Stereolithographic 3D printing of extrinsically self-healing composites

Abstract

We demonstrate for the first time the direct stereolithographic 3D printing of an extrinsically self-healing composite, comprised of commercial photocurable resin modified with anisole and PMMA-filled microcapsules. The composites demonstrate solvent-welding based autonomous self-healing to afford 87% recovery of the initial critical toughness. This work illustrates the potential of stereolithographic printing to fabricate self-healing composites with user-defined structures, avoiding the need for extensive rheological optimization of printing inks, like in direct-write 3D printing. Importantly, this work also demonstrates the inclusion of microcapsules into 3D printing resins to incorporate additional functionality into printed composites, which could be adapted for applications beyond self-healing materials.

Smart polymers and nanocomposites for 3D and 4D printing

“…PMMA participated in a solvent-welding based process and improved the healing functionality of the material. Damage recovery at room temperature was achieved up to 87% using this approach [299].…”

Self-Healing Mechanisms for 3D-Printed Polymeric Structures: From Lab to Reality

“…Self-healing mechanisms of polymer structures can be classified into two broad categories: intrinsic and extrinsic [ 10 ]. For the extrinsic approach, healing agents are sequenced through the main matrix, planted in microcapsules [ 29 , 82 , 83 , 84 ], or a 3D vascular network of hollow fibers [ 79 , 80 ] and channels [ 10 , 53 , 75 , 81 ], though it should be noted that the quantity and amount of transmission of the healing precursor are somewhat restricted [ 10 ]. External microcapsule layers and vascular walls are subjected to stress, when crack growth takes place and ruptures, and releases the healing agents that either react with each other or interact with the matrix to seal the crack [ 49 ].…”

“…External microcapsule layers and vascular walls are subjected to stress, when crack growth takes place and ruptures, and releases the healing agents that either react with each other or interact with the matrix to seal the crack [ 49 ]. Stiff polymer products can be incorporated, since the molecular diffusion of the matrix is not a prerequisite [ 65 , 82 ], and for other practical applications, extrinsic self-healing has opted to make use of hard polymer structures [ 76 ]. The correct option for a self-healing procedure will vary with nature and location of the likely damage, the chosen repair resin, the operational environment, the proximity size of the damaged zone, and the healing precursor container [ 75 ].…”

Self-Healing EPDM Rubbers with Highly Stable and Mechanically-Enhanced Urea-Formaldehyde (UF) Microcapsules Prepared by Multi-Step In Situ Polymerization

“…Among them, the extrinsic self-healing system using microcapsule has many industrial advantages: (1) it can be realized by a simple mixing technique; (2) it possesses excellent self-healing properties [ 4 ]; and (3) it can be applied to paints and coating agents in large volumes [ 5 , 6 , 7 , 8 ]. Furthermore, it is capable of providing excellent self-healing properties regardless of material’s physical characteristics [ 9 ]. In contrast, the intrinsic self-healing system can be realized only when the materials have soft physical properties like rubber [ 10 ].…”