On-chip Ultrasonic Sample Preparation

Detta är en avhandling från Stockholm : KTH Royal Institute of Technology

Sammanfattning: Acoustofluidics has become a well-established technology in the lab-on-a-chip scientific community. The technology involves primarily the manipulation of fluids and/or particles in microfluidic systems. It is used today for variety of applications such as handling, sorting, washing and separation of cells or micro-particles, and for mixing and pumping of fluids. When such manipulation functions are integrated in micro-devices, the technology has been used for clinical sample preparation as well as for studying various fundamental bio-related questions.In this doctoral thesis, we have developed different acoustic methods and micro-devices with the aim to create a multi-functional sample preparation platform. We introduced a simple method for in-situ measurements of acoustic energy densities inside a microfluidic channel, from which acoustic pressure amplitudes can be extracted. The method has been used for determining the magnitude of acoustic radiation forces acting on suspended particles and cells inside an acoustofluidic system. For optimization of acoustophoresis (i.e. manipulation of particles into the nodes of standing waves), we have investigated different designs of ultrasonic transducers based on tunable-angle wedges and backing layers attached to glass-silicon microfluidic chips. Furthermore, we have investigated the implementation of frequency-modulated actuation methodology combined with broadbanded ultrasonic transducers, and the implementation of multiple ultrasonic manipulation functions localized to spatially separated zones in a complex microchannel network. We demonstrate two different bio-applications useful for multi-step and multi-functional sample preparation. First, we demonstrate a micro-device for size-based separation, isolation and up-concentration of cells, followed by microscopy-based dynamic monitoring of individual cell properties when introducing different reagents. This holds great promise for use in cellular and molecular diagnostics. Second, we demonstrate an acoustic method for micro-vortexing in µL-volume reaction chambers in disposable polymer chips. The method is used for fast mixing of fluids, for disaggregating and re-suspending magnetically trapped and clumped micro-beads, and for cell lysis followed by DNA extraction. Finally, we demonstrate a temperature-controlled device compatible with high-acoustic-pressure (1 MPa) ultrasonic manipulation of cells, and we demonstrate that cells can be exposed to standing-wave ultrasound at 1 MPa for one hour without compromising the cell viability.

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