Effect of temperature variation on fluid flow across a

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 02 Issue: 11 | Nov-2013, Available @ http://www.ijret.org 207
EFFECT OF TEMPERATURE VARIATION ON FLUID FLOW ACROSS A
Cu–MICA MICROCHANNEL
Harneet KourKhajuria1
, Simranjit Kaur2
, Parveen Lehana3
1
M.tech student, 2
Assistant Professor, Dept. of E&C, SSCET, Badhani, Pathankot, Punjab, India
3
Associate Professor, Dept. of Physics & Electronics, University of Jammu, Jammu, India
harneet.destiny@gmail.com, simran2013@yahoo.com, klehanajournals@gmail.com
Abstract
Microfluidics is a science of fluid mechanics involving micro-scale dimensions. The research in miniaturization of microfluidic
devices and its use for microfluidic applications is increasing exponentially. The success of microfluidics owes to its inherent potential
of influencing other fields such as chemical synthesis, biological analysis, optics, and information technology, etc. Various factors
may affect the microfluidic behavior such as nature of microfluids, surface tension, contact angle, channel shape, temperature,
viscosity, etc. The objective of this paper is to investigate the effect of temperature on microfluidic flow across a Cu–Mica
microchannel. The microchannel was fabricated using a screen printing technique followed by substrate etching. Three different
microfluids namely Ethanol, Methanol, and Chloroform were considered for investigations. The angle of elevation of the
microchannel was maintained constant during all the investigations. The analysis of results showed that the flow rate of microfluids is
temperature and fluid dependent.
Keywords: Cu-Mica Microchannel, Microfluid, Microfluidics, Microfludic Flow.
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1. INTRODUCTION
Microfluidics is considered as an interdisciplinary field in its
adolescence. The success of microfluidics owes to its inherent
potential of influencing other fields such as chemical
synthesis, biological analysis, optics, and information
technology, etc. Microfluidics is defined technically as science
of fluid mechanics studied at micro scale [1]. It is formed by
integration of many parental fields such as molecular biology,
molecular analysis, bio defense, and microelectronics and thus
microfluidics has become the only solution to overcome the
problems associated with development of high resolution and
highly sensitive analytical methods used in microanalysis
purposes [1, 2].
Microfluidics deals with the study of the behavior, precise
control, and the manipulation of fluids constrained to sub-
millimeter scale that is at micro scale [1]. When different
micro-components capable of processing are integrated
together with precisely manipulated small volumes of fluids
preferably varying in range from pico-liter to micro- liter; a
fluidic system is formed at micro scale called microfluidic
system [1-3]. Microfluidic systems possess the ability to carry
out high resolution and sensitive separations and detections
using very small quantities of samples and reagents which
make this system inexpensive requiring short time analysis
[1]. Microfluidic devices essentially contain one or more
microchannels of dimensions not greater than 1mm to perform
fluid analysis at micro domains [1, 2]. Most of microscale
investigations of fluids are carried out using flow injection
analysis as discussed in the succeeding section.
1.1 Flow Injection Analysis
Flow injection analysis (FIA) is a continuous flow technique
used for chemical analysis using syringes. It provides a precise
and good analytical performance with high reproducibility and
sensitivity. Faster and high throughput analysis can be
obtained at low costs using FIA techniques. Microfluidic
devices are more advantageous than simple fluidic analysis
since they require very small amount of reagents and
chemicals which makes the analysis scalable to faster and high
throughput oriented analysis [1-3].
The paper is divided into various sections. Dynamics of fluidic
flow includes introduction to various parameters essential for
microfluidic analysis such as surface tension, contact angle,
and viscosity as discussed in Section 2. Section 3 describes the
methodology involved for proposed investigations followed
by results and discussions in Section 4. Conclusions are drawn
in Section 5.
2. DYNAMICS OF FLUIDIC FLOW
The important factors affecting dynamics of microfluidic flow
are surface tension, contact angle, and viscosity. These are
described as follows.

