Fibrous field-effect transistors

The transistor as a component of the e-textile plays a crucial role in the textile electronic circuit. The existing fibrous transistors can be divided into two categories wire thin film transistors (WTFTs Lee and Subramanian, 2003 Maccioni et al., 2006 Locci et al., 2007) and wire electrochemical transistors (WECTs Hamedi et al., 2007 De Rossi, 2007 Tao et al., 2011). WTFT, also called WFET, is based on the field-effect transistor (FET) technology and WECT is based on electrochemical technology. With the help of these transistors, the textile electronic circuit can be achieved without loss of mechanical properties such as flexibility or softness. 

Transistors as the basic and crucial component for electronic circuits have been vigorously studied since 1947. The essential function of a transistor comes from its ability to control a larger signal by an apphed small signal between one pair of its terminals. This property makes the transistor as an amplifier or switch. According to the mechanism of the generation of carriers in the channel, transistors can be divided into three categories bipolar junction transistor, field-effect transistor, and electrochemical transistor. In electronic textile applications, the EET and ECT are employed to realize fibrous transistors. 

The same research team published their theoretical modeling for the cylindrical OFET in 2007 (Locci et al., 2007). They considered the field-effect fibrous transistor as thin film transistor (Fig. 25.15) and reduced the source-drain current in linear and samration regimes as Eqs. [3.1] and [3.2] ... 

Under the hypotheses that no = N and rj ds, the threshold voltage is equal to the pinch-off voltage Vp = Vth, and all the terms in the second row of Eq. [3.2] can be neglected to obtain Eq. [3.3]. In this case, the field-effect fibrous transistor can be considered as a planar thin film FET. 

---