# FLUID DYNAMICS & MICRO-FLUIDIC MIXING USING MICRO-CHANNELS IN

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24 Οκτ 2013 (πριν από 5 χρόνια και 3 μήνες)

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FLUID DYNAMICS &
MICRO
-
FLUIDIC MIXING USING

MICRO
-
CHANNELS IN
HIGH SCHOOL SC
I
ENCE AND MATH
EMATICS
.

Jason Bledsoe

Pullman High School

Pullman, WA

&

Jon
athan

Heflick

Lewis
-
Clark State College

Lewiston, ID

Washington State University Mentors

Dr. Prashanta
Dutta

Mechanical Engineering

&

Nazmul Huda

July 2006

The project herein was supported by the National Science Foundation Grant
#

EEC
-
0338868:
Dr. R
ichard
L
. Zollars, Principal Investigator and Dr. Donald C. Orlich, co
-
PI. The module
was developed by the authors and does not necessarily represent an official endorsement by the
National Science Foundation.

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Summary

This module attempts to enhance student under
stan
ding of

fluid dynamics using the context of
the emerging discipline of micro
-
fluidic mi
xing

and “Lab
-
on
-
a
-
Chi
p” fluid analysis

technology
.
Students will explore the basics of fluid dynamics before attempting to

tackle the more
sophisticated concepts of micro
-
flu
id
ics and nanotechnology.

Intended Audience

This module is intended for use in a 9
th

cience course or equivalent level general
science class. The labs

are intended to be adapted for teaching mathematica
l applications in
basic

algebra, and are
scalable up to the high school p
hysics level

in science and algebra II level
in mathematics
.

Est
imated Duration

The duration for this module is
just under three weeks, incorporating
seven

100

minute class
periods

or 12
-
14 standard 55 minute sessions
.

A brief summary of the project follows:

Session 1

Introduction to fluid dynamics presentation/discus
sion

-
Fluid Flow Worksheet

Session

2

Introduction to fluid dynamics

II

M
athematical applications.

-
Unit of Measure and Capillary Action worksheets

Session

3

Fluid Dynamics Lab #1

Viscosity and rate of flow.

-
Stokes’ Law Worksheet

Session

4

Fluid Dy
namics Lab #2

Stoke’s Law
.

Session

5

Micro

fluidic Mixing Presentation.

-
Macro to Micro Worksheet.

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-
Start Fluid Dynamics Lab #3

microchannels.

Session 6

Complete microchannel lab. Unit review

Session 7

Assessment

Introduction

S
urveys indicate that s
t
udents in middle and high school
typically
do not have enough
information to thoroughly con
sider engineering as a career.
As

teachers
, we

are
less likely

to
stimulate interest
if we have not

ies

engineering.
Beyond career
consi
derations, understanding engineering is important so that citizens can make informed
decisions about the impact of technology on society.
So as to improve the learning curve across
the board,
Washington State University, with funding from the National Scie
nce Foundation,
conducts a 6
-
week, hands
-
on engineering program
that
serves

to

familiarize
middle and high
school
teachers with engineering processes, which they
can
then carry into their classrooms in
the form of comprehensive
, in
-
depth

learning modules

(
SWEET
, 2006
)
. The goal of
the program

is to develop teachers who
are

prepared and committed to

nurture

student
-
interest in
the
sustained
study and application of
various forms of
engineering
.

This module
represents

one
product of that effort.

A Brief
Histo
ry of Fluid
Mechanics

Fluid mechanics owes its development to
numerous

minds

but
in

part
icular is

indebted to the
work of Isaac Newton, Leonard Euler, and Ludwig Prandtl.
Newton

s contr
ibutions include t
he
development of calculus and the fundamental laws o
f physics.

H
is name is also attached to the
linear stress
-
rate of strain
, which in conjunction with

Newton's 2nd Law
facilitated the Navier
-
Stokes equations

that
provide

the modern
basis

of fluid mechanic
s
.
Euler introduced the idea of a
material partic
le

to the study of fluid mechanics, as well as the classical differential element of
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material on which forces act.
With

these discoveries the mo
tion of fluids
was

no longer limited
to endless exercises in geometry or physical reasoning but for the first time
could be analyzed
quantitative
ly
.

