The Permanent Freezing of ER Fluids at Room Temperature

Over a duration of time, films of certain all-liquid electrorheological (ER) fluids between stationary electrodes charged only with alternating current voltage will freeze. The word freeze is used here to describe a lock which extends beyond the time the electrodes are charged. In other words, the electrodes are not moveable even when the voltage is removed. This freeze is in addition to the instantaneous lock in between charged electrodes that occurs with either alternating current or direct current. With either current, this instantaneous lock breaks when voltage is removed. However, continued application of alternating current over time with stationary electrodes will induce a permanent freeze. While this permanent freeze lasts indefinitely, it immediately breaks into a liquid when the electrodes are pried apart.