Materials, Device Design, And Integration Approach for Biodegradable 3D Printable Structural Bioelectronics

Abstract

This thesis presents the development of an additive manufacturing-enabled electronic material that allows for the integration of passive/active electronic components within a customized 3D structure for wirelessly controllable bio interfaced electronics that can provide electrical stimulation and sensing bio-cues in biodegradable form. Furthermore, the thesis includes metamaterials with conductor/frame that is resistant to multi-axial deformation and photoresist that can be primarily patterned onto a 3D structure for in-situ vapor deposition.

In Chapter 1, the needs of additive manufacturing in bio-interfaced electronics is discussed. Conventional approaches, such as thin film/soft electronics for customized contact to bio-construct, employ rigid islands, fully stretchable materials, or reverse engineering. However, these approaches can face reliability issues during attachment, high costs associated with complexity, and limited 3D spatial utilization in terms of designing freedom. Furthermore, claiming needs of integrated voxelated active components for biomedical applications in wireless operation. To address these challenges, the thesis aims to fabricate electronic components in primarily 3D bespoke structure using additive manufacturing.

Chapter 2 focuses on the development of 3D printable biodegradable electronic inks, including conductive, semiconductor, and dielectric inks. Strategies to enhance conductivity in electronic inks are explored, along with novel ideas for semiconductor materials. The investigation of junctions between different inks enables the fabrication of active components based on ohmic, Schottky, and PN junctions. Furthermore, the chapter demonstrates the customized contact of physical, chemical, and biosensors on complex 3D static/dynamic structures. In Chapter 3, leveraging the biodegradable electronic inks and components developed in Chapter 2, the thesis presents the development of devices for various conformal contact modes, such as surrounding contact, penetration contact, and embedded contact. These devices enable wireless electrical stimulation, 3D spatially organized transduction, and wireless pressure monitoring. Pre-clinical studies involving small and large animal experiments demonstrate the feasibility of wireless stimulation and the therapeutic effects of the developed devices.

Chapter 4 aims to fabricate electronics capable of stable operation under multi-axis deformation. Segregation of both the structural and electronic components within singular negative Poisson's structure entity via multi-material printing. Various sensors/heaters based on structured passive components are fabricated, and integration with pneumatic actuators is demonstrated, showcasing the applicability of the devices on dynamic structures.

In Chapter 5, methods to enable vapor deposition on bespoke forms was explored incorporating new photoresist. An eco-friendly and 3D patternable photoresist is developed, composed of materials known for their biodegradability and high biocompatibility. The patternability of the photoresist is validated on three-dimensional objects, porcine skin, and leaves. It is shown that the photoresist can be developed using water and removed using weak alkaline water or propylene carbonate. It can be used as a mask for electronic fabrication through in-situ vapor deposition or as a mold for fluidics fabrication.