Lijun Ye

Fast mixing digital micro-fluids in PDMS microchannel based on surface acoustic wave

Mixing liquid in small volumes is a key operation for the development of micro-fluidic devices. In this paper, a new method for fast mixing digital micro-fluids has been developed. Two orthogonal interdigital transducers were fabricated on a 128° YX-axis-rotated cut LiNbO 3 substrate. Each interdigital transducer was 35 straight finger pairs in a simple repeating patter, 4.32mm aperture, and a wavelength of λ=144µm. T-type PDMS micro-channel with 2.5 mm in width and 0.5mm in depth was mounted on the substrate for directing digital micro-fluids. Amplified RF signals were then fed to the IDTs in succession to actuate digital micro fluids along PDMS micro channel. The mixture was characterized using 2µl water-2µl red dye digital micro-fluids and 2µl glycerol-2µl red dye digital micro-fluids. Mixture performances of the digital micro-fluids were accessed by our developed soft. The results show that the mixture velocity and mixture degree of digital micro-fluids in PDMS micro-channels are greatly improved by help of surface acoustic wave than that by free diffusion.

Surface acoustic waves as the energy source for droplet-based micro-reactor with oil encapsulation

A SAW-based micro-reactor for biochemical assay using droplets encapsulated inside oil droplets is reported. Two interdigital transducers (IDTs) with 35 finger pairs, apertures of 4.32mm, and a center frequency of 27.7MHz were fabricated on a 127.86° rotated Y-cut X-propagating LiNbO 3 substrate. Biochemical reagent droplets encapsulated in oil droplets, which the reagent evaporation rate was greatly reduced, were pipetted onto the substrate. SAW generated by the IDTs heated the oil droplets and then raised the temperature of the reagent droplets. A color development reaction of starch has been tested. Gray value of an image has been used to analyze reaction response. Results show that the reaction velocity is accelerated with increased RF signal power fed onto the IDTs. The micro-reactor has the potential to systematically perform economical biochemical analysis on a chip.