3D-printed OECT for Flexible Complementary Circuits

Silicon-based (Si) complementary metal-oxide-semiconductor (CMOS) field-effect transistors have been one of the main components in the field of the integrated circuit (IC) since the 1980s, mostly due to their low power consumption. For this reason, Si-based CMOS devices have been researched for Internet of Things (IoT) applications, acting as low-power sensors (e.g., motion, light, temperature). In the last decades, there have been a growing interest in developing flexible and soft IoT modules, capable of conforming to different shapes and eventually even placed on skin/inside the body, acting as smart biological sensors.<br/>For this kind of applications, the perfect candidate is represented by organic electrochemical transistors (OECT). Indeed, OETCs typically operate with &lt; 1 V and possess high transconductance, exploiting a mixed ionic-electronic semiconducting polymer as an active material and a highly ionically conducting electrolyte.<br/>Here, we report the development of functional inks for 3D printing a flexible complementary OECT-based circuit. The electrical connections are 3D printed using carbon/silver-based flexible blends. The channel area is defined using 3D-printable green alcohol-based formulations of a n/p-type organic semiconducting materials. Finally, we print a PDMS formulation to insulate the electrical connections and define the channel area. These printed OECTs show excellent electrical and mechanical properties. In addition, we demonstrate the possibility of exploring alternative geometries to improve the circuit integration into smaller footprints as well as demonstrating low power consumption and operational voltage.<br/>These fully 3D-printed inverters thus represent an interesting step towards the development of conformable, and wearable devices for IoT applications. In addition, the low operation voltage (&lt;1V) offers the possibility of having self-powered devices (e.g. by light, heat, wireless power), thus paving the way to battery-free wearable electronics.