fig4

Figure 4. Mechanisms of responsive bending and folding of the films. (A) Humidity and temperature-responsive films with controlled bending and folding due to the creation and destruction of hydrogen bonds. Copyright 2020, John Wiley and Sons^[99]; (B) A 3D twining film based on the melt transition of the shape memory substrate. Copyright 2019, American Association for the Advancement of Science^[24]; (C) Responsive folding implantation through crystallization transition at high temperature triggered via HIFU. Copyright 2024, Springer Nature^[123]. HIFU: High-Intensity Focused Ultrasound.