Junju Wang,Jie Tang,Yichao Lin,Hong He,Chaoshan Zhao,Wenrui Ma,Xiang Wang,Muling Zeng,Shunbo Li
Solvent responsive hydrogel is a kind of intelligent soft material, which can be used in soft robots. Currently, most of the solvent responsive hydrogels are based on pure organic materials which has limited stiffness for actuations. Herein, a novel organic–inorganic composite hydrogel is designed and prepared. Calcium phosphate oligomers nanoclusters are incorporated in polymer solution containing polyvinyl alcohol (PVA) and sodium alginate to form organic–inorganic hybrid copolymer suspensions. The solvent responsive hydrogel is simply prepared using co-evaporation method by optimizing the components in the colloid system. The inorganic nanoparticles work as the scaffold in the porous PVA network and the evaporation caused nonuniformity distribution further induces the formation of heterostructure, which has different shrinkage ratios along the thickness direction. The prepared hydrogel demonstrates excellent shape memory property by changing the environmental solvents between water and ethanol and its repeatability is also verified. The stiffness of hydrogel is enhanced and it has large deformation after incorporation of calcium phosphate nanoparticles. The bending angle of hydrogel can be well controlled by different water to ethanol ratios, allowing for underwater actuation. The functionality of an artificial gripper based on responsive hydrogel with high stiffness is demonstrated to transfer objects in ethanol. The design of organic–inorganic composite hydrogel with high stiffness may provide new insights for preparation of intelligent soft materials for underwater applications.
Physically cross-linked hydrogels have great potential for tissue engineering because of their excellent biocompatibility and easy fabrication. However, physical cross-linking points are typically weaker compared to chemical ones and therefore cannot form robust hydrogels with excellent water stability, which greatly hinder their further applications. In this work, a novel hydrogel with high stiffness and outstanding antiswelling performance cross-linked by hydrophobic polymer chains entanglements is reported. The hydrophobic polymer polyimide (PI) is mixed with the hydrophilic polymer poly-(vinyl pyrrolidone) (PVP) to form cross-linking points between the chains. At the equilibrium swelling state, tensile modulus of the hydrogel can be up to 22.57 MPa (higher than most existing hydrogels) and the equilibrium water swelling ratio ( ESR ) can be as low as 125.0%. By decreasing the PI mass ratio, tensile modulus and ESR of the hydrogel can be tuned in a wide range from 22.57 to 0.005 MPa and 125.0% to 765.6%, respectively. Using PVP/PI solutions as inks, uniform structures and multi-material structures are fabricated having mechanical properties close to cartilage through a direct ink writing 3D printing platform. This current work demonstrates that entangled PVP/PI hydrogels have excellent tailoring capabilities and are promising candidates for tissue engineering applications.
危险品化学品经营许可证（带存储）