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Chameleon Panel Final Report Group 12, May 2010
Team - Ryan Wubbens, Tyler Keeton,, Keng Gee Chameleon Panel
4/27/2010
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Table of Contents Frontal Material ............................................................................................................................................ 4
1.1 List of Figures ................................................................................................................................ 4
1.2 List of definitions ........................................................................................................................... 9
Introductory materials ................................................................................................................................ 10
2.1 Executive summary: .......................................................................................................................... 10
2.2 Acknowledgement: ........................................................................................................................... 10
2.3 Problem Statement ........................................................................................................................... 11
2.4 Operating Environment .................................................................................................................... 11
2.5 Intended User ................................................................................................................................... 11
2.6 Intended Use ..................................................................................................................................... 12
2.7 Assumptions and Limitations ............................................................................................................ 12
2.8 Expected End Product ....................................................................................................................... 12
Approach ..................................................................................................................................................... 14
3.1 Application of Engineering Principles ............................................................................................... 14
3.2 Design Objectives .............................................................................................................................. 16
3.3 Functional Requirements .................................................................................................................. 16
3.4 Design Constraints ............................................................................................................................ 16
3.5 Technical Approach Considerations .................................................................................................. 16
3.6 Design Trade-offs .............................................................................................................................. 17
3.7 Platform ............................................................................................................................................ 18
3.8 Testing Considerations ...................................................................................................................... 18
3.9 Testing Evaluation ............................................................................................................................. 18
3.10 Recommendations Regarding Project Continuation ...................................................................... 19
Design .......................................................................................................................................................... 20
4.1 Function Decomposition ................................................................................................................... 20
4.2 Detailed Design ................................................................................................................................. 21
Implementation .......................................................................................................................................... 23
5.1 Microfluidic ....................................................................................................................................... 23
5.2 Electrospraying ................................................................................................................................. 24
Testing ......................................................................................................................................................... 25
6.1 Testing Background ........................................................................................................................... 25
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6.2 Testing of Thermosensitive Liquid Crystals (Microfluidic Formation) .............................................. 25
6.3 Testing of Electrosensitive Liquid Crystals (Microfluidic Formation) ................................................ 26
6.4 Testing of Thermosensitive Liquid Crystals (Electro-Spraying) ......................................................... 26
6.5 Testing of Electrosensitive Liquid Crystals (Electro-Spraying) .......................................................... 26
Evaluation: .................................................................................................................................................. 28
7.1 Evaluation of Thermosensitive Liquid Crystal ................................................................................... 28
7.2 Evaluation of Electrosensitive Liquid Crystal .................................................................................... 28
Resources and Schedules ............................................................................................................................ 29
8.1 Personnel Effort Requirements......................................................................................................... 29
8.2 Financial Requirements..................................................................................................................... 31
8.3 Deliverable Schedule ......................................................................................................................... 31
8.4 Project Schedule ............................................................................................................................... 32
Operation Manual ....................................................................................................................................... 37
9.1 Operation Manual ............................................................................................................................. 37
Closure Material .......................................................................................................................................... 40
10.1 Client Information ........................................................................................................................... 40
10.2 Faculty Advisor Information ............................................................................................................ 40
10.3 Student Team Information .............................................................................................................. 40
10.4 Closing Summary ............................................................................................................................. 40
10.5 References ...................................................................................................................................... 41
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Frontal Material
1.1 List of Figures
Figure 1:
Figure 2:
Page 5
Figure 3:
Figure 4
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Figure 5
Figure 6
Figure 7
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Figure 8
Microscope
Substrate
Stage
White Light Mirror
Polarizer
Figure 9
Product tested at 42 degrees
celsius
90 300
SECONDS
TEMPERATURE
42
21
Degrees Celsius
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Figure 10
Microscope
Glass Substrate
White Light Mirror
Polarizer
ITO SlidesVoltage
Figure 11
Voltage at 3.7 Volts 1 Voltage at 0 Volts 1
Figure 12
Increasing
Darkness
3.7 Volts
Voltage Applied
0V
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1.2 List of definitions
Liquid crystal- a condition in which a substance possesses the flow properties of a liquid and, to
a degree, the molecular order of a crystalline solid
Thermosensitive liquid crystal- a liquid crystal that changes its photon absorption profile with a
changing external temperature
Electrosensitive liquid crystal- a liquid crystal that changes its photon absorption profile with a
changing voltage potential
Polymer- a compound consisting of long chain-like molecules
Microshell- a polymer shell ranging in size from 10-6 meters to 10-9 meters
Electrospraying-a method that uses an electrical spray microshells from a liquid
Microfludic formation-a method that manipulates the flow of a liquid through a microfabricated
channel
Monomer - small molecule that may become chemically bonded to other monomers to form a
polymer.
phase transition - is the transformation of a thermodynamic system from one phase to another.
nematic phase - A phase of a liquid crystal in the mesomorphic state, in which the liquid has a
single optical axis in the direction of the applied magnetic field, appears to be turbid and to have
mobile threadlike structures, can flow readily, has low viscosity, and lacks a diffraction pattern.
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Introductory materials
2.1 Executive summary:
Sunlight is renewable source of energy that we need to take full advantage of. We are purposing
to build a chameleon panel that can change color respective to temperature. By adding this
chameleon panel to the roof of a building, this panel can help absorb and reflect solar thermal
energy to maintain the temperature of the building (See figure 1). When the temperature rises,
the device will nearly turn white, reflecting the solar energy, and when the temperature drops,
the device will turn black, absorbing solar energy. The absorbed and reflected solar thermal
energy will reduce the work needed by HVAC systems. This increases the life of the HVAC
system and reduces the running cost at the same time. The material developed during this
project could also be applicable to industrial machinery that operates best in specific
temperature ranges.
