Fig. 1

Schematic illustration of the design strategy of the piezoelectric CG/PHA/PBT hydrogels and the bone regeneration mechanism. a The preparation process of the piezoelectric CG/PHA/PBT hydrogels. b The application and potential biological mechanism of the piezoelectric hydrogels for rapid bone regeneration. c Schematic illustration of the possible self-powered mechanism of the piezoelectric CG/PHA/PBT hydrogels. The dipoles in the BT nanoparticles are oriented in the same direction in the piezoelectric hydrogels. The electric polarization is presented in the direction of the oriented dipoles and can produce a piezoelectric potential in the BT piezoelectric nanoparticles. In the absence of external stimuli, there is a positive and negative charge balance in the hydrogel. Once a pressure stimulus is applied to the piezoelectric hydrogels, the electrons in the hydrogels flow out of the hydrogel. Once the pressure disappears, the cumulative free charges flow back into the piezoelectric hydrogels. BT barium titanate, HA hydroxyapatite, Cs chitosan, Gel gelatin, PHA polydopamine coated-hydroxyapatite, PBT polydopamine coated-barium titanate, e⁻ electron, R resistance, M0 mφ unpolarized macrophage, M1 mφ type 1 macrophage, M2 mφ type 2 macrophage, IL-6 interleukin-6, IL-4 interleukin-4, TNF-α tumor necrosis factor-α, iNOS inducible nitric-oxide synthase, CD86 cluster of differentiation 86 protein, Arg1 arginase, BMSC bone marrow stromal cell, HUVEC human umbilical vein endothelial cell