Mechanical Properties of Polyelectrolyte Multilayer Capsules

Ana L. T. Cordeiro^1,2, Michelle Prevot³, Manuel A. N. Coelho², Yuri Lvov³, Ronald B. Besser³, Gleb B. Sukhorukov¹, and Helmuth Möhwald¹
¹Max-Planck-Institute of Colloids and Interfaces, Am Mühlenberg 1, D-14476 Golm, Germany,
²Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, P-4200-465 Porto, Portugal, and
³Institute for Micromanufacturing and Department of Chemical Engineering, Louisiana Tech University, 911 Hergot Ave., Ruston, LA 71271, U.S.A.
e-mail: Ana.Cordeiro@mpikg-golm.mpg.de
URL: http://www.mpikg-golm.mpg.de/gf/

The formation of polymeric artificial micro-sized capsules was recently developed. These shells enable the encapsulation of various materials and are therefore of scientific technological interest. The production essentially involves the coating of a colloidal polymeric template that is later destroyed and removed via pH or solvent change.

The mechanical properties knowledge of these novel structures is essential to develop capsules fabrication, as well as for the understanding of transport phenomena through different types of filters or vessels. Two systems were designed and setup to analyze capsules morphological changes and study their mechanical properties.

A parallel-plate flow chamber was projected in order to study the shear stress effect on the microcapsules when adsorbed on a modified surface under different flow conditions. The observation of the capsules under shear is suggested to extend the understanding of their mechanical behavior and obtain information about adhesion strength between differently modified surfaces.

A microfluidic system was build in order to study capsules deformation and squeeze trough when flowing in channels with dimensions and geometries simulating blood vessels. A silicon chip component was fabricated using lithography and bulk micromachining methods. The device allows the in-situ imaging of the capsules deformation under stimuli.