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Emergence of reconfigurable wires and spinners via dynamic self-assembly.

Kokot G, Piet D, Whitesides GM, Aranson IS, Snezhko A - Sci Rep (2015)

Bottom Line: The energy injection rate, and properties of the environment are important control parameters that influence the outcome of dynamic self-assembly.The spinners emerge via spontaneous breaking of the uniaxial symmetry of the energizing magnetic field.Demonstration of the formation and disaggregation of particle assemblies suggests strategies to form new meso-scale structures with the potential to perform functions such as mixing and sensing.

View Article: PubMed Central - PubMed

Affiliation: Complex Matter Department, Jozef Stefan Institute, Jamova 39, 1000 Ljubliana, Slovenia.

ABSTRACT
Dissipative colloidal materials use energy to generate and maintain structural complexity. The energy injection rate, and properties of the environment are important control parameters that influence the outcome of dynamic self-assembly. Here we demonstrate that dispersions of magnetic microparticles confined at the air-liquid interface, and energized by a uniaxial in-plane alternating magnetic field, self-assemble into a variety of structures that range from pulsating clusters and single-particle-thick wires to dynamic arrays of spinners (self-assembled short chains) rotating in either direction. The spinners emerge via spontaneous breaking of the uniaxial symmetry of the energizing magnetic field. Demonstration of the formation and disaggregation of particle assemblies suggests strategies to form new meso-scale structures with the potential to perform functions such as mixing and sensing.

No MeSH data available.


Hydrodynamic surface flow generated by self-assembled dynamic spinners.(a),(b) Magnitude of the hydrodynamic flow velocity generated by spinners at the air-liquid interface at time t1 = 6.88 s and t2 = 18.28 s respectively. The system was energized for 4 minutes before the start of the image acquisition in a fully developed spinner phase. Flow velocity fields were obtained by a particle-image velocimetry (PIV), see Methods. The in-plane applied alternating magnetic field is 29 Oe, 70 Hz. Scale bar is 2 mm. (c) A typical streamline pattern of hydrodynamic surface flows. The data was collected for spinners generated at 29 Oe, 70 Hz applied field. Spinners produce a complex time dependent vorticity distribution at the liquid interface. Scale bar is 2 mm. (d) Space-time diagram of the flow vorticity field along a fixed slice of the system shown as a dashed line in (b). The time interval spans 40 s and includes 200 slices. Spinners, advected by the flow, create rapidly changing flow velocity fields at the liquid interface. Domains of fast/slow flow appear as short red and blue dashes in the space-time plot. Slope of red/blue dashed lines characterizes advection velocity of the spinners. Scale bar is 2 mm. (e) Average spinner size as a function of frequency of the applied in-plane magnetic field. Solid line is a fit to the L log−1/2 (L/a) ~ω−1/2 law following from the balance between magnetic and hydrodynamics torques. Here L is a spinner length, a is a particle diameter. The data was collected for 29 Oe amplitude of the applied magnetic field.
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f3: Hydrodynamic surface flow generated by self-assembled dynamic spinners.(a),(b) Magnitude of the hydrodynamic flow velocity generated by spinners at the air-liquid interface at time t1 = 6.88 s and t2 = 18.28 s respectively. The system was energized for 4 minutes before the start of the image acquisition in a fully developed spinner phase. Flow velocity fields were obtained by a particle-image velocimetry (PIV), see Methods. The in-plane applied alternating magnetic field is 29 Oe, 70 Hz. Scale bar is 2 mm. (c) A typical streamline pattern of hydrodynamic surface flows. The data was collected for spinners generated at 29 Oe, 70 Hz applied field. Spinners produce a complex time dependent vorticity distribution at the liquid interface. Scale bar is 2 mm. (d) Space-time diagram of the flow vorticity field along a fixed slice of the system shown as a dashed line in (b). The time interval spans 40 s and includes 200 slices. Spinners, advected by the flow, create rapidly changing flow velocity fields at the liquid interface. Domains of fast/slow flow appear as short red and blue dashes in the space-time plot. Slope of red/blue dashed lines characterizes advection velocity of the spinners. Scale bar is 2 mm. (e) Average spinner size as a function of frequency of the applied in-plane magnetic field. Solid line is a fit to the L log−1/2 (L/a) ~ω−1/2 law following from the balance between magnetic and hydrodynamics torques. Here L is a spinner length, a is a particle diameter. The data was collected for 29 Oe amplitude of the applied magnetic field.

Mentions: Spinners move (seemingly randomly) due to magnetic interactions and the flows generated by other spinners. Their collective motion creates an overall gas-like appearance of the phase (see Supplementary Video 2). The structure of each spinner is not fixed. Spinners collide, disintegrate and reassemble, and thus create complex time-dependent hydrodynamic patterns at the interface. The hydrodynamic surface flows generated by spinners have been characterized by particle-image velocimetry (Methods). Fig. 3a,b shows snapshots of the velocity field for the same system at two different times.


