Stretchable and Durable Kirigami Inspired Electronics Based on Conductive Polymers

Wearable and flexible electronics are new technologies that attract many researchers’ attention because of their potential applications in numerous fields such as sensors, energy storage, energy harvesters and displays. The main challenge of stretchable electronic devices is to maintain their electrical and mechanical performance under high cyclic strain. Mixing an elastomeric polymer with a conductive filler and structural design are among the strategies for fabricating stretchable and durable systems. Kirigami pattern is a kind of structural design that potentially meets these criteria due to its unique geometry. Kirigami is an ancient papercraft technique created by cuts of a substrate. This method has been used to develop functional hierarchical structures for a wide range of applications such as sensors, tissue engineering, energy conversion and energy storages. In this thesis, conductive poly (3,4-ethylene-dioxythiophene): poly(styrene sulfonate) (PEDOT:PSS)/ polydimethylsiloxane (PDMS) polymer composite and kirigami patterning were used to make stretchable and reliable conductors. A laser cutting technique was used to fabricate kirigami structured specimens. PEDOT:PSS as conductive filler was mixed with PDMS (i.e., elastomeric polymer) to make stretchable conductive PEDOT:PSS/PDMS composite. In this composite, glycerol and polyethylene glycol were added to the mixture to improve conductivity and stretchability, respectively. The mechanical properties (i.e., tensile strength and viscoelastic properties), electrical and electromechanical properties of PEDOT:PS S/ PDMS polymer composite were investigated. In addition, the properties of kirigami structured PEDOT:PSS/PDMS polymer composite were compared to the properties of kirigami structured PEDOT:PSS coated PDMS, non -kirigami structured PEDOT:PSS coated PDMS substrate and non-kirigami structured polymer composite. To study the effect of PEDOT:PSS coating on the mechanical properties, non -kirigami and kirigami structured PEDOT:PSS coated PDMS were compared to non-kirigami and kirigami structured PDMS specimens. Furthermore, the application of kirigami structured PEDOT:PSS polymer composite as strain sensor was examined for body movement detection by attaching it to a human wrist. When the sensor was subjected to loading and unloading, the sensitivity and hysteresis of electrical resistance were investigated and compared to the kirigami structured PEDOT:PSS coated PDMS specimen.