Wang Yiliang, Willenbacher Norbert
Institute of Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology, Karlsruhe, 76131, Germany.
Department of Chemistry, Tsinghua University, Beijing, 100084, China.
Adv Mater. 2022 Apr;34(15):e2109240. doi: 10.1002/adma.202109240. Epub 2022 Mar 4.
Soft silicone is an ideal flexible material for application, e.g., in soft robotics, flexible electronics, bionics, or implantable biomedical devices. However, gravity-driven sagging, filament stretching, and deformation can cause inevitable defects during rapid manufacturing, making it hard to obtain complex, high-resolution 3D silicone structures with direct ink writing (DIW) technology. Here, rapid DIW of soft silicone enabled by a phase-change-induced, reversible change of the ink's hierarchical microstructure is presented. During printing, the silicone-based ink, containing silica nanoparticles and wax microparticles, is extruded from a heated nozzle into a cold environment under controlled stress. The wax phase change (solid-liquid-solid) during printing rapidly destroys and rebuilds the particle networks, realizing fast control of the ink flow behavior and printability. This high-operating-temperature DIW method is fast (maximum speed ≈3100 mm min ) and extends the DIW scale range of soft silicone. The extruded filaments have small diameters (50 ± 5 µm), and allow for large spans (≈13-fold filament diameter) and high aspect ratios (≈1), setting a new benchmark in the DIW of soft silicone. Printed silicone structures exhibit excellent performance as flexible sensors, superhydrophobic surfaces, and shape-memory bionic devices, illustrating the potential of the new 3D printing strategy.
柔软的硅胶是一种理想的柔性材料，可应用于例如软机器人技术、柔性电子学、仿生学或可植入生物医学设备等领域。然而，在快速制造过程中，重力驱动的下垂、细丝拉伸和变形会导致不可避免的缺陷，使得难以通过直接墨水书写（DIW）技术获得复杂、高分辨率的三维硅胶结构。在此，提出了一种通过墨水的分级微观结构的相变诱导、可逆变化实现的软硅胶快速DIW方法。在打印过程中，含有二氧化硅纳米颗粒和蜡微颗粒的硅胶基墨水在受控应力下从加热的喷嘴挤出到寒冷环境中。打印过程中蜡的相变（固-液-固）迅速破坏并重建颗粒网络，实现对墨水流动行为和可打印性地快速控制。这种高操作温度的DIW方法速度快（最大速度≈3100毫米/分钟），并扩展了软硅胶的DIW规模范围。挤出的细丝直径小（50±5微米），允许大跨度（≈细丝直径的13倍）和高纵横比（≈1），为软硅胶的DIW设定了新的基准。打印的硅胶结构作为柔性传感器、超疏水表面和形状记忆仿生设备表现出优异的性能，说明了这种新的三维打印策略的潜力。