__________________________________________________________________________________________
2.1 Surface Tension
It is a contractive tendency of a liquid which allows it to resist
an external acting force. Since the behavior of the liquid
depends on cohesion forces acting between similar molecules,
it has the dimension of force per unit length or energy per unit
area [4, 5]. The capillary action achieved is termed as perfect
capillary action theoretically, when the gas pressure of fluid
nearly equals the atmospheric pressure acting on the open end
of channel [4, 5]. The increase in capillary forces with time
depends on channel aspect ratio. Higher the aspect ratio of the
micro channel, faster is the displacement and this leads to
increase of capillary forces with time [5]. The surface tension
is determined by equation [4, 6] as follows:
2
2
U
γ
δ
=
Where γ is surface tension (N/m), u is average cohesive energy
of a molecule, δ is characteristic dimension of a molecule and
δ2
represents the effective surface area of molecule.
Total energy (E) stored in the interface is [6] given as
E Sγ=
Where S is total surface area of the interface
2.2 Contact Angle
Contact angle is an important parameter in slug formation
process and wall adhesion equations. It is used to determine
the shape of the fluid interface. It is calculated using Young’s
modulus law [7]. The capillary flow requires the maintenance
of surface tension equilibrium which further can be achieved
by varying the contact angle. The contact angle at a point of
intersection of three interfaces is obtained by balancing the
surface tensions at each interface. The range of contact angle
is used to classify surfaces as wetting (hydrophilic) and non-
wetting (hydrophobic). The wetting surfaces include the
contact angle range as 0≤θ<900
where as the range of
900
≤θ≤1800
refers to non-wetting surfaces [6, 7]. The contact
angle is given as.
LG SG SL
COSγ θ γ γ= −
Fig.-1: Young’s contact angle configuration [7].
The interaction of gas and liquid phases with the channel wall
can be determined by specifying the contact angle which also
affects their shape, size as well as velocity [7, 8]. There are
different factors that can influence a contact angle. These
factors are surface topography, liquid purity, equilibration
time, temperature, surface impurities, sessile drop size as well
as thermodynamic stabilities [6, 7, 8]. The effect of
temperature changes on contact angle holds an important
consideration in microfluidic analysis. It is a deterministic
factor to acquire desired précised results of applications for
which the microfluidic system is designed. However in case of
liquids, surface tension of liquids is observed to be more
sensitive to effects of temperature changes [9]. Sessile drop
size is another factor that affect contact angle [9]. Capillary
length is a parameter that determines the maximum size of the
droplet allowed to flow across a microchannel and is given as.
1
2
1 L
L gK
γ
ρ
 
=   
 
Where L is density of liquid and 1/k is the capillary length
[10].
2.3 Viscosity
The property of fluid which poses a friction or internal
resistance to the flow of fluid is termed as the viscosity. The
fluids with low viscosity are faster flowing as compared to
highly viscous fluids. The choice of microfluids for proposed
investigations owes to their properties and applications in
various fields such as bio-medicinal research [11, 12, 13], bio-
detections [14, 15, 16] and industrial applications [12, 16, 17].
A few of these characteristics are described in Table1.
Table.-1: Fluid Characteristics.

