Yang Qing, Yu Haiyang, Wang Xiaolu, Li Yunze, Li Dan, Guo Fu
College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China.
Key Laboratory of Advanced Functional Materials, Education Ministry of China, Beijing University of Technology, Beijing 100124, China.
Polymers (Basel). 2025 Apr 15;17(8):1065. doi: 10.3390/polym17081065.
New 3D printing aerogel materials are environmentally friendly and could be used in environmental protection and biomedical fields. There is significant research interest in 3D printing cellulose-based aerogels since cellulose materials are biocompatible and are abundant in nature. The gel-like nature of the cellulose water suspension is suitable for 3D printing; however, the complexity and resolution of the geometry of aerogels are quite limited, mainly due to the inks' low viscosity that fails to maintain the integrity of the shape after printing. To address this limitation, a carefully optimized formulation incorporating three key ingredients, i.e., nanofibrils (TEMPO-CNFs), 2,2,6,6-tetramethyl-1-piperidinyloxy modified cellulose nanocrystals (TEMPO-CNC), and sodium carboxymethyl cellulose (CMC), is utilized to enhance the viscosity and structural stability of the ink. This combination of cellulose derivatives utilizes the electrostatic repulsive forces between the negatively charged components to form a stable and uniformly distributed suspension of cellulose materials. Our ink formulations improve printability and shape retention during 3D printing and are optimal for DIW printing. We print by employing an all cellulose-based composite ink using a modified direct ink writing (DIW) 3D printing method, plus an in situ freezing stage to form a layer-by-layer structure, and then follow a freeze-drying process to obtain the well-aligned aerogels. We have investigated the rheological properties of the ink formulation by varying the concentration of these three cellulose materials. The obtained aerogels exhibit highly ordered microstructures in which the micropores are well-aligned along the freezing direction. This study demonstrates a strategy for overcoming the challenges of 3D printing cellulose-based aerogels by formulating a stable composite ink, optimizing its rheological properties, and employing a modified DIW printing process with in situ freezing, resulting in highly ordered, structurally robust aerogels with aligned microporous architectures.
新型3D打印气凝胶材料环保，可用于环境保护和生物医学领域。由于纤维素材料具有生物相容性且在自然界中储量丰富，因此对3D打印纤维素基气凝胶有着浓厚的研究兴趣。纤维素水悬浮液的凝胶状性质适合3D打印；然而，气凝胶几何形状的复杂性和分辨率相当有限，主要是因为墨水的低粘度导致打印后无法保持形状的完整性。为了解决这一限制，一种精心优化的配方被采用，该配方包含三种关键成分，即纳米原纤（TEMPO-CNFs）、2,2,6,6-四甲基-1-哌啶氧基改性纤维素纳米晶体（TEMPO-CNC）和羧甲基纤维素（CMC），以提高墨水的粘度和结构稳定性。这种纤维素衍生物的组合利用带负电荷成分之间的静电排斥力形成稳定且均匀分布的纤维素材料悬浮液。我们的墨水配方提高了3D打印过程中的可打印性和形状保持性，是直接墨水书写（DIW）打印的最佳选择。我们采用改良的直接墨水书写（DIW）3D打印方法，使用全纤维素基复合墨水进行打印，再加上原位冷冻阶段以形成逐层结构，然后经过冷冻干燥过程获得排列良好的气凝胶。我们通过改变这三种纤维素材料的浓度来研究墨水配方的流变特性。所获得的气凝胶呈现出高度有序的微观结构，其中微孔沿冷冻方向排列良好。本研究展示了一种策略，即通过配制稳定的复合墨水、优化其流变特性以及采用带有原位冷冻的改良DIW打印工艺，来克服3D打印纤维素基气凝胶的挑战，从而得到具有排列良好的微孔结构、高度有序且结构坚固的气凝胶。
