Since the discovery of the first conductive polymer, organic electronics helped disclosing a whole new world of possibilities in the realization of, among several other applications, flexible displays, mechanically compliant (but also implantable and bioresorbable) sensors and biosensors, and tactile sensors for next generation artificial skin applications. Despite these remarkable achievements and more than 5 decades of technical advancements, the field of application of organic electronic devices is still relatively narrow, due to the intrinsic properties of the semiconductive materials usually employed. In particular, common limitations are the low switching speed caused by the intrinsic low mobility of the charge carriers within the most common polymers and small molecules used (this limitation preventing most of the organic transistor to be used for logic applications), and the limited devices resolution, the latter issue being mainly due to the difficulty of fabricating short channel transistors while at the same time using low-cost and large area fabrication techniques.
In order to overcome these apparently unavoidable issues, during the last 15 years a new type of organic transistor has been introduced, namely the vertical organic transistor (vOFET). This peculiar “vertical approach” allows to obtain short channels without the need of expensive fabrication techniques, thus representing a very interesting technological advancement with respect to pre-existing OFETs. In this work we report about a novel and easy approach to the realization of vertical organic transistors that includes the use of Parylene C as both the “core” of the vertical structure and the gate insulator. The fabrication process has been optimized in order to have the possibility to obtain highly flexible and ultra-conformable transistors, being such devices fabricated on micrometer-thick films (either Parylene C or polyamide-imide) that, after the device fabrication, can be conveniently detached from the carrier substrate allowing it to be transferred onto whatever kind of surface. Moreover, we will also demonstrate that such approach is particularly suitable for the fabrication of sensing devices. In particular, we employed a double-gated organic transistor called organic charge modulated FET (OCMFET), which has established itself during the past 10 years as a versatile sensor with an ultra-high sensitivity.
The combination of the proposed novel and convenient approach to the fabrication of vertical organic transistors (with the possibility of realizing high-resolution and faster switching devices) and the remarkable features of the OCMFET represents an interesting advancement within the organic electronics scenario, in that it will allow to obtain reference-less, ultra-sensitive sensors arranged in conformable high-density arrays, while keeping the process low-cost, thus offering considerable advantages to the field of organic sensing and biosensing.