps prevents the deformation during pressing. Finally, an example μCP is given to transfer titania precursor gel and produce TiO2 micropatterns on flexible polymer substrates. The SiOx/COP stamps and the μCP of TiO2 provide simple and cost-effective patterning techniques, which should contribute to the future design and creation of flexible devices.

Room temperature bonding of cycloolefin polymer by vacuum ultraviolet surface photoactivation

We have applied vacuum ultraviolet (VUV) irradiation to room temperature bonding (RTB) of cyclo-olefin polymer (COP). The COP surface was oxidized into oxygen functional groups through the VUV irradiation in air. The extent of oxygenation was evaluated by water contact angle (WCA), X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The obtained results showed that the concentration of oxygen functional groups increased with VUV-irradiation time. The VUV-irradiation conditions for RTB were optimized based on our finding that prolonged irradiation resulted in a decrease in bonding strength. Observation of the fractured surfaces indicated that cohesive failure occurred after the appropriate irradiation time, but deterioration of the surface layer occurred with longer irradiation times.

Control of Protein Adsorption to Cyclo Olefin Polymer by the Hofmeister Effect

Cyclo olefin polymer (COP) is an attractive plastic because it has low protein adsorption despite its hydrophobic chemical structure. Here, the adsorption of model proteins to the COP was evaluated in comparison with a representative plastic, polystyrene (PSt), using reflectometry interference spectroscopy (RIfS) technology. The effects of different salts on adsorption were then examined. The adsorption of bovine serum albumin onto COP increased in the presence of kosmotropic salts, whereas adsorption of IgG increased in the presence of chaotropic salts. By contrast, the adsorption of these 2 proteins to PSt was unaffected by these Hofmeister salts. Langmuir–Freundlich model of COP adsorption suggested that the COP surface is more homogeneous for protein binding than the PSt surface. Furthermore, RIfS and sum frequency generation analyses indicated that water molecules bind more weakly to COP than to PSt. Our data propose a novel viewpoint of the way protein binds to COP surface that is different from the way it binds to PSt.

Formation of submicron-sized silica patterns on flexible polymer substrates based on vacuum ultraviolet photo-oxidation.

Formation of precise and high-resolution silica micropatterns on polymer substrates is of importance in surface structuring for flexible device fabrication of optics, microelectronic, and biotechnology. To achieve that, substrates modified with affinity-patterns serve as a strategy for site-selective deposition. In the present paper, vacuum ultraviolet (VUV) treatment is utilized to achieve spatially-controlled surface functionalization on a cyclo-olefin polymer (COP) substrate. An organosilane, 2,4,6,8-tetramethylcyclotetrasiloxane (TMCTS), preferentially deposits on the functionalized regions. Well-defined patterns of TMCTS are formed with a minimum feature of ∼500 nm. The secondary VUV/(O)-treatment converts TMCTS into SiOx, meanwhile etches the bare COP surface, forming patterned SiOx/COP microstructures with an average height of ∼150 nm. The resulting SiOx patterns retain a good copy of TMCTS patterns, which are also consistent with the patterns of photomask used in polymer affinity-patterning. The high quality SiOx patterns are of interests in microdevice fabrication, and the hydrophilicity contrast and adjustable heights reveal their potential application as a “stamp” for microcontact printing (μCP) techniques.

Heterogeneous bonding between cyclo‐olefin polymer (COP) and glass‐like substrate by newly developed water vapor‐assisted plasma, Aqua Plasma Cleaner

AbstractTo develop high‐performance and low‐cost microfluidic devices, heterogeneous bonding with cyclo‐olefin polymer (COP) and glass substrate was investigated by low‐pressure plasma using water vapor. COP and glass‐like substrate were bonded at room temperature under its own weight, and the bonding strength reached the breaking point of base material strength. Water contact angle of the COP and glass surface after water vapor plasma was less than 1° (superhydrophilic) and showed stable hydrophilicity even after 30 days. Water vapor plasma and COP surface were analyzed by optical emission spectroscopy (OES) and x‐ray photoelectron spectroscopy (XPS) to study the reaction of room temperature bonding.

Sentinel Wraps: Real-Time Monitoring of Food Contamination by Printing DNAzyme Probes on Food Packaging.

Here, we report the development of a transparent, durable, and flexible sensing surface that generates a fluorescence signal in the presence of a specific target bacterium. This material can be used in packaging, and it is capable of monitoring microbial contamination in various types of food products in real time without having to remove the sample or the sensor from the package. The sensor was fabricated by covalently attaching picoliter-sized microarrays of an E. coli-specific RNA-cleaving fluorogenic DNAzyme probe (RFD-EC1) to a thin, flexible, and transparent cyclo-olefin polymer (COP) film. Our experimental results demonstrate that the developed (RFD-EC1)-COP surface is specific, stable for at least 14 days under various pH conditions (pH 3-9), and can detect E. coli in meat and apple juice at concentrations as low as 103 CFU/mL. Furthermore, we demonstrate that our sensor is capable of detecting bacteria while still attached to the food package, which eliminates the need to manipulate the sample. The developed biosensors are stable for at least the shelf life of perishable packaged food products and provide a packaging solution for real-time monitoring of pathogens. These sensors hold the potential to make a significant contribution to the ongoing efforts to mitigate the negative public-health-related impacts of food-borne illnesses.

