Materials that contain special polymer molecules may someday be able to warn us when they are about to fail. Researchers have improved previously developed force-sensitive molecules, called mechanophores, to produce reversible, rapid, and vibrant color change when a force is applied.
The color change is the result of stress applied to the bonds that connect the mechanophores to a polymer chain. The mechanophores are bonded to polymer chains using an arrangement scheme called an oxazine structure. The new structure allows for an instantaneous and reversible color change, so instead of the polymer slowly becoming darker over time, the color changes quickly when the force is applied and disappears when the force is removed.
Materials that contain the new mechanophores could be used as stress sensors to enable researchers to study the effects of stress on materials before they fail. The rapid response and reversibility will allow engineers to better monitor, quickly detect, and respond rapidly to an overstressed structure in the lab and eventually in the field.
A long-standing challenge in materials science has been making observations regarding mechanical load and other stresses in materials at the single-molecule level. Although this advancement cannot do this, the goal is nearer with the development of this new type of mechanophores. In the area of biomechanics, for example, the research could be a stepping stone toward better monitoring of how our bodies react to external forces from the cellular level and beyond.