4D printing of Pickering emulsion: Temperature-driven color changes

Pickering emulsion inks were employed to demonstrate the temperature-driven 4D printing method. The Pickering emulsion consisted of water phase containing NaHCO3 and oil phase containing curcumin. Upon heating, the movement of pigment molecules was induced, resulting in color changes. The formation mechanism, rheological properties, printing properties and color changes of Pickering emulsion as well as the release kinetic mechanism of curcumin were investigated. The results indicated that relationships were also established between quantified color values (L*, a*, b*) and heating time. Moreover, the release of the curcumin in the Pickering emulsion, which was designated as a swelling process, followed the non-Fickian mechanism due to the occurrence of diffusion and erosion. The Hixson-Crowell model exhibited the highest linearity (R2: 0.9430 to 0.9825) of Pickering emulsions. In conclusion, the research offers a new perspective for the development of personalized Pickering emulsion food with bright colors.