The project will take two different approaches to create the chameleon panel. The two
methods, electrospraying and microfluidic formation, both will encapsulate Thermosensitive
and Electrosensitive liquid crystals with polymer. There will be six end products to study the
differences between. Three will be made by electrospraying, and Three from microfluidic
formation. Each process will have one panel made with Thermosensitive liquid crystals and the
other panel will be made with Electrosensitive liquid crystals. Each panel will be covered by
these liquid crystals that can change refractive index. The Thermosensitive panels will change
refractive index dependant on the incident temperature, and the Electrosensitive panels will
change refractive index dependant on the electric field dependant on the crystals. By changing
the refractive index of the panels, we can manipulate how much solar thermal energy we would
like to absorb or reflect.
This report includes all topics that studied by the design team needed to complete the project.
Operating environment, intended uses, commercialization, project approach, and the schedule
to complete the project are discussed in this document.
Major issues that are outstanding include finding an appropriate polymer, finding the best size
of microshells, and finding a material to encapsulate the microshells.
2.2 Acknowledgement:
All of the equipment and technical advice will come from Dr. Dong. We have two funding
sources. The senior design class will provide $250 and Dr. Dong will provide $750 towards the
project.
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2.3 Problem Statement
General problem statement
For areas with a changing climate, a mono-chromatic roof is detrimental to the heating and
cooling of a structure. A dark colored roof will absorb heat while a light colored roof will reflect
heat. If the color of the roof became darker in cold temperatures, and lighter in warm
temperatures, the energy efficiency of the building would improve.
General solution approach
By encapsulating Thermosensitive and Electrosensitive liquid crystals in a polymer or oil
solution, a large liquid crystal can be formed. This liquid crystal will be able to reflect or absorb
light dependent upon the thermal or electrical input. When a coating of this liquid crystal is
applied to a shingle on a roof or a different industrial roofing material, it will help maintain the
desired temperature of the building.
For structures in changing environments, darker colors would reduce heat loss through the roof
in the winter. In the summer, lighter colors would reflect heat and help cool the structure.
2.4 Operating Environment
The chameleon roof will be operating in a changing climate. It will have to accommodate all
weather conditions where residential and industrial structures exist.
The Chameleon Roofing Material and Device is going to be operating in an ever changing
environment. The final product will be used in temperatures from -20 degrees Celsius to 50
degrees Celsius. The end product will have to be able to accommodate all different types of
weather and changes in weather. The primary operating environments are going to be
commercial buildings, industrial buildings, residential homes, and industrial equipment. The
chameleon panels will also need to be placed in an area where they are absorbing the thermal
heat that surrounds it.
2.5 Intended User
The intended users of the chameleon panel include the owners or investors of residential
homes, commercial buildings, and industrial buildings. In addition, construction companies,
heavy machinery manufacturers, and those whom work with and maintain heavy machinery
could benefit from this technology.
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2.6 Intended Use
The intended use of the chameleon panel is to decrease the energy cost of heating and cooling a
structure or piece of industrial equipment.
2.7 Assumptions and Limitations
Assumptions
Lab equipment is sufficient enough to produce prototype and end product
1” by 1” prototype will perform the same on a larger scale
Liquid crystal being used can be encapsulated in the polymer being used
The budget of $1000 is enough to create prototypes
The prototype will not heat up to the point that it changes from black to white in the winter
The prototype will not cool down to the point that it changes from white to black in the summer
The liquid crystal selected by the client will fulfill their needs
The polymer selected by the client will fulfill their needs
Limitations
Cost of raw materials should not exceed $1000
Lab equipment producing a certain sized panel in a certain amount of time
The two types of liquid crystal are preselected
The polymer and oil is preselected
Time to come up with a successful prototype
2.8 Expected End Product
This project has 7 deliverables
The first panel will use the microfluidic method of encapsulating liquid crystals within
microshells. The liquid crystal should change color in response to changing temperatures.
The second panel will use the microfluidic method of encapsulating liquid crystals within
microshells. The liquid crystal should change color in response to changing voltage.
The third panel will use the electrospraying method of encapsulating liquid crystals within
microshells. The liquid crystal should change color in response to changing temperatures.
The fourth panel should use the electrospraying method of encapsulating liquid crystals within
microshells. The liquid crystal should change color in response to changing voltage.
The fifth panel should use the microfluidic method of encapsulating liquid crystals within
microshells. The second type of liquid crystal should change color in response to changing
temperatures.
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The sixth panel should use the electrospraying method of encapsulating liquid crystals within
microshells. The second type of liquid crystal should change color in response to changing
temperatures.
Documentation that explains how the device will perform in the operating environment.
