2 - Conducting Polymer Sensors, Actuators and Field-Effect Transistors

Abstract

Conducting polymers are polymers with conjugated chain structures. To achieve high conductivity in conducting polymers, doping is necessary, which can be achieved by redox reaction and protonation. However, when an electron is added to or withdrawn from a conducting polymer, a chain deformation takes place around the charge, which costs elastic energy and puts the charge in a lower electronic state. The competition between elastic energy and electronic energy determines the size of the lattice deformation, which can be of the order of 20 polymer units long. A key requirement in the synthesis of conducting polymers is that the conjugated nature of the monomer should be conserved during the synthesis process. Conducting polymers are synthesized from their respective monomers using electrochemical, chemical oxidation, or interfacial polymerization processes. Conducting polymers, such as polypyrrole doped with dodecylbenzenesulphonate (PPy-DBS), have been shown to work as soft actuators or artificial muscle fibers, based on the principle of volume change on redox process. Using conducting polymers, various types of sensors, such as chemiresistive, diode, FET, surface acoustic wave (SAW), optodes and amperometric, have been widely fabricated. In addition, conducting polymer field-effect transistor (CP-FET) platform is a promising technology for low-cost, large-area, and flexible electronics in displays and sensors. Among various polymers, poly(3-hexylthiophene) (P3HT) has most often been used as the active semiconducting layer in CP-FET owing to its high mobility.