Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published March 2016 | Published + Supplemental Material
Journal Article Open

Acoustic trapping of active matter

Abstract

Confinement of living microorganisms and self-propelled particles by an external trap provides a means of analysing the motion and behaviour of active systems. Developing a tweezer with a trapping radius large compared with the swimmers' size and run length has been an experimental challenge, as standard optical traps are too weak. Here we report the novel use of an acoustic tweezer to confine self-propelled particles in two dimensions over distances large compared with the swimmers' run length. We develop a near-harmonic trap to demonstrate the crossover from weak confinement, where the probability density is Boltzmann-like, to strong confinement, where the density is peaked along the perimeter. At high concentrations the swimmers crystallize into a close-packed structure, which subsequently 'explodes' as a travelling wave when the tweezer is turned off. The swimmers' confined motion provides a measurement of the swim pressure, a unique mechanical pressure exerted by self-propelled bodies.

Additional Information

© 2016 Macmillan Publishers Limited. This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ Received 23 October 2015; Accepted 13 January 2016; Published 10 March 2016. S.C.T. is supported by a Gates Millennium Scholars fellowship and a National Science Foundation (NSF) Graduate Research Fellowship (No. DGE-1144469). R.D.D. is supported by a doctoral fellowship of the fund for scientific research (FWO-Vlaanderen). This work is also supported by NSF Grant CBET 1437570. Author contributions: All authors participated in designing the project and performing the research. S.C.T. and R.D.D. performed the experiments and numerical simulations. All authors participated in writing the paper. The authors declare no competing financial interests.

Attached Files

Published - ncomms10694.pdf

Supplemental Material - ncomms10694-s1.mov

Supplemental Material - ncomms10694-s2.mov

Supplemental Material - ncomms10694-s3.mov

Supplemental Material - ncomms10694-s4.mov

Supplemental Material - ncomms10694-s5.avi

Supplemental Material - ncomms10694-s6.mov

Files

ncomms10694.pdf
Files (33.7 MB)
Name Size Download all
md5:36b3ebeded38752bf969e791e61081be
1.6 MB Download
md5:9019b7204c341acb5f2b799fd57ab55e
4.4 MB Download
md5:df47f2aea118876b3832619ec8e1a95a
12.8 MB Download
md5:569beb0861ff5a607bbf4589cff26919
999.1 kB Download
md5:533e7dd56296ae8ee4fbf7816d0c3ae4
2.0 MB Download
md5:f8fe32f84e88a4c3c48b3b0122403dcc
1.4 MB Preview Download
md5:d3daae63e756d95deae153e889e88d2b
10.5 MB Download

Additional details

Created:
August 20, 2023
Modified:
October 18, 2023