Lu
dwig Prandtl's contributions
include his development of
aerodynamic
lifting
line theory
and his work in turbulence
.
H
is discovery of the boundary layer is regarded as one of
the most important breakthroughs

in fluid mech
anics of all time,
earn
ing

him

the title of Father
of Modern Fluid Mecha
nics (Cramer, 2004).

Current Application

of Fluid Mechanics

Fluid
mechanics

has a wide range of
modern

applications, including calculating forces and
moments on aircraft, determining
the mass flow rate of petroleum through pipelines, and
predicting weather patterns. Some of its principles are even used in traffic engineering, where
traffic is treated as a continuous fluid. Fluid dynamics
problems
typically consider various
properties o
f a fluid, such as surface tension and viscosity, and calculate for
flow
variables such
as
volume,
velocity, pressure, temperature, and density

as functions of space and time
(
Fluid
Dynamics
, 2006).

twenty years ago

the field of
micro
-
fluidics

emerge
d

with the
manufacture of

inkjet printers, in which the

inkjet

tubes combine and isolate from each other to
change the
hue

of colors
that

are imparted

on the
printed
page.

The Future of Fluid Mechanics

Modern micro
-
fluidics involves the handling and manip
ulation of minute amounts of fluids;
volumes thousands of times smaller than a common droplet, which requires measuring in micro

lit
er
s, nano
-
liters or even pico
-
liters. M
icro
-
fluidics lies at the interfaces between biotechnology,
the
medical industry, che
mistry and micro
-
electro
-
mechanical systems (MEMS).
MEMS

involves

the integration of mechanical elements, sensors, actuators, and electronics on a silicon
substrate through microfabrication technology. While the electronics are fabricated using
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integrated
circuit process sequences, the micromechanical components a
re fabricated using
compatible “
micromachining

processes that selectively etch away parts of the silicon wafer or
add new structural layers to form the mechanical and electromechanical devices.

On

these
microchips complete laboratories
can be created,
comprised of

channels, mixers, reservoirs,
diffusion chambers, integrated electrodes, pumps,
and
valves. With the lab
-
on
-
a
-
chip technology,
complete laboratories on a square centimeter can be created
.

The goal of the technology is to
automate standard laboratory processes
, improving speed

and cost efficien
cy
;
lab

results can be
obtained within a few seconds instead of hours or days. Lab
-
on
-
a
-
chip devices are commonly
used for capillary electrop
horesis,

drug development, high
throughput screening and
biotechnological assays.
Microelectronic integrated
circuits can be thought of as the

brains

of a
system
while

MEMS augments this decision
-
making capability with

eyes

and
“arms
,

allow
ing

micro
-
systems t
o sense and control the environment. Sensors gather information from
the environment through measuring mechanical, thermal, biological, chemical, optical, and
magnetic phenomena. The electronics then process the information derived from the sensors and
thr
ough some decision making capability direct the actuators to respond by moving, positioning,
regulating, pumping, and filtering, thereby controlling the environment for some desired
outcome or purpose.

MEMS and n
anotechnology are still the subject of broad

and diverse
research efforts, and the field is constantly changing.

Rationale for Module

This module is intended to introduce
students

to fluid dynamics and micro fluidic mixing. The
intent was to create a module that could be plugged into several differ
ent areas of a physical
science classroom to provide enrichment and application. The basic module can be used as an
introduction to physical science

unit or as part of the
properties of matter

section in the
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chemistry unit. The module may also be used as

the capstone to a basic mechanics module, with
buoyant forces, types of pressure,
capillary action, sedimentation, etc. The engineering and fabrication aspect of the module also
makes it appropr
iate as part of a materials science or applied technology program.

Science

The unit will cover several basic concepts in fluid dynamics
,

including:

Fluid Pressure

(Pascal’s Principle
: P
out

= P
in
)
.

Pascal's principle states that when pressure is
applied to
a confined liquid, this pressure is transmitted, without loss, throughout the entire
liquid and to the walls of the container.

See discussion at:
http://theoryx5.uwinnipeg.ca/mod_tech/node6
6.html
. S
ee web applet at:
http://webphysics.davidson.edu/physlet_resources/bu_semester1/c23_pressure_pascal.html

Bouyancy

(Archimede
s

Principle)
.
The

buoyant force on a submerged object is equal to the
weight of the fluid
it
displace
s
.

