Liquid plug propagation in flexible microchannels: A small airway model.
In the present study, we investigate the effect of wall flexibility on the plug propagation and the resulting wall stresses in small airway models with experimental measurements and numerical simulations. Experimentally, a flexible microchannel was fabricated to mimic the flexible small airways using soft lithography. Liquid plugs were generated and propagated through the microchannels. The local wall deformation is observed instantaneously during plug propagation with the maximum increasing with plug speed. The pressure drop across the plug is measured and observed to increase with plug speed, and is slightly smaller in a flexible channel compared to that in a rigid channel. A computational model is then presented to model the steady plug propagation through a flexible channel corresponding to the middle plane in the experimental device. The results show qualitative agreements with experiments on wall shapes and pressure drops and the discrepancies bring up interesting questions on current field of modeling. The flexible wall deforms inward near the plug core region, the deformation and pressure drop across the plug increase with the plug speed. The wall deformation and resulting stresses vary with different longitudinal tensions, i.e., for large wall longitudinal tension, the wall deforms slightly, which causes decreased fluid stress and stress gradients on the flexible wall comparing to that on rigid walls; however, the wall stress gradients are found to be much larger on highly deformable walls with small longitudinal tensions. Therefore, in diseases such as emphysema, with more deformable airways, there is a high possibility of induced injuries on lining cells along the airways because of larger wall stresses and stress gradients.
Zheng
Y
Y
Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2099, USA.
Fujioka
H
H
Bian
S
S
Torisawa
Y
Y
Huh
D
D
Takayama
S
S
Grotberg
J B
JB
J Appl Physiol (1985). 1995 Nov;79(5):1717-28
8594034
Pediatr Pulmonol. 1988;5(3):132-8
3194153
J Appl Physiol Respir Environ Exerc Physiol. 1977 Sep;43(3):537-44
914724
Am J Physiol. 1997 Nov;273(5):L1013-9
9374729
Am Rev Respir Dis. 1990 Aug;142(2):321-8
2116748
J Appl Physiol (1985). 1994 May;76(5):2095-105
8063673
J Appl Physiol. 1970 Sep;29(3):340-4
5451310
Anal Chem. 1998 Dec 1;70(23):4974-84
21644679
Anesth Analg. 1989 Dec;69(6):805-18
2686493
Respir Physiol. 1970 Jan;8(2):191-203
5413420
Am J Respir Crit Care Med. 2004 Nov 1;170(9):1000-5
15271694
Pediatrics. 1999 Dec;104(6):1229-46
10585972
Am J Respir Crit Care Med. 2000 Aug;162(2 Pt 1):357-62
10934053
J Appl Physiol (1985). 2004 Jul;97(1):269-76
15004001
Lancet. 1999 Apr 10;353(9160):1232-7
10217084
Phys Fluids (1994). 2005;17(3):31502
23745044
Am J Respir Crit Care Med. 1998 Jan;157(1):294-323
9445314
J Appl Physiol (1985). 1997 Jul;83(1):120-8
9216953
J Biomech Eng. 1993 Aug;115(3):271-7
8231142
J Appl Physiol Respir Environ Exerc Physiol. 1982 Jul;53(1):121-5
6288636
J Appl Physiol (1985). 2001 Aug;91(2):589-95
11457769
Am J Respir Crit Care Med. 2002 Mar 15;165(6):781-7
11897644
J Clin Invest. 1997 Mar 1;99(5):944-52
9062352
Eur Respir J. 1997 Sep;10(9):1983-8
9311489
J Biomech Eng. 1995 Aug;117(3):245-53
8618375
N Engl J Med. 2004 Jun 24;350(26):2645-53
15215480
J Biomech Eng. 2004 Oct;126(5):567-77
15648809
Curr Opin Genet Dev. 1994 Jun;4(3):466-71
7522673
Respir Physiol. 1989 Feb;75(2):141-56
2711049
J Appl Physiol (1985). 1990 Jul;69(1):74-85
2394665
J Appl Physiol. 1975 Jun;38(6):1117-25
1141127
J Appl Physiol (1985). 2003 Feb;94(2):770-83
12433851
Annu Rev Biomed Eng. 1999;1:47-72
11701482
J Appl Physiol (1985). 1994 Mar;76(3):1372-7
8005884
J Biomech. 2003 Oct;36(10):1529-53
14499302
J Pediatr. 1991 Apr;118(4 Pt 1):595-605
2007938
Proc Natl Acad Sci U S A. 2007 Nov 27;104(48):18886-91
18006663
J Appl Physiol (1985). 1990 Dec;69(6):2057-61
2077000
Annu Rev Biomed Eng. 2001;3:421-57
11447070
J Appl Physiol (1985). 2005 Feb;98(2):672-9
15448123