  A chemical turnstile is a device for transporting small, well-characterised
doses of atoms from one location to another. A working turnstile has yet to be
built, despite the numerous technological applications available for such a
device. The key difficulty in manufacturing a chemical turnstile is finding a
medium which will trap and transport atoms. Here we propose that ferroelastic
twin walls are suitable for this role. Previous work shows that twin walls can
act as two-dimensional trapping planes within which atomic transport is fast.
We report simulations showing that a stress-induced reorientation of a twin
wall can occur. This behaviour is ideal for chemical turnstile applications.
