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Title: Organic mixed ionic/electronic conductors for bioelectronics applications
Author: Pacheco Moreno, Celia Maria
ISNI:       0000 0004 6421 0234
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2016
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The bioelectronics field has incorporated an increasing variety of conducting polymers in applications that involve mixed ionic/electronic transport, yet there is still a lack of design rules to purposefully tune the electronic and ionic contributions to a material's conductivity, as well as processing methods to further control and understand their interplay. New undoped co-polymers were explored as electroactive materials in aqueous media. The range of materials allowed establishing a simple design rule with potential to be explored in other model semiconductors. The most hydrophilic system showed promising response when benchmarked with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) in order to be employed in new operation modes of devices which rely on the electrochemical doping of the active layer, such as organic electrochemical transistors (OECTs). The capabilities of the most promising system were further exploited as an ion-to-electron converter by creating multicomponent systems that included a polar insulator to tune their ionic transport. The straight-forward and chemically inert blending approach showed enhanced transport of ionic species while maintaining their electronic transport as well as displaying characteristic response times linked to the presence of the polar phase. By using the semiconductor as a model system and controlling the volume of aggregates present in the solid-state by means of processing, a phenomenological description was given of ionic transport in different regions of semicrystalline polymers along with their associated decay rates. Finally, the effect of humidity in the charge transport of the undoped co-polymers was explored, with a focus on elucidating ionic contributions from electronic ones. The incorporation of a ionic conductor, Nafion, in a bilayer structure was explored and showed an intimate interaction between the proton conductor and the electronic conductor. The potential of the multilayer structures as humidity sensors and other remarkable features found in their charge transport make these promising systems for further applications in bioelectronics.
Supervisor: Stingelin, Natalie ; Stevens, Molly M. Sponsor: Engineering and Physical Sciences Research Council ; KAUST ; Obra Social "la Caixa"
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral