3D Nanoprinted Liquid-Core-Shell Microparticles

The ability to fabricate core-shell microparticles with high control over the three-dimensional (3D) microarchitecture of each particle offers unique potential to advance applications such as cell/tissue engineering, diagnostics, and drug delivery. Despite significant progress, current barriers include undesired polydispersity ( e.g. , for particle size and shape) as well as limited design customization with respect to the 3D geometric complexity of individual microparticles. To address such challenges, here we introduce a novel strategy that leverages the submicron-scale additive manufacturing (or "3D printing") technology, "direct laser writing (DLW)", to fabricate core-shell microparticles with liquid-phase cores and individually tunable shell architectures. This approach consists of three fundamental steps: ( {i} ) DLW-based printing of a photomaterial shell with a top orifice, ( ii ) vacuum-loading of a liquid-phase core, and then ( iii ) DLW-based printing of a "cap" atop the orifice to complete the shell (while sealing the core). In this work, we investigated the relationships between the initial shell orifice size and microfluidic core encapsulation efficacy. Fabrication and experimental results for microfluidic vacuum-loading of cores comprising a methylene blue-dyed aqueous solution revealed that shell orifice diameters ( {D} ) of 1.71\pm 0.14~\mu \text{m} exhibited poor core-loading performance, whereas {D} \geq 3.61\pm 0.13~\mu \text{m} all led to effective core-loading. Results for fluorescence quantification after the final encapsulation step, however, revealed that each increase of approximately 2~\mu \text{m} in {D} from 3.61\pm 0.13~\mu \text{m} up to 11.69\pm 0.16~\mu \text{m} corresponded to a significant reduction in retention performance of the microfluidic core. In combination, the presented methodology opens new avenues for core-shell microparticle design and manuf