Detection and High-Precision Positioning of Liquid Droplets Using SAW Systems

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2007-10, Vol.54 (10), p.2146-2151
• Main Authors: Bennes, Jonathan, Alzuaga, Sebastien, Cherioux, Frederic, Ballandras, Sylvain, Vairac, Pascal, Manceau, Jean-Francois, Bastien, Francois
• Format: Article
• Language: English
• Subjects: Acoustic transducers; Acoustic wave devices, piezoelectric and piezoresistive devices; Acoustic waves; Acoustics; Applied sciences; Assessments; Biochemical analysis; Biological and medical sciences; Biosensors; Biotechnology; Channels; Chemical analysis; Chemical processes; Chemical Sciences; Delay lines; Devices; Displacement; Droplets; Electrodes; Electronics; Engineering Sciences; Exact sciences and technology; Excitation; Frequency; Fundamental and applied biological sciences. Psychology; Fundamental areas of phenomenology (including applications); Liquids; Mechanical engineering. Machine design; Mechanics; Methods. Procedures. Technologies; Organic chemistry; Physics; Precision engineering, watch making; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Studies; Surface acoustic wave devices; Surface acoustic waves; Transduction; acoustical devices for the generation and reproduction of sound; Various methods and equipments
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2007.510

The capability to accurately handle liquids in small volumes is a key point for the development of lab-on-chip devices. In this paper, we investigate an application of surface acoustic waves (SAW) for positioning micro-droplets. A SAW device based on a 2 times 2 matrix of inter-digital transducers (IDTs) has been fabricated on a (YXl)/128deg LiNbO 3 substrate, which implies displacement and detection in two dimensions of droplets atop a flat surface. Each IDT operates at a given frequency, allowing for an easy addressing of the active channel. Furthermore, very low cross-talk effects were observed as no frequency mixing arose in our device. Continuous as well as pulsed excitations of the IDTs have been studied, yielding, respectively, continuous and step-by-step droplet displacement modes. In addition, we also have used these two excitation types to control the velocity and the position of the droplets. We also have developed a theoretical analysis of the detection mode, which has been validated by experimental assessment.