BioTube: Designing and Fabricating Biodegradable Hollow Tubular Devices Through Progressive Crosslinking Alginate

We present BioTube, a sustainable and highly accessible DIY fabrication approach for creating hollow tubular alginate, and demonstrate its potential for making biodegradable transient devices. This technique involves extruding alginate into a calcium solution, initiating a progressive crosslinking process that starts from the outer shell and progresses inward. This controlled process removes the uncrosslinked core before complete gelation, yielding hollow alginate fibers. To further enhance the capabilities of BioTube, we explored three further crosslinking strategies to customize the fiber shape, local cross-sectional geometry, and stiffness. The versatility of this method is demonstrated through three key functional primitives: shape, morphing, and sensing. These capabilities are further illustrated through five application examples, including transient wearables, edible shape-changing interfaces, experimental gastronomy, underwater grippers, and sacrificial casting molds. We believe that BioTube will expand the design possibilities for alginate, enabling the creation of innovative biodegradable devices.