title: Programmable light-controlled shape changes in layered polymer nanocomposites.
abstract: We present soft, layered nanocomposites that exhibit controlled swelling anisotropy and spatially specific shape reconfigurations in response to light irradiation. The use of gold nanoparticles grafted with a temperature-responsive polymer (poly(N-isopropylacrylamide), PNIPAM) with layer-by-layer (LbL) assembly allowed placement of plasmonic structures within specific regions in the film, while exposure to light caused localized material deswelling by a photothermal mechanism. By layering PNIPAM-grafted gold nanoparticles in between nonresponsive polymer stacks, we have achieved zero Poisson's ratio materials that exhibit reversible, light-induced unidirectional shape changes. In addition, we report rheological properties of these LbL assemblies in their equilibrium swollen states. Moreover, incorporation of dissimilar plasmonic nanostructures (solid gold nanoparticles and nanoshells) within different material strata enabled controlled shrinkage of specific regions of hydrogels at specific excitation wavelengths. The approach is applicable to a wide range of metal nanoparticles and temperature-responsive polymers and affords many advanced build-in options useful in optically manipulated functional devices, including precise control of plasmonic layer thickness, tunability of shape variations to the excitation wavelength, and programmable spatial control of optical response.
authors.affiliation: Department of Chemistry, Chemical Biology and Biomedical Engineering, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, New Jersey 07030, United States.
authors.forename: Zhichen
authors.initials: Z
authors.lastname: Zhu
authors.forename: Erkan
authors.initials: E
authors.lastname: Senses
authors.forename: Pinar
authors.initials: P
authors.lastname: Akcora
authors.forename: Svetlana A
authors.initials: SA
authors.lastname: Sukhishvili
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D006046:Gold / Q000737:chemistry; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry; D053761:Nanocomposites / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D013696:Temperature
chemical_list: D000180:Acrylic Resins; C052970:poly-N-isopropylacrylamide; D006046:Gold