Flexible and Printed Integrated Circuits and Sensors

Direct printing of thin-film transistors (TFTs) has enormous potential for ubiquitous and lightweight wearable electronic applications. This talk presents our recent advances in flexible and printed integrated circuits and sensor arrays. First, A 3D integration approach is introduced to achieve technology scaling in printed transistor density, analogous to Moore's law driven by lithography. We present the scalable 3D integration of single- and dual-gate organic transistors on plastic foil by printing with high yield, uniformity, and year-long stability. Second, we propose a 3D static random-access memory based on the 3D integration technology. Two pairs of three (n-/n-/p-type) organic TFTs are stacked vertically to fabricate SRAM composed of six transistors. Next, we use our robust 3D TFT printing process to design and fabricate wearable active-matrix multi-sensor arrays. We fabricate active-matrix TFT arrays with high yield and uniformity where array sizes can be customizable and integrated with highly sensitive piezoresistive sheets. The sensor array creates a spatiotemporal pulse wave map on the wrist and overcomes the positional inaccuracy of conventional single-point sensors. Finally, an active matrix organic photodiode array monolithically inkjet-printed on an ultrathin substrate is reported. We achieve low pixel power consumption down to 50 nW, and demonstrate the applications of static and dynamic spatial sensing of optical signals.