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Approach
3.1 Application of Engineering Principles
Electro-spraying
For this project, a type of electro-spinning known as electro-spraying will be used. When a
sufficiently high electric field is applied to a liquid droplet, the electrostatic repulsion of the
droplet becomes equal to the surface tension of the liquid. This point is known as the Rayleigh
Limit. The electric field formed in the droplet of water is governed by this equation, where 𝑟 is
the radius of the droplet, 𝑉is a positive voltage, and 𝑑 is the distance from the electrode to
ground:
𝐸 =2 𝑉
𝑟 ∗ ln 4 ∗ 𝑑𝑟
As the electric field, 𝐸, increases, the droplet contracts. However, when 𝐸 surpasses the
Rayleigh Limit, the droplet can no longer contract. At these voltages, a Taylor cone is formed. A
Taylor cone (Figure 2)has an equipotential surface and exists in steady-state equilibrium. The
solution to this is:
𝑉 = 𝑉0 + 𝐴𝑟12𝑃1
2(cosθ0)
In this equation, r is the radius of the cone, P is the Legendre polynomial with and order of 0.5,
and 𝐴 = 4.53 ∗ 105 𝛾 , where 𝛾 is the surface tension of the liquid. At the apex of this cone, a
singularity develops when the hydrodynamic relaxation time becomes greater than the charge
relaxation time.
Depending on the viscosity of the liquid, a jet or spay is emitted from this singularity. For our
purposes, we will want a spray consisting of polymer micro-spheres.
Micro fluidics
The field of micro fluidics encompasses many different topics and processes. This paper will
focus only on those portions that are relevant to our project.
A micro fluidic chip is a piece of material with small channels that constrict the flow of liquids.
The chip used for our project will be constructed from a glass slide with a polymer coating. The
polymer coating will contain the channels used to control the flow of liquid polymer and liquid
crystal. The chip will guide the liquids to a ultra-violet light where the polymer shell will form
trapping liquid crystal inside.
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Polymerization
A polymer is a large molecule made of repeating units, or chains of monomers. Polymers can
create strong bonds and can be constructed on a nanometer scale. Beyond that, polymers have
a wide variety of properties and uses, most of which go beyond the scope of this project.
Polymerization is the chemical process by which a polymer is formed. Monomer molecules
reach together to form three dimensional networks. These networks are also known as polymer
chains. A wide variety of processes can lead to polymerization, most of which go beyond the
scope of this project.
Liquid crystal
Liquid crystal is a state of matter that has properties between those of solid crystals and
traditional liquid. The liquid crystal we will be using will flow like a liquid but its molecules will
orient themselves to like a solid. The orientation of the molecules will determine the refractive
index of the material.
Both the Thermosensitive liquid crystals and Electrosensitive liquid crystal are or thermotropic.
This means they are composed of organic molecules. These molecules will exhibit a phase
transition into liquid crystal in response to temperature and the concentration of liquid crystal
respective to solvent. This causes the molecules of the liquid crystal to reorder themselves and
thus change their refractive index when exposed to heat. The changing refractive index causes
the color of the molecule to change.
Unlike the Thermosensitive liquid crystal, the Electrosensitive will only operate in the nematic
phase. In the nematic phase, the molecules can be arranged by using an external magnetic or
electric field.
There are many more phases and properties of liquid crystal, however the discussion of these
goes beyond the scope of this project.
Thermodynamics
The zeroth law of thermodynamics states “If two thermodynamic systems are separately in
thermal equilibrium with a third, they are also in thermal equilibrium with each other.” The first
law states “The change in the internal energy of a closed system is equal to the sum of the
amount of heat energy supplied to or removed from the system and the work done on or by the
system.”
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In this project, when the panel is darker it traps more heat. The trapped heat should flow to the
cooler surface that the panel is placed upon as it attempts to establish thermal equilibrium. This
heat can then be used to heat a machine or building.
Light Mineral Oil
The light mineral oil will be used in the microfluidic process in order to encapsulate the liquid
crystal. Mineral oil has a density of around 0.8 g/cm3. It also has a higher refractive index.
Surfactant
Surfactant will be added to the mineral oil to keep the liquid crystal droplets separated from one
another. The surfactant will lower the surface tension of the mineral oil and keep it from
recombining.
3.2 Design Objectives The final design is a product that will have encapsulated liquid crystals in a polymer or in oil. The
liquid crystals will have the ability to change refractive index with respect to temperature or
electric field.
3.3 Functional Requirements
A polymer shell must enclose the liquid crystals
The Thermosensitive liquid crystal must become darker to absorb sunlight at colder
temperatures
The Thermosensitive liquid crystal must become lighter to reflect sunlight at higher
temperatures
The Electrosensitive liquid crystal must become lighter or darker by changing the electric field
applied to the crystal
3.4 Design Constraints
The panel must be able to work in the temperatures ranging from -20 degrees Celsius to 50
degrees Celsius
The panel must be applicable to residential and industrial roofs
The polymer used must be pla/pdlla
The thermosensitive liquid crystals are type 5BC
The electrosensitve liquid crystal must be MBC
3.5 Technical Approach Considerations
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Many prototypes will be created using both the electrospraying and microfluidic encapsulation
methods. Each prototype will have a different size nanoshell/microshell. Each shell size will be
tested for use with our panel and the optimal sizes will be used in our final prototypes.
Electrospraying is a process that applies a high voltage to a polymer liquid, charging the liquid
(reference figure 2). As the liquid polymer is introduced into an electrical field it is dispensed
from a nozzle. As the liquid is dispensed from the nozzle, the surface tension on the liquid erupts
and a Taylor cone is formed at the end of the nozzle. The electric field is increased on the
polymer liquid to deposit the liquid on the grounded substrate located ten to thirty centimeters
from the nozzle. The polymer will form a nanoshere spray with beads of liquid crystals
encapsulated by the polymer. As the polymer and liquid crystals are continuously ejected from
the nozzle the substrate becomes more covered with the nanospheres. The end product should
be a substrate that is completely covered with encapsulated liquid crystals.
