SAW nanopump for handling droplets in view of biological applications

This paper reports on the fabrication and development of a surface acoustic waves (SAW) platform dedicated to digital micro fluidics for biological applications. SAW at about 20 MHz are generated by InterDigital Transducers (IDT) laid on a LiNbO3 piezoelectric substrate. An electrical characterization of the IDT is reported and first results related to droplet handling with the SAW platform are given. We show that accurate droplet displacement is the result of both a radio frequency (RF) pulsed excitation and a chemical pre-treatment of the platform surface. For biological applications the droplet carrying the biomaterial is squeezed between the platform and a cover to increase the surface exchange between the droplet and hydrophilic functionalized areas. Out of such areas the free displacement is significantly improved by a surface hydrophobic pre-treatment. Moreover, the fabrication of additional hydrophilic micro tracks is shown to be a solution for crossing these areas without droplet splitting. This result is a key point to validate the structure of the novel micro fluidic platform proposed in this paper. (c) 2005 Elsevier B.V. All rights reserved.