University of Michigan scientists have created a thin film that produces circularly polarized light. They have polarized waves in a three-dimensional helix that can move both clock- and counter-clockwise. Their stretchable film is being developed for cancer patient monitoring, but has potential applications for data transmission and even cloaking technology.

Thin film produced for cancer detection.Circular polarization is rare in the natural world. While it has many potential applications, it traditionally has been costly to create and needs large machinery to produce. The Michigan team’s film, although in early development, could signal an easier and lower-cost method to induce the process.

The research team’s goal is to create a portable sensor device that could be worn by cancer patients to quickly analyze blood samples. The sensor would zero in on biomarkers, which are proteins and DNA that are present in the earliest stages of cancer recurrence. Using synthetic biological particles that are highly attracted to these biomarkers, the sensors react to a small amount of the patient’s blood. This allows diagnosticians the ability to accurately read the sample under circularly polarized light.

Using a standard thin film of PDMS (the same material used for contact lenses), the researchers twisted both ends of a small rectangle 360 degrees and clampedthem down. They then deposited five alternating layers of gold nanoparticles and clear polyurethane to the film. The resulting film has sufficient layers to produce reflectivity, but is still transparent enough that it doesn’t inhibit light passage. When the material is untwisted, the nanoparticles buckle, forming a pattern of S shapes that cause the circular polarization. Stretching alters the degree of polarization, while releasing the shape returns it to its normal state. The material can be stretched and released thousands of times and maintain its mechanical properties, the researchers say.

The thin film is easy to manufacture and the team anticipates it will find its way into many new applications. One may be to create devices that bend light around objects, giving them partial invisibility.