Colourchanging

Colourchanging refers to the phenomenon where an object or substance alters its colour in response to specific environmental stimuli. This alteration is usually a reversible process, meaning the original colour can be restored when the stimulus is removed or changed. The underlying mechanism for colourchanging often involves chemical reactions or physical state changes that affect how light is absorbed and reflected.

One common type of colourchanging material is thermochromic, which changes colour with temperature fluctuations. These materials are widely used in novelty items like mood rings, baby bottles that indicate safe feeding temperatures, and labels for food and beverages to show if they are hot or cold. Another category is photochromic material, which changes colour when exposed to ultraviolet (UV) light, such as sunlight. Eyeglasses that darken outdoors and lighten indoors are a prime example of photochromic technology. Hydrochromic materials change colour in the presence of water, while electrochromic materials alter their colour when an electric voltage is applied.

The applications of colourchanging technologies are diverse, extending beyond novelty uses. They are employed in security features on currency and important documents, in smart windows that can regulate the amount of light and heat entering a building, and in medical diagnostics for temperature monitoring. Research continues to explore new stimuli-responsive colourchanging materials for advanced applications in areas like sensors, displays, and adaptive camouflage.