See discussion at:
http://theoryx5.uwinnipeg.ca/mod_tech/node67.html#2169
.

See applet at:
http://www.lon
-
capa.org/~mmp/applist/f/f.htm
.

Flow Rate
. (Continuity Equation: A
1
V
1

= A
2
V
2
).

See discussion and diagram at:
http://t
heoryx5.uwinnipeg.ca/mod_tech/node65.html
.

See web applet at:
http://www.grc.nasa.gov/WWW/K
-
12/airplane/mflow.html
.

Laminar
F
low
.
A flow in which

thin

l
ayers of
fluid

flow over one an
other at different speeds
with virtually no mixing between layers. The flow velocity profile for laminar flow in circular
pipes is parabolic in shape, with a maximum flow in the center of the pipe and a minimum flow
at the pipe walls. The average flow velo
city is approximately one half of the maximum velocity.

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Turbulent Flow.
A

flow
which
is characterized by the irregular movement of particles of the
fluid. The flow velocity profile for turbulent flow is fairly flat across the center section of a pipe
and d
rops rapidly extremely close to the walls. The average flow velocity is approximately equal
to the velocity at the center of the pipe.

Transitional Flows
:
For fluids flowing in pipes, the transition from laminar to turbulent motion
depends on the diameter

of the pipe and the velocity, density, and viscosity of the fluid. The
larger the diameter of the pipe, the higher the velocity and density of the fluid, and the lower its
viscosity, the more likely the flow is to be turbulent.

Viscosity (
Stokes

Law
)
.
Vi
scosity is the fluid property that measures the resistance of the fluid
to deforming due to a shear force. For most fluids, temperature and viscosity are inversely
proportional.

See Appendix for detailed discussion of Stokes’ Law for falling spheres.

Surfa
ce tension
.
The

tendency of liquids to reduce their exposed surface to the smallest possible
area. The phenomenon is attributed to cohesion, the attractive forces acting between the
molecules of the liquid. The molecules within the liquid are attracted equ
ally from all sides, but
those near the surface experience unequal attractions and thus are drawn toward the center of the
liquid mass by this net force. The surface then appears to act like an extremely thin membrane
.

Capillary Action
.
Capillary action is

water to the walls of a vessel will cause an upward force on the liquid at the edges and result in a
meniscus which turns upward. The surface tension acts to hold the surface intact, so instead of
ju
st the edges moving upward, the whole liquid surface is
pulled

upward.

Kinetic Theory
.
The Kinetic Molecular Theory is a single set of descriptive characteristics of a
substance known as the Ideal Gas. All real gases require their own unique sets of descri
ptive
characteristics. Considering the large number of known gases in the
w
orld, the task of trying to
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describe each one of them individually would be an awesome task. In order to simplify this task,
the scientific community has decided to create an imagin
ary gas that approximates the behavior
of all real gases. In other words, the Ideal Gas is a substance that does not exist. The Kinetic
Molecular Theory describes that gas. While the use of the Ideal Gas in describing all real gases
means that the descript
ions of all real gases will be wrong, the reality is that the descriptions of
real gases will be close enough to
ideal

that any errors can be overlooked.

Engineering

The engineering aspects of the module cover a broad range of areas from fabrication to
tec
hnologies to overcome key issues.
Micro
-
channel fabrication
,

for example
,

requires the use of
clean rooms and computer automated design and fabrication machines (CAD/CNC).

Mixing is the primary challenge for most micro fluidic systems, resulting in inno
vations in how
materials are pumped and channel design. The small diameter of the channels (<10
-
6

meters)
provide for only laminar flow under most conditions. T
hus, diffusion rather than turbulence is
the primary method for
mixing.

Solutions include inc
orporating hundreds of tiny turns into the
channels as well as placing tiny portions of each fluid in the tubes in tandem rather than side by
side, in order to maximize the amount of surface area in contact.

Controlling the flow through micro and nano
-

channels is also a challenge. Normal pressure
pumps lack the precision necessary on these small scales. Thus, this technology requires the
a
pplicati
on of micro scale voltage pumps

to use electromagnetic charges to generate the
‘pressure’ to move fluids t
hrough the micro channels.

