Fabrication Of Soft Photomasks On Organic Substrates And Micropatterns On Organic Polymer Substrates

Materials and environmental interaction occurs mainly in the material surface, such as printing, adsorption, adhesive, coating, dyeing, anticorrosion, micropatterns, and etc., which all required its surface with appropriate surface properties. Organic polymer materials have received increasing attentions because they have unique benefits including low cost, easy processibility, high transparency, flexibility, light-weight, recyclability and disposability, but chemically inert and hydrophobic surface of polymer materials lead to poor hydrophilicity, moisture content, adhesion, biocompatibility, and etc., which limit them to use in some fields mentioned above, so the surface modification or functionalization is an important research topic. While surface micropattern fabrication is an important way in realizing materials function, and it is also a key technique in modern science and engineering. Photolithography techniques due to its accurate, precise, and high output has been leading technology in the field of micropattern fabrication. The lithography mask (chromium mask) is the key component in the transformation of the micropatterns, but its fabrication requires special and complex equipment, strict experimental conditions, and complicated processing technology and so on, which limits its applications in many fields of nonphotolithographic microstructure fabrication. Based on the above consideration, we fully researched the existing micropatterning fields and photomask fabrication methods. Firstly, we fabricated organic/inorganic hybrid (BOPP/SiOx, PET/SiOx) film by spin-coating method via Sol-Gel reaction, and then by inkjet printing any desired micropattern can be printed, such as multicolor micropattterns, and color gradation patterns. As an alternative mask to lithography mask, we did some applications on polymer surface modification controlled by these special printing photomasks.The main results and significance are summarized as follows:1. Presented a new technology for fabrication of a UV-visible photomask. The processes included:(1) photomask substrate preparation:We did wettability modification through " Confined Photo-catalytic Oxidation" (CPO) reaction on the transparent polymer film or sheet such as biaxially oriented polypropylene (BOPP) film, polyethylene terephthalate (PET) film, and then fabricated organic/inorganic (BOPP/SiOx and PET/SiOx) hybrid film through Sol-Gel via spin-coating silica, which had nanometer thickness of the silica surface. The film was absolutely transparent and flexible hybrid film. (2) Inkjet printed any desired micropattern onto this hybrid film to form a kind of soft photomask technology through the pigment-based inkjet printer EPSON R800. Parameters such as the ink adhesion to the substrate was adjusted by inorganic layer, the thickness of light blocking (opaque ink) layer (0.5μ-1.3μ), light transmittance (absorbed almost all the light with wavelengthλ<500nm) and line width (w> 50μm) were controlled by the designed depth of color and designed line width. Compared to traditional chromium mask/metal mask, the printing photomask is suitable for non-planar substrates, scalable for large area production, and extremely low cost, which is much preferable to the conventional chrome-mask fabrication methods. So this photomask has widespread applications in fabrication of micropatterns in many kinds of shapes of organic substrate surface.2. Polymer surface modification and the photochemical reaction are a hot topic and cutting-edge issues in recent years. From the practical point of view, the soft UV-visible photomask was used in polymer surface modification fields to prove its operational performance and value. Combining CPO reaction of our lab, controlled by this inkjet printing soft photomask, it was very convenient to make the wettability patterns via UV-induced hydroxyl formation on BOPP or PET surface, and further deposited conductive polymers such as polyaniline (PANI) and inorganic zinc oxide (ZnO) semiconductor micropatterns; by photografting polymerization, we grafted patterned functional monomer such as crylic acid (AA) and acrylamide (AM) polymerization on the organic polymer PET or BOPP substrates controlled by the photomask and thus fabricated micropatterning grafting PAA brushes and PAM microstructures; and for the photomask is very soft and thin, we photografted AA polymerization on non-planar plastic substrate.3. Polymer substrate immobilizing abstract hydrogen photoinitiators, such as isopropyl thioxanthone (ITX) and camphorquinone (CQ) has different absorption characteristics to different wavelength lights. We did some research on the mechanism of grafting, the type of photograft (one-step and two-step), grafting rules, and etc. It was found that ITX can absorbλ=200-300nm UV light andλ=300-400nm far ultraviolet light which wavelengths can induce surface grafting vinyl polymer (AA or AM) polymerization on organic (polyethylene PE, BOPP, PET) by one-step or two-step method. As to CQ, it can absorb 200-300nm UV light and did similar photograft (one-step) (AA or AM) polymerization on the same polymer surface. Meanwhile, CQ can absorbλ=400-500nm visible-light. It was found that UV light can induced immobilization initiator CQ, and then visible light induced photografted AA on BOPP or PE surface by two-step method, it can also induced living surface photografting polymerization via two-step visible light induced AA polymerization on aminated PET film surface.4. Based on the above results, different abstract hydrogen photoinitiators (ITX and CQ) have different characteristics to different light absorbance. For ITX can absorbλ=300-400nm far UV light and CQ can absorbλ=400-500nm visible light. Meanwhile, different color inks have some corresponding transmitted light, so it is very convenient to fabricate a wavelength controllable photomask technology. Controlled by this printing photomask, we provided a novel and alternative route to generate covalent photografting of binary component polymer brushes on aminated PET film surface. For example, we printed black, blue, and yellow three kinds of color ink, which have different transmittance to light. For black ink, it can almost absorb all the light with wavelength range less thanλ=500nm, yellow ink transmitλ=300-400nm far UV light, and blue ink can transmit k=400-500nm visible light, while according to rules of the ITX and CQ mentioned above, the procedure involved fabrication of wavelength controllable photomask by inkjet printing technology, immobilization of two kinds of patterned photoinitiating system which attacted to aminated PET surface by covalent bonds, and two-step UV-visible light irradiation on polymer film via surface-initiated controlled radical polymerization, and thus fabrication binary component grafts PAA/PAM micropatterns on the same organic substrates. Compared to other methods, it avoided complex lithographic schemes and the passivation of the "living" chain ends when graft the second monomer. This method can easily be applied to graft a large variety of chemical functional materials onto polymer substrates with potential utility in molecular recognition, directed cell selective adhesion, switchable surface wettability, and other microscale polymeric surface applications.5. Hybrid BOPP/SiOx film can be served as substrate for inkjet printing gradation photomask designed by software program such as Auto CAD, Chemdraw, Freehand. The transmitted light intensity from the photomask shows a gradient distribution. According to this rule, we successfully implemented CPO reacton, confined photografting polymerization with AA and precipitation-photografting polymerization with AM grafted onto the surface of BOPP or PE film. ART-FTIR, X-ray photoelectron spectroscopy (XPS), water contact angle, fluorescence microscope and scanning electron microscopy (SEM) analysis showed that the gradient surfaces could be the different gradient distributed functional surface such as surface energy, grafting chain density and grafting thickness gradient distributed polymer surfaces. This is by far the most convenient reported method in preparation of gradient surfaces, and it is a versatile facile method in preparation of a gradient surface by UV light-induced-reaction. These fabricated special surfaces could be used widely in the fields such as biomedical materials, microfluidics devices, cell adsorbance, improve the efficiency of heat conduction adsorption etc..