Generation Of Digital Micro-fluids Based On Surface Acoustic Wave

Digitization of fluid is a precondition for microfluidic chip working with digital microfluid toimplement microfluidic analysis.This paper presents two methods for digitization of fluids.The presented two methods for digitaizing fluids were realized on a128°YX-LiNbO3piezoelectric substrate, on which an interdigital transducers (IDT) with27.7MHz centerfrequency and a reflector for reducing power losses were fabricated.(1) In the first method, a uniform flow of fluids was obtained by an ejector jet pump, whichwas connected with a fine needle by a silicone hose. The fine needle was vertically fixed on thepiezoelectric substrate with small distance. When the aggregated micro-fluid at the top of the fineneedle was touched with the piezoelectric substrate, the micro-fluid was split due to acousticradiation force exerted by surface acoustic wave, which was excited by the IDT.(2) In the second method, a PDMS slant microchannel was fabricated and mounted on thepiezoelectric substrate at first. A hydrophobic aluminum sheet, which had treated by Teflon AF1600, was then fixed on the outlet. An ejector jet pump was used to provide uniform flow offluids. As soon as the micro-fluid with enough volumes was slide off the aluminium sheet on thepiezoelectric substrate due to gravity, it was actuated by SAW excited by the IDT, and a digitalmicrofluid was then generated.In addition, a method for calculating the distance between the end of fine needle and thepiezoelectric substrate was presented, and conditions to generate digital micro fluids were alsogiven in the first mehod for generating digital microfluds. In the second method for generatingdigital microfluds, force exerted on a microfluid, which was on surface of the aluminum sheet, wastheoretically analysised. Since most biochemical reagents were water solution, water was used todigitizing experiments. The results showed that digital microfluids can be generated using theproposed two methods. This work solves a problem of microfluidic accession for microfluidicchips, which is helpful for researching microfludic device to implement microfludic analysis.