When players tackle each other in sports like football or wrestling, or get punched in the head while boxing, or while falling off a motorcycle, sometimes it feels fine. You might feel a little jarred but on the surface you look all right, although in reality you might have just gotten yourself a pretty serious head injury and by the time it’s been discovered, it might be too late.

However thanks to researchers at the University of Pennsylvania, they have created a polymer that can change color depending on how much force has been applied to it. This means that if you were hit very strong in the head, its color would signify that. However if the impact isn’t that heavy, it won’t show or change too much color.

This is thanks to the use of holographic lithography to create photonic crystals. These crystals have structures that can change color when they deform, and best of all it does not require any power or an external power source for it to work. It also seems that they are light enough where they can be applied to sporting equipment like helmets without impacting its weight.

In the meantime the researchers have also figured out a molding technique that will allow these crystals to be mass-produced, thus making them more accessible to sporting good companies or companies selling protective gear that might want to take advantage of the technology.

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