THREE-DIMENSIONAL BIOPATTERNING TECHNOLOGY AND APPLICATION FOR ENZYME-BASED BIOELECTRONICS
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Integration of biomaterials with 3-D micro/nano devices and systems offers exciting opportunities for developing miniature bioelectronics with enhanced performances and advanced modes of operation. However, the limited wetting property of such small scale 3-D structures (Cassie-Baxter wetting) presents a potential challenge in these developments considering most biological materials require storage in buffered aqueous solutions due to their inherently narrow stability window. In this thesis research, an electrowetting-assisted 3-D biomanufacturing technology has been developed enabling highly selective and programmable biomolecular assembly on 3-D device components. The successful integration of microscale 3-D device structures created via conventional microfabrication techniques with a nanoscale molecular assembly of Tobacco mosaic virus (TMV), enabled hierarchical and modular material assembly approaches for creating highly functional and scalable enzyme-integrated microsystems components. The potential limitation in 3-D bio-device integration associated with the surface wettability has been investigated by adapting Si-based micropillar arrays (μPAs) as model 3-D device structures, and a cysteine-modified TMV (TMV1cys), as the biomolecular assembler which can functionalize onto electrode surfaces via a self-assembly. The comparative studies using μPAs of varying pillar densities have provided clear experimental evidence that the surface coverage of TMV1cys self-assembly on the μPA is strongly correlated with structural density, indicating the structural hydrophobicity as a key limiting factor for 3-D bio-device integration. The 3-D electro-bioprinting (3D-EBP) technology developed in this work leverages the hydrophobic surface wettability by adapting a capacitive wettability-control technique, known as electrowetting. The biological sample liquid was selectively introduced into the microcavities using a custom-integrated bioprinting system, allowing for patterning of the TMV1cys self-assembly on the μPA substrates without the limitations of the structural density. The functional integrity of the TMV1cys post 3D-EBP allowed conjugations of additional biological molecules within the 3-D substrates. Particularly in this work, immobilization of glucose oxidase (GOx) has been achieved via a hierarchical on-chip immobilization method incorporating 3D-EBP. Combined with the enhanced and scalable enzymatic reaction density on-chip and the electrochemical conversion strategies, the innovative 3D biomanufacturing technology opens up new possibilities for next-generation enzyme-based bioelectronics.