Self-aligned nanofabrication for neuroscience

This thesis focuses on applying concepts in nanotechnology and cleanroom fabrication to address the fabrication challenges of moving towards higher throughput methods for electrically measuring neuronal microcircuits. Emphasis is placed on scalable manufacturing approaches, leveraging self-aligned cleanroom fabrication for producing tunable nanostructures in a manner more readily transferable to foundry production. Additionally, microfluidic integration is investigated for creating neural microcircuit while maintaining compatibility with existing nanofabrication approaches. Chapter 1 introduces the state of the art nanostructures related to in vitro electrophysiology on chip, providing an overview of the extracellular and intracellular approaches. Chapter 2 introduces the various nanofabrication concepts which are used throughout the thesis, including corner lithography, edge retraction, and sidewall oxidation, with emphasis placed on the self-aligned and wafer scale way these techniques can be employed, and how they can be used be used to produce tunable structures to be used as templates. Chapter 3 provides an overview of existing fabrication techniques for producing gold nanofeatures, and the key concepts behind a novel method for microscale and nanoscale patterning gold using sacrificial silicon molds are then explained. The fabrication approach is demonstrated for producing microscale gold interconnects. This was then applied to the nanoscale using templates produced using the concepts in chapter 2, and achieves gold features as small as 12.5 nm, with a radius of curvature less than 2 nm. Chapter 4 presents a potential bridge between silicon based nanostructures for electrophysiology and the typical PDMS based microfluidic structures used for providing structure to neuronal microcircuits. A convergent feedforward microcircuit based on two different populations of neurons is demonstrated for directional axon guiding using a silicon-on-insulator and glass based material stack. Chapter 5 consists of the conclusions and outlook of the work presented in the thesis, focusing on the novel achievements and potential directions of future work.