Honeycomb-patterned Polymer Films Research Articles

Self-Assembly of CsPbBr3 Perovskites in Micropatterned Polymeric Surfaces: Toward Luminescent Materials with Self-Cleaning Properties.

In this work, we present a series of porous, honeycomb-patterned polymer films containing CsPbBr3 perovskite nanocrystals as light emitters prepared by the breath figure approach. Microscopy analysis of the topography and composition of the material evidence that the CsPbBr3 nanocrystals are homogeneously distributed within the polymer matrix but preferably confined inside the pores due to the fabrication process. The optical properties of the CsPbBr3 nanocrystals remain unaltered after the film formation, proving that they are stable inside the polystyrene matrix, which protects them from degradation by environmental factors. Moreover, these surfaces present highly hydrophobic behavior due to their high porosity and defined micropatterning, which is in agreement with the Cassie–Baxter model. This is evidenced by performing a proof-of-concept coating on top of 3D-printed LED lenses, conferring the material with self-cleaning properties, while the CsPbBr3 nanocrystals embedded inside the polymeric matrix maintain their luminescent behavior.

Effect of Pore Size of Honeycomb-Patterned Polymer Film on Spontaneous Formation of 2D Micronetworks by Coculture of Human Umbilical Vein Endothelial Cells and Mesenchymal Stem Cells.

The geometrical control of micronetwork structures ( NSs) formed by endothelial cells is an important topic in tissue engineering, cell-based assays, and fundamental biological studies. In this study, NSs are formed using human umbilical vein endothelial cells (HUVECs) by the coculture of HUVECs and human mesenchymal stem cells (MSCs) confined in a honeycomb-patterned poly-l-lactic acid film (honeycomb film (HCF)), which is a novel cell culture scaffold. The HCF is produced using the breath figure method, which uses condensed water droplets as pore templates. The confinement of the HUVECs and MSCs in the HCF along with the application of centrifugal force results in NS formation when the pore size is more than 20 m. Furthermore, NS development is geometrically restricted by the hexagonally packed and connected pores in the horizontal direction of the HCF. Network density is also controlled by changing the seeding density of the HUVECs and MSCs. The threshold pore size indicates that NSs can be formed spontaneously by using an HCF with a perfectly uniform porous structure. This result provides an important design guideline for the structure of porous cell culture scaffolds by applying a blood vessel model in vitro.

Synthesis, Characterization and Property of Amphiphilic Copolymer

Atom transfer radical polymerization (ATRP) has been employed for the synthesis of an amphiphilic diblock copolymer MeOPEO-b-PBMA. The macroinitiator was prepared by poly(ethylene oxide) monomethyl ether with 2-Bromoisobutyryl bromide. The amphiphilic diblock copolymer was obtained by the macroinitiator and monomer n-Butyl methacrylate (BMA). The block copolymer was characterized by means of proton nuclear magnetic resonance (1H NMR). The honeycomb-patterned polymer films was obtained by the breath figure method. Water contact angle measurements revealed that a hydrophobic surface is obtained. The amphiphilic polymers expected to the application as the hydrophobic materials.

Reversible change of wettability in poly(ɛ-caprolactone/azobenzene) honeycomb-patterned films by UV and visible light illumination

A new type of photosensitive poly(ɛ-caprolactone) (PCL) composites containing 4-dimethylamino-4′-(6-hydroxy hexyloxy) azobenzene (Azo) was synthesized by in situ ring-opening polymerization of ɛ-caprolactone in the presence of different Azo amounts. The PCL-Azo composites were characterized using Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and UV–vis spectroscopy. Honeycomb-patterned porous polymer films were fabricated by casting the polymer solution under humid conditions: and for comparison, flat films were also prepared by drying the polymer solution at ambient conditions. Water contact angle was compared between porous and flat films, and was reversely changed by UV and visible light illuminations. The contact angle of PCL-Azo composite films was decreased by UV illumination and was recovered with visible light illumination both on the patterned and flat films. Reversibility in contact angles by UV and visible light can be interpreted by photo-switched isomerization of the Azo component in the polymer composite films due to isomeric structural changes between trans and cis isomers inducing the changes in dipole moment of the films.

Biomimetic Bubble-Repellent Tubes: Microdimple Arrays Enhance Repellency of Bubbles Inside of Tubes.

