Abstract
Complex three-dimensional (3D)-shaped particles could play unique roles in biotechnology, structural mechanics and self-assembly. Current methods of fabricating 3D-shaped particles such as 3D printing, injection moulding or photolithography are limited because of low-resolution, low-throughput or complicated/expensive procedures. Here, we present a novel method called optofluidic fabrication for the generation of complex 3D-shaped polymer particles based on two coupled processes: inertial flow shaping and ultraviolet (UV) light polymerization. Pillars within fluidic platforms are used to deterministically deform photosensitive precursor fluid streams. The channels are then illuminated with patterned UV light to polymerize the photosensitive fluid, creating particles with multi-scale 3D geometries. The fundamental advantages of optofluidic fabrication include high-resolution, multi-scalability, dynamic tunability, simple operation and great potential for bulk fabrication with full automation. Through different combinations of pillar configurations, flow rates and UV light patterns, an infinite set of 3D-shaped particles is available, and a variety are demonstrated.
Highlights
Complex three-dimensional (3D)-shaped particles could play unique roles in biotechnology, structural mechanics and self-assembly
One of the promising technologies capable of producing shaped particles is 3D printing[11]. This technology allows for the creation of complex geometries from a wide range of materials, including plastics[12,13], ceramics[14,15], metal[16,17] and even human tissue18,19, 3D printing is still limited by its slow layer-by-layer printing process and low resolution (typical minimum printable size is approximately 45 mm)
The presented optofluidic fabrication provides many fundamental advantages when compared to existing 3D particle generation methods
Summary
Generated by the side-pillar case, as shown in Fig. 1b), the centrepillar case creates four vortices with opposite rotational directions, causing the core fluid to be widened along the channel centre and pulled away from the channel top and bottom. The deformation characteristic length (particle area/ particle perimeter) was plotted for each Reynolds number case (Fig. 5c), showing a trend similar to pillars 0 to 6 from Fig. 4e. Even with the same channel, complex flow cross-sectional shapes can be achieved with higher Reynolds numbers[43,44], higher Re operation is not desired because of potential channel damage (for example, leakage) from larger pressure drops and increased time required to stop the flow before UV illumination, inducing unwanted diffusion. A thin-slit-shaped photomask was used for Fig. 7a,b to capture the evolution of flow deformation, but by using other light patterns, various complex 3D-shaped particles were created, as can be seen in Fig. 7c–e (see Fig. 1a for more examples). By combining different pillar configurations with various Reynolds numbers and UV light patterns, a large set of complex shapes are available
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