A US company, Kent Displays, has developed "no power" Liquid Crystal Displays using Polymer Stabilized Cholesteric Liquid Crystals: these are known as ChLCD screens. A drawback of ChLCD screens is their slow refresh rate, especially at low temperatures. In 2009, Kent demonstrated the use of a ChLCD to cover the entire surface of a mobile phone, allowing it to change colours, and keep that colour even when power is cut off.