Ribosome display was used to select peptide aptamers from a random library composed of hydrophilic amino acids for a conducting polymer, poly(3-hexylthiophene-2,5-diyl). Binding of aptamers was measured by quartz crystal microbalance, and the secondary structure of the peptide was investigated by circular dichroism. (c) 2013, The Society for Biotechnology, Japan. All rights reserved.