Functionalized Cycloolefin Polymer Capillaries for Open Tubular Ion Chromatography.

We describe novel cycloolefin polymer (COP)-based open tubular capillary ion exchange columns. COP capillaries (inner diameter of 19-28 μm) were successfully sulfonated at room temperature using a cocktail of ClSO3H (85-95% w/w) and HOAc or H2SO4. The cation exchange capacity is controlled by the sulfonation time and the sulfonation solution composition and can be as high as 300 pequiv/mm2. Following sulfonation, the capillaries were coated with 65-nm-diameter anion exchanger (AEX) latex nanoparticles that attach electrostatically. The typical anion exchange capacities were ∼20 pequiv/mm2. The chromatographic behavior of the AEX latex-coated COP capillaries are greatly dependent on the degree of sulfonation. When the base is heavily sulfonated, neutrals elute after the anions. The position of the water dip varies with the degree of sulfonation; the elution order is normal (water dip appear before anions) only with lightly sulfonated columns. On silica (-SiOH) or poly(methyl methacrylate) (-COOH) surfaces, AEX latex attachment is not stable over long periods in significant concentrations of strong base (e.g., ≥10 mM NaOH). Latex attachment on sulfonated COP surfaces are much stronger; several types show sufficient binding to be used over long periods at practical eluent concentrations, paving the way for suppressed hydroxide eluent ion chromatography (IC), which is discussed in a companion paper. Another interesting feature of COP capillaries lies in their flexibility. If softened at modestly elevated temperatures (e.g., boiling water), they can be coiled down to <1 mm coil radii, revealing, for the first time, the beneficial effects, albeit small, of centrifugal force on mass transfer in open tubular columns.

Three-dimensional plasma micro–nanotextured cyclo-olefin-polymer surfaces for biomolecule immobilization and environmentally stable superhydrophobic and superoleophobic behavior

Cyclo-olefin polymer (COP) surfaces are micro–nanotextured using O2 plasma chemistry in one-step process. These surfaces subsequently display multiple functionality, (A) they are stable in time (i.e. non ageing), functional, high surface area, substrates suitable for biomolecule binding, after thermal annealing in order to induce accelerated hydrophobic recovery while preserving the chemical functionality created by the plasma. (B) Alternatively, they are robust and environmentally stable superhydrophobic and superoleophobic surfaces, after mechanical stabilization via wetting–drying and gas-phase coating with a perfluoroctyltrichlorosilane monolayer (PFOTS) or plasma deposited Teflon-like polymer layer. The plasma treated, micro–nanotextured surfaces used for biomolecule binding exhibit remarkable retention of the initially immobilized biomolecule compared to untreated COP surfaces (up to 75%), after washing with aggressive washing solutions (sodium dodecyl sulfate), while showing excellent intensity, uniformity and sensitivity. The superoleophobic COP material surfaces exhibit very high static contact angles (SCA >150°) and very low hysteresis (CAH <10°), for a wide range of liquids from water (surface tension: 72.8mN/m) to hexadecane (surface tension: 27mN/m). In addition, these superhydrophobic and superoleophobic surfaces exhibit excellent stability against environmental ageing after 60 continuous cycles of exposure to various harsh environmental conditions (heat, moisture, UV irradiation) in a controlled environment. Finally, the two presented functionalities are combined for the first time on the same COP substrate, creating localized rough hydrophilic and antifouling patterns that exhibit spatially selective biomolecule immobilization inside a microfluidic device.

Nanoscale Mechanical and Tribological Properties of Plasma Nanotextured COP Surfaces with Hydrophobic Coatings

Cyclo olefin polymer (COP) surfaces, treated in oxygen plasmas under highly anisotropic conditions to favor roughness formation, are coated with thin hydrophobic films to form surfaces of enhanced hydrophobicity. As hydrophobic coatings, plasma-deposited fluorocarbon or spin-coated Teflon thin films are implemented. Nanoindentation and nanoscratch experiments have been employed to elucidate the effect of plasma treatment on the mechanical and tribological performance of the synthesized materials. It is shown that short-time plasma treatment slightly changes mechanical and tribological properties of plasma-nanotextured COP, as compared to untreated. The plasma deposited hydrophobic film on the COP surfaces presents good adhesion and it effectively protects the surfaces, reducing plastic deformation.

Automatic droplet transportation on a plastic microfluidic device having wettability gradient surface

This paper presents a microfluidic device that can automatically transport a droplet on a plastic plate. This device consists of a Cyclo Olefin Polymer (COP) plate and a SiO2 membrane and has wettability gradient surface. Lithographic patterns of hydrophilic SiO2 permitted wettability modification of a hydrophobic COP surface. A series of alternate hydrophobic and hydrophilic wedge-shaped patterns generated a required gradient in wettability. When we dropped a droplet on the wettability gradient surface, it moved along the wettability gradient due to an imbalance between surface tension forces acting on the opposite sides of the droplet edge. The droplet transportation test was carried out using water of 5 μl. As a result, we succeeded in automatically transporting the droplet on the SiO2/COP wettability gradient pattern. We also carried out droplet transportation in an enclosed microchannel for preventing droplet evaporation using DI (Deionized) water of 5 μl. In this case, the droplet was automatically transported by forming the wettability gradient pattern at the top and bottom in an enclosed microchannel without evaporation.

