Natural polyelectrolyte: Major ampullate spider silk for electrolyte organic field-effect transistors

Abstract The major ampullate (MA) silk collected from giant wood spiders Nephila pilipes consists of 12% glutamic acid (Glu) and 4% tyrosine (Tyr) acidic amino residues. The MA silk may act as a natural polyelectrolyte for organic field-effect transistors (OFETs). Pentacene and F 16 CuPc OFETs were fabricated with the MA silk thin film as the gate dielectric. The MA silk thin film with surface roughness of 4 nm and surface energy of 36.1 mJ/m 2 was formed on glass using a hexafluoroisopropanol (HFIP) organic process. The MA silk gate dielectric in pentacene OFETs may improve the field-effect mobility ( μ FE,sat ) value in the saturation regime from 0.11 in vacuum to 4.3 cm 2  V −1  s −1 in air ambient at ca. 70% RH. The corresponding threshold voltage ( V TH ) value reduced from −6 V in vacuum to −0.5 V in air ambient. Similar to other polyelectrolytes, the changes of μ FE,sat and V TH may be explained by the generation of electric double layers (EDLs) in the MA silk thin film in air ambient due to water absorption.