A research team constructed a new dye molecule from the area of mechanophores. Thanks to this molecule, stress of different magnitudes in plastic components can be visualized continuously by color changes.
The concept of such dyes is not new but most previous mechanophores were able to only indicate the presence or absence of stress in plastics. The new molecule enables the differentiation between stresses of different magnitudes. This is important to map stress distributions in macroscopic plastic components to monitor integrity of the material at all times. The team is developing this form of deformation and damage analysis, bringing it closer to practical applications.
By combining a molecularly designed dye with a suitable and non-brittle plastic, macroscopic forces can now be brought down to the molecular scale. These acting forces can be, for example, external pressure or tension. The dye molecule thus “feels” the force acting within the plastic components and continues to indicate changes in force by increasing changes in color. If the external load is taken off, the dye molecule returns into its original state — a molecular spring that stretches and springs, depending on external tension.
Compared to existing molecular switches that translate stress in plastics by changing color, the advantages with the new technology lie in the stepless mapping of forces of different magnitudes as well as the spring-like behavior of the molecule, which can be used again and again.
The technology could also allow a more fundamental understanding of damping properties of synthetic materials and natural systems. For example, there are large and heavy fruits that fall from trees from large heights but remain undamaged. Nature serves as a model here and molecular springs could help to better understand and imitate such systems. Future efforts will therefore focus on adapting molecular force springs for use in various plastics.