Papers by Keyword: Micropatterning

Abstract: Digital light processing (DLP) can be used as a rapid photopatterning technique with micrometer resolution. To ensure high levels of precision and accuracy, it is required to clearly understand the actual dimensional capabilities in the horizontal plane of a patterning setup. A methodology to assess these capabilities was suggested in this study, and the following parameters were determined: The effective pixel size, the planar dimensional reproducibility, and the dimensional precision in dependence of the angular feature orientation in the x-y plane. Experimental verification of the suggested approach was carried out by using a DLP-based 3D printer. This demonstrated that the nominal pixel size stated in the technical data sheet can deviate from the effective pixel size by more than 1%. Furthermore, dimensional inaccuracies of ±5.1% depending on the feature location within the x-y plane were indicated. The dimensional precision was affected by the angular orientation in relation to the pixel grid, and small errors equivalent to ±0.05 pixels were only achievable with features placed in parallel or diagonal orientation. These results characterize the planar accuracy of DLP equipment and help minimize dimensional errors in the direct digital manufacture of microchannel and strut-like patterns.

Abstract: Polyethylene glycol (PEG) hydrogel microstructures with various shapes and sizes on a glass chip were prepared by a simple and rapid ultraviolet (UV) irradiation method using a metal mask. Photocurable PEG solution prepared by mixing 95 wt.% polyethylene glycol diacrylate and 5 wt.% 2-hydroxy-2-methylpropiophenone as a photo-initiator was injected to the gap between bottom and upper glasses in a simply assembled glass chip. After a metal mask with line-and-space or complex patterns was placed on the glass chip, UV light from a spot UV irradiation device was exposed to the glass chip through the metal mask for 7 seconds at UV intensity of 26 mW/cm². Then the PEG hydrogel micropatterns on the glass chip were obtained after removing unreacted PEG solution by air blowing. To prepare more rigid microstructure, the prepared PEG micropatterned chip was exposed under UV light for 20 seconds. Then the PEG hydrogel micropattern chip was fabricated by a simple and rapid procedure. Micropattern transferring was performed from the PEG hydrogel chip to polydimethyl siloxane (PDMS) replica by a solution casting. The prepared micropatterned PDMS replicas showed similar shape and size of microstructures compared to that of the corresponded PEG hydrogel chip. Thus the PEG hydrogel microstructures on a glass chip could be used as a mold to fabricate micropattern PDMS chips for nanobio-chip applications. Furthermore, the present method provides large scale chip fabrication, more than 4 cm-length and 4 cm-width in a single step, not only PEG hydrogel chips but also PDMS chips.

Abstract: Several studies have shown that 65 % of expanded poly (tetrafluoroethylene) (ePTFE) vascular prostheses had to be explanted within 10 years of implantation in humans. The reasons for these explantations relied on thrombosis formation and poor hemocompatibility of synthetic polymers. It has been shown that surface modification of ePTFE arterial prostheses could enable their endothelialization therefore improving their biocompatibility and hemocompatibility. Indeed, endothelial cells naturally cover the biological blood vessel wall and consequently, an endothelial layer constitutes the best achievable hemocompatible surface. In this context, our strategy consisted in micropatterning cell adhesion (RGD) and proliferation (WQPPRARI) peptides on the surface of plasma-functionalized PTFE, therefore enabling covalent conjugation of the peptides. Basically, the technology consisted in spraying a solution of the adhesion peptide, therefore leading to 10 µm-diameter RGD spots semi-randomly distributed over the sample and covering 20 % of the whole polymer surface. In a second step, proliferation peptide was applied to the remaining surface by soaking, therefore covering the unreacted surface. The 20 % coverage was obtained by using an x-y table, programmed to move from side to side of the surface on x value, with an increment on y value that has been calibrated.

Abstract: Poly (ethylene glycol) hydrogel (PEG) micropatterns fabricated by photolithography and various other microfabrication techniques have been used as a platform to analyze cell-biomaterial interactions in cell culture studies. Numerous innovative techniques have been described about photolithography and the use of Poly (dimethyl siloxane) stamp (PDMS) based pressure moulding technique for the microfabrication of PEG hydrogel micropatterns. We herein this literature describe a simple and a versatile method for fabricating Poly (ethylene glycol) hydrogel-diacrylate (PEG-DA) hydrogel micropatterns using the ‘Soft-photolithography’ technique which is a combination of pressure moulding using a PDMS stamp and photolithography. Using this simple technique, PEG-DA hydrogel micropatterns were fabricated on a silicon substrate of varying dimensions from 40μm to 10μm within the same substrate. Such a three-dimensional microenvironment with varying sizes can serve as an excellent platform to study cell behaviour in culture. These PEG-DA hydrogel micropatterns can further be functionalized by adding a variety of biomolecular cues within the PEG-DA hydrogel matrix or these biomolecules can be patterned on the PEG-DA micropatterns after photopolymerization using micro-contact printing for analysis of cell-biomaterial interactions and tissue engineering purposes.