Emergence of reconfigurable wires and spinners via dynamic self-assembly.

Kokot G, Piet D, Whitesides GM, Aranson IS, Snezhko A - Sci Rep (2015)

Hydrodynamic surface flow generated by self-assembled dynamic spinners.(a),(b) Magnitude of the hydrodynamic flow velocity generated by spinners at the air-liquid interface at time t1 = 6.88 s and t2 = 18.28 s respectively. The system was energized for 4 minutes before the start of the image acquisition in a fully developed spinner phase. Flow velocity fields were obtained by a particle-image velocimetry (PIV), see Methods. The in-plane applied alternating magnetic field is 29 Oe, 70 Hz. Scale bar is 2 mm. (c) A typical streamline pattern of hydrodynamic surface flows. The data was collected for spinners generated at 29 Oe, 70 Hz applied field. Spinners produce a complex time dependent vorticity distribution at the liquid interface. Scale bar is 2 mm. (d) Space-time diagram of the flow vorticity field along a fixed slice of the system shown as a dashed line in (b). The time interval spans 40 s and includes 200 slices. Spinners, advected by the flow, create rapidly changing flow velocity fields at the liquid interface. Domains of fast/slow flow appear as short red and blue dashes in the space-time plot. Slope of red/blue dashed lines characterizes advection velocity of the spinners. Scale bar is 2 mm. (e) Average spinner size as a function of frequency of the applied in-plane magnetic field. Solid line is a fit to the L log−1/2 (L/a) ~ω−1/2 law following from the balance between magnetic and hydrodynamics torques. Here L is a spinner length, a is a particle diameter. The data was collected for 29 Oe amplitude of the applied magnetic field.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4374141&req=5

f3: Hydrodynamic surface flow generated by self-assembled dynamic spinners.(a),(b) Magnitude of the hydrodynamic flow velocity generated by spinners at the air-liquid interface at time t1 = 6.88 s and t2 = 18.28 s respectively. The system was energized for 4 minutes before the start of the image acquisition in a fully developed spinner phase. Flow velocity fields were obtained by a particle-image velocimetry (PIV), see Methods. The in-plane applied alternating magnetic field is 29 Oe, 70 Hz. Scale bar is 2 mm. (c) A typical streamline pattern of hydrodynamic surface flows. The data was collected for spinners generated at 29 Oe, 70 Hz applied field. Spinners produce a complex time dependent vorticity distribution at the liquid interface. Scale bar is 2 mm. (d) Space-time diagram of the flow vorticity field along a fixed slice of the system shown as a dashed line in (b). The time interval spans 40 s and includes 200 slices. Spinners, advected by the flow, create rapidly changing flow velocity fields at the liquid interface. Domains of fast/slow flow appear as short red and blue dashes in the space-time plot. Slope of red/blue dashed lines characterizes advection velocity of the spinners. Scale bar is 2 mm. (e) Average spinner size as a function of frequency of the applied in-plane magnetic field. Solid line is a fit to the L log−1/2 (L/a) ~ω−1/2 law following from the balance between magnetic and hydrodynamics torques. Here L is a spinner length, a is a particle diameter. The data was collected for 29 Oe amplitude of the applied magnetic field.
Mentions: Spinners move (seemingly randomly) due to magnetic interactions and the flows generated by other spinners. Their collective motion creates an overall gas-like appearance of the phase (see Supplementary Video 2). The structure of each spinner is not fixed. Spinners collide, disintegrate and reassemble, and thus create complex time-dependent hydrodynamic patterns at the interface. The hydrodynamic surface flows generated by spinners have been characterized by particle-image velocimetry (Methods). Fig. 3a,b shows snapshots of the velocity field for the same system at two different times.

Bottom Line: The energy injection rate, and properties of the environment are important control parameters that influence the outcome of dynamic self-assembly.The spinners emerge via spontaneous breaking of the uniaxial symmetry of the energizing magnetic field.Demonstration of the formation and disaggregation of particle assemblies suggests strategies to form new meso-scale structures with the potential to perform functions such as mixing and sensing.

View Article: PubMed Central - PubMed

Affiliation: Complex Matter Department, Jozef Stefan Institute, Jamova 39, 1000 Ljubliana, Slovenia.

ABSTRACT
Dissipative colloidal materials use energy to generate and maintain structural complexity. The energy injection rate, and properties of the environment are important control parameters that influence the outcome of dynamic self-assembly. Here we demonstrate that dispersions of magnetic microparticles confined at the air-liquid interface, and energized by a uniaxial in-plane alternating magnetic field, self-assemble into a variety of structures that range from pulsating clusters and single-particle-thick wires to dynamic arrays of spinners (self-assembled short chains) rotating in either direction. The spinners emerge via spontaneous breaking of the uniaxial symmetry of the energizing magnetic field. Demonstration of the formation and disaggregation of particle assemblies suggests strategies to form new meso-scale structures with the potential to perform functions such as mixing and sensing.

No MeSH data available.