Volume 6, Issue 1, May 2009
Index of content:
- Biomedical Ultrasound/Bioresponse to Vibration
Acoustofluidics: theory and simulation of radiation forces at ultrasound resonances in microfluidic devices6(2009); http://dx.doi.org/10.1121/1.3186746View Description Hide Description
Theoretical analysis is combined with numerical simulations to optimize designs and functionalities of acoustofluidic devices, i.e. microfluidic devices in which ultrasound waves are used to anipulate biological particles. The resonance frequencies and corresponding modes of the acoustic fields are calculated for various specific geometries of glass/silicon chips containing water-filled microchannels. A special emphasis is put on taking the surrounding glass/silicon material into account, thus going beyond the traditional transverse half-wavelength picture. For the resonance frequencies, where the largest possible acoustic powers are obtained in the microfluidic system, the time-averaged acoustic radiation force on single particles is determined. Schemes for in situ calibration of this force are presented and discussed.
6(2009); http://dx.doi.org/10.1121/1.3266907View Description Hide Description
The use of ultrasound in resonators for manipulating particles in various biomedical applications is a relatively well studied topic. These studies were mostly concerned with steady-state processes. However, in certain important applications, such as stirring and mixing fluids in microfluidics and biosensors, the time scale of a process plays a crucial role. Here we consider some of these applications. In particular, the radiation force-induced motion of microparticles and micro-bubbles in a swept-frequency ultrasonic resonator is considered. The particles are forced to move due to switching the resonance modes in a resonator cell, thus providing effective stirring of the fluid. Another field of potential medical application where transient processes are of crucial importance, is ultrasonic treatment of tissues. In this new field of ultrasonic therapy, standing waves can be used for producing lesions in the tissue with simultaneous monitoring the lesion formation by automatic controlling the field parameters. Dynamics of temperature changes in the tissue under the action of a standing ultrasound wave, which is important for optimizing tissue treatment regimes, is evaluated. Experimental data illustrating theoretical results are presented.