Controlled shape morphing of plant-based protein bilayers via surface engineering under thermal food processing conditions

This study introduces a simplified approach to predictable and controlled shape morphing in plant protein-based bilayer food structures through precisely engineered surface cuts. Bilayer protein sheets (4 mm thickness) consisting of pea protein isolate (PPI) and faba bean protein isolate (FPI) were semi-automatically fabricated (2D) using a simplified stamping method, incorporating variations in their cut depth (1 mm and 2 mm) and cut orientation (0°, 15°, 30°, 45°, and 60°). Morphing (4D) was triggered during drying (55 °C, 180 min) and frying (210 °C, 30 s). Quantitative image analyses indicated significantly enhanced morphing in bilayers with PPI as the upper (cut-exposed) layer, achieving a maximum bending angle of 211.2 ± 3.4° at a 2 mm cut depth, compared to 162.0 ± 2.6° for bilayers with FPI on top. Increasing cut orientation angles transformed deformation from uniform bending (∼180° at 0°) to complex twisting (∼490° at 60°), producing unique morphologies including spirals, saddles, and dome shapes. Frying also resulted in rapid morphing but with overall reduced final curvature due to rapid surface crust formation and protein denaturation at high temperatures. These results demonstrate the effectiveness of precise surface cuts combined with material asymmetry with bilayer for controlled and visually appealing 2D to 4D morphing, offering a sustainable design strategy for plant protein-based snack products.