Strain-induced elastic buckling instability for mechanical measurements (SIEBIMM) on colloidal assemblies

PMSE 117

Zekeriyya Gemici, zgemici@mit.edu1, Patrick Smadbeck1, Michael F. Rubner, rubner@mit.edu2, and Robert E. Cohen, recohen@mit.edu1. (1) Department of Chemical Engineering, Massachusetts Institute of Technology, 32 Vassar Street Room 13-5128, Cambridge, MA 02139, (2) Department of Materials Science and Engineering, Massachusetts Institute of Technology, 13-5106, 77 Massachusetts Avenue, Cambridge, MA 02139
Nanoscale colloidal assemblies and thin films have attracted much attention due to their novel dielectric, wetting, and optical properties. The mechanical properties of such ultrathin assemblies are also of much interest. However, the extreme thinness of these materials has limited the applicability of traditional testing methods (e.g., nanoindentation) and has underscored undesired substrate effects in such measurements. SIEBIMM and nanoindentation measurements of polymeric and sol-gel ultrathin films yield essentially identical Young's moduli, except SIEBIMM come at a fraction of the cost and effort required by nanoindentation experiments. We have assembled layer-by-layer (LbL) ultrathin all-nanoparticle and polymer-nanoparticle films on PDMS, whereby multiple conformal layers of positively and negatively charged polymers and/or nanoparticles were electrostatically adsorbed on the substrate. Chemical and mechanical substrate-film interactions were studied. Unfavorable interactions were eliminated to some extent using barrier layers between the colloidal films and the PDMS substrates. Young's moduli are reported as a function of humidity.