Ultrasonic manipulation in microfluidic chips for accurate bioparticle handling.

Abstract

Micro-manipulation of cells or other bioparticles has important applications in biological and biomedical research. Dielectrophoresis and optical tweezers are the classical tools in this field. Ultrasonic standing wave (USW) technology is presently emerging as powerful alternative, especially in microfluidic chips and other miniaturized systems. In this contribution we will review our present activities in USW-based particle manipulation in microfluidic chips. Recent experiments and simulations allow us to tailor the spatial distribution of the USW force field by multi-frequency actuation and appropriate microchannel/transducer resonance design. We introduce the concept of ultrasonic micro-cages for single-cell or single-particle 3-D ultrasonic manipulation. It is shown that these manipulation tools can be combined with high-resolution optical microscopy, thereby allowing state-of-the-art characterization of individual cells. Frequency-modulation is shown to stabilize the manipulation performance as well as allowing flow-free transport of particles and cells. Environmental control inside the channels has been achieved and proliferation and viability studies are promising. Finally, for bio-analysis, we demonstrate potential for femtomolar bio-analytical sensitivity in bead-based assays using USW enrichment.