Molecular sensors

Case Western Reserve University researchers have created light-emitting polymer blends that show mechanical stress by changing colours when deformed.

Using a mixture of conventional polymers, such as polyethylene and polypropylene, with small amounts of tailored fluorescent dyes, Case Western Reserve University researchers have created light-emitting polymer blends that ‘show’ mechanical stress by changing colours when deformed.

Christoph Weder, associate professor of macromolecular science and engineering at the Case School of Engineering, points out that ‘only a small amount of dye is needed to make the polymer glow,’ and that ‘the polymer blend’s colour contrast upon deformation is unparalleled.’

To demonstrate the potential of the new material, Weder’s research team created laboratory samples of a “smart” fishing line based on the light-emitting polymer materials. The colour of the line indicated when it had been stressed too much.

One exciting aspect of Weder’s research is how straightforward it may be to commercialise. “Some applicable dyes are affordable, easily made, and can be used in concentrations as low as 0.1%,” he said.

Weder says he is excited by the wide variety of potential applications for the simple technology that his group discovered unexpectedly.

It could, for example, be useful to develop early internal failure indicators in machinery, anti-counterfeiting devices, as well as tamper-resistant packaging for food or medicines.

In other work, scientists at Duke Scientific have developed fluorescent polymer microspheres that emit bright and distinctive colours when illuminated by light of shorter wavelengths than their emission wavelength. Developed for general laboratory use, thay can be used in applications such as flow tracing and fluid mechanics.