Thermochromic ink
Thermochromic inks can either have a reversible or permanent (irreversible) color change based on how they’re made:
- Reversible Thermochromic Inks: These change color with temperature fluctuations but return to their original color when the temperature resets. This is achieved by using leuco dyes or liquid crystals, which change structure temporarily with temperature. Examples include:
- Mood rings: Change color based on the wearer’s body temperature.
- Battery charge indicators: Indicate if a battery is hot from extended use.
- Thermally sensitive mugs: Show hidden designs when filled with hot liquid.
- Irreversible Thermochromic Inks: These change color only once when a certain temperature is reached, and the change is permanent. This type of ink is often used for items requiring a lasting color change for safety or quality assurance. Examples include:
- Sterilization indicators: Used on medical instruments to show if they’ve been autoclaved or heat-sterilized.
- Food freshness indicators: On packaging, to show if perishable food has been exposed to unsafe temperatures.
- Fire safety labels: On fire extinguishers or emergency equipment, to show if they’ve been exposed to fire temperatures.
Each type serves unique applications where a temporary or lasting color response to temperature is useful.