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Temperature and trapping characterization of an acoustic trap with miniaturized integrated transducers - towards in-trap temperature regulation

Johansson, Linda; Evander, Mikael LU ; Lilliehorn, Tobias; Almqvist, Monica LU ; Nilsson, Johan LU ; Laurell, Thomas LU and Johansson, Stefan (2013) In Ultrasonics 53(5). p.1020-1032
Abstract
An acoustic trap with miniaturized integrated transducers (MITs) for applications in non-contact trapping of cells or particles in a microfluidic channel was characterized by measuring the temperature increase and trapping strength. The fluid temperature was measured by the fluorescent response of Rhodamine B in the microchannel. The trapping strength was measured by the area of a trapped particle cluster counter-balanced by the hydrodynamic force. One of the main objectives was to obtain quantitative values of the temperature in the fluidic channel to ensure safe handling of cells and proteins. Another objective was to evaluate the trapping-to-temperature efficiency for the trap as a function of drive frequency. Thirdly,... (More)
An acoustic trap with miniaturized integrated transducers (MITs) for applications in non-contact trapping of cells or particles in a microfluidic channel was characterized by measuring the temperature increase and trapping strength. The fluid temperature was measured by the fluorescent response of Rhodamine B in the microchannel. The trapping strength was measured by the area of a trapped particle cluster counter-balanced by the hydrodynamic force. One of the main objectives was to obtain quantitative values of the temperature in the fluidic channel to ensure safe handling of cells and proteins. Another objective was to evaluate the trapping-to-temperature efficiency for the trap as a function of drive frequency. Thirdly, trapping-to-temperature efficiency data enables identifying frequencies and voltage values to use for in-trap temperature regulation. It is envisioned that operation with only in-trap temperature regulation enables the realization of small, simple and fast temperature-controlled trap systems. The significance of potential gradients at the trap edges due to the finite size of the miniaturized transducers for the operation was emphasized and expressed analytically. The influence of the acoustic near field was evaluated in FEM-simulation and compared with a more ideal 1D standing wave. The working principle of the trap was examined by comparing measurements of impedance, temperature increase and trapping strength with impedance transfer calculations of fluid-reflector resonances and frequencies of high reflectance at the fluid-reflector boundary. The temperature increase was found to be moderate, 7 degrees C for a high trapping strength, at a fluid flow of 0.5 mm s(-1) for the optimal driving frequency. A fast temperature response with a fall time of 8 s and a rise time of 11 s was observed. The results emphasize the importance of selecting the proper drive frequency for long term handling of cells, as opposed to the more pragmatic way of selecting the frequency of the highest acoustic output. Trapping was demonstrated in a large interval between 9 and 11.5 MHz, while the main trapping peak displayed FWHM of 0.5 MHz. A large bandwidth enables a more robust manufacturing and operation while allowing the trapping platform to be used in applications where the fluid wavelength varies due to external variations in fluid temperature, density and pressure. (C) 2013 Elsevier B. V. All rights reserved. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Acoustic trapping, Temperature analysis, Micro total analysis system, FEM simulation, Temperature regulation
in
Ultrasonics
volume
53
issue
5
pages
1020 - 1032
publisher
Elsevier
external identifiers
  • wos:000317184400013
  • scopus:84876058561
ISSN
0041-624X
DOI
10.1016/j.ultras.2013.01.010
language
English
LU publication?
yes
id
8f24b2e8-c085-4d4b-9801-2b0efaf213d1 (old id 3738818)
date added to LUP
2013-05-22 14:23:21
date last changed
2018-06-03 04:02:52
@article{8f24b2e8-c085-4d4b-9801-2b0efaf213d1,
  abstract     = {An acoustic trap with miniaturized integrated transducers (MITs) for applications in non-contact trapping of cells or particles in a microfluidic channel was characterized by measuring the temperature increase and trapping strength. The fluid temperature was measured by the fluorescent response of Rhodamine B in the microchannel. The trapping strength was measured by the area of a trapped particle cluster counter-balanced by the hydrodynamic force. One of the main objectives was to obtain quantitative values of the temperature in the fluidic channel to ensure safe handling of cells and proteins. Another objective was to evaluate the trapping-to-temperature efficiency for the trap as a function of drive frequency. Thirdly, trapping-to-temperature efficiency data enables identifying frequencies and voltage values to use for in-trap temperature regulation. It is envisioned that operation with only in-trap temperature regulation enables the realization of small, simple and fast temperature-controlled trap systems. The significance of potential gradients at the trap edges due to the finite size of the miniaturized transducers for the operation was emphasized and expressed analytically. The influence of the acoustic near field was evaluated in FEM-simulation and compared with a more ideal 1D standing wave. The working principle of the trap was examined by comparing measurements of impedance, temperature increase and trapping strength with impedance transfer calculations of fluid-reflector resonances and frequencies of high reflectance at the fluid-reflector boundary. The temperature increase was found to be moderate, 7 degrees C for a high trapping strength, at a fluid flow of 0.5 mm s(-1) for the optimal driving frequency. A fast temperature response with a fall time of 8 s and a rise time of 11 s was observed. The results emphasize the importance of selecting the proper drive frequency for long term handling of cells, as opposed to the more pragmatic way of selecting the frequency of the highest acoustic output. Trapping was demonstrated in a large interval between 9 and 11.5 MHz, while the main trapping peak displayed FWHM of 0.5 MHz. A large bandwidth enables a more robust manufacturing and operation while allowing the trapping platform to be used in applications where the fluid wavelength varies due to external variations in fluid temperature, density and pressure. (C) 2013 Elsevier B. V. All rights reserved.},
  author       = {Johansson, Linda and Evander, Mikael and Lilliehorn, Tobias and Almqvist, Monica and Nilsson, Johan and Laurell, Thomas and Johansson, Stefan},
  issn         = {0041-624X},
  keyword      = {Acoustic trapping,Temperature analysis,Micro total analysis system,FEM simulation,Temperature regulation},
  language     = {eng},
  number       = {5},
  pages        = {1020--1032},
  publisher    = {Elsevier},
  series       = {Ultrasonics},
  title        = {Temperature and trapping characterization of an acoustic trap with miniaturized integrated transducers - towards in-trap temperature regulation},
  url          = {http://dx.doi.org/10.1016/j.ultras.2013.01.010},
  volume       = {53},
  year         = {2013},
}