Multi-Material Extrusion-Based 3D Printing of Hybrid Scaffolds for Tissue Engineering Application

TL;DR

This paper introduces a 3D printing system for creating hybrid scaffolds combining hydrogels and thermoplastics, useful for tissue engineering.

Contribution

A modular multi-material extrusion platform with an empirical calibration procedure for gel dosing is developed.

Findings

The system achieves precise gel dosing with mass discrepancy below prescribed tolerance.

Hybrid scaffolds with hollow channels and self-supporting structures are successfully fabricated.

The scaffolds remain stable after crosslinking and can be converted into porous structures.

Abstract

Additive manufacturing of hydrogel-based scaffolds requires concurrent control of material rheology and extrusion dynamics, especially in multi-material architectures. In this work, we develop a modular multi-material extrusion-based 3D-printing platform that combines a filament-fed extruder for thermoplastic polymers with a piston-driven extruder for viscous gel inks, together with an empirical calibration procedure for gel dosing. The calibration algorithm optimizes the pre-extrusion and retraction displacement (EPr/R) based on stepwise extrusion experiments and reduces the discrepancy between theoretical and measured deposited mass for shear-thinning alginate gels to below the prescribed tolerance. The calibrated system is then used to fabricate two representative hybrid constructs: partially crosslinked sodium alginate scaffolds with an internal hollow channel supported by a removable polycaprolactone framework, and self-supporting structures based on a sodium alginate–chitosan polyelectrolyte complex obtained by sequential co-extrusion. The resulting constructs remain mechanically stable after ionic crosslinking and solvent treatment and can subsequently be converted into highly porous scaffolds by freeze- or supercritical drying. The proposed combination of hardware architecture and extrusion calibration enables reproducible multi-material 3D printing of hydrogel–thermoplastic hybrid scaffolds and can be readily adapted to other gel-based inks for tissue engineering applications.

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