Force and temperature sensors based on organic thin-film transistor and ferroelectric co-polymer

Student thesis: Doctoral Thesis

Abstract

This thesis presents the development of tactile force and temperature sensors formed by coupling an organic thin-film transistor with a ferroelectric polymer-based parallel-plate capacitor. Ferroelectric material polyvinylidene fluoride trifluoroethylene (P(VDF-TrFE)) sandwiched between two metal electrodes in a parallel plate capacitor structure was coupled to the gate electrode of a low-voltage organic thin-film transistor (OTFT) for signal amplification and voltage readout. To ensure low-voltage operation of the sensing circuit, low-voltage transistor operation was necessary. This was enabled through use of an ultra-thin bi-layer gate dielectric comprised of aluminium oxide (AlOx), formed by the UV/ozone oxidation of aluminium, and a self-assembled monolayer (SAM) of phosphonic acid produced by vacuum deposition. The OTFT was optimised with respect to its dielectric and semiconductor; whereby the length of the SAM’s alkyl chain and semiconductor deposition conditions on OTFT electrical and structural properties were studied. An air-stable organic semiconductor dinaphtho[2,3-b:2’,3’-f]thieno[3,2-b]thiophene (DNTT) was implemented to create OTFTs with improved mobility and electrical stability. Furthermore, two commercially available polyethylene naphthalate (PEN) plastic foils were compared for use as flexible substrates for OTFTs. Response of the P(VDF-TrFE)/OTFT sensor to force and temperature was investigated and results show that the sensor has a linear response to applied constant temperature whereas it responds logarithmically to static compressive force, regardless of whether P(VDF-TrFE) is in the ferroelectric or paraelectric state.
Date of Award1 Apr 2017
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council) & University of Strathclyde
SupervisorHelena Gleskova (Supervisor) & Deepak Uttamchandani (Supervisor)

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