Fully 3D printed Organic Electrochemical Transistors for biosensing applications

  • Author / Creator
    Majak, Darren
  • Biosensors are a large market that is quickly gaining traction and is a large industry that is projected to continue its rapid growth. One of the main challenges with biosensors are developing reliable, high sensitivity, repeatable sensors economically and rapidly. In this work, I have used 3D printing for developing organic transistors and logic gates for biosensing applications. These sensors are based on organic electrochemical transistors (OECTs) with Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as the channel material. Recreational use of cannabis was legalized in Canada in 2018, however, the detection of impairment has remained elusive for law enforcement. The psychoactive ingredient in cannabis, Δ9-Tetrahydrocannabinol (THC), can be sensed in saliva and other body fluids thus indicating impairment. We have established that by using a platinum gate coupled with an OECT, concentrations of THC down to 0.05 nM can be sensed in DI water. This is the first step in creating THC sensors for saliva, which can detect impairment.These OECT based sensors were also used as melatonin concentration sensors. Due to the nature of melatonin, the Redox reaction is not reversible. This means that the sensors are single-use sensors and can only be used once. These sensors show a distinct difference between the response for 1 μM and 10 nM. These are preliminary results show the capabilities of OECTs as Melatonin sensors.Normally, one requires signal processing including multiplexing for the signal from these sensors and these are done off the sensor circuitry. Multiplexing is an important aspect of sensing as it allows for multiple entities to be sensed. Here, fully 3D printed multiplexers (MUX) based onii iorganic electrochemical transistors (OECTs) with Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as the channel material. We have established that by arranging single OECTs, logic gates can be created that can then be arranged to make a MUX. A MUX can then be used to process signals from multiple sensors, thus allowing for a more complete biosensing platform to be created.These logic gates show sensing capabilities as the results have predictable shifts depending on the concentration of cations used on the OECT channels. These sensing capabilities are explored using an inverter logic gate. These inverters show a distinction between various concentrations as well as a distinction between different cations. These sensors have a LOD of 1mM. Preliminary results for pH detection using NOT logic gates are also presented.

  • Subjects / Keywords
  • Graduation date
    Fall 2020
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.