The microfluidic formation utilizes the large increase in surface area relative to volume to create
emulsions, or one liquid being dispersed in another. A microfluidic chip utilizing a ‘T’ type of
junction of channels (figure 3), forces two flows of immiscible liquids to dispense one inside the
other. As liquid crystals are forced to flow into the oil, the oil will encapsulate the liquid crystals
due to the hydraulic force of the microfluidic chip puts on the oil. The microshells will then be
deposited onto a glass substrate. The substrate will be completely covered by the microshells
for the final product.
3.6 Design Trade-offs The cost and time involved in constructing a 6”x6” test panel may be too great. In order to get
the project done on time and budget, the test panels that will be constructed will be smaller.
We are currently planning to create prototypes no bigger than a glass slide. If time allows, we
may opt to create larger versions.
The cost of Electrosensitive liquid crystal is much higher than that of Thermosensitive liquid
crystal. Instead of working with both Thermosensitive and Electrosensitive liquid crystal
separately, we will attempt to create a working process with Thermosensitive crystal before
attempting an Electrosensitive version.
A spray on version that could be applied directly to an existing structure or machine was
considered. We opted not to create a spray-on version at this time. We do not know enough
about the properties of the micro-spheres to know if this option is feasible. This may be a good
next step if the material we produce is suitable.
For the electrospraying method, the shells will be placed disorderly on the panel. Disorder of the
shells could affect the ability of the panel to reflect and absorb light due to unexpected light
scattering issue.
The size of the shells will affect the final design performance. Smaller shells should be more
efficient; however it is unknown how small the lab equipment can create. Every effort to
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minimize the size of the shells will be made, however the exact parameters of the final product
remain unknown.
There are two potential substrates that may be used. A glass substrate is being considered for
ease of evaluation. Another substrate for the Electrosensitive liquid crystals will be the glass
slide combined with the ITO. The suitability of each substrate cannot be determined at this time.
The processes used to form microspheres may have an adverse affect on the substrate so it
must be experimentally evaluated.
3.7 Platform There will be two processes used to encapsulate liquid crystals in polymer or oil for the
prototypes. The first method, microfluidic formation, will use a microfluidic chip made from a
polymer known as IBA to encapsulate the liquid crystals. The electrospraying of microshells is
the second method to be used to make a prototype. The final product and prototypes will be
implemented on top of a building.
3.8 Testing Considerations There are three major milestones that need to be tested before a prototype may be made and submitted as a final product: successful microfluidic channels, successful electrospraying and microfluidic encapsulation, and the encapsulated liquid crystal's ability to change its refractive index with respect to temperature. Testing microfluidic channels- After any microfluidic chips have been formed, ethanol is forced into an opening on one side of the chip. A pump then pulls the ethanol through the channels. A chip can be used with the polymer and liquid crystals after ethanol flows freely through all channels on the chip. While testing the Electrosensitive and Thermosensitive panels, the glass substrate will be tested. Testing the electrospraying process and microfluidic formation process for encapsulation-
The microscope located in Dr. Dong’s lab will be used to view the microshells formed by both the electrospraying and the microfluidic formation. A careful inspection by microscope of each attempted encapsulation will be done after each process. Testing the ability to change refractive index-
The thermo sensitive microshells will be place in a cold box and on the lab hot plate to test the refractive index with respect to temperature. The temperature will be closely monitored to record when the color of the microshells changes.
3.9 Testing Evaluation
To evaluate the prototype, the prototype’s refractive index will be observed by observing the
color change. For the prototype to be working properly, it must show a definitive color change
when going from a much warmer temperature to a much colder temperature. The substrates
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will be evaluated by durability and thermal transfer. An ideal prototype will change colors
continuously across the operational environment however due to our limited choice in liquid
crystals and our limited funding; we will just look for a definite change in the final product.
3.10 Recommendations Regarding Project Continuation When the microshells are successfully encapsulated and the technology is proven, the next step
would be to test the material using different types of substrates, polymers and liquid crystal.
Our design is one approach, but it is not guaranteed to be optimal for every problem. Also,
because the specific liquid crystals were requested by the client, we cannot guarantee that they
will be optimal for this application.
Weather proofing material for the tiles will be necessary for implementation. However due to
time and money constraints, it will not be addressed in this project.
In order to lower the cost of manufacturing and installation the microshell material may be
suspended in a spray-on solution.
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Design
4.1 Function Decomposition
The components of the chameleon panel are shown in figure 5 and figure 6. The figures
displayed the three layers. Polymer liquid crystals shown represent the thermo sensitive and
electro sensitive microshells. The substrate shown is representing all possible substrates that
will be tested. The functional decomposition of each component is as follows:
Figure 5 Figure 6
Liquid Crystal-
Thermo-sensitive Liquid Crystal - Type 5BC, and another yet to be specified - Changes
refractive index with respect to temperature to reflect or absorb solar thermal heat.
Electro-sensitive Liquid Crystal - Type MBC - Changes refractive index with respect to
electric field to reflect or absorb solar thermal heat.
Substrate – grounded substrate the nanoshells will be placed on
The substrate will be composed of glass
Polymer – PLA/PDLLA - Encapsulation material used to encapsulate the liquid crystals.
ITO – A clear conductor that will be placed on top and on the bottom of the panel to create an
electrical field in the Electrosensitive liquid crystals. The electric field will change the refractive
index of the liquid crystals.
