New surfaces (PDMS, PMMA and parylene)
Teflon AF is typically employed as a hydrophobic coating in droplet based microfluidic devices to promote a large potential-induced contact angle change. However, we have recently shown that a large contact angle is not necessary for actuation on our microfluidic devices as it was previously believed. Due to this discovery, it is now possible to employ coatings other than Teflon AF that might be easier to handle, less expensive, or exhibit less denaturation and sticking of biological samples such as proteins on the surface (biofouling). As a result, we have begun investigating droplet movement on alternate surfaces include polydimethylsiloxane (PDMS), Parylene-C, and polymethyl methacrylate (PMMA), all of which are more hydrophilic than Teflon AF. These surfaces, due to their increasing affinity for water are also being used to probe the role of surface chemistry and molecular interactions in impeding droplet movement. By employing these new coatings we predict we will be able to expand the functionality of our devices and will come to a better understanding of the forces that impede droplet movement.