Particle Shape Effects in Membranes Arjun G. Yodh , University of Pennsylvania, DMR 0804881

1. Particle Shape Effects in MembranesArjun G. Yodh, University of Pennsylvania, DMR 0804881 We explored the influence of particle shape on the elastic properties of the particle-coated air-water membranes (PRL 2012). These membranes are important for myriad applications ranging from the drying paint films and to stabilized emulsions. Briefly, novel elastic membranes were created by evaporating a colloidal drop of confined between two glass plates (a). As the drops evaporate, particles adsorb onto the air-water interface forming a colloidal-monolayer membrane. By characterizing membrane buckling during drying we were able to deduce membrane bending rigidity that was found to increase as the particles became more anisotropic (i.e., less spherical). and then undergo buckling events. We find that membrane bending rigidity increases as particles become more anisotropic. As was the case in our previous experiments (Nature 2011) particle deposition after drying is strongly dependent on particle shape. Ellipsoids are deposited uniformly, spheres are not. a b Bending Rigidity Particle Shape Anisotropy • Cartoon depicting formation of membranes • Plot of membrane bending rigidity vs. particle shape. • Inset: Image of evaporating drop after buckling event.

2. Particle Shape Effects in Membranes ArjunG. Yodh, University of Pennsylvania, DMR 0804881 b a • Besides creating new members of the scientifically literate US work-force, this research has potential technological applications. A patent application (UPNA-0156 / Y6008) has been filed; it is oriented towards using suspended particle shape as a means to produce uniform depositions in various geometries. • Uniform coatings are desirable for many applications, including: • Ink jet printing • Paint • Thin film coatings Heterogeneous final deposition of Spheres after drying Uniform final deposition of ellipsoids after drying We are working with Rhodia-Solvay, Inc., a specialty chemical company with a research plant in Bristol, PA, to develop useful applications of this approach.