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4.2 Detailed Design Electrospraying Process
Figure 4
Figure 4 illustrates the process being used. Polymer, model pda/pdlla, is first dissolved in a
solution. Different solvents are being used including chloroform and toluene. The solution’s
proportions will be based upon laboratory data. The solution needs be viscous enough to form
stable spheres. However, it should not be so viscous as to form threads instead of spheres. This
solution is placed in the first syringe.
The second syringe is filled with liquid crystal. Thermosensitive liquid crystals (5BC) and
Electrosensitive liquid crystal (MBC) will be attempted.
The polymer will be pumped through a tube such that the polymer solution will surround the
liquid crystal when it is pumped out of the inner needle. Flow rates will be determined
experimentally.
A 20kV DC charge will be placed upon the tip of the coaxial needle and the substrate will be
grounded. This will cause a Taylor cone to form at the tip of the syringe (Figure 2) ejecting
polymer and liquid crystal. The electric field will cause the polymer’s solvent to evaporate. This
will make the solution polymerize around the liquid crystal forming microspheres.
The microspheres will then be deposited on the substrate below. For this process, we will be
using a glass substrate. This process continues until the substrate is covered or the syringes
need to be refilled.
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Microfluidic Formation
Figure 7
Figure 7 illustrates the process being used. First, A ‘T’ mask is placed over the glass slide. Then
an IBA solution is put between the ‘T’ mask and the glass slide. The IBA solution is composed of
isobornyl acrylate (IBA), tetra ethylene glycol dimethacrylate and DMPA in the weight ratio of
31.66:1.66:1.0. The mask and the IBA covered glass chip are exposed to a UV light for 24
seconds with an intensity of 7.7 mW cm-2 [6]. This process polymerizes the IBA solution and
forms a microfluidic chip with T channels.
Liquid crystal is discretely pumped through the center channel. A Thermosensitive liquid crystal
(5BC) and one Electrosensitive liquid crystal (MBC) will be attempted.
Oil solution will be pumped discretely through the side channels. This will cause the liquid oil to
surround the liquid crystal.
This will form a sphere around the liquid crystal. The microspheres will then be pumped out of
the channel and onto a substrate. This process is also going to be using a glass substrate.
Substrates
There is on substrate that we used for these processes. A glass substrate is being used for its
ease of evaluation.
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Implementation
5.1 Microfluidic The first step in the implementation was the design of the microfluidic chip. To make the chip a
IBA solution is polymerized in the shape of the microfluidic channels needed, then a polymer
mold is placed over the IBA to create the mold of the chip.
IBA (see page 20) is placed on a glass side then covered with a photo-resist mask in the shape of
the chip needed. The mask was placed 125 micro-meters above the glass slide. This depth
controls the depth of the channels on the chip. After the IBA on the glass slide is covered by an
appropriate mask and placed under a UV light, the UV light will polymerize the IBA on the
exposed areas to the UV light. The polymerized IBA is the negative shape of the microfluidic chip
being made.
The polymerized IBA is cleaned with ethanol and covered with a PDMS solution. The PDMS
solution is a solution made of silicone elastomeric base and a silicon elastomeric curing agent.
The ratio of these two solutions is 10:1 mass ratio. After the PDMS is poured onto the chip, it is
then placed into a vacuum for 20 minutes to rid the solution of air bubbles that formed in the
PDMS.
After the vacuum the PDMS sets in twenty-four. When the PDMS is solid, the mold is removed
from the IBA slide and holes are punctured through the mold for the tubing to connect later.
The mold is then adhered to a new, clean, glass slide by way of Oxygen Plasma. Ethanol is run
through the channels to ensure a successful chip.
The chip and process of encapsulation with oil is first tested with water and oil. This test is done
to familiarize the users of the chip with the process and effects of different pressures on liquids.
The cost of performing these tests with water and oil is negligent, compared to a high material
cost of liquid crystal.
A syringe filled with water dyed blue will be sent through the middle channel and two syringes
filled with the oil will be sent through the two side channels. We will then set up the syringe
with oil and the syringe with water on two different syringe pumps. Different speeds of the
liquids are tested to study the effects on the encapsulations. The droplets ranged from 90 micro-
meters to 250 micro-meters in diameter.
After the water testing, trials using the Thermosensitive liquid are attempted. The center
channel is filled with liquid crystals, the two other tubes, filled with oil, will be applied to the two
side channels. The forth tube will be inserted at the other end where the encapsulated liquid
crystals will come out. From there, the liquid crystals will be placed onto the glass substrate with
a plastic covering. Three different prototypes were made, all having a different size of liquid
crystal droplet. As the prototypes are filling up with oil and LC droplets, the excess oil from the
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sample needs to be drained. This will allow for more droplets to be added to the prototype. The
prototypes took approximately six hours to complete.
5.2 Electrospraying First a coaxial needle is made and drilled a hole on the outer part of the needle. This is so a tube
can be connected to the coaxial needle in which we will flow the polymer solution through.
There are two different needles. One is the inner needle which has the liquid crystal solution
and the second is the coaxial needle which has the hole for the polymer filled tube. After making
the coaxial needle, we will have to dissolve the polymer (PDLA) in specific solvents which are the
chloroform and toluene. Once the polymer is dissolved, add rhodamine B. Rhodamine B is a
material which shows a red color when a green light is shined upon it. Now add fluorescence to
the liquid crystal and shined a blue light in order to observe the encapsulated liquid crystal.
