Sensor applications of polymer field effect transistors

Abstract

This thesis presents the fabrication and characterization of organic field effect transistors (OFETs) for sensor applications using polymeric semiconductor of poly (3- hexyl thiophene)(P3HT). Utilizing deionized (DI) water as gate insulator, operation voltages of polymer field effect transistors (polymer FETs) are reduced below 1V. To ease the micro uidic channel integration of polymer FETs, a novel structure called planar OFET is designed and introduced. Comparing the output characteristics of planar OFET with the one of top-gate, bottom-contact OFET using gate probe in stead of deposited gate electrode, it is shown that this planar OFET topology operates successfully as eld e ect transistor providing on-o ratio of about 50. It is stated that P3HT lm deposition by spin-coating method leads higher on-off ratios than drop-casting method for top-gate, bottom-contact OFET topology. Then, durability of P3HT to microfabrication processes is examined. In addition, sensitivity of P3HT to NaCl and KCl solutions is searched. Finally, microfluidic channel encapsulation of planar polymer FETs with three different materials, polyvinyl alcohol (PVA), parylene and polydimethylsiloxane (PDMS) is searched. PVA microfluidic channels providing liquid ow are successfully formed. On-off ratios of 4 and 10 are obtained with planar polymer FETs integrated into parylene and PDMS microfluidic channels, respectively.