Four-dimensional (4D) printing of smart responsive materials, offering innovative solutions for building complex structures. However, compared to flexible materials, ceramics face significant technical challenges in realising 4D printing because of their inherent brittleness and ultra-low deformation capability. In this study, inspired by origami and the chameleon colour-changing mechanism, a multi-responsive ceramic 4D printing method based on vat photopolymerisation (VPP) technology is proposed. A colour-changing flexible ceramic precursor with a synergistic magnetic-thermal-deformation response was successfully prepared. The two-layer structural design adopted for the precursor comprises a temperature-sensitive colour-changing upper layer and a magnetic lower layer. Magnetic induction heating generated by the magnetic layer was transferred to the colour-changing layer, triggering colour change. The magnetic field modulation, dehydration/absorption drive and sintering process can induce shape reconstruction, in which planar surfaces are deformed into complex 3D structures. The performance differences in the microstructures of the upper and lower layers of the colour-changing flexible ceramic precursor, along with the water-absorption-driven mechanism, are explained through molecular dynamics simulations. The precursor showed great potential as a flexible sensor for real-time monitoring of finger (90° bending), wrist and foot movements through resistance changes, for various applications in the fields of health monitoring, smart driving and sports science.
Wu et al. (Mon,) studied this question.