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Fabricating nanomembranes with novel properties
24 October 2005
Miniaturisation is a common theme of research for many technologies, microelectromechanical (MEMS) devices being typical candidates.
Freely suspended membranes are key components of MEMS for which inorganic membranes function well on the millimetre scale. Further minimisation requires softer membranes, and for this nanocomposite membranes (nanomembranes), consisting of nanostructures in a polymer matrix, show great potential, attracting wide research interest.
Vladimir Tsukruk and Chaoyang Jiang of the Department of Materials Science and Engineering at Iowa State University have developed a novel and versatile approach to fabricating freely suspended multilayer nanomembranes containing microarrays of nanostructures. They have combined spin assisted layer-by-layer assembly with microcontact printing and sacrificial layer methods to make nanomembranes containing organised arrays of structures.
Layer-by-layer assembly is already a popular technique in nanomembrane fabrication. It allows the properties to be tailored by the addition of functional nanostructures to the layers. Precise control over the in-plane composition on the micrometre scale is achieved by lithographic patterning and microcontact techniques.
What Tsukruk and Jiang have done is to apply a combination of techniques and so extend the in-plane structure control to produce long range microarrays of nanostructures such as gold nanoparticles or carbon nanotubes in nanomembranes. These membranes, which are less than 100 nm thick, not only show the enhanced mechanical properties expected with fillers, but also new anisotropic mechanical behaviour.
Intriguingly, Raman scattering investigations suggest that these nanomembranes also possess interesting optical properties, giving a tantalising glimpse at the potential to tune a wide range of properties with this versatile technique which could be applied to many different types of filler. Tsukruk and Jiang are currently investigating the novel mechanical and optical properties and they are also looking at ways of reducing the minimum thickness of these promising structures.
V Tsukruk and C Jiang, Soft Matter, 2005, 1, 334 (DOI: 10.1039/b510716d)