A humidity-responsive bilayer actuator has been developed that consists of an oriented polyamide-6 substrate and a liquid-crystalline polymer coating. The oriented substrate acts as an alignment layer for the liquid crystal. The liquid-crystalline polymer consists of a supramolecular network having hydrogen-bonded entities that, after activation with an alkaline solution, exhibit deformation in response to a change in humidity. The bending behavior of the bilayer actuator was analyzed, showing a large response to a change in the humidity.

1360 wileyonlinelibrary.com layers in combination with simple photomasks in a contactless process, [ 4,5 ] spontaneously generating unique wrinkling patterns in any arbitrarily complex fashion.Wrinkling can be induced in bilayer systems consisting of a thin fi lm of a relatively stiff material on top of a foundation of a softer material as a result of a strain mismatch between the layers, usually induced by mechanical or heat-driven deformation of the foundation or the top layer. It is a well-studied and well-understood process. [6][7][8][9] Many applications for wrinkled surfaces have been demonstrated, including preparation of superhydrophobic [ 10 ] and antifouling surfaces, [ 11 ] actuators, [ 12 ] alignment of living cells, [ 13 ] optical focusing, [ 14 ] fabrication of microlens arrays, [ 15 ] fabrication of patterned electrodes, [ 16 ] stretchable conductors, [ 17 ] and strain-sensitive diffraction gratings. [ 18 ] Achieving precise control over the wrinkling properties is vital for the further development of these applications. The amplitude and period of the wrinkles can be easily tuned by changing the thickness of the thin, stiff top layer, [ 19,20 ] and the preparation of homogeneously wrinkled surfaces is rather straightforward. [ 1,9,20,21 ] A limited number of patterns over small surface areas have been reported. [ 6,[22][23][24][25][26] However, it is desirable to introduce a fl exible method of generating complex wrinkle patterns on demand, scalable to cover large areas. We demonstrate the power of our method by generating intricate multidomain patterns and continuous circular structures including azimuthal, radial, and even higher complexity arrangements as examples, without the need of multiple master patterns and the possibility of rapidly switching between patterns with simple rearrangement of light source, polarizers, and masks. Results and DiscussionWe make our wrinkling patterns using photoalignment of polymerizable LCs. [ 27,28 ] Alignment cells were prepared by combining two glass plates coated with a linearly photopolymerizable polymer which was photoaligned by exposure to polarized ultraviolet light through a variety of photomasks (Figure 1 b,c). [ 4 ] The cells were fi lled with a mixture of polymerizable LCs (Figure 1 d) at 80 °C in the isotropic phase, and were photopolymerized at 60 °C in the nematic phase into a polymer fi lm having a glass transition temperature of around 45 °C. [ 4 ] The cell was opened by removing one of the glass plates, and a gold On-Demand Wrinkling Patterns in Thin Metal Films Generated from Self-Assembling Liquid Crystals Laurens T. de Haan , Philippe Leclère , Pascal Damman , Albertus P. H. J. Schenning , and Michael G. Debije * In this work, a new, universal method is described that uses the photopatterning of liquid crystals, which is accurately translated into a controlled, intricately wrinkled metal surface. Remarkably, the patterns have an oscillation in amplitude of the wrinkles. This rapid method allows generation of intricate multidomain patt...