The purpose of this study was to develop a selective patterning process with functional nanoparticles, using the selective hydrophobic treatment which can give surface energy differences. It is important to selectively pattern the nanoparticles in solution, to the desired site in a variety of fields such as transparent electrodes, displays, and bio-sensors. Selective hydrophobic treatment can reduce the additional post processes such as cleaning to remove particles unwanted position, which is a drawback of the existing solution process. Various patterns with sub-micron size that can’t be achieved with other solution processes could be fabricated by nanoimprint lithography, selective surface treatment, and a solution coating process. The transparent conductive electrode (TCE) using silver mesh patterns on the flexible substrate created from our study showed 24 Ω of sheet resistance and more than 82% transmittance. To verify the possibility of nano-patterning of various materials, quantum dot (QD) was also patterned by selectively filling. Selective surface treatment technology has significantly improved the filling process of nanoparticles into fine patterns less than 1 μm wide.

Micro-stereolithography technology has made it possible to fabricate a freefonn 3D microstructure. This technology is based on conventional stereolithography, in which a UV laser beam irradiates the open surface of a UV-curable liquid photopolymer, causing it to solidify. In micro-stereo lithography, a laser beam of a few ㎛ diameter is used to solidify a very small area of the photopolymer. This is one of the key technological elements, and can be achieved by using a focusing lens. Thus, the solidification phenomena of the liquid photopolymer must be carefully investigated. In this study, the photopolymer solidification phenomena in response to variations in the scanning pitch of a focused laser beam was investigated experimentally. The effect of layer thickness on the solidification width and depth was also examined. These studies were conducted under the conditions of relatively lower laser power and relatively higher scanning speed. Moreover, the photopolymer solidification phenomena for the relatively higher laser power and lower scanning speed was investigated, too. In this case, comparing to the case of lower laser power and higher scanning speed, the photopolymer absorbed large amount of irradiation energy of the laser beam. These results were compared with those obtained from a photopolymer solidification model. From these results, a new laser-scanning scheme was proposed according to the shape of the 3D model. Samples by each method were fabricated successfully.

Micro-stereolithography is a newly proposed technology as a means that can fabricate a 3D micro-structure of free form. It makes a 3D micro-structure by dividing the shape into many slices of relevant thickness along horizontal surfaces, hardening each layer of slice with a focused laser beam, and stacking them up to a desired shape. In this technology, differently from the conventional stereolithography, scale effect is dominant. To realize micro-stereo lithography technology, we developed the micro-stereolithography apparatus which is composed of an Ar+ laser, x-y-z stages. controllers, optical devices and scan path generation software. Related processes were developed, too. Using the system, a number of micro-structures were successfully fabricated. Some of these samples are shown for prove this system. Laser scan path generation algorithm and software considering photopolymer solidification phenomena as well as given 3D model were developed. Sample fabrication of developed software shows relatively high dimensional accuracy compared to the uncompensated result.