The adhesion of bubbles underwater remains the greatest cause of malfunctions in applications such as microfluidics, medical devices, and heat exchangers. Recently, the combination of oxidization and peeling the top layer of self-organized honeycomb films with an adhesive tape resulted in the formation of an ultra-bubble-repellent and pillared polymer surface structure. However, the fabrication of honeycomb films on the inner surface of tubes and the formation of structured hydrophilic textures by peeling the top layer of honeycomb films still remain problematic. In this report, a simple fabrication technique for producing a honeycomb-patterned polymer film on the interior of a tube by dip-coating a polymer solution and blowing humid air in the tube is described. Furthermore, an ultra-bubble-repellent dimple-arrayed structure was fabricated by applying ultrasonication to the honeycomb structure formed on the interior surface of the tubes.

Selective adhesion and controlled activity of yeast cells on honeycomb-patterned polymer films via a microemulsion approach.

Selective adhesion, growth promotion, proliferation inhibition and in situ transformation of Saccharomyces cerevisiae cells have been realized in a limited space of honeycomb-patterned polystyrene films prepared through a microemulsion method.

Preparation of biomimetic high adhesive superhydrophobic polymer pillar surfaces with crown-like metal microstructures.

High adhesive superhydrophobic polymer pillar surfaces with dispersed metallic crown-like micro structures were prepared by electroless plating on self-organized honeycomb patterned polymer films and peeling off the top layer of the metal covered honeycomb films. Thus obtained polymer pillar surfaces with metallic crown-like microstructures possessed conflicting properties of water repellency and adhesion. The adhesion property was tuned by number density of metallic crown-like microstructures which were adjusted by polymer concentration in a catalytic solution for electroless plating.

Micropatterned culture of HepG2 spheroids using microwell chip with honeycomb-patterned polymer film

Microwell chip culture is a promising technique for the generation of homogenous spheroids. We investigated the relationship between the structure of the bottom surface of microwell chip and the properties of HepG2 spheroid. We developed a microwell chip, the bottom surface of which consisted of a honeycomb-patterned polymer film (honeycomb film) that had a regular porous structure (HF chip). The chip comprised 270 circular microwells; each microwell was 600μm in diameter and 600μm in depth. At the center of the honeycomb film, an area, 200μm in diameter, was modified with collagen to facilitate cell adhesion. With the exception of the collagen-coated area, the entire microwell was modified with polyethylene glycol to eliminate cell adhesion. HepG2 cells formed uniform spheroids when cultured in the microwells of HF chip. Furthermore, the cells passed through the porous structure of honeycomb film and formed spheroids at its opposite side. The spheroid growth of HepG2 cells cultured in HF chip was greater than that when the cells were culture in a microwell chip, the bottom surface of which was made of poly-methylmethacrylate (PMMA chip). The albumin secretion activity of HepG2 spheroids in HF chip was equal to that in PMMA chip. These results indicate that the microwell bottom with a porous structure enhances the cell growth and maintains well the spheroid function. Thus, HF chip is a promising platform for spheroid cell culture.

Formation and control of line defects caused by tectonics of water droplet arrays during self-organized honeycomb-patterned polymer film formation

This study describes the formation of macro-scale defects of the honeycomb-patterned polymer film and we discovered two types of new line defects which differ from the defects reported in the past studies. We examined the formation mechanisms of the line defects and clarified two types of formation mechanisms of the "Divergent" mode line defects and the "Convergent" mode line defects caused by the "tectonics" of water droplet arrays on polymer solutions. The regions causing the macro-scale line defects are made clear in the phase diagram represented by the radius and the density of the micro-scale water droplets. In addition, the results of our calculations made it possible to theoretically predict the water droplet growth time for the water droplets to grow to the ideal size for uniform packing that is necessary for fabrication of the defect-free honeycomb-patterned polymer film. With the use of these techniques, A4-sized, defect-free, honeycomb-patterned polymer films can be fabricated.

