Fabrication of flexible and transparent single-wall carbon nanotube gas sensors by vacuum filtration and poly(dimethyl siloxane) mold transfer

We report on the fabrication of density controlled single-wall carbon nanotube (SWCNT) thin-films on poly(dimethyl siloxane) (PDMS) substrates by vacuum filtration and PDMS direct molding. The vacuum filtration method made it possible to form a thin-film of SWCNTs having uniform density over a large area. The optical transmittance of the SWCNT thin-films showed inverse proportionality to SWCNT density and conductivity indicating that the SWCNT's PDMS surface coverage was directly related to the thin-film's optical and electrical characteristics. The flexible SWCNT thin-film showed high mechanical stability with negligible change in conductance after being bent by 180^o. It was shown that SWCNT thin-film conductance had high sensitivity to NH"3 gas partial pressure and that the lower the density of SWCNTs the higher the sensitivity. The results show that the flexible SWCNT thin-films may be applicable to future high sensitivity mobile sensors.