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