Reductive Nucleation of Palladium Nanoparticles on a Cycloolefin Polymer Surface Oxidized with Active Oxygen Species Generated by Vacuum Ultraviolet Excitation

Abstract The ability to reduce palladium (Pd) ions to Pd nanoparticles has been provided on the surface of cycloolefin polymer (COP). The origin of this reductive function is aldehyde and alcoholic hydroxy groups formed by oxidizing the COP surface with active oxygen species, which were generated through the irradiation of atmospheric oxygen and water molecules with vacuum ultraviolet light of 172 nm in wavelength. The Pd nanoparticles successfully served as catalysts for electroless plating.

Surface activation of cyclo olefin polymer by oxygen plasma discharge: a molecular dynamics study

Thermoplastic substrates made of cyclo olefin polymer (COP) are treated with oxygen plasma discharges to introduce polar groups at the surface. This is the first step in the process of surface functionalization of COP substrates used in biosensor devices. A molecular dynamics model of basic COP structure is implemented using the second-generation reactive empirical bond order (REBO) potentials for hydrocarbon–oxygen interactions. The model includes covalent bond and Van der Waals interactions. The bombardment of a COP surface with mono-energetic atomic oxygen ions, energy in the range 1-35 eV, is simulated and reported here. The dynamics of the substrate modification reveals that the substrate top layer is de-hydrogenated and subsequently builds up an oxygen–carbon matrix layer, ∼10 Å thick. Analysis of the modified substrates indicates that surface yield is predominantly peroxide groups.

Patterned Surface Activation of Cyclo-Olefin Polymers for Biochip Applications

Two different surface activation methods (UV/ozone and oxygen plasma treatment) were applied for patterned surface activation of cyclo-olefin polymer (COP) surfaces combined with different masking techniques (metal shadow mask and protective tape). Surface properties were characterized by various methods such as contact angle measurement, ATR-IR, XPS and Surface enhanced ellipsometric contrast (SEEC) microscopy. UV/ozone and oxygen plasma allowed for patterned surface modification of COP leading to the formation of carboxylic and hydroxyl groups on the activated part of the surface. Stability against organic solvents was determined by rinsing the activated substrates with 2-propanol. For UV/ozone treatment it was found that a thin film of degradation products remains on the COP surface and is at least partly removed in the following washing or rinsing steps.

Biochip applications of DLC films on a resin material

AbstractRecent studies of diamond‐like carbon (DLC) coated medical devices have indicated possibility for developing biochip applications. We have deposited DLC film on cyclo‐olefin polymer (COP) sheet by using radio frequency plasma chemical vapor deposition technique. To enhance the adhesion strength between the COP sheet and the DLC films, the COP surface was modified by oxygen (O2) or nitrogen (N2) plasma treatment before the film coating. The critical load of samples was measured by using a scratch test. The result showed the adhesion strength of films was improved by the plasma treatment. After the DLC film coating, we performed the plasma post‐treatment of O2, N2 or hexafluoroethane (C2F6) gases to control the wettability of the material surface. The wettability, structure, roughness, and chemical composition of the samples have been investigated by a contact angle measurement, Raman spectroscopy (Raman), atomic force microscopy (AFM), and X‐ray photoelectron spectroscopy (XPS). These measurements indicated that wettability on the surface condition of DLC films was easily controlled by plasma post‐treatment of O2, N2 and C2F6. Furthermore, results of XPS showed that wettability of the surface condition is strongly dependent on chemical components with existemce of oxygen, nitrogen and flourine. We have estimated the wettability of hydorphilicity and hydrophobicity on DLC coating under plasma post‐treatment for biochip applications (© 2012 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Adhesion Characteristics of Magnetron-Sputter-Deposited Copper on Smooth Cycloolefin for Realizing Wiring with High-Frequency Signal Propagation

Copper wiring formation on a resin material with a low dielectric constant, a low dielectric loss and a smooth surface is indispensable to realize high-frequency signal propagation with fine wiring patterns. Cycloolefin polymer (COP) resin is a promising material to meet these requirements. We propose adhesive copper seed layer formation on the COP by magnetron sputtering as an alternative to the electroless deposition which usually requires an intentional roughnessinduced process to obtain practical adhesion between the resin and the metal. The proposed process steps include plasma nitridation of the COP surface, thin CuN film deposition and Cu film deposition before the electroplating. Excellent adhesion strength between the COP and the metal, greater than 1 kN/m, can be obtained while maintaining a smooth surface, which is attributed to the strong chemical bond generated between the nitrided COP surface and the CuN film. The coplanar transmission line was fabricated using the proposed process steps with semi-additive processes, and we found that the introduction of relatively high-resistive CuN film does not cause degradation of the propagation characteristics.