Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore.
School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Republic of Singapore.
ACS Appl Mater Interfaces. 2023 May 3;15(17):21575-21584. doi: 10.1021/acsami.3c00149. Epub 2023 Apr 20.
Immersion precipitation three-dimensional printing (3DP) and freeform polymer precipitation (FPP) are unique and versatile methods of 3D printing to fabricate 3D structures based on nonsolvent-induced phase separation direct ink writing (DIW). Immersion precipitation involves complex dynamics among solvents, nonsolvents, and dissolved polymers, and the printability of 3D models in these methods requires further understanding. To this end, we characterized these two methods of 3D printing using polylactide (PLA) dissolved in dichloromethane (7.5-30% w/w) as model inks. We analyzed the rheological properties of the solutions and the effect of printing parameters on solvent-nonsolvent diffusion to achieve printability. The PLA inks exhibited shear-thinning properties, and their viscosities varied over three orders of magnitude (10∼10 Pa·s). A processing map was presented to understand the ideal ranges of the concentration of PLA in inks and the nozzle diameter to ensure printability, and the fabrication of complex 3D structures was fabricated with adequate applied pressure and nozzle speed. The processing map also highlighted the advantages of embedded 3D printing over solvent-cast 3D printing based on solvent evaporation. Lastly, we demonstrated that the porosity of the interface and inner structure of the printed objects was readily tailored by the concentration of the PLA and the porogen added to the ink. The methods presented here offer new perspectives to fabricate micro-to-centimeter objects of thermoplastics with nanometer-scale inner pores and provide guidelines for successful embedded 3D printing based on immersion precipitation.
浸没沉淀三维打印（3DP）和自由形状聚合物沉淀（FPP）是独特且多功能的 3D 打印方法，可基于非溶剂诱导相分离和直接墨水写入（DIW）来制造 3D 结构。浸没沉淀涉及溶剂、非溶剂和溶解聚合物之间的复杂动力学，这些方法中 3D 模型的可打印性需要进一步理解。为此，我们使用溶解在二氯甲烷（7.5-30%w/w）中的聚乳酸（PLA）作为模型墨水来表征这两种 3D 打印方法。我们分析了溶液的流变性能以及打印参数对溶剂-非溶剂扩散的影响，以实现可打印性。PLA 墨水表现出剪切稀化特性，其粘度变化跨越三个数量级（10∼10 Pa·s）。提出了一个加工图来理解墨水和喷嘴直径中 PLA 浓度的理想范围，以确保可打印性，并使用足够的施加压力和喷嘴速度制造了复杂的 3D 结构。该加工图还突出了基于溶剂蒸发的嵌入式 3D 打印相对于溶剂浇铸 3D 打印的优势。最后，我们证明了通过添加到墨水中的 PLA 和致孔剂的浓度可以轻松调整打印物体的界面和内部结构的孔隙率。这里提出的方法为制造具有纳米级内部孔的热塑性微到厘米级物体提供了新的视角，并为基于浸没沉淀的成功嵌入式 3D 打印提供了指导。
