Multi-stimuli responsive (MSR) chromic materials which can exhibit a color change when exposed to external stimuli demonstrate huge potential in developing new intelligent devices. However, they commonly require complicated synthesis processes that are not suitable for mass production. To facilitate the fabrication of MSR devices, for the first time, we propose a facile 3D integration strategy to rationally assemble various commercial chromic materials, light shielding layers, and a stretchable substrate into a set of MSR devices equipped with thermo-/photo-/mechanochromic characteristics with negligible cross-interferences. Notably, the mechanochromic sensitivity can be readily adjusted to multiple levels via facile pre-stretching methods. Moreover, two types of MSR units are integrated into an interactive electronic device, which exhibits thermo-/photo-/electrochromic responses, and two levels of mechanochromic responses with color changes at 100% and 200% strain, respectively. In addition, another highly sensitive MSR unit is applied to a wearable motion/environmental monitoring chromic device, which can detect finger bending within 30% strain, and monitor environmental stimuli (UV, temperature) with thermal mapping capability. A smartphone-based colorimetric analysis app was also developed for finger bending detection. Comprehensive quantitative characterization and finite element analysis are used to elucidate the performance and intrinsic mechanisms of these MSR responses.

Mechanochromic materials have recently received tremendous attention because of their potential applications in humanoid robots, smart windows, strain sensors, anti-counterfeit tags, etc. However, improvements in device design are highly desired for practical implementation in a broader working environment with a high stability. In this article, a novel and robust mechanochromism was designed and fabricated via a facile method. Silica nanoparticles (NPs) that serve as a trigger of color switch were embedded in elastomer to form a bi-layer hybrid film. Upon stretching under ambient conditions, the hybrid film can change color as well as transparency. Furthermore, it demonstrates excellent reversibility and reproducibility and is promising for widespread application.

A stretchable, 3D tubular structure formed due to processing-induced wrinkles is proposed as a platform to develop adaptive stretchable electronics. This integrated structure is fabricated by releasing a pre-stretched 2D film-substrate precursor, resulting in a wrinkled surface, that shows a strong directional dependence that drives the tube formation. This 3D shape adaptivity can control the radial opening and closing of the tube through longitudinal strain, which inspires the development of a dual-channel piezoresistive strain sensor/switch concomitant with mechanochromic effect and an intriguing tactile responsive artificial Mimosa pudica device. In addition, the system is compatible with 2D film deposition technologies, which allows customized electrode patterns to be coated on the pre-stretched 2D precursor followed by wrapped inside as precursor released. Upon sealing the tube, this “coating and self-wrapping” feature allows for the invention of a highly stretchable tactile switch, and a stretchable tubular supercapacitor with dual stimuli-responsiveness.