3D Printing of Composite Organic Semiconductor Microdevices for Biosensors and Organic Bioelectronics

Bioelectronic devices aim to alleviate symptoms or return function to patients suffering from neural disorders / injuries. Choice of functional material and employment of advanced fabrication techniques constitute key elements in ultimate success of these devices. As an alternative to traditional metallic platforms, organic electroactive materials have garnered tremendous attention in neural devices. Consequently, the emerging field of organic bioelectronics has sought to interface the organic-based devices with the soft and ion-dominated neural tissue. Organic semiconductor materials (OSs), i.e. conjugated polymers, have emerged as one of the ideal candidates for neural interfaces, owing to their biocompatibility, soft mechanical properties, and mixed electronic / ionic conductivity. This thesis is primarily focused on development of soft and conductive micron-scale platforms for applications in organic bioelectronics and biosensors. In the course of the projects, much attention has been devoted towards design of microelectronic devices, employing advanced fabrication techniques, and formulation of composite biomaterials based on two common OSs; poly(3,4-ethylenedioxythiophene) and polypyrrole. The theme of research projects falls into two main categories: 1. Soft and bioactive platforms for neural regeneration, and 2. 3D-printed conductive microelectronic devices for organic bioelectronics and biosensors. In the first category, we have developed a micro-patterning technique and have created various profiles of laminin gradients on surface of OS thin films, which can be potentially employed for neural regeneration. The second category deals with design, fabrication and characterization of 3D-printed microelectronic devices. First, we have explored 3D printing of soft, conductive, and bioactive microstructures via direct laser writing, also known as multi-photon polymerization lithography (MPL). We have formulated conductive photosensitive inks, and fabrication and characterization of microelectronic devices such as hybrid neural microelectrodes, bioactive microstructures and high-performance glucose biosensors have been successfully demonstrated. We also report on development of an in-house 3D printing technique for fabrication of OS microdevices based on in-situ electrochemical polymerization. Microelectronic devices, bioactive structures and glucose biosensors have been fabricated using this technique. Overall, we envision that these microelectronic devices and platforms pave the way towards development of next-generation neural interfaces for organic bioelectronics and biosensing applications.