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Goals

The goal of this module is to convey an understanding of the basic principles of fluid

dynamics
,
while at the same time drawing a connection between current applications of fluid dynamics and
the quickly evolving future

of
micro fluidics
. M
icro
-
c
hannel mixing
is
context
ually employed

in
order t
o
present a vision of the future while
enhanc
ing
student
s

understanding of
general
fluid
dynamics.

Grade Level Expectations (GLEs) and EALRS met.

The following are extracts from t
this module. This includes the GLEs themselves as well as vocabulary and detailed investigation
criteria.

1.1.2 Apply an understanding of direction, speed, and accelerat
ion when describing the linear
motion of objects

1.1.4 Analyze the forms of energy in a system, subsystems, or parts of a system

1.2.1 Analyze how systems function, including the inputs, outputs, transfers, transformations,
and feedback of a system and its

subsystems

1.2.2 Analyze energy transfers and transformations within a system, including energy
conservation

1.2
.3 Understand the structure of atoms, how atoms bond to form molecules, and that molecules form
solutions.

1.3.1 Analyze the forces acting on

objects

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1.3.3 Analyze the factors that affect physical, chemical, and nuclear changes and understand that matter
and energy are conserved

2.1.1 Understand how to generate and evaluate questions that can be answered through scientific
investigations.

2.1
.2 Understand how to plan and conduct systematic and complex scientific investigations

2.1.3
Understand how to construct a reasonable explanation using evidence

2.1.3
Synthesize a revised scientific explanation using evidence, data, and inferential logic.

2.1.4 Understand how to use simple models to represent objects, events, systems, and processes.

2.1.4 Analyze how physical, conceptual, and mathematical models represent and are used to investigate
objects, events, systems, and processes.

2.1.5 Apply

understanding of how to report complex scientific investigations and explanations of objects,
events, systems, and processes and how to evaluate scientific reports

2.2.1 Understand that all scientific observations are reported accurately and honestly even

when the

2.2.2 Analyze scientific theories for logic, consistency, historical and current evidence, limitations, and
capacity to be investigated and modified.

3.1.2 Evaluate the scientific design process used to d
evelop and implement solutions to problems or
challenges.

3.2.3 Analyze the scientific, mathematical, and technological knowledge, training, and experience needed
for occupational/career areas of interest.

controlled variable

el
ectrical charge

electrical force

experiment

experimental control
condition

frictional force

investigative control

investigative plan

investigative question

Joules (J)

manipulated variable

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principle

relationship

reliability

research question

solubility

sol
ute

solvent

theory

thermal energy

validity

work

Controlled Scientific Investigations

Make a hypothesis (prediction with cause
-
effect reason) related to an investigative question.

Identify two of the controlled variables (kept the same) in a given investig
ation.

Identify the manipulated (independent) variable in a given investigation.

Identify the responding (dependent) variable in a given investigation.

Make a logical plan for a second investigation for a different investigative question that can
ed using a similar plan [with a different manipulated (changed) variable for a
controlled investigation]. A logical plan includes step
-
by
-
step instructions clear enough that
others could do the investigation.

Describe appropriate materials, tools, and tech
niques, including mathematical analysis and
available computer technology, to gather and analyze data.

Describe an experimental control condition when appropriate for an investigation
.

Describe validity measures, in addition to controlled and manipulated
variables, for an
investigation.

Record data (measurements) in a systematic way using tables, charts, graphs, or maps.

Organize and analyze data to look for patterns and trends. When appropriate sort
measurements (observations) into categories; calculate m
eans, modes, or medians; create
graphs, tables, or maps; compare data to standards; and perform statistical analysis to

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Answer the investigative (study) question or respond to the hypothesis using supporting dat
a.

Compare data to standards, when appropriate, to answer a larger question.

Equipment

See

individual

labs.

Prerequisite Knowledge

Prior to
beginning this module
, students should have a basic understanding of the following:

Graphical analysis
.

Mathematical

relationships to include direct, inverse and exponential proportions.

Basics of unit conversions
.

Models of the atom and
Kinetic Theory.

Mass, Volume and Density
.

Relationship between pressure, volume and temperature for ideal gasses.

