Highly Flexible and Transparent Single Wall Carbon Nanotube Network Gas Sensors Fabricated on PDMS Substrates Chi-Won Cho 1 , Chae-Hyun Lim 2 , Chang-Seung Woo 2 , Hyung-Suk Jeon 2 , Bonghyun Park 2 , Heongkyu Ju 2 , Cheol-Jin Lee 3 , Sunglyul Maeng 4 , Ki-Chul Kim 4 , Sang Hyeob Kim 4 , and Seung- Beck Lee 1,2 1 Electronics and Computer Engineering, Hanyang University, 17 Haengdangdong, Seongdonggu, Seoul, 133-791, Korea, Republic of 2 Nanotechnology, Hanyang University, 17 Haengdangdong, Seongdonggu, Seoul, 133-791, Korea, Republic of 3 Electronics and Computer Engineering, Korea University, 5-1 Anamdong, Seongbukgu, Seoul, 136-701, Korea, Republic of 4 Cambridge-ETRI Joint R&D Centre, Electronics and Telecommunications Research Institute, Daejeon, 305-350, Korea, Republic of ABSTRACT We report on the basic characteristics and gas sensing operation of density controlled single-walled carbon nanotube (SWCNT) thin films on poly(dimethyl siloxane) (PDMS) substrates. The vacuum filteration and PDMS mold transfer method allowed the density of SWCNT distributed to have non-local uniformity. The optical transparency of the SWCNT thin films was inversely proportional to SWCNT density and conductivity. The flexible SWCNT thin film showed high mechanical stability with negligible change in conductance after being bent by 180 o . We evaluated its gas sensing operation depending on SWCNT density and bias voltage. It was shown that lower SWCNT density thin films had higher sensitivity to NH 3 gas, which may be due to higher exposed surface area for lower density SWCNT thin films. Also, we found that lower bias voltage devices showed faster recovery times. The results show that vacuum filteration and mold transfer method produced flexible SWCNT thin films that have stable mechanical and electrical characteristics and also stable gas sensing capabilities making them applicable to future flexible integrated sensors. INTRODUCTION Single wall carbon nanotubes (SWCNTs) have been considered as one of the key candidate materials for future electronic device application, due to many outstanding characteristics such as high mechanical strength, chemical stability, high electrical conductivity and high thermal conductivity [1]. Especially, their high surface to volume ratio and one dimensional transport nature allows them to be highly sensitive to changes in the surface potential states, which makes them ideal for highly sensitive chemical sensor application [2]. However, for industrial application of SWCNTs to high sensitivity sensors a few fundamental and technical obstacles must be overcome. As synthesized, about 2/3 of SWCNTs are semiconductors while the rest are metallic [3]. Also, metallic contacts to SWCNTs results in Mater. Res. Soc. Symp. Proc. Vol. 922 © 2006 Materials Research Society 0922-U11-10