What if instead we could create a paint that can change from white to transparent under the influence of ultrasound or vibration? If the paint has a broadband response and is sensitive to different types of ultrasonic wave, it would be able to show visually the waves when they reach the sample surface. This would open up a wide variety of opportunities such as embedded sensors, smart coatings that help identify problems visually and at low cost. Important structural safety data could be collected by anyone with mobile phone with a camera, and sent to a monitoring centre, instead of having to train people in rather complex testing procedures. But how can one achieve this?

The answer may be by using liquid crystals.