Density and Shape Effects in the Acoustic Propulsion of Bimetallic Nanorod Motors

Suzanne Ahmed, Wei Wang, Lanjun Bai, Dillon T. Gentekos, Mauricio Hoyos, Thomas E. Mallouk

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Bimetallic nanorods are propelled without chemical fuels in megahertz (MHz) acoustic fields, and exhibit similar behaviors to single-metal rods, including autonomous axial propulsion and organization into spinning chains. Shape asymmetry determines the direction of axial movement of bimetallic rods when there is a small difference in density between the two metals. Movement toward the concave end of these rods is inconsistent with a scattering mechanism that we proposed earlier for acoustic propulsion, but is consistent with an acoustic streaming model developed more recently by Nadal and Lauga (Phys. Fluids 2014, 26, 082001). Longer rods were slower at constant power, and their speed was proportional to the square of the power density, in agreement with the acoustic streaming model. The streaming model was further supported by a correlation between the disassembly of spinning chains of rods and a sharp decrease in the axial speed of autonomously moving motors within the levitation plane of the cylindrical acoustic cell. However, with bimetallic rods containing metals of different densities, a consistent polarity of motion was observed with the lighter metal end leading. Speed comparisons between single-metal rods of different densities showed that those of lower density are propelled faster. So far, these density effects are not explained in the streaming model. The directionality of bimetallic rods in acoustic fields is intriguing and offers some new possibilities for designing motors in which shape, material, and chemical asymmetry might be combined for enhanced functionality.

Original languageEnglish (US)
Pages (from-to)4763-4769
Number of pages7
JournalACS Nano
Volume10
Issue number4
DOIs
StatePublished - Apr 26 2016

Fingerprint

propulsion
Nanorods
Propulsion
nanorods
Acoustic streaming
rods
Acoustics
Metals
acoustics
Acoustic fields
acoustic streaming
metals
metal spinning
chemical fuels
asymmetry
Scattering
levitation
Fluids
radiant flux density
polarity

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

Cite this

Ahmed, S., Wang, W., Bai, L., Gentekos, D. T., Hoyos, M., & Mallouk, T. E. (2016). Density and Shape Effects in the Acoustic Propulsion of Bimetallic Nanorod Motors. ACS Nano, 10(4), 4763-4769. https://doi.org/10.1021/acsnano.6b01344
Ahmed, Suzanne ; Wang, Wei ; Bai, Lanjun ; Gentekos, Dillon T. ; Hoyos, Mauricio ; Mallouk, Thomas E. / Density and Shape Effects in the Acoustic Propulsion of Bimetallic Nanorod Motors. In: ACS Nano. 2016 ; Vol. 10, No. 4. pp. 4763-4769.
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Ahmed, S, Wang, W, Bai, L, Gentekos, DT, Hoyos, M & Mallouk, TE 2016, 'Density and Shape Effects in the Acoustic Propulsion of Bimetallic Nanorod Motors', ACS Nano, vol. 10, no. 4, pp. 4763-4769. https://doi.org/10.1021/acsnano.6b01344

Density and Shape Effects in the Acoustic Propulsion of Bimetallic Nanorod Motors. / Ahmed, Suzanne; Wang, Wei; Bai, Lanjun; Gentekos, Dillon T.; Hoyos, Mauricio; Mallouk, Thomas E.

In: ACS Nano, Vol. 10, No. 4, 26.04.2016, p. 4763-4769.

Research output: Contribution to journalArticle

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Ahmed S, Wang W, Bai L, Gentekos DT, Hoyos M, Mallouk TE. Density and Shape Effects in the Acoustic Propulsion of Bimetallic Nanorod Motors. ACS Nano. 2016 Apr 26;10(4):4763-4769. https://doi.org/10.1021/acsnano.6b01344