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3. METHODOLOGY
The methodology for proposed investigations to study effect
of temperature on fluid flow across a Cu-Mica microchannel is
divided into three stages: Cu-Mica microchannel fabrication,
pattern etching, and temporal FIA.
Stage 1: Cu-Mica microchannel fabrication
A Cu-Mica microchannel of channel length 3.6 cm is
fabricated using screen printing fabrication method. The shape
of this Cu-Mica microchannel is chosen as ‘Y’ shaped
designed using coral draw and fabricated on Mica base with
Copper as boundaries. The channel width is fixed as 1 mm.
The microchannel pattern is transferred to Cu-Mica board.
Stage 2: Pattern etching
The microchannel patterned substrate is subjected to etching
in which unwanted Copper from substrate is removed from
unexposed areas leaving behind the Cu microchannel on Mica
base. The etchant used is Ferric Chloride solution prepared in
the ratio of 3:1 with water in a plastic tray stirring
continuously using a glass rod. The complete etching took 12-
15 minutes. After the pattern is etched completely the
substrate is washed under running water and then swab
coating of substrate using acetone was done to ensure the dirt
free channel fabrication for FIA. The etched pattern used for
FIA to carry out proposed investigations is as shown in Fig. 2.
Fig.-2: Etched Cu-mica microchannel.
Stage 3: Temporal FIA
The proposed investigations were accomplished using three
fluids- Ethanol, Methanol, and Chloroform. These fluids are
taken in three metal syringes separately and then made to flow
across a Cu–Mica microchannel fixed at 450 angle of
elevation and flow injection analysis is made by raising the
temperature from room temperature to two different
temperatures 400 and 500. The flow of these fluids at different
temperature and fixed elevation angle of channel is observed
and recorded using a digital movie camera. The temperature of
micro channel is raised using an IR lamp set up as shown in
Fig. 3. For convenience of representation, the unit second
represents centisecond in all the measurements in this paper.
Fig.-3: IR set up
4. RESULTS AND DISCUSSIONS
The results obtained from the analysis of video clips of the
microfluids flow in the Cu-Mica microchannel are listed in
Table II and plotted in Fig. 4 and Fig. 5. Flow time of fluids at
different temperatures (Fig. 4) shows that flow time of
chloroform is less as compared to Ethanol and Methanol.
Ethanol takes comparatively more time to flow across the
microchannel even at higher temperature. At higher
temperature Chloroform flow is more streamline and that of
Ethanol is irregular.
At room temperature all the fluids – Ethanol, Methanol, and
Chloroform flow in a laminar way, i.e., stream lined flow is
observed. Flow rate varies with the fluid used, Chloroform is
the fastest fluid followed by Methanol, and then Ethanol in
terms of speed of the flow.
At higher temperatures the flow pattern is irregular in case of
Methanol and Ethanol but the flow pattern of Chloroform
remains stream line or laminar. The speed of all fluids is
higher as compared to the flow rate observed at room
temperature.
Table 2 Effect of Temperature Change on Fluid Flow
Microfluid Time (s)
for Temperature
Speed (cm/s)
for Temperature
300
C 400
C 500
C 300
C 400
C 500
C
Ethanol 0.07
0
0.05
0
0.04
0
51.43 72.00 90.00
Methanol 0.04
0
0.03
0
0.02
0
90.00 120.0
0
180.0
0
Chlorofor
m
0.02
5
0.02
0
0.01
0
144.0
0
180.0
0
360.0
0

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Fig.-4: Flow time at different temperatures.
The flow time for all liquids reduces with increase in
temperature. Chloroform takes very less time to flow across
channel at 500
C and maximum flow time at room temperature
i.e. 300
C. Ethanol takes maximum time to flow across the
channel at 300
C and minimum flow time at 500
C. Flow time
for methanol is maximum at 300
C and minimum at 500
C.
Velocity plot for all three liquids (Fig. 5) shows that the
velocity of liquids flowing across the microchannel is
temperature dependent The velocity of all liquids increases
with increase in temperature. Chloroform is fastest among
Methanol and Ethanol with maximum velocity at 500
C and
minimum at room temperature i.e. 300
C. Calculated
temperature gradient of velocity at different temperatures is
listed in Table III. It is observed that it decreases for Ethanol
but increases for both Methanol and Chloroform. The
investigations showed that the fluid can be identified
automatically on the basis of microchannel flow rate and
hence, the results may be very useful for developing
microchannel based fluid sensors.
Fig 5 Velocity at different temperatures
The temperature gradient of velocity at different temperatures
is given below in Table 3.
Table 3 Temperature Gradient of Velocity
Microfluid Temperature gradient of velocity at
temperature (cm/s0
C)
300
C 400
C
Ethanol 2.1 1.8
Methanol 3.0. 6.0
Chloroform 3.6 18
CONCLUSIONS
Investigations were carried out to study the effect of
temperature on the flow of Ethanol, Methanol, and
Chloroform in a microchannel. It was observed that as the
temperature increases to a higher value the flow pattern of
Methanol and Ethanol becomes irregular as compared to
regular flow shown by Chloroform. At higher temperature the
speed of each fluid is more than that observed at room
temperature. Thus fluid flow rate varies with changes in
temperature. Higher the temperature faster is the speed of fluid
flow across the microchannel. At high temperature the flow
pattern transits from streamline to turbulent flow except for
Chloroform. The investigations showed that the fluid can be
identified automatically on the basis of flow analysis and
hence, the results may be very useful for developing
microchannel based fluid sensors.
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