PhD Defence by Mohammad Ramezannezhad

Principal supervisor

Professor Stephan Sylvest Keller, DTU

Examiners

Professor Eugen Stamate, DTU
Professor Chunlei Wang, University of Miami
Professor Joerg Peter Kutter, University of Copenhagen

Chairperson at defence

Senior Researcher Radu Malureanu, DTU

Abstract

This thesis explores innovative methods for fabricating 3D pyrolytic carbon structures, a material highly valued for its exceptional electrochemical properties, biocompatibility, and versatility. By leveraging advancements in micro- and nanofabrication, the research addresses key challenges such as increasing electrode surface area and improving structural precision, with the goal of enhancing applications in energy storage, sensing, and bioelectronics.

The work introduces several groundbreaking approaches. First, maskless photolithography was used to fabricate dense, high-aspect-ratio pyrolytic carbon micropillar arrays, significantly boosting electrochemical performance. These structures demonstrated enhanced electron transfer rates, making them suitable for applications like microbial solar cells. A second strategy involved a dual-photoresist technique to create suspended 3D pyrolytic carbon microstructures, enabling multilayered designs with increased surface area for energy storage and bioelectrical systems. Additionally, the integration of silicon trench geometries filled with SU-8 before pyrolysis provided new opportunities to increase electrode surface area while ensuring material compatibility.

To overcome limitations in resolution and shrinkage during pyrolysis, dry etching techniques were employed, allowing the fabrication of precise interdigitated electrode patterns. This approach, combined with UV and DUV lithography, achieved finer geometries and opened new possibilities for advanced applications. The research also
explored sustainable precursors, such as cellulose diacetate, for pyrolytic carbon fabrication, aligning with the growing focus on environmentally friendly materials.

Overall, this thesis demonstrates the potential of combining advanced photolithography, dry etching, and sustainable materials to create scalable, high-performance pyrolytic carbon structures. These innovations pave the way for next-generation devices, offering significant advancements in energy storage, biosensing, and other micro- and nanofabrication applications.