The attached will be presented at the JSC Science Symposium as a preview of the ACE-T5 flight experiment. The Principal Investigator (PI) for this experiment is Professor Ali Mohraz at the University of California - Irvine.Bijels (bicontinuous interfacially jammed emulsion gels) were discovered in 2007 at the University of Edinburgh. These materials feature a tubular, bicontinuous arrangement of two fluid phases separated by a monolayer of jammed colloidal particles at the interface.Because of their unique morphological characteristics, bijels hold significant promise as next-generation materials for energy and biotechnology applications. But in order to fully realize their potential, their physics and mechanical properties must be better understood. The mechanical properties and stability of bijels is mediated by an interplay between interfacial forces that impart elasticity to the system, and external stresses. Unfortunately, the interfacial forces are inherently coupled with density differences and cannot be studied systematically in the presence of gravity

Bohurjak, Michael

Chao, David

Ching, Herman

Eustace, John

Meyer, William V.

Mohraz, Ali

Sicker, Ron

English

NASA Technical Reports Server

National Aeronautics and Space Administration
1
Presented by:
Dr. William V. Meyer (a.k.a. Bill Meyer)
ACE NASA Project Scientist
USRA at  NASA GRC, Tel: (216) 433-5011, Email: William.V.Meyer@NASA.Gov
ACE NASA Project Manager: Ron Sicker, Tel.: (216) 433-6498
ACE-T5 NASA Project Scientist: David Chao, Tel.: (216) 433-8320
ZIN-Technologies ACE Project Manager: Michael  Bohurjak, Tel: (440) 625-2264
ZIN-Technologies Science Lead: John Eustace, Tel:  (440) 625-2244
September 2019
Science Symposium, ISS Inc. 61-62
Advanced Colloids Experiment (Temperature controlled) – ACE-T5
Prof. Ali Mohraz, U of California (PI) and Herman Ching, U of California (PhD Student)
https://ntrs.nasa.gov/search.jsp?R=20200000052 2020-03-11T13:57:53+00:00Z
New Bijel Chemistries for Long-
Duration Microgravity and Ground-
Based Experiments
NASA Research Opportunities in Complex Fluids
and Macromolecular Biophysics
80NSSC18K1554
PI: Ali Mohraz
University of California, Irvine
Department of Chemical and Biomolecular Engineering
Outline
• Science Team
• Science Background, Hypothesis, and Objectives
– Introduction to bijels
– Unresolved scientific questions
– Need for new chemistries
– Importance of long-duration microgravity
• Earth Benefits and Applications
– Applications in energy materials
– Applications in tissue engineering and biomaterials
• Ongoing Ground-Based Experiments
Science Team
Ali Mohraz (Principal Investigator)
Associate Professor of Chemical and Biomolecular 
Engineering
University of California, Irvine
Herman Ching (Graduate Student Researcher)
PhD Student in Chemical and Biochemical Engineering
University of California, Irvine
Abstract
Bijels (bicontinuous interfacially jammed emulsion 
gels) were discovered in 2007 at the University of 
Edinburgh. These materials feature a tubular, 
bicontinuous arrangement of two fluid phases 
separated by a monolayer of jammed colloidal 
particles at the interface.
Because of their unique morphological 
characteristics, bijels hold significant promise as 
next-generation materials for energy and 
biotechnology applications. But in order to fully 
realize their potential, their physics and 
mechanical properties must be better understood.  
The mechanical properties and stability of bijels is mediated by an interplay 
between interfacial forces that impart elasticity to the system, and external 
stresses.  Unfortunately, the interfacial forces are inherently coupled with density 
differences and cannot be studied systematically in the presence of gravity.
Bicontinuous Interfacially Jammed Emulsion Gels
I. Pagonabarraga et al. 
New J. Phys. (2001)
K. Stratford et al, Science (2005)
A. Herzig et al, Nature Materials (2007)
Spinodal Decomposition Arrested by Particle Jamming at the Interface
Rapid temperature 
quench
ttttt
Bijel Formation (Confocal Video)
t (~15 s)
Bijel Morphology
Bicontinuous emulsion mechanically stabilized by a jammed 
particle monolayer in macroscopic (several mm) samples
Magnification
Unique Opportunity for Materials Synthesis
ξ
Control of Domain Size
For monolayer 
coverage,
Decreasing ϕ
ξ
Early Stage Late Stage
Bijel Processing Method Pioneered at UC Irvine
Monomer: 1,6 hexanediol diacrylate; polyethyleneglycol diacrylate, and more  
