Organic semiconductor strain sensors

In this paper, the authors report the first strain sensors using an organic semiconductor as the active element. The authors have used a doped organic semiconductor as the active element for low Young´s modulus strain sensors. The sensor cross-section is shown. For these sensors 2 nm thick Ti and 20 nm thick Au were deposited on 50 micron thick polyimide substrates by thermal evaporation and patterned to form sensor electrodes and wiring. Next, a 50 nm thick pentacene layer was deposited, again by thermal evaporation. The pentacene layer was then doped p-type by exposure to a 1 % solution of ferric chloride in water. The doped pentacene film was then patterned using an aqueous polyvinyl alcohol photolithography step and oxygen reactive ion etching. The maximum process temperature used to fabricate the organic strain sensors is 110 degC