Non-contact and non-destructive detection of structural defects in bioprinted constructs using video-based vibration analysis

Bioprinting technology has advanced significantly in the fabrication of tissue-like constructs with complex geometries for regenerative medicine. However, maintaining the structural integrity of bioprinted materials remains a major challenge, primarily due to the frequent formation of hidden defects, such as pressure-induced inconsistencies, geometric voids, and interlayer separations. Traditional defect detection approaches often require physical contact that may not be suitable for hydrogel-based biomaterials due to the inherently soft nature of bioinks, making non-invasive and straightforward structural evaluation necessary in this field. To advance the state of the art, this study presents a novel non-contact method for non-destructively detecting structural defects in bioprinted constructs using video-based vibration analysis. Ear-shaped constructs were fabricated via extrusion-based bioprinting using an acellular bioink composed of sodium alginate and κ-carrageenan to systematically analyze the mechanical effects induced by printing defects. To simulate printing defects, controlled geometric, interlayer, and pressure-induced defects were systematically introduced into the samples. The dynamic response of each structure was recorded under excitation using a high-speed camera and analyzed using phase-based motion estimation techniques. Experimental results demonstrate that all defective samples exhibit consistent changes in the dynamic characteristics compared to baseline samples, with increasingly pronounced deviation observed as defect severity increases. These shifts reflect changes in effective stiffness and mass distribution induced by internal anomalies, even when such defects are not detectable through surface inspection. The experimental trends were also validated through finite element simulations. Overall, this work demonstrates that video-based vibrometry is a powerful approach for assessing the quality of acellular bioprinted constructs, offering a practical pathway toward robust structural health monitoring in next-generation bio-additive manufacturing workflows.