Polyanion cluster patterning on polymer surface through microemulsion approach for selective adsorption of proteins

A facile method to fabricate honeycomb-patterned polymer films bearing cavities that are locally decorated with inorganic component is developed in this study. By mixing poly(methyl methacrylate) dichloromethane solution containing P123 with polyoxometalate (POM) aqueous solution through shaking, a reversed hybrid microemulsion is obtained. The evaporation of solvent in the microemulsion on solid surface yields an ordered porous film accompanied by the accumulation of P123 and POMs on the inner surface of the cavities. The formation of patterned structure is proved to be independent from the type of POMs, but the size of the cavities can be adjusted to some extent by changing the concentration of surfactant and polymer, and the volume ratio of water and dichloromethane in the solution used for casting. The locally anchored POMs can be readily applied for the selective recognition of proteins. BSA and hemoglobin patterns are then fabricated through their electrostatic interactions with POMs. At lower pH, POM pattern could prior recognize hemoglobin from its mixed solution of BSA, generating a characteristic pattern. The reported work creates an efficient way of patterning organically incompatible components, such as water-soluble molecules and nanoparticles, on porous polymer films for the fabrication of multi-functional hybrid surface structures.

Tunable Morphology of 2D Honeycomb-Patterned Films and the Hydrophobicity of a Ferrocenyl-Based Oligomer

Honeycomb-patterned polymer films with tunable pore size and regularity of ordered two- or three-dimensional hexagonal arrays have met with widespread interest in recent years in different areas, for instance as separation and superhydrophobic materials. Herein, 2D honeycomb-patterned films of amphiphilic ferrocenyl-based oligomer with cholesterol as side chains were prepared by the breath-figure method on solid surfaces and their surface-wetting behavior were tested. These films can be simply prepared by spreading a mixture of polymer and organic solvents on a solid surface under moist airflow and at an air/water interface without any extra moist airflow. An ordered 2D hexagonal array of pores with monodisperse size distribution can be obtained over a large area by changing various influencing factors, including humidity, wet volume, concentration, selective solvent, and spreading method, which provides a facile route to regulate the morphology of patterned porous films. The surface-wetting behavior indicates that a higher hydrophobicity of the ferrocenyl-based oligomer honeycomb films can be obtained by modulating the pore size and regularity. It is expected that this could promote the potential application of ordered porous polymer films in hydrophobic materials and biochemistry.

Biomedical Application of Surface Science: Honeycomb Patterned Polymer Films as Novel Biomedical Materials

This report describes universities-industries collaborations on biomedical applications of self-organized honeycomb-patterned polymer films, which are prepared by using physical surface phenomena based on water droplet condensation during evaporation processes of polymer film casting. The film company has established engineering processes of regularly porous polymer film fabrication. The textile company has developed high-performance adhesion preventing polymer films having asymmetric nano-honeycomb structure under collaboration with the film company. Covered biliary stents are newly developed and released by the medical device company. Honeycomb-patterned polymer films are supplied to the medical device company from the film company.

Preparation of Metal-polymer Hybrid Films by Electroless Plating of Honeycomb Structures

Several types of metal-polymer hybrid films were prepared by electroless plating of self-organized honeycomb-patterned polymer films. The polystyrene honeycomb film was fabricated by a template method of hexagonally ordered condensed water droplets, and composed of a micrometric porous array and nanometric pillar structures that hold top and bottom porous layers together. Chemical adhesion of palladium catalysts for nickel electroless plating was controlled by difference of wettability of the honeycomb structures. After electroless plating and peeling off the top layer of the honeycomb film, various kinds of the metal-polymer hybrid films such as metal-coated honeycomb-patterned polymer films, metal-coated pillar-structured polymer films, ring-like-structured metal in the honeycomb-patterned polymer film, ball-like-structured metal array in the honeycomb-patterned polymer film, and dome-like-structured metal in the pillar-structured polymer film were obtained.

Formation of ceramic microstructures: honeycomb patterned polymer films as structure-directing agent

Here, we show a facile and versatile method preparing highly ordered ceramic microstructures on solid substrates by pyrolyzing UV cross-linked copolymer films to circumvent the expensive lithographic technique. The employed block copolymer, poly(dimethylsiloxane)-block-polystyrene (PDMS-b-PS), in this study was synthesized by controlling radical polymerization. The highly ordered microporous polymer films were formed using a static breath figure process. After 4 h UV irradiation, the PS composition was effectively cross-linked. The cross-linked microporous polymer matrix served as a structure-directing agent in the following pyrolysis process, in which the PDMS composition was converted into silica to form honeycomb structured micropatterns on the substrate. The chemical components of the ceramic microstructures were adjusted by simply mixing different functional precursors. Moreover, the ceramic microstructures on substrate could be replicated to prepare textured PDMS stamps. This simple technique offers new prospects in the fields of micropatterns, soft lithography and templates.

