4D shape morphing in 3D-printed pea protein structures through designed surface grooves under drying and frying conditions

Abstract

Shape morphing, a deformable property of food, can be controlled and programmable, which allows the creation of uniquely designed foods to achieve desired properties. In this context, the present study investigated the four-dimensional (4D) shape morphing behaviour of 3D-printed pea protein structures, focusing on the influence of groove depth and orientation under drying and frying conditions. A formulation consisting of pea protein isolate (60 g), water (40 g), and xanthan gum (5 g) was found optimal for 3D printing, as it provided the necessary rheological properties for consistent extrusion. Drying experiments at 45 °C, 55 °C, and 65 °C revealed that deeper grooves (3 mm) accelerated drying rates and enhanced controlled shape morphing. At 65 °C, grooved samples exhibited significant morphing, with a maximum bending angle of 183 ± 3.14° and curvature of 0.187 ± 0.03 μ mm⁻¹. The orientation of grooves further influenced morphing, with a 45° groove direction producing the most significant controlled twisting, reaching a twisting angle of 320 ± 3.56° and a curvature of 0.215 ± 0.09 μ mm⁻¹. Porosity analysis showed increased pore formation at higher temperatures, particularly in grooved samples, with porosity reaching 0.62 ± 0.05 for 3 mm grooves at 65 °C. Nuclear Magnetic Resonance (NMR) analysis revealed that grooved samples had slightly faster structural changes and water loss. SEM images demonstrated distinct surface changes in grooved and dried samples, which helped to explain their morphing behaviour. Thus, this research highlights the possibility of using 3D food printing (3DFP) to precisely design and print programmable groove geometries, activating post-processing 4D shape morphing in food materials.