Figure 23.

(A) Schematic presentation of the preparation of free-standing (PEI/PAA)/(PU/PAA) multilayer actuator membranes, which are responsive to water and organic solvent vapours. Reproduced from [156]. (B) Photographs of 1.0 mm-thick NBA and bromocresol green-loaded palm-shaped bilayer gels consisting of polyacid P(NIPAAm-co-CIPAAm) and polybase P(NIPAAm-co-DMAPAAm) layers in a time sequence under the illumination of a UV lamp on the polyacid side of the gels (c). As a control, gels were exposed to ambient light (a). To demonstrate local UV exposure, one half of the bilayer gel was continuously exposed to UV light (b). The colour of the gel started to change instantaneously from blue to yellow (pH < 3.8) in the photo-illuminated region. Reproduced from [196].