Collective motion of reciprocating self-propelled colloidal - - PowerPoint PPT Presentation

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Nov 11, 2022 329 likes •405 views

Collective motion of reciprocating self-propelled colloidal particles Airi KATO (Sano lab. U. Tokyo) 8th July, 2016@RIKEN-Osaka-OIST Joint Workshop 2016 H. Wioland et al, Phys. Rev. Lett. 110 268102 (2013). 1/15 Deseigne, et al. Phys. Rev.

SLIDE 1

Collective motion of reciprocating self-propelled colloidal particles

Airi KATO (Sano lab. U. Tokyo) 8th July, 2016@RIKEN-Osaka-OIST Joint Workshop 2016

SLIDE 2

Self-propelled particle: motivation

1/15

fish school

H. Wioland et al, Phys. Rev. Lett. 110 268102 (2013).

Bacterial suspension

Deseigne, et al. Phys. Rev. Lett.105, 098001 (2010).

bird flock

Vibrated disks

SLIDE 3

Experimental Setup: colloidal particles rolling on a electrode

ITO coated slides double-sided tapes 30μm

Electric field a few mm of droplet

microscope

high speed camera

suspension: colloidal particles ( polystyrene, Φ5μm) + AOT / hexadecane 0.15 mol/l

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How is the mechanism of propulsion?

SLIDE 4

Rolling mechanism: the Quincke effect

https://de.wikipedia.org/wiki/Georg_Hermann_Quincke

Original paper: G. Quincke, Ann. Phys. Chem. 59, 417-486 (1896).

Charge relaxation time

N. Pannacci et al., Phys. Rev. Lett. 99, 094503(2007).

unstable stable

Electric torque

G. Quincke

=(dielectric constant)/(conductivity) (dielectric) surpass the viscous torque in

start to rotate!

(instantaneous) (viscous torque) (electric torque) induced by the surface charge

steady stable sol.: steady rotation 3/15

SLIDE 5

Properties of Quincke rollers

➤ relax in 1ms and then constant speed

typical speed:
cf. speed of bacteria

⚠ NOT electrophoresis. Always external field ⊥ propelling direction ✓easy preparation ✓easy to control propulsion speed ✓relaxation time to steady state is small

uniformly ramdom in 2D plane

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SLIDE 6

➤ Other slides are deleted (unpulblished).