We first encapsulate with water using chloroform as our solvent since we know that chloroform
is not easily mixed with water. The ratio of the polymer and chloroform is around 1:17 in order
to form a water droplet. We set the syringe pump rate of water to 0.18ml/hr and 0.50ml/hr for
the polymer. After the droplet is formed at the emitter of the coaxial needle, we apply a high
voltage around 5KV to 20KV and it will spray droplets on the glass slides. After successfully
encapsulating the water inside of the polymer, liquid crystal is tested next.
For the Liquid Crystal, the same flow rates as the water trial are attempted first. The tests result
in a mix encapsulation of liquid crystal and polymer. After trial and error, it is decided to change
the solvent for the polymer since the chloroform will have mix encapsulation with the liquid
crystal. The next trials use toluene as the solvent and the ratio increased to 21:1. From the color
observation, it is observed that the liquid crystal is successfully encapsulated by the polymer.
Now continuing the experiment by using a flow rate of 0.15ml/hr for liquid crystal and 0.65ml/hr
for polymer by not adding any fluorescence and rhodamine B. All successful samples were sent
to the third party for testing.
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Testing
6.1 Testing Background Once the final products are acquired by two methods, they will be sent to get tested by an
outside source in Nebraska. All though there was some successful encapsulation of the liquid
crystals inside of the polymer and the oil, this process is relatively new. This is a type of
exploratory project to see whether the refractive index as well as the orientation of the droplets
can be manipulated in order to reflect light or take in more light.
6.2 Testing of Thermosensitive Liquid Crystals (Microfluidic Formation) The thermo sensitive liquid crystal was sent out to a private firm in Nebraska. This firm added a
stabilizer to the final product and went ahead with the testing. Spectrosopic test was performed
on the liquid crystals while changing the temperature. The results below are shown from when
the product was held at a certain temperature then the temperature was increased. The final
product was put onto a stage that was equipped with a Kapton heater with a temperature
control unit which would change the temperature from 15 degrees to 50 degrees Celsius. Then a
mirror is placed underneath the setup and a white light is shown through the bottom to record
whether the droplets changed. To view this change in the droplets, the amount of light that
came through the product was recorded. For setup, see figure 8. For the spectroscopy, the
temperature started at 0 and was slowly increased to 42 degrees Celsius. The time it took to go
from 0 to 42 was 90 seconds. It was then held constant for some time and then refractive index
was recorded by the amount of light coming through the system. The system then was cooled
for 300 seconds, then temperature was increased back up to 21 degrees Celsius. The refractive
index was again recorded and this time, there was more light coming through the product than
there was with the higher temperature. This is opposite of what we were expecting
TEPERATURE TESTING:
Before Temperature Increase 1
After Temperature Increase 1
Before Temperature Increase 2
After Temperature Increase 2
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SPECTROSCOPY TESTING:
6.3 Testing of Electrosensitive Liquid Crystals (Microfluidic Formation) Unlike the Thermosensitive liquid crystals, the Electrosensitive liquid crystals could not stabilize
with light mineral oil with %1 surfactant. While being sent through the microfluidic chip, the
liquid crystal was unable to successfully separate each droplet from the other. This caused us to
not get a successful encapsulation for a final product. No prototypes with Electrosensitive
crystals formed by microfluidic formation were sent out.
6.4 Testing of Thermosensitive Liquid Crystals (Electro-Spraying) The electro-spraying was unable to successfully encapsulate the Thermosensitive liquid crystal.
Like the microfluidic method, there was not a distinction between the polymer and the liquid
crystal. The Thermosensitive liquid crystal kept mixing in with the polymer and this kept the
process from making the liquid crystal become encapsulated inside the polymer.
6.5 Testing of Electrosensitive Liquid Crystals (Electro-Spraying) The Electrosensitive liquid crystal was able to be fully encapsulated by the polymer through
Electrospraying. The testing for the Electrosensitive and the Thermosensitive liquid crystals are
very similar but the Electrosensitive is going to require the use of the transparent ITO slides
mentioned earlier. The setup has a polarizer right against the microscope like the first test. This
time though, the final product will have 2 transparent ITO electrodes on each side (one for each
side). The electrodes will allow there to be an electric field across the liquid crystals. Then there
is a voltage that is applied ranging from no voltage up to 5 volts (see figure 10 for setup). At
each voltage, the orientation of the liquid crystal shells will be tested to find out what the
optimal voltage is for the orientation of the liquid crystal. When the voltage applied was at 0 V,
the orientation of the microshells was “flat” which then allowed a lot of light to come through.
When the voltage started to increase, the orientation of the shells was starting to become at an
angle to the surface. This made for a darker appeal from the liquid crystal than before. Once the
At 42 degrees Celsius 1 At 21 degrees Celsius 1
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voltage climbed up to around 3.7 V, the liquid crystals were completely dark and the only thing
that showed up was the polymer. At this point, the liquid crystals were completely uniformed
(see figure 11). The voltage was then raised more but the orientation of the shells became
cluttered and inconsistent. The microshells started to come together all though they did not
recombine.
ELECTRIC FIELD TESTING:
The optimal voltage that was applied to the system to create the darkest product is around 3.7
Volts. This is where the orientation of the liquid crystals is uniform and aligned in a way where
there is really no light let through.
