Photonic polymer multilayers for colorimetric radiation sensing

• New approach for colorimetric radiation sensing using photonic polymer multilayer films.
• Sensors rely on reflected structural color that depends on the degree of swelling.
• Sensitivity to electron-beam irradiation in the range of ∼100 kGy.
• Flexible colorimetric radiations sensors are also prepared on flexible plastic substrates.

We introduce a new approach for colorimetric sensing of ionizing radiation based on photonic polymer multilayer films. Upon immersion in a solvent, the multilayers give rise to reflected structural color in the visible region of the spectrum, with a coloration that depends on the degree of swelling of the low-index layers. Exposure to ionizing radiation leads to either preferential degradation or crosslinking of the low-index polymer, yielding a change in color in the swelled state. We demonstrate the operation of both red- and blue-shifting colorimetric sensors, with sensitivity to electron-beam irradiation in the range of ∼100 kGy, and also show that this approach allows for the preparation of sensors on flexible plastic substrates.