Photonic crystals are able to change the macroscopic color by regulating the center wavelength of band gap with altering the lattice constant of nano-structures. Herein, stretchable photonic crystals, with periodic cylinder shaped air holes non-close-packed in triangular lattice, are designed and fabricated for mechanochromism in entire visible light range. Numerical simulation has verified the excellent mechanochromic ability for the proposed nano-structure. Then the stretchable photonic crystals with this structure are successfully prepared by nano-imprinting technology on PDMS. Subsequently, the mechanochromic properties of the prepared materials are studied, and color change over the entire visible light range from red to blue is observed under a small strain of 29%. In addition, cyclic stretching tests up to 2000 times show that the materials are capable of maintaining shape recovery ability as well as mechanochromic ability. Finally, a stretchable visual strain sensor is prepared using the stretchable photonic crystal. This sensor can distinguish three strain ranges below 30% of strain rate by its color change that offers a visual observation of strain ranges. The stretchable visual strain sensors is more sensitive to small strain than resistance sensors, which may have great potential for applications of visual monitoring stretching strain.

A structure-colorable flexural artificial muscle (FlexAM) is developed by integrating both a flexible two-dimensional grating pattern layer and dielectric elastomers via additive laminated object manufacturing. The FlexAM harnesses the view angle-dependence to deliver a voltage-activated and ultrafast coloration performance at a rate of 2.814 nm ms ⁻¹ .

20CrMnTi carburized steel is widely used in the manufacturing of gear transmission components. Gears often operate under complex working conditions that involve high pressure and temperature, and intermittent alternating loads. The material is frequently subjected to repeated compression and resilience cycles, which significantly affect dimensional accuracy and stability. This study investigates the influence of different temperatures and pressures on the compression resilience properties and microhardness of 20CrMnTi steel. The results indicate that temperature and pressure lead to a nonlinear increase in the compression curve, reduce resilience properties and the microhardness of the carburized layer, and affect the microhardness of the matrix. Microstructural analysis indicated that plastic deformation, carbide coarsening, and a lower elastic modulus led to the enlarged compression and diminished microhardness in the carburized layer. Work hardening, dynamic recrystallization, and plastic deformation in the matrix material weaken resilience properties and influence the distribution of microhardness in the matrix.