Ridge approximation for thin nematic polymer networks

Nematic polymer networks (NPNs) are nematic elastomers within which the director is enslaved to elastic deformation. The free energy of a NPN sheet thickness $h$ has both stretching and bending components (the former scaling like h, latter $h^3$). sheets bear field $\mathbf{m}$ imprinted in them (usually, uniformly throughout their thickness); they can be activated by changing order (e.g. illumination or heating). This paper illustrates an attempt compute show role it play determining shape. Our approach approximate: surface consists flat sectors connected ridges, where unit normal jumps concentrated. By increasing number we should get closer real situation, smooth distributed on it. method applied disk with spiraling hedgehog. It shown that upon activation disk, tiny hand, able grab rigid lamina.