title: 3D Printing of Ultratough Polyion Complex Hydrogels.
abstract: Polyion complex (PIC) hydrogels have been proposed as promising engineered soft materials due to their high toughness and good processability. In this work, we reported manufacturing of complex structures with tough PIC hydrogels based on three-dimensional (3D) printing technology. The strategy relies on the distinct strength of ionic bonding in PIC hydrogels at different stages of printing. In concentrated saline solution, PIC forms viscous solution, which can be directly extruded out of a nozzle into water, where dialyzing out of salt and counterions results in sol-gel transition to form tough physical PIC gel with intricate structures. The printability of PIC solutions was systematically investigated by adjusting the PIC material formula and printing parameters in which proper viscosity and gelation rate were found to be key factors for successful 3D printing. Uniaxial tensile tests were performed to printed single fibers and multilayer grids, both exhibiting distinct yet controllable strength and toughness. More complex 3D structures with negative Poisson's ratio, gradient grid, and material anisotropy were constructed as well, demonstrating the flexible printability of PIC hydrogels. The methodology and capability here provide a versatile platform to fabricate complex structures with tough PIC hydrogels, which should broaden the use of such materials in applications such as biomedical devices and artificial tissues.
authors: Fengbo
authors: F
authors: Zhu
authors: The State Key Laboratory of Fluid Power and Mechatronic Systems, Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province, School of Mechanical Engineering, Zhejiang University , Hangzhou 310028, China.
authors: Libo
authors: L
authors: Cheng
authors: The State Key Laboratory of Fluid Power and Mechatronic Systems, Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province, School of Mechanical Engineering, Zhejiang University , Hangzhou 310028, China.
authors: Jun
authors: J
authors: Yin
authors: Zi Liang
authors: ZL
authors: Wu
authors: Jin
authors: J
authors: Qian
authors: The State Key Laboratory of Fluid Power and Mechatronic Systems, Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province, School of Mechanical Engineering, Zhejiang University , Hangzhou 310028, China.
authors: Jianzhong
authors: J
authors: Fu
authors: Qiang
authors: Q
authors: Zheng
keywords: 3D printing; gelation; polyion complex hydrogel; printability; rheology; tough hydrogel