Ghosh, SuvojitTehrani, MehranAl-Haik, Marwan S.Puri, Ishwar K.2017-09-202017-09-202015-01-30Ghosh, S.; Tehrani, M.; Al-Haik, M.S.; Puri, I.K. Patterning the Stiffness of Elastomeric Nanocomposites by Magnetophoretic Control of Cross-linking Impeder Distribution. Materials 2015, 8, 474-485.http://hdl.handle.net/10919/79226We report a novel method to pattern the stiffness of an elastomeric nanocomposite by selectively impeding the cross-linking reactions at desired locations while curing. This is accomplished by using a magnetic field to enforce a desired concentration distribution of colloidal magnetite nanoparticles (MNPs) in the liquid precursor of polydimethysiloxane (PDMS) elastomer. MNPs impede the cross-linking of PDMS; when they are dispersed in liquid PDMS, the cured elastomer exhibits lower stiffness in portions containing a higher nanoparticle concentration. Consequently, a desired stiffness pattern is produced by selecting the required magnetic field distribution <i>a priori</i>. Up to 200% variation in the reduced modulus is observed over a 2 mm length, and gradients of up to 12.6 MPa·mm⁻¹ are obtained. This is a significant improvement over conventional nanocomposite systems where only small unidirectional variations can be achieved by varying nanoparticle concentration. The method has promising prospects in additive manufacturing; it can be integrated with existing systems thereby adding the capability to produce microscale heterogeneities in mechanical properties.application/pdfenCreative Commons Attribution 4.0 Internationalfunctional gradingnano compositesnanoindentationmagnetic nanoparticlesArticle - Refereed2017-09-20https://doi.org/10.3390/ma8020474