3D printable and stimuli-responsive colorimetric silicone composites

Silicone composites represent one of the most widely used soft, stretchable and biocompatible materials for a variety of applications such as medical implants, cosmetics, and soft robots. However, most of the existing silicone composites are either colorless or non-stimuli-responsive, which limits their applications as sensors. Herein, we report additive manufacturing of 3D printable and stimuli-responsive colorimetric silicone composites mixed with different functional dyes. Specifically, colorimetric silicone composites in the form of 2D films and 3D complex geometries such as baskets have been printed by the direct ink writing of thermally crosslinkable organosilicon compounds mixed with two fluorescent dyes of fluorescein and rhodamine derivatives. We further demonstrate the applications of these composites as colorimetric sensors to detect trace amounts of the ammonia atmosphere and spoilage of seafood products such as shrimp. Our facile and versatile protocols of ink formation and 3D printing are applicable to a variety of other pH-sensitive dyes such as commercially available bromocresol blue and cresol red as well as synthetic metal-ligand complexes such as zinc phthalocyanine.