自己組織化ハニカムフィルムに対するラット骨髄間葉系幹細胞の応答

自己組織化ハニカムフィルムに対するラット骨髄間葉系幹細胞の応答

B134 水の凝縮を利用したポーラス有機薄膜生成(OS-4:マイクロ・ナノ熱工学(I))

B134 水の凝縮を利用したポーラス有機薄膜生成(OS-4:マイクロ・ナノ熱工学(I))

Spontaneous Formation of Microwrinkles on Metal Microdot Arrays by Shrinkage of Thermal Shrinkable Substrate

Honeycomb-patterned polymer films prepared by the simple casting of a polymer solution under humid conditions were used as templates for metal microdot arrays formed on shrinkable polymer substrates by metal sputtering. After thermal shrinkage of the substrate, the periodicity of the metal microdots was reduced. In addition, microwrinkles were formed on the metal microdots. The wavelength and arrangement of the microwrinkles were changed with the metal sputtering time and the diameter of the metal microdots. A clear confinement effect was observed in the formation of the microwrinkles.

Micropatterning of liquid crystalline polyacetylene derivative by using self-organization processes

Side-chain type liquid crystalline polyacetylene, which has mesogenic moieties as side chains, is one of the promising materials for practical applications in the electronics. Micropatterning of the conductive polymer is a significant issue in this field. We show a simple method to fabricate micropatterns of side-chain type liquid crystalline polyacetylene derivative. Under dry condition, stripes patterns and lattice pattern were formed based on the fingering instability and stick-slip motion of the receding meniscus. Honeycomb-patterned polymer film was obtained by casting polymer solution under humid condition. The micropatterns drastically changed by changing solution concentration and preparation conditions.

Interfacial tension governs the formation of self-organized honeycomb-patterned polymer films

Hexagonally packed water droplets condensed on a polymer solution are potential templates for the formation of honeycomb-patterned porous polymer films. A small number of surface-active molecules is indispensable for the stabilization of water droplets during solvent evaporation. Biocompatible surfactants; e.g., phospholipids, are required for the fabrication of biodegradable honeycomb-patterned polymer films, which can be used as novel biomedical materials, mainly in vivo. Among various kinds of phospholipids, dioleoylphosphatidylethanolamine (DOPE) has been reported to be the most suitable surfactant for the formation of honeycomb-patterned PLA films. Interfacial tension between a water droplet and the polymer solution is largely dependent on the chemical structure of the phospholipids. DOPE shows high interfacial tension, resulting in the stabilization of water droplets during solvent evaporation. Dierucoylphosphatidylcholine (DEPC) and dierucoylphosphatidylethanolamine (DEPE), both of which display high interfacial tension, were also found to be suitable biocompatible surfactants.

Selective metal deposition in hydrophobic porous cavities of self-organized honeycomb-patterned polymer films by all-wet electroless plating

We report selective metal deposition of self-organized honeycomb-patterned polymer (hp) films possessing hydrophobic surfaces by all-wet electroless plating. Nickel/phosphorus (Ni/P) coated hp films were fabricated as follows. A catalytic nucleus of electroless plating was adsorbed on hp films by immersion in a saturated ethanol solution of palladium(II) chloride (PdCl2). Homogeneous metal deposition on the hydrophobic surface of the hp film was easily carried out by all-wet process. In addition an ultrahydrophobic surface of pincushion-structured polymer (ps) films having periodic pillars which was obtained by peeling off a top layer of the hp film was metal-coated by the same all-wet process. It was found that immersion in the saturated ethanol solution of PdCl2 is suitable for catalyzation on hydrophobic surfaces for metal deposition by all-wet electroless plating. To use differences of wettability of honeycomb structures between inner and outer surfaces of porous cavities, site-selective Ni/P deposition in porous cavities was carried out by immersion in a palladium chloride acid aqueous solution after ethanol treatment.