Continuous fiber extruder for desktop 3D printers toward long fiber embedded hydrogel 3D printing.

Recent advances in Freeform Reversible Embedding of Suspended Hydrogels (FRESH), a technique that is compatible with most open-source desktop 3D printers, has enabled the fabrication of complex 3D structures using a wide range of natural and synthetic hydrogels, whose mechanical properties can be modified by embedding long fibers into printed hydrogels. However, fiber extruders dedicated for this application are not commercially available or previously reported. To address this, we have designed a continuous fiber extruder (CFE) that is compatible with low-cost, open-source desktop 3D printers, and demonstrated its performance using a Flashforge Creator-pro printer with a Replistruder-2.0 print-head. Key characteristics of the CFE include: (1) it is affordable, accessible and user-friendly to the 3D printing community due to its low fabrication cost and compatibility with open-source hardware and software, (2) it can embed user-defined 2D and 3D features using long fibers into different types of hydrogels, (3) it works with fibers of different mechanical properties and sizes, (4) it can modify mechanical properties of FRESH printed hydrogels via long fiber embedding.