PEDOT: PSS psödo-kapasitör ve AlSb nanokristalleri tabanlı optoelektronik nöral arayüzler

Neural interfaces are the transducers that connect biological systems with artificial systems. They can read and/or write biophysical cues through electrical, mechanical, thermal and chemical mechanisms. The writing part, neural stimulation, have been widely used in biological applications such as understanding of the complex biological processes and treatment of neurological disorders. Particularly, semiconductor and metal devices were already used in biointerfaces, however, their spatial resolution, interference with recording systems and potential hazardous effects limit their efficacy. Optoelectronic stimulation with photovoltaic systems is a wireless alternative to electrode-based stimulation techniques. In these platforms, neural stimulation can be achieved by faradaic, thermal and capacitive processes. The later has gained significant attention since it is based on the perturbation of ions in the interface and resulting electrochemical gradient to induce membrane potential changes near device/cell interface. The biointerfaces that are designed for capacitive photocurrent generation rely on the double-layer capacitance at the electrode/electrolyte interface. However, this limits the total charge injection capacity. In this thesis, we developed three different approaches to increase total capacitive charge injection efficiency. Firstly, we combined a pseudocapacitive interface with an organic photovoltaic unit. Secondly, we utilized aluminum antimonide nanocrystals as the interfacial hole transport layer and showed successful neural activation on primary hippocampal neurons. Finally, we integrated PEDOT:PSS hydrogels with an organic photovoltaic device, which significantly increased the charge injection efficiency. Moreover, the potential of hydrogel integration was demonstrated with stimulation of primary hippocampal neurons and modulation of the cardiac myocyte beating frequency. Owing to their soft, organic, and biocompatible nature, organic/inorganic hybrid photovoltaic biointerfaces reduce the device-tissue mechanical mismatch, cytotoxic effects, and increase functional lifetime in biological medium. Hence, they hold high promise for future cardiac and retinal implants.