Biomimetic differently structured and multi-branched hydrogel tubes inspired by bud-growth of plants

Multi-branched hydrogel tubes have promising applications in various fields. However, it remains a great challenge to prepare such structures using a convenient method. Herein, an innovative method inspired by the bud-growth of plants (bud-notching and bud-picking) was proposed to prepare multi-branched hydrogel tubes based on sodium alginate/copper ions (Na-Alg/Cu²⁺). The bud-notching technique refers to the selective decrosslinking of Na-Alg/Cu²⁺ gels by controlled ethanolamine treatment, resulting in an "opening" in the tube wall. By adjusting the location and number of bud-notching on the primary tube and combining the apical growth technique, branched hydrogel tubes with diverse dimensions (two and three-dimensional) and structures ("zigzag"-shaped and "helical"-shaped) could be prepared on demand, without the need for templates and expensive equipment. Furthermore, biomimetic multi-segment hydrogel tubes were fabricated as simplified models to investigate the stability at the connection sites. The results demonstrated that the secondary hydrogel tubes prepared through multi-step growth retained approximately 70% of the elongation at break and 90% of the fracture force compared to the directly formed monolithic hydrogel tubes. Furthermore, the perfusion experiments showed that connections between branches were stable, which made the developed multi-branched hydrogel tubes have promising applications in some <i>in vitro</i> models and fluidic transport application areas. This kind of biomimetic method will also be meaningful for broadening the preparation of multi-branched materials.