Voltage Applied at 3.7 Volts Voltage Applied at 0 Volts
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Evaluation:
7.1 Evaluation of Thermosensitive Liquid Crystal The Thermosensitive liquid crystal was only encapsulated with one method. The microfluidic
method was able to successfully encapsulate the liquid crystal without too much recombination.
After the testing, the results did show that it is possible to change the refractive index of the
crystal and change the color according to the temperature applied. There was a definite change,
but this was not according to what we assumed in the first place. The color was darker when it
was at 42 degrees Celsius and was a lighter color when it was at 21 degrees Celsius. This result is
opposite of what we were assuming. As the temperature increases, the refractive index of the
liquid crystal is becoming more and more parallel to the final product. By having these refractive
indexes go parallel as opposed to perpendicular, there is less light that is going towards the
observer. The refraction is taking the light in another direction than towards the observer’s eye.
All though this is not the result we expected, it does show that the liquid crystal can be
encapsulated and that the refractive index, according to temperature, can be changed.
7.2 Evaluation of Electrosensitive Liquid Crystal The Electrosensitive liquid crystal showed a definite color change as the voltage was applied to
the product. When the voltage climbed, the product became increasingly darker to a certain
voltage. At 3.7 volts, the product was the darkest and let in the least amount of light possible.
On the other hand, the liquid crystal was the clearest at 0 volts which is where the most light
will be let in. If the voltage was raised above the 3.7 Volts, it would start to let in more light.
After this optimal voltage, the orientation of the microshells started to have numerous
orientations. This created an random set which allowed for more light to be let it.
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Resources and Schedules
8.1 Personnel Effort Requirements
Ryan Wubbens
Tyler Keeton
Keng Gee William Zimmerman
Total hours per task
Problem Definition 33 29 9 28 99
Problem definition with advisor 2 2 2 5
Requirement identification 3 3 3 5
Project plan completion 28 24 4 18
Technological considerations and project research
14 14 14 20 62
Research of electrospinning encapsulation of liquid crystals
4 4 4 7
Research of microfluidic encapsulation of liquid crystals
4 4 4 7
Research and understanding of processes
6 6 6 6
Lab Training 17 17 17 17 68
Safety review 3 3 3 3
Equipment review 4 4 4 4
Material review 2 2 2 2
Equipment constraint identification 8 8 8 8
Final product design 23 23 23 23 92
Identify target size of microshell 7 7 7 7
Identify substrate material 2 2 2 2
Identify encasing material 2 2 2 2
Documentation of design 12 12 12 12
Design microfluidic chip 25 25 0 0 50
Identify specifications 4 4
Configure chip 15 15
Test chip 5 5
Document results 1 1
Encapsulation of liquid crystals 80 80 80 240
Encapsulate Thermosensitive liquid crystal by electrospinning
40
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Encapsulate Electrosensitive liquid crystal by electrospinning
40
Encapsulate Thermosensitive liquid crystal by microfluidic formation
40 40
Encapsulate Electrosensitive liquid crystal by microfluidic formation
40 40
Implement prototype 11 11 11 33
Cover the substrate with microshells 8 8 8
Encase the microshells and substrate 3 3 3
Initial testing of product 8 8 8 24
Test the Thermosensitive microshells response to temperature
3 3 3
Test Electrosensitive microshells response to electric field
3 3 3
Test the chameleon panel durability 2 2 2
Third Party Testing 2 2 2 6
Send final prototype to third party for testing
1 1 1
Review results 1 1 1
Final product documentation 20 20 20 60
Create project poster 4 4 4
Final project report 16 16 16
Final product demonstration 2 2 2 6
Faculty advisor demonstration 1 1 1
Review panel demonstration 1 1 1
Total hours : 235 231 186 88 740
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8.2 Financial Requirements Below are the estimated material and labor costs for the project.
Material: Cost:
Polymer PDA/PDLLA Donated
Polymer Coating PDA/PDLLA Donated
Electro-sensivitve liquid crystal MBC $ 200
Thermosensitive-liquied crystal 5BC and other $ 200
Microfluidic chip Donated
Substrate Donated
Solvents Donated
ITO 1” x 3” Donated
Total $ 400
Labor
Hours @ $15
Ryan Wubbens 226.5 $ 3397.5
Tyler Keeton 191 $ 2865
William Zimmerman 95 $ 1425
Keng Gee 151.5 $ 2272.5
Total Labor 882 $ 9960
Total Cost $ 11360
8.3 Deliverable Schedule The delivery date for the multiple tested prototypes is April 9th, 2009. The associated
documentation will be available April 28th, 2010.
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8.4 Project Schedule
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Operation Manual
9.1 Operation Manual Operational Manual of the System (2-3 pages)
Senior Design 491/492 class, Iowa State University
492 Project title: High Efficiency and Low Cost Solar Cells toward Next Generation Photovoltaic
(Chameleon Panel)
492 Project team (students, advisor, client): Ng Keng Gee, Tyler Keeton, Ryan Wubbens
Author of the document: Michelle Tan
1. What is the high-level objective of the project? (2-4 sentences)
The high level objective of this project is to find the characteristic possibilities of a liquid crystal
based roof. In order to accomplish this project, two techniques are used. They are
Electrospraying and Microfluidic Formation will be used to create a thin liquid crystal layer.
