Buckling instability of droplet chains in freely suspended smectic films

A buckling instability of chains of isotropic droplets in smectic films is investigated. The c -director field in a free-standing film is prepared as a target pattern with a continuous radial deformation. In such a pattern, isotropic liquid droplets are induced by light irradiation of the photochromic mesogenic material. The droplets align tangentially in regular chains in the regular structure of the c -director field. Incorporation of additional droplets lengthens the chains at a given ring diameter until they form complete rings. Further chain growth introduces a reversible buckling with a characteristic wave length. The phenomenon is similar in many respects to growth processes in biosystems or Euler buckling in polymer foils. A simple model of the wavelength selection mechanism is introduced.