Thermal Energy, temp
erature and heat.

Position, velocity, acceleration and forces
.

Procedures

See

individual

labs.

Safety Precautions

The following are
GLE guide

for science
. OSPI has a color
safety poster available at:
http://www.k12.wa.us/CurriculumInstruct/Science/default.aspx
.

All science teachers must be involved in an established and ongoing safety training program,
relative to the established safety procedu
res, that is updated on an annual basis.

Teachers shall be notified of individual student health concerns.

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Materials intended for human consumption shall not be permitted in any space used for
hazardous chemicals and or materials.

Students and parents w
ill receive written notice of appropriate safety regulations to be
followed in science instructional settings.

More specific to these labs: Ensure students wash the
ir

hands after the labs (especially after
.

Ensure students do not try to eat
/drink the simple sugar or glycerin.

Instructional Strategies

This module was designed to minimize direct instruction and maximize student involvement.
The focus is on generating student interest through cognitive dissonance and/or inquiry
questions. A s
hort discussion of some possible strategies follows:

Scientific Inference
:
Labs and activities are
structured to enable inferences

predictions for how

s
ystem
s

work.

Hypothesizing
:
Focus on

scientific methods. Students are given suff
icient information to create
a
n

explanation that can be tested.

Interpreting
:
Labs require students to analyze data both quantitatively and qualitatively.

Questions require them to interpret

causality

from
their measurements, and then
predict future
out
comes by explaining how the manipulated variable caused the responding variable to change.

Data Collection

See individual labs.

Data Analysis

See individual labs.

Conclusions

See individual labs.

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Evaluation Protocols

See individual labs

and worksheets
.

App
endix A
-
Instructional Materials

Fluid Dynamics Presentation

Micro Fluidics Presentation

Stoke’s Law Background

Appendix B

Laboratory Write
-
Ups

Fluid Dynamics #1

Flow Rate and Viscosity

Fluid Dynamics #2

Stoke’s Law

Fluid Dynamics #3

Micro Cha
nnel Mixing

Appendix C

Student Worksheets

Worksheet I
-

Fluid Flow and the Continuity Equation

Worksheet II
-

Micro to Macro

Worksheet IIb

Unit of Measure Conversions (supplemental)

Worksheet III

Capillary Action

Worksheet IV

Stoke’s Law

Appe
ndix D

Supplemental Materials

-

Channel Construction and Relevant Difficulties

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References

Blaber, Michael. (1996). Intermolecular forces. Tallahassee: FSU.

Council of State Science Supervisors (CSSS). (1998). Science Safety:
Making the Connection.
Available:
http://csss.enc.org/media/scisafe.pdf
>.

Cramer, M.S.

(2004)

Fluid Mechanics
. NY: Cambridge Univ. Press
.
Retrieved July 12, 2006,
from

http://www.fluidmech.net
.

Drakos, N. (1997). Computer Based Learning Unit. Physics 1501
-

Modern Technology. UK:
University of Leeds.

Fluid
D
ynamics. (2006, July 18). In Wikipedia, The Free Encyclopedia. Retrieved July 18, 2006,
from
http://en.wikipedia.org/w/index.php?title=Fluid_dynamics&oldid=64494029
.

Johnson, John & George Petrina. (Jul 2005). Microfluidic Mixing Using Microchannels in High
School Sci
ence and Math. Pullman, WA: WSU.

NSTA. (2004). Inquiring Safely: A Guide for Middle School Teachers.

N
STA. (2004). Investigating Safely: A Guide for High School Teachers.

OSPI. (2000). OSPI: Health an
d Safety Guide, section K.

OSPI (2004).
Science K

1
0 Grade Level Expectations: A New Level of Specificity
.
OSPI
Document Number 04
-
0051
.

RSC. (Sept. 2003).
AMC Technical Brief. Analytical Methods Committee, Royal Society of
Chemistry.
London.

Stokes’ Law:
http://www.spacegrant.hawaii.edu/class_acts/ViscosityTe.html
.

SWEET
.

(
2006
)
.
Summer at WSU
-

Engineering Experiences for Teachers
.
Brochure.
Retrieved
July 17, 2006 from

http://wsta.net/html/modules.php?name=News&file=article&sid=371
.