The effect of polymer matrix on laser microfabrication of Au nanoparticles dispersed polymer resists Hiromasa Yagyu a,b, *, Osamu Tabata a a Graduate School of Engineering, Kyoto University, Yoshida-honmachi Sakyo-ku, Kyoto 606-8501, Japan b Mitsuboshi Belting Ltd., 4-1-21 Hamazoe-dori, Nagata-ku, Kobe 653-0024, Japan 1. Introduction Nanoparticle has attractive characteristics such as novel optical absorption, melting point depression, and quantum size effects because of small size compared with bulk materials. These characteristics were applied to metal ink for realizing electric circuit with fine line and space by low temperature sintering [1], metallic microstructure for three-dimensional microelectro- mechanical system [2], and coloring paint using metal and semiconductor nanoparticle [3]. In these applications, nanocom- posite materials such as composition of nanoparticle and poly- mer are studied to realize a high performance device. A new nanocomposite polymer resist in which Au nanoparticles with mean diameter of 3.4 nm were densely dispersed in ethylcellulose have been developed by authors [4]. Since this resist shows strong absorption in the visible wavelength region (around 530 nm) induced by plasmon resonance vibration of Au nanoparticles, it can be micromachined using a focused Nd:YVO 4 -SHG laser beam (CW, wavelength of 532 nm, output power below 30 mW). Laser processing has been known as a technique having a flexible controllability for the processing shape. For the conventional laser processing, it is common to use a high power (average power output of 100 W) and a high pulse rate (peak power output of 10 MW per pulse) laser such as YAG laser [5,6] and excimer laser [7,8]. One of the features of the laser fabrication technique using Au nanoparticles dispersed polymer resist is that a micro-scale channel and hole with high aspect ratio can be fabricated using a low power output laser without the photolithography step and using neither a poisonous reagent nor the gas. This processing system is compact and low-cost because of using low power and visible laser in addition to use of conventional optical parts such as lens, mirror, and filter. Using the processing ability of our polymer resist, development of the fabrication process of microneedle array was reported [9]. However, the processing mechanism of the resist such as the effects of polymer matrix and nanoparticle size is not clear. For example, in previous work [4], Au nanoparticles Applied Surface Science 255 (2008) 2237–2243 ARTICLE INFO Article history: Received 23 April 2008 Received in revised form 7 July 2008 Accepted 8 July 2008 Available online 15 July 2008 PACS: 52.38.Mf 61.46.+w 81.07.b 82.35.Np 85.40.Hp Keywords: Nanoparticle Laser processing Polymer resist Thermal property ABSTRACT The effect of polymer matrix on laser processing of Au nanoparticles dispersed polymer resist was reported. Au nanoparticles dispersed polymer is a resist in which Au nanoparticles with average diameter of around 3 nm was dispersed. Since the resist has a strong absorption at the wavelength of around 530 nm, it can be micromachined using focused low power Nd:YVO 4 -SHG laser (CW, wavelength of 532 nm). From the evaluation of a dispersibility of Au nanoparticle in the different polymer using X-ray diffraction and visible ray absorbance, it was confirmed that the dispersibility of Au nanoparticle induced by the kind of polymer matrix influenced laser-processed shape. Moreover, from thermal properties and the calculation of temperature rise distribution by laser beam in polymer resist, it was predicted that the processing mechanism for thermoplastic polymer resist was related with melt and grain growth of Au nanoparticle. ß 2008 Elsevier B.V. All rights reserved. * Corresponding author at: Mitsuboshi Belting Ltd., Technical Department, R&D Section, 4-1-21 Hamazoe-dori, Nagata-ku, Kobe 653-0024, Japan. Tel.: +81 78 682 3952; fax: +81 78 681 1006. E-mail addresses: h-yagyu@mitsuboshi.co.jp, hiyagyu@yahoo.co.jp (H. Yagyu). Contents lists available at ScienceDirect Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc 0169-4332/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2008.07.075