We present a controlling technique of microporous structure by laser irradiation during self-organization process. Self-organization process is fabrication method of microstructure. Polymer solution was dropped on the substrate at high humid condition. Water in air appears dropping air temperature below the dew point. The honeycomb structure with regularly aligned pores on the film was fabricated by attaching water droplets onto the solution surface. We demonstrate that it was possible to prevent forming pores at the region of laser irradiation and flat surface was fabricated. We also demonstrated that a combination structure with two pore sizes and flat surface was produced by a single laser-pulse irradiation. Our method is a unique microfabrication processing technique that combines the advantages of bottom-up and top-down techniques. This method is a promising technique that can be applied to produce for photonic crystals, biological cell culturing, surface science and electronics fields, and so forth. 1. Introduction Microfabrication techniques have been studied by many researchers with the developments of nanotechnologies [1]. Microfabrication techniques are categorized as top-down or bottom-up fabrication techniques. The top-down fabrication technique creates nanoscale and submicron scale devices by using externally controlled equipment to direct their assembly. One of typical top-down methods is photolithography. The advantages of the top-down methods are high precision and high reproducibility in the fabrication process [2]. The top-down method, however, requires expensive equipment, long processing time, and complicated procedures. On the other hand, the bottom-up fabrication technique builds smaller components to more complex assemblies. The bottom-up techniques are known as self-organization process. The bottom-up methods have the advantages of short process time and low cost. They easily produce a uniform pattern in large area, while the arbitrary structures are difficult to be produced by bottom-up techniques. It has been reported that microporous films are formed by the cast on the glass substrate under high humid condition by self-organization process of solution casting method [3–17]. The microstructures by self-organization process are expected to be used in many applications as follows. The microporous structure of regular aligned pores is made of polystyrene, and the line defect in this microporous structure is applied for photonic crystal [18, 19]. Micropatterned substrates by self-organization process are used as potential scaffolds
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