This Telluride Science Research Center (TSRC) workshop will bring together experts in synthetic chemistry, theory and computation, biology, materials science and engineering, and device physics to scout the pathways forward to synthetically regulate the mixed (ionic and electronic) conduction of organic semiconductors for facile interfacing with biological systems. Since the early demonstration by Luigi Galvani that electrical impulses could trigger motion in a frog's leg, the field of bioelectronics has produced significant advances towards electronic devices that interact with biological systems, revolutionizing research, diagnosis and therapy. Sensors that allow for electrical read-out of important disease markers, and implants/stimulators used for the detection and treatment of pathological cellular activity, are only a few examples of what such technologies can offer. A long-term challenge for developing high performance bioelectronic devices lies in the difference between the signal transduction mechanisms of conventional electronic materials and biological systems. Conducting both ionic and electronic charge carriers, organic semiconductors are impacting on a large variety of biology-related applications as the electronic material interfacing with living systems. The device form factors that arise from the inherent mechanical flexibility of so-called "plastic" materials, and the ability to readily tune the material electronic and optical properties as well as interactions with water-born systems through well-established synthetic chemistry principles make these materials particularly suitable for bioelectronics.
While research in organic bioelectronics is rapidly progressing, the evolution of this technology relies heavily on improving mixed transport properties of semiconducting films. Our current understanding of how thin organic semiconducting films conduct charge at the biotic interface is limited due to the challenges in monitoring simultaneous conduction of ions and electrons in the film, and is challenged by the gaps in terminology as the study of these materials lies at the intersection of materials science, solid-state physics, and electrochemistry. Establishing structure/function relationships for organic bioelectronics is the key for breakthroughs in organic bioelectronics. The ability to tune microstructure by materials chemistry and processing gives a tool to control transport properties, but also to develop the ideal material structure and optimize device geometry/operation conditions. There is a strong need to develop in situ techniques that monitor dynamically changes in the structure, optical and electrical properties of the film as (aqueous) electrolyte interfaces have constant interactions with film microstructure. Moreover, computational methods are necessary to understand the impact of aqueous environment and biasing conditions on film properties to develop devices with reversible operation for biosensing or actuation but also those with hysteretic behavior for neuromorphic computing.