3D-printed thermoplastic polyurethane metamaterial sheets for enhanced mechanical protection of strawberries during transport

This study explores the use of 3D-printed metamaterial-based covers made from thermoplastic polyurethane (TPU) to protect strawberries during transport. Strawberries are highly susceptible to postharvest damage, particularly from vibration and impact. To address this, structural sheets with vibration isolation properties were designed and integrated into standard transport boxes. The sheets were fabricated via 3D printing and evaluated through three experimental procedures: (1) vibration tests using random noise signals, (2) impact tests with controlled free-fall drops from 100 mm and 200 mm, and (3) real transport trials assessing damage and degradation over time. Packaging configurations included corrugated cardboard (CC), TPU sheets and a hybrid CC + TPU setup. Results showed that TPU-based configurations significantly reduced vibrational and impact accelerations compared to CC alone. Under vibration, TPU and CC + TPU achieved attenuation levels above 21%, versus 3% for CC. In impact tests, TPU and CC + TPU reduced peak accelerations by up to fourfold compared to corrugated cardboard (CC). During real transport on rural roads, TPU-based boxes caused three times less damage than cardboard, while degradation over subsequent days remained comparable. These findings demonstrate that TPU metamaterial sheets offer enhanced mechanical protection without compromising shelf life. The approach leverages additive manufacturing and metamaterial design to improve packaging performance, offering a sustainable alternative to conventional materials in postharvest logistics.