Humido- and Thermo-Responsive Free-Standing Films Mimicking the Petals of the Morning Glory Flower

The mimic of petals of the morning glory flower can produce novel humido- and thermo-responsive membranes. In this work, humido- and thermo-responsive film has been fabricated by vacuum deposition of a nanoscale-thick aluminum layer on top of the thermally cross-linked poly(acrylic acid) (PAA)/poly(allylamine hydrochloride) (PAH) free-standing film. The bilayer Al/(PAA/PAH) film can undergo bending/unbending movements when the environmental humidity and/or temperature changes, which mimics the petals of morning glory flowers. The bending/unbending movement of the bilayer films is caused by the large difference in response of the aluminum layer and the PAA/PAH polymeric film toward humidity and temperature. The present study provides a simple and flexible way to prepare novel humido- and thermo-responsive film materials.