2. What are the key functional requirements of the system? (2-4 requirements)
a) The liquid crystal droplets should be separated and stabilized
b) The thermo-sensitive liquid crystal must be able to change refractive index with respect to
temperature.
c) The electro-sensitive liquid crystal must be able to change refractive index with respect to
electric field.
d) Need to test with Electrospraying and Microfluidic Formation
3. What has been actually implemented? (1-2 paragraphs)
implemented system, the hardware,
software, and other equipments used in the system.
No hardware or software within the system. All materials used are raw. With Microfluidic
Formation, there are three different channels. The liquid crystal comes through the middle
channel and the mineral oil comes through the two outer channels to allow the liquid crystal to
be encapsulated. As the liquid crystal has a slower rate, the oil will go in front of the liquid
crystal and then pinch off a droplet. The oil has a solution inside of it called span80 which will
help to separate the oil droplets apart and keep the liquid crystals from recombining. The
product has different droplets that are closely packed at the size of 200 micrometer in a
diameter of each droplet.
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With electrospraying, it uses 2 different materials. One is the liquid crystal and the other is a
type of polymer (PDLLA) and a solver (chloroform). The polymer will be around the liquid crystal
so that encapsulation will happen. The two liquids will then form a single droplet at the tip of
the syringe. Once there is a droplet at the tip, a very high voltage (5~10KV) will be applied to the
drop which will allow the liquid crystal and polymer to swirl in zone where it transitions from a
liquid to a solid onto a substrate (ground).
4. How to setup the system? (~1 page in bulleted list form)
-by-step instruction on how to setup/demo and test the operational system
For Microfluidic Formation:
1. Run Light mineral oil with 1% surfactant at 0.5uL/h
2. Run liquid crystal at 50uL.h
3. Turn on system
4. Observe that the oil and liquid crystal with combine in the channel
5. Capture the droplets in the 3rd chamber
6. Drain as much oil as possible from glass chamber (will increase droplets density)
For Electrospraying:
1. Run liquid crystal (syringe) in a large syringe of polymer
2. Observe both the liquid form a droplet (Polymer encapsulate the liquid crystal)
3. Apply a very high voltage (5~10KV)
4. Observe liquid crystal and polymer to swirl in zone where it transitions from a liquid to a solid
onto a substrate (ground).
5. Test results observed? (one paragraph)
Results were sent in for testing. Microfluidic formation remains not combined thus works for the
project. The liquid crystals change from white to black. But only some do, it is presumed that
only the smaller encapsulations are the ones changing refractive index. But that will not be
known until the full results are in. Results for electrospraying failed. There are leaking of the
liquid crystal from the polymer and resulted in mix encapsulation. I am working on another type
of solvent now. Team proceeds with a different kind of polymer.
6. Critique of the project
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weakness of the implemented system (2-4
bullets)
Strength: Experiment with 2 techniques (determines which might work best)
Weakness: Process can’t be used for large panels.
Does the implementation meet the specification? In either case, provide a brief discussion. (2-
3 sentences)
Yes and no. For microfluidic formation, we saw from pictures that the panel does change its
characteristics and color from black to white. Some do recombine and stabilized but some still
do. More testing should be done.
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Closure Material
10.1 Client Information Liang Dong Mailing Address: 2115 Coover Hall Ames IA 50011.United States Contact Number: 515-294-0388 Fax Telephone Number: 515-294-0388 Email address: ldong iastate.edu
10.2 Faculty Advisor Information Liang Dong Mailing Address: 2115 Coover Hall Ames IA 50011.United States Contact Number: 515-294-0388 Fax Telephone Number: 515-294-0388 Email address: ldong iastate.edu
10.3 Student Team Information First and Second Semester Team: Wubbens, Ryan Major: Electrical Engineering Mailing Address: 3819 Tripp St #5 Ames, IA 50014 Email Address: [email protected] Keeton, Tyler Major: Electrical Engineering Mailing Address: 5121 Frederiksen Ct Ames, IA 50010 Email Address: [email protected]
Gee, Keng Major: Electrical Engineering Mailing Address: 4138 Frederiksen Ct Ames, IA 50010 Email Address: [email protected]
First Semester Only: Zimmerman, William Major: Electrical Engineering Mailing Address: 1310 Garfield Ave Ames, IA 50014-3814 Email Address: [email protected]
10.4 Closing Summary
For areas with a changing climate, a mono-chromatic roof can be detrimental to the heating and
cooling of a structure. When the chameleon panel covers the roof of a structure, it will reduce
the work needed by heating and cooling systems on a structure by utilizing a renewable
resource. Our chameleon panel will be made using electrospraying and microfluidic formation
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of encapsulated liquid crystals. The liquid crystal’s ability to change refractive index will be used
to absorb or reflect solar thermal energy.
10.5 References
1. Polymer 40(1999) 4585-4592: Beaded nanofibers formed during electrospinning
2. Composites Science and technology 63 (2003) 2223-2253: A review on polymer nanofibers by
electrospinning and their applications in nanocomposites
3. Journal of Material Chemistry, 2005, 15, 735-738: Electrospinning of nanofibers with core-
sheath, hollow, or porous structures.
4. Langmuir 2009, 25(14), 7857-7861: Synthesizing Microcapsules with Controlled Geometrical
and Mechanical Properties with Microfluidic Double Emulsion Technology
5. Allen J. E, “A Note on the Taylor Cone”App. Physics L59-62, (1985)
6.Dong, L., A. K. Agarwal, D. J. Beebe, and H. Jiang. “Adaptive Liquid Microlenses Activated by
Stimuli-responsive Hydrogels.” Nature 442, (2006): 551–554