Abstract: Cell behaviour such as adhesion, morphology, proliferation and functional activity are highly influenced by surface properties including hydrophobicity, roughness, texture and morphology. These surface properties may be controlled using a mixture of additive coating techniques to produce glass coatings by sol-gel process and soft lithography on dental ceramics. The purpose of this work was to compare cell adhesion and early orientation of Human Bone Marrow (HBM) cells cultured on micro-patterned (micro-PGC) and on flat glass coatings (FGC) produced by sol-gel processing. Spin coating was used to apply SiO2 flat coatings on glass substrates as model surfaces. Photolithography was applied to produce master patterns with microscale dimensions. A moulding technique was used to print micropatterned SiO2 glass coatings produced by a sol-gel process. The coatings were then sintered, sterilized and cultured with HBM cells derived from primary cultures, using a standardized protocol, for 1 and 7 days. Cell morphology and orientation were observed using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Flat and MPGC with line shaped features were produced. Cells presented a typical osteoblastic morphology on flat surfaces while slimmer, preferentially oriented and more elongated morphologies could be seen on line micro-patterned surfaces. HBM cells cultured on flat glass coatings showed increased tendency to spread and to assume more randomized proliferation when compared to the cells on the micro-patterned glass coatings. Micro-patterned glass coatings showed higher orientation control and smaller delay in the rate of proliferation, in early stages of in vitro culture as compared to flat coatings. These preliminary studies revealed that Micro-PGC induce significant morphological changes and controlled orientation of HBM cells during early stages of cell proliferation.

Abstract: A novel selective metallization process to fabricate the fine conductive line based on drop-on-demand (DoD) inkjet printing was studied. Direct inkjet printing is an alternative and costeffective technology for patterning and fabricating objects directly from design or image files without making masks and patterns. The conductive ink used in this experiment consists of 1 to 50 nm silver particles that are homogeneously suspended in an organic carrier. A piezo-electric inkjet print head driven by a bipolar voltage signal is used to dispense 20-40μm diameter droplets. Repeatability of circuitry fabrication is closely related to the formation of steady, satellite-free droplets. Therefore, the ability to form small and stable droplets with a same size, constant velocity and the correct flight angle must be taken into consideration for fine and precise conductive lines. In this study, parameters affecting the pattern formation such as drop formation, drop placement accuracy and velocity deviation between each nozzle have been investigated. As a result, direct inkjet patterning systems equipped with several functioning modules and fine metallic patterns have been developed.

Abstract: Micropatterned PEGylated substrates with two-dimensional arrays of plasma-etched circular domains (diameter:100 micro-m) were prepared by coating of mercapto-functionalized poly(ethylene glycol) (PEG) on Au surface, followed by plasma-etching through a metal mask pattern with circular holes. The PEGylated region on the patterned substrate works to repel proteins, consequently, inhibits cell adhesion. Then the micro-patterning of bovine articular chondrocytes or rat primary hepatocytes hetero-spheroids underlaid with human umbilical endothelial cells (HUVEC) was achieved on the plasma-etched circular domains, exposing the base gold surface. Obtained results suggested that the efficiency of inhibiting non-specific protein adsorption significantly affects on construction of micro-patterned cell adhesion and hetero-spheroids. The formation of hetero-spheroid thus suggested is significantly modulated by suface properties, particularly non-fouling character of PEG region. These arrayed spheroids is promising materials for tissue and cell-based biosensors (TBB/CBB) as well as tissue engineering technologies.

Abstract: Micropatterns of phenylsilsesquioxane thick films have been prepared by electrophoretic sol-gel deposition using ITO-coated substrates with a hydrophobic-hydrophilic patterned surface. After the electrophoretic deposition, phenylsilsesquioxane thick films were formed only on hydrophilic areas on the pattern. These thick films obtained immediately after the electrophoretic deposition were opaque due to light scattering. However, phenylsilsesquioxane particles in the films were morphologically changed from aggregates of the spherical particles to continuous phase by a heat treatment process, and finally convex shaped phenylsilsesquioxane micropatterns were formed only on the hydrophilic areas.

Abstract: A new technique for micropatterning surfaces for cell growth support is described and characterized. This technique allows covering of large three-dimensional surfaces at low cost with controllable micropatterns. This method takes advantage of the random properties of aerosols and the principles of liquid atomization. Parameters of interest were the pressure of atomization air, the flow rate and volume of the atomised liquid, and the distance between the spray nozzle and the surface of the sample. The experimental setup permitted to obtain mean diameters of spots between 10 and 20 microns with a maximum surface coverage of 20%. In an initial step, polytetrafluoroethylene (PTFE) films were treated with ammonia plasma to insert amino groups on the surface. The ammonia plasma treated films were immersed in a solution containing sulfosuccinimidyl 4-(N-maleidomethyl)cyclohexane-1-carboxy-late (SSMCC) to permit the introduction of maleimido groups on the PTFE surface to subsequently conjugate peptides through a sulfhydryl containing N-terminal cystein residue. Plasma/S-SMCC pretreated surfaces were then sprayed with peptide sequences CGRGDS and CWQPPRARI. Our data showed that spots of CGRGDS peptides over a background of CWQPPRARI peptides were the most effective combination to enhance endothelialization.

Abstract: Micrometer wire consisting of microbeads was successfully fabricated onto a patterned conductive electrode substrate by an electrophoretic deposition (EPD) process with precise control of electric field distribution generated in the colloidal suspension. Monodisperse polystyrene microspheres with 320 nm in diameter and an interdigitated microarray Au electrode having 10 μm in width and 5 μm in spacing were used in this EPD system. A micropattern of polystyrene particles with two dimensional arrays was formed onto the patterned electrode by the EPD process with two electrode system using an electrostatic interaction between the electrodes and the charged particles in the suspension.