Domain-wall tension allows bistability in imperfect laminar cholesteric twist cells

Tension in domain walls between adjacent regions of opposite state in bistable laminar cholesteric twist cells can prevent growth of very small domains. This fact makes permanent bistability possible even when dust particles are available to nucleate the unwanted state. A crude model of a wall yields an approximate relation between allowable variation of cell thickness or of holding voltage and the maximum allowable size of dust particles or similar imperfections. If imperfections are smaller than this maximum a picture element can remain in either state indefinitely.