Colloidal Drop Spreading, Evaporation and Particle Deposition...
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Colloidal Drop Spreading, Evaporation and Particle Deposition – A Lattice Boltzmann Study Abhijit S. Joshi and Ying Sun, Complex Fluids and Multiphase Transport Lab Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia PA 19104 Evaporation with a “Pinned” Contact Line For rough surfaces, experiments reveal that the contact line can remain pinned during drop evaporation until the receding contact angle is reached. The LBM simulation above demonstrates this effect for a receding contact angle of 15°. Like experiments, suspended particles inside the liquid are observed to flow towards the contact line in the LBM. Isothermal Evaporation Model Effect of Drop Spacing on Deposit Morphology A large spacing between successive drops (top row) leads to isolated deposits. When the spacing between the drops is reduced (bottom row), the spreading contact lines of adjacent drops connect with each other and the final deposit shows continuity. Reducing spacing between drops can lead to line deposits. Inkjet printer nozzle Flexible Substrate Liquid drop with suspended material Functional material deposit z y x Motivation: Functional Material Deposition using Inkjet Printing 0.70 1.04 1.40 Drop spacing / Drop diameter Initial particle volume fraction Morphology Map: Final Particle Deposition 10% 5% Conclusions & Future Work Vapor outflow boundary condition induces isothermal evaporation of the liquid drop Fixed solid substrate Suspended solid particles Vapor Liquid Lattice Boltzmann Method SUBSTRATE 1 3 2 LIQUID VAPOR A three-dimensional (3D), multi-phase (liquid + vapor) particle suspension model has been developed based on the 2D model of Joshi and Sun (2009)*. The computer code has been developed using FORTRAN 90 and runs on a parallel supercomputer. Suspended particles are spherical in shape and their motion is coupled to the fluid flow. Inter-particle forces prevent particles from overlapping with each other, or with the solid substrate at the bottom. Particles can be trapped by the liquid-vapor interface. * Joshi A. S