Self-Sensing, Self Healing Materials 

   

As the use of structural composites increases, there is a corresponding need for these materials to be able to monitor and assess their structural health and mitigate any damage, all without human intervention. Current work in our group focuses on developing an integrated self-sensing, self-healing system for use in composite materials:

• Self-sensing – Polymeric materials can be made to sense impending damage via mechanophores (stress-sensitive molecules) linked into the polymer backbone. Mechanophores undergo a chemical reaction upon action of a mechanical force. They are designed to emit a measurable signal (e.g. color change, fluorescence) that can be used to detect high stresses and damage in the material.

 

Spiropyran-linked PMMA specimen after torsion tests.The bright purple color in the gage section

indicates activation of the spiropyran (SP) mechanophore. Reference: Celestine, PhD Thesis, 2014.

 

Sequence of fluorescence images of spiropyran-linked PMMA specimen during fracture tests showing the evolution of

fluorescence with crack propagation. Scale bar: 2 mm. Reference: Celestine et al., Polymer, 2014.

• Self-healing – The development of self-healing polymers draws inspiration from biological systems where functions such as blood clotting and the development of scar tissue repair damage without any outside intervention. Multiple avenues exist for self-healing in synthetic materials including the use of microcapsules or microchannels filled with healing fluid that are embedded in the host material. These vessels are ruptured during damage and release their healing fluid into the damage zone thereby healing the damage and restoring material properties.

PMMA specimen containing solvent-filled microcapsules for self-healing. Scale bar: 5 mm.

References: Celestine et al., Polymer 2015; Gladman, Celestine et al., Advanced Healthcare Materials 2015.