Description
Microfluidic technologies have become indispensable in tissue engineering, primarily due to their ability to manipulate fluids at a scale commensurate with biological microenvironments. However, while biological parameters are frequently prioritized, there remains a critical need to evaluate these platforms from a rigorous engineering perspective to achieve high-throughput optimization and structural fidelity. This study provides a comprehensive characterization of three distinct additive manufacturing (AM) modalities—Fused Deposition Modelling (FDM), Stereolithography (SLA), and Two-Photon Polymerization (2PP)—and compares them against a novel ABS-PDMS hybrid casting methodology for the fabrication of microfluidic chips.
The evaluation focused on critical engineering metrics: surface roughness (Ra), minimum unblocked channel resolution, dimensional accuracy, fabrication lead time, cost-efficiency, and practical viability for biological integration. Surface topography is a determinant factor in microfluidic performance, as it directly influences the transition from laminar to turbulent. In this work, the internal topography of microchannels fabricated via the aforementioned methods was quantified using contactless focus variation microscopy.
A standardized microfluidic design was implemented across all fabrication platforms to produce hollow alginate microfibers via a coaxial core-shell flow mechanism. The stability of this coaxial jet is maintained by the low Reynolds number (Re) inherent to the microscale geometry, ensuring a stable laminar interface. The resulting hollow fibres were subjected to rigorous mechanical testing to evaluate their tensile strength and elastic modulus, which are crucial for maintaining structural integrity under physiological perfusion pressures.
To assess the biological functionalization of these fibres, the chemistry of fibres was optimized to facilitate a cell-friendly environment for Human Umbilical Vein Endothelial Cells (HUVECs). By refining the physical and chemical properties of the alginate matrix, we achieved significant cell attachment and proliferation. Longitudinal observations confirmed the self-organization of HUVECs into an integrated, confluent lumen within the hollow fibres. Our findings demonstrate a direct correlation between fabrication resolution and biological biomimicry; specifically, the high-resolution capabilities of 2PP and optimized hybrid casting allowed to produce narrower hollow fibres, yielding cellular lumens with diameters approaching those of native human blood capillaries. This study establishes a benchmark for selecting fabrication techniques based on the required balance between architectural complexity and biological functionality.