Photoinitiator: Darocur 1173
Lee and Mohraz, Advanced Materials (2010Magnification
Dipentaerythritol Pentaacrylate
Esters
(PEGDA, 2 repeat units on 
average) 
Ethoxylated Trimethylolpropane
Triacrylate Esters 
(ETA, 20 total repeat units)
Biocompatible Bijel-Templated Sponges
Lee and Mohraz, Advanced Materials (2010);  J. Amer. Chem Soc. (2011
Bijel-Derived Porous Metals and Ceramics
Morphological Characteristic of Bijel-Derived 
Materials, Compared to Other Relevant Systems
• Bicontinuity
• Negative Gaussian Curvatures
• Uniform Domain Size
• Low Degree of Branching
EARTH BENEFITS AND 
APPLICATIONS
Polymer removed 
completely at            
T ~ 450°C
Control over 
crosslinking density 
opens new routes 
for materials 
processing
Materials Processing
Lee and Mohraz, Advanced Materials (2010)
Electrochemical Energy Storage
Increasing Active Material Thickness (δ )I
nc
re
as
in
g 
Su
rfa
ce
 A
re
a/
Vo
lu
m
e 
(S
V)
Control of Domain Size & Active Material Thickness
Gravimetric Ragone Plot
1. H. Wang et al, J. Am. Chem. Soc. (2010)
2. K Liang et al, J. Mater. Chem. (2012)
3. K Liang et al, Mater. Res. Bull. (2013)
4. S. Meher et al, ACS Appl. Mater. Interf. (2011)
5. T. Zang et al, Adv. Funct. Mater (2012)
.
1
2
3
4
J. A. Witt, D. R. Mumm, A. Mohraz, J. Mat. Chem. A (2016)
Extension to Other Chemistries (ZnO here)
K. McDevitt, D.R. Mumm, A. Mohraz, to be submitted
Application in Biomaterials
T.J. Thorson, E.L. Botvinick and A. Mohraz, ACS Biomat Sci & Eng (2018)
T.J. Thorson et al, Acta Biomaterialia, to appear (2019)
For monolayer coverage,
A. Herzig et al, 
Nature Mat (2007)
Outstanding Question: What causes the deviation from the 
expected linear scaling?
Hypothesis: A matter of mechanical stability against gravity.
Control of Domain Size
Expanding the Synthesis Platform
Water + 2,6-Lutidine Ethylene Glycol + Nitromethane
Critical point: xL = 0.064  Tc = 34.1°C Critical point: xNM = 0.64  Tc = 40°C
Microwave 
heating
Ethanol Bath Cooling
A. Herzig et al, Nature Mat (2007) J.W. Tavacoli et al, Adv Func Mat (2011)
New bijel chemistries can expand the range of materials possible.
However, so far our materials processing methods have only 
been successful with the W/L system.
Clues from Bijel Rheology
Lee et al, Advanced Functional Materials (2013)
With most bijel chemistries, 
the scaffold breaks down 
upon fluid remixing
Fluid remixing
The W/L system can form a 
monogel (withstands remixing)
shear
Lee et al, Advanced Functional Materials (2013)
Clues from Bijel Rheology
Fluid remixing
Bijel Rheology and Processability
Outstanding Question: Why can’t we process bijels
with other chemistries into co-continuous composites?
Hypothesis: During monomer diffusion, concentration 
gradients lead to Marangoni forces along the interface 
and cause structural breakdown in weak samples.
Must better understand bijel rheology and response to Marangoni forces
Patel and Russel, 
J. Coll Int Sci (1989)
Interactions in BIJELs:
- Van der Waals
- Electrostatic
- Capillary Interparticle interactions are quite complicated! 
Bijel Rheology and Processability
Role of Microgravity - 1
For monolayer coverage,
A. Herzig et al, 
Nature Mat (2007)
Outstanding Question: What causes the deviation from the 
expected linear scaling?
Hypothesis: A matter of mechanical stability against gravity.
Mechanical stability 
hypothesis can be 
tested by preparing in 
microgravity at least 
one bijel at volume 
fractions below Φc
Role of Microgravity - 2
Temperature dependence of σ can be exploited to 
systematically study the effect of Marangoni forces on bijels.  
However, such effects must be decoupled from density 
differences.
NEW CHEMISTRIES FOR LONG-
DURATION MICROGRAVITY 
EXPERIMENTS (REQUIRED FOR 
ASTRONAUT SAFETY)
Cloud Point Measurements for Phase Diagram
Candidate Binary Fluid Mixtures Considered
PROPOSED EXPERIMENTS
Materials and Methods
Propylene Glycol + Nitroethane, prepared at critical 
composition of xNE = 0.64 
1 μm
Fluorescent silica particles, diameter D ~ 400 nm 
Surface chemistry modified by grafting hydrophobic 
moieties hexamethyldisilazane (HMDS) onto the 
surface
ACE-T Hardware at the ISS utilized to prepare 
bijels and subject them to controlled temperature 
gradients  
Using 10x and 20x air objectives, images recorded 
after bijel formation to assess domain size 
dependence on Φ, and after temperature gradient to 
assess stability against Marangoni forces
2 × 3 cells, prepared at volume fractions ranging 
from Φ = 0.005 to Φ = 0.04, (Φ = 0.005, 0.01, 0.025; 
Φ = 0.005, 0.0075, 0.015)  
REQUIRED HARDWARE
• Transparent cuvettes with inner dimensions (50 mm x 3 mm x 0.5 mm) and wall 
thickness 0.3 mm or lower
• Capability to heat sample to 25°C and perform mixing at this temperature
• Capability to rapidly and uniformly quench sample at a rate of at least 10°C/min, 
to a final temperature of 0°C
• Confocal imaging with rhodamine filter
• 2.5x air objective for overall sample inspection
• 10x (and potentially 20x or 40x) air objectives for microstructural imaging
• Capability to apply a temperature gradient of 12°C or more along the cuvette 
length
• Capability to record videos at 2 fps, ideally while end temperatures are being 
changed
Images courtesy of NASA
EXPERIMENTAL PROTOCOL
• Heat sample up to 25°C
• Perform in-situ mixing
• Apply a temperature quench at 10°C/min from 25°C to 0°C (phase separation)
• Define XYZ offsets, adjust camera parameters using 2.5x objective and B/S cube 
• Survey capillary cell at 2.5x; determine test locations (away from stir bar or bubble)
• Adjust and record best camera parameters using 10x air objective and dye filter
• Survey and record best z depth where bicontinuous domains can be observed at 
least 150 µm away from the cell walls at each primary test location
• Record one full frame image at this location and z depth
• Back off the height to the cell wall
• Collect a z-stack of 100 images at spacing ∆z = 5 µm (stack covers entire cell width)
• Return to recorded z location where bicontinuous domains were seen
• While recording images at 1 fps, increase the temperature at one end from 0°C to 
4°C at a rate of 1°C/min
• Back off the height to the cell wall
• Collect a z-stack of 100 images at spacing ∆z = 5 µm (stack covers entire cell width)
• Return to recorded z location where bicontinuous domains were seen
• While recording images at 1 fps, increase the temperature at one end from 4°C to 
8°C at a rate of 1°C/min
Continued on next page
EXPERIMENTAL PROTOCOL
Continued
• Back off the height to the cell wall
• Collect a z-stack of 100 images at spacing ∆z = 5 µm (stack covers entire cell 
width)
• Return to recorded z location where bicontinuous domains were seen
• While recording images at 1 fps, increase the temperature at one end from 8°C to 
12°C at a rate of 1°C/min
• Back off the height to the cell wall
• Collect a z-stack of 100 images at spacing ∆z = 5 µm (stack covers entire cell 
width)
• Shutter lamp between image sets to prevent sample bleaching
ONGOING GROUND-BASED 
EXPERIMENTS
PARTICLE SURFACE CHEMISTRY
1 gr of particles (D ~ 600 nm) treated with 1.75 mL HMDS during synthesis
Day 0 Day 2
Particle surface chemistry is dynamic, changing to more hydrophilic behavior over time
θt
Desired
Hydrophobic Particle Surface
Hydrophilic Particle Surface
?
Can we use this strategy?
1 gr of particles (D ~ 600 nm) treated with 1.75 mL HMDS during synthesis
Day 0 Day 2
PARTICLE SURFACE CHEMISTRY
SURFACE CHEMISTRY AGING TESTS
QUESTIONS?
SUCCESS CRITERIA
Minimum Success
• Homogenize samples completely, apply a temperature quench to initiate 
phase separation, and observe bijel formation in 33% of the samples.
• Have images with sufficient quality and clarity to determine the characteristic 
domain size for at least two different colloid volume fractions.
• Be able to demonstrate the breakdown of at least one bijel structure under 
Marangoni forces (temperature gradients).
Significant Success
• Homogenize samples completely, apply a temperature quench to initiate 
phase separation, and observe bijel formation in 66% of the samples
• Have images with sufficient quality and clarity to determine the characteristic 
domain size for at least four different colloid volume fractions.
• Be able to demonstrate the breakdown of at least two bijel structures at 
different colloid volume fractions under Marangoni forces.
Complete Success
• Homogenize samples completely, apply a temperature quench to initiate 
phase separation, and observe bijel formation in all samples.
• Have images with sufficient quality and clarity to determine the characteristic 
domain size for all samples.
• Be able to demonstrate the temperature gradient needed to cause structural 
breakdown for each colloid volume fraction tested.


Advanced Colloids Experiment (Temperature Controlled)  ACE-T5

Advanced Colloids Experiment (Temperature Controlled) ACE-T5

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