Farnaz Rezaei: 3D printing of high-detail resolution structures for biotechnological applications

Abstract

This thesis is focused on developing and optimizing 3D printing techniques and materials to fabricate high-resolution, functional structures for diverse applications, including membranes for bioseparation and tissue engineering applications. 

The research focuses on methods that enable precise fiber placement at the micrometer scale, evaluating two-photon polymerization, direct ink writing (DIW) and electroprinting. Due to the limited availability of suitable printable materials, two-photon polymerization was not pursued further. DIW was used to fabricate multi-layered structures, achieving over 300 printed layers through parameter optimization and it was possible to print structures with 10 µm pitch. To overcome the challenges of DIW such as nozzle clogging and bending and enhance printing resolution, electroprinting was explored. By reducing the nozzle-to-collector distance to 10 µm, this technique (near-collector electroprinting) enabled the fabrication of high-resolution structures with a 5 µm pitch, increasing the precision of conventional electroprinting. Several critical parameters, such as nozzle size, printing speed and applied voltage, were optimized to achieve stable and detailed structures.

Cellulose acetate (CA) was chosen as the primary material. To introduce ion-exchange functionality to the structure for membrane applications, polyethyleneimine (PEI) was incorporated into CA, improving the functional properties of the printed structures. Additionally, the feasibility of electroprinted scaffolds for tissue engineering was studied, with a focus on how pore size influences cell attachment and growth. Also, the potential of composite printing was explored by incorporating lignosulfonate (LS) into CA. The antibacterial properties of CA-LS structures were evaluated and compared to pure CA scaffolds, demonstrating the potential for infection-resistant biomaterials.