CONJUGATED POLYMER NANOFIBERS FOR ORGANIC BIOELECTRONICS AND BIOACTUATORS

The emerging field of organic bioelectronics bridges the electronic world of organic-semiconductor-based devices with the soft, predominantly ionic world of biology. Conjugated polymers (CPs) are one of the most promising organic materials for biointerfaces owing to their biologically relevant mechanical characteristics, ability to be chemically modified, mixed electronic and ionic charge transport, and facile and versatile fabrication routes. CP nanofibers have been of great attention because of their extensive porosity and extremely high surface area to volume ratio that result in their high electronic/ionic conductivity and unique electro-chemo-mechanical properties. Thus far, CP nanofibers have been employed for biomedical applications such as biosensors, nerve tissue regeneration, controlled drug delivery devices, and surface modification of neural interfaces. This thesis is mainly focused on the state-of-the-art utilization of CP nanofibers for development of high performance organic bioactuators and for articulating flexible neural microelectrodes with movable recording sites. We first explored the ion transportation mechanisms in actuation of the two most versatile CPs, poly(pyrrole) and poly(3,4-ethylenedioxythiophene), in the form of randomly oriented nanofibers through direct mass measurement under cyclic voltammetry coupled with electrochemical quartz crystal microbalance. Understanding the actuation behavior of the CP nanofibers, we developed a high-performance bilayer beam actuator based on poly(pyrrole) nanofibers (PPy NFs) that efficiently operate in liquid and gel-polymer electrolytes. We studied the dynamics of the actuator using theoretical analysis and experimental measurements of motion and mass transport. The actuator demonstrated an impressive performance, including low power consumption per strain percentage, large deformation, fast response, and excellent actuation stability. Ultimately, the concept of PPy NFs actuators was deployed for microfabrication of flexible neural microelectrodes with movable projections that enable to control the position of electrode recording sites in cerebral environment. We anticipate that the CP nanofiber-based actuators will be utilized for advancement of next generation actuators in the fields of soft robotics, artificial muscles, and biomedical devices.