We can tune the flexibility and magnetic response of our biomimetic arrays by changing the materials we use in our fabrication process. To this end, we have developed two materials in which magnetic nanoparticles are dispersed into a flexible polymer. The cilia retain the flexibility of the polymer but can be magnetically actuated to mimic the beat of biological cilia. The basis of our materials is a rubber-like polymer, polydimethysiloxane (PDMS).
The first and most promising material consists of maghemite nanoparticles suspended in PDMS, which we call FFPDMS. This FFPDMS can be heated and crosslinked into a flexible, magnetic solid. We can fabricate cilia with magnetic material making up 18% of their weight. A disadvantage of this material is the tendency of the cilia to clump together. We have attempted to address this with a new material, called FFPDMS-NH2. FFPDMS-NH2 combines magnetite nanoparticles and polydimethylsiloxane with amine groups. These added amine groups should allow us to attach charged groups to our cilia in order to prevent clumping. FFPDMS-NH2 is also different from FFPDMS because the amine groups in the PDMS are covalently bonded to the nanoparticle surface. With FFPDMS-NH2 we have fabricated cilia with magnetic material making up 65% of their weight.