Elastic/viscoelastic polymer bilayers: a model-based approach to stretch-responsive constructs.

The use of polymers in the fabrication of bilayers for stimuli-responsive systems is well-known, yet viscoelasticity and viscoelastic models representing bilayer behavior have received surprisingly little attention. Of particular recent interest to us are simple polymeric bilayers in which one material, such as styrene-ethylene-propylene-styrene (SEPS) or styrene-isobutylene-styrene (SIBS), shows typical rubbery elastic response upon extension and retraction, and the other, an unvulcanized, low- polymer such as butyl rubber (butyl), exhibits a viscoelastic response. When such a bilayer strip is extended to a fixed strain and held for several seconds followed by sudden release of this strain, rapid curling is observed, achieving a maximum curvature within 1 second, with a gradual uncurling, typically taking 300-600 seconds to eventually return to a flat strip.

Critical Salt Loading in Flexible Poly(vinyl alcohol) Sensors Fabricated by an Inkjet Printing and Plasma Reduction Method.

We report a low-temperature inkjet printing and plasma treatment method using silver nitrate ink that allows the fabrication of conductive silver traces on poly(vinyl alcohol) (PVA) film with good fidelity and without degrading the polymer substrate. In doing so, we also identify a critical salt loading in the film that is necessary to prevent the polymer from reacting with the silver nitrate-based ink, which improves the resolution of the silver trace while simultaneously lowering its sheet resistance. Silver lines printed on PVA film using this method have sheet resistances of around 0.