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M. Arif et al.
b
slip length of fluid
P
pressure
P a
atmospheric pressure
P c
cavitation pressure
P n
dimensionless pressure ((P − P c )/P a )
U
velocity of moving surface
N
number of revolutions per minute
μ
dynamic viscosity of lubricants
α
dimensionless speed
6μU R/c
2
r
g
switch function
φ
fractional film content
β
bulk modules of fluid
β
dimensionless bulk modules of fluid (β/P a )
x
co-ordinate along bearing circumference
z
co-ordinate along bearing length
y
co-ordinate along lubricant film thickness
θ
angular co-ordinate along bearing circumference
Z
dimensionless co-ordinate along bearing length
w
load carrying capacity
W
dimensionless load carrying capacity (w/P a RL z )
Nt θ number of textures along θ direction of bearing
Nt z umber of textures along Z direction of bearing
γ
slip zone coefficient along θ direction of bearing
λ
slip zone coefficient along Z direction of bearing.
1 Introduction
Micro-electro-mechanical systems (MEMS) have undergone significant development over the last two decades with researchers fabricating a variety of miniaturized devices with dimensions ranging from a couple to a few thousand microns.
Many MEMS contain (sliding/rotating) surfaces and thus effective lubrication of
these devices is important to reduce friction [1]. The use of wettable surfaces for
lubrication purpose in MEMS causes high friction forcer as compared to applied
external force. It has been found experimentally [2] that conventional no-slip condition not valid for non-wettable surface. This disagreement with no-slip condition for
non-wettable surfaces provides an effective way to reduce friction force in MEMS
devices. The work performed by Spikes [3, 4] has shown the advantages of nonwettable surface in MEMS device applications. Fortier et al. [5, 6] used modified
Reynolds equation to investigate the effect of slip on slider and journal bearing.
They observed significant improvement in load carrying capacity and friction reduction on heterogeneous wettable/non-wettable (slip/no-slip) surfaces. Experimental
work performed by Choo et al. [7] also agrees with the result of numerical analysis
M. Arif et al.
b
slip length of fluid
P
pressure
P a
atmospheric pressure
P c
cavitation pressure
P n
dimensionless pressure ((P − P c )/P a )
U
velocity of moving surface
N
number of revolutions per minute
μ
dynamic viscosity of lubricants
α
dimensionless speed
6μU R/c
2
r
g
switch function
φ
fractional film content
β
bulk modules of fluid
β
dimensionless bulk modules of fluid (β/P a )
x
co-ordinate along bearing circumference
z
co-ordinate along bearing length
y
co-ordinate along lubricant film thickness
θ
angular co-ordinate along bearing circumference
Z
dimensionless co-ordinate along bearing length
w
load carrying capacity
W
dimensionless load carrying capacity (w/P a RL z )
Nt θ number of textures along θ direction of bearing
Nt z umber of textures along Z direction of bearing
γ
slip zone coefficient along θ direction of bearing
λ
slip zone coefficient along Z direction of bearing.
1 Introduction
Micro-electro-mechanical systems (MEMS) have undergone significant development over the last two decades with researchers fabricating a variety of miniaturized devices with dimensions ranging from a couple to a few thousand microns.
Many MEMS contain (sliding/rotating) surfaces and thus effective lubrication of
these devices is important to reduce friction [1]. The use of wettable surfaces for
lubrication purpose in MEMS causes high friction forcer as compared to applied
external force. It has been found experimentally [2] that conventional no-slip condition not valid for non-wettable surface. This disagreement with no-slip condition for
non-wettable surfaces provides an effective way to reduce friction force in MEMS
devices. The work performed by Spikes [3, 4] has shown the advantages of nonwettable surface in MEMS device applications. Fortier et al. [5, 6] used modified
Reynolds equation to investigate the effect of slip on slider and journal bearing.
They observed significant improvement in load carrying capacity and friction reduction on heterogeneous wettable/non-wettable (slip/no-slip) surfaces. Experimental
work performed by Choo et al. [7] also agrees with the result of numerical analysis