[�5�]� �H�.� �N�o�g�u�c�h�i� �a�n�d� �G�.� �G�o�m�p�p�e�r�,� �P�N�A�S� �1�0�2�,� �1�4�1�5�9� �(�2�0�0�5�)�.��[�6�]� �J�.� �L�.� �M�c�W�h�i�r�t�e�r�,� �H�.� �N�o�g�u�c�h�i�,� �a�n�d� �G�.� �G�o�m�p�p�e�r�,� �P�N�A�S��1�0�6�,� �6�0�3�9� �(�2�0�0�9�)�.��[�7�]� �H�.� �N�o�g�u�c�h�i�,� �e�t� �a�l�. �E�P�L� �8�9�,� �2�8�0�0�2� �(�2�0�1�0�)�.

Simple shear flow [1-4]Fluid vesicles exhibit transitions of their shapes and dynamics modes.Elongational transitions (from discocyte, stomatotye, or buded shape to prolate )and shrinking transition (prolate to discocyte) are found.

Capillary flow [5-7]As flow velocity increases, shear-elastic vesicles transit from a non-axisymmetric discocyte to an axisymmetric parachute shape, while fluid vesiclestransit from a discocyte to a prolate ellipsoid.In dense suspensions, the hydrodynamic interacitions induce orderedalignmens: single-file parchute and two-file.

CONCLUSION

[1] H. Noguchi and G. Gompper, Phys. Rev. Lett. 93, 258102 (2004).[2] H. Noguchi and G. Gompper, Phys. Rev. E 72, 011901 (2005).[3] H. Noguchi and G. Gompper, Phys. Rev. Lett. 98, 128103 (2007).[4] H. Noguchi, J. Phys. Soc. Jpn. 78, 041007 (2009).

Dynamics of Red Blood Cells and Fluid Vesicle in flows

Red blood cells and lipid vesicles exhibit rich behaviors in flows. We have studied their dynamics using a particle-based hydrodynamic simulationmethod, multi-particle collision (MPC) dynamics. Several transitions of their shapes and dynamic modes are discovered. In simple shear flow, threetypes of dynamic modes, tank-treading, tumbling, swinging, occur. They are coupled with shape deformation. In capillary flow, shape transition to para-chute shape and alignments of cells are observed. These results show good agreement with experiments.

capillary flow

!

/kBT R0 /kBT2bending modulus shear modulus

Linear dependence of transition velocities vm.(a) fluid and shear-elastic vesicles at R0 /kBT=112.(b) shear-elastic vesicles at /kBT=10.

c2

v m 0

/Rca

pc

!v m

0 /R

cap

c

0

100

0 500 10000

100

200

0 20 40

shear-elasticvesicle

fluidvesicle

discocyteto parachute

parachuteto discocyte

(a) (b)

Hiroshi Noguchi1 and Gerhard Gompper21Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan2Institut für Festkörperforschung, Forschungszentrum Jülich, 52425, Jülich, Germany

noguchi@issp.u-tokyo.ac.jp

"

t /!0

0.5

1

20 40time

asph

erec

ity

Lipid vesicle in simple shear flow

Stomatocyte to pro late

s m a l l s h e a r

l a r g e s h e a r

s t o m a t o c y t e

p r o l a t e

Red blood cel lsin glass capi l laryt s u k a d a e t a l .M i c r o v a s c . R e s . 6 1 , 2 3 1 ( 2 0 0 1 ) .

sp

-0.5

0

0.5

0 50 100

0

0.2

0.4

t/ !

#/$

%!=0.92.

shear jump

%!=3.68.

"sp

0

0.5

1

t/!

"#/$

-0.5

0

0.5

0 50 100

spprolate(rod-like)

discocyte(red-blood-cell shape)

tank-treadingprolate

tumblingbuddedvesicle

Prolate to d iscocyteDashed l ines: s impletheoret ica l model

Budded vesic le to pro late( tumbl ing) ( tank- t reading)

mean pressure gragient

mea

n di

stan

ce b

etw

een

cellsIsolated fluid vesicle

Vesicle with shear elasticity

slow flow fast flow

slow flow fast flow

Red blood cel lsin microvesselS k a l a k e t a l . S c i e n c e 1 6 4 , 7 1 7 ( 1 9 6 9 ) .

Slipper in zigzag alignment

Parachute in single file alignment

Discocyte in random order

Discocyte

Slipper

Parachute

Dense system (L.J. McWhirter)

0

2

4

6

0 100 200

mean flow rate vm!0/Rcap

pres

sure

dro

p pe

r ves

icle

&

P ves

/Rca

p/v m

'0

shear-elasticvesicle

prolate

discocyte

parachute

fluid vesicle