Fabrication and Integration of Solution Processed Electronic Devices using Printed Technologies

Abstract

Recently there has been a growing interest in the realization of low cost, flexible and wearable electronic systems including flexible displays, RFID tags and biomedical sensors. Printed Electronics has emerged as one of the most promising alternative manufacturing technologies because of its ambient manufacturing processing. From electronic market point of view, if we consider the sensors and smart systems to be fully manufactured with a printed process it will capture around $1B by 2020. In growing printed electronic market, solution processed materials including organic and inorganic are playing vital role in the rapidly improving performance of the printed electronic devices. In addition to these materials, the advance open-air manufacturing techniques such as electrohydrodynamic EHD, inkjet and spin coating are also contributing in improvement of the performance of printed electronic devices, circuits and systems. This thesis focuses on the fabrication of printed, flexible and stretchable electronic devices based on solution processed materials and utilization of printed techniques. Materials are synthesized to make it printable through printed techniques for the realization of electronic devices and circuits. The printed techniques used in device manufacturing are electrohydrodynamic EHD, Inkjet material printing, magnetic sputtering, and spin coating. In this work, I have used different substrates according to the manufacturing process requirement and device in flexible, stretchable and transparent applications. The main substrates utilized in fabrication of devices are glass, PDMS, PET and paper. The fabricated devices were characterized against their electrical, mechanical, optical and chemical behavior to verify the solution processed device fabrication approach. In addition to the printed devices, some printed circuits and systems were also fabricated and characterized such as conventional crossbar passive array with pull-up resistors and asymmetric memristor to minimize the sneak current problem in nonvolatile resistive memory (ReRAM), and printed state memorable organic light emitting device (SMOLED) for the flexible programmable display applications. Several types of printed devices are fabricated and discussed in this thesis includes: memristors, memory units, capacitors, diodes, temperature sensors, humidity sensor and biomedical sensors. I have fabricated different memristors based on graphene quantum dots (GQDs), zinc stannate (ZnSnO3), poly(4-vinylphenol) (PVP) and zirconium oxide (ZrO) to improve retention time, on/off ratio and endurance cycles. These memristors were utilized for the cross bar resistive memory applications. A printed differential temperature sensor (DTS) based on silver nanoparticles (AgNPs) is fabricated which measures temperature of a flexible or curved body as well as its strain. To measure humidity sensor in a wide range with high sensitivity, an inkjet printed humidity sensor based on graphene and methyl-red composite is fabricated that converts the relative humidity (%RH) level into its terminal resistor with 96% sensitivity in 5-96% RH. Comb type electrodes were decorated with silver nanowires (AgNWs) to realize a biomedical printed sensor that detects and classify three popular bacteria types JM-109, DH5-𝜶 and salmonella through impedance analysis. Flexible and stretchable photo sensors based on perylene/graphene composite on a PDMS and PET substrates were fabricated to detect the visible light with 25% axial strain. Printed diodes for rectification applications in printed electronic circuits based on organic materials N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD) and fullerene (C60). The prototype of printed electronic devices and circuits fabricated by utilizing solution-processed materials are good achievements and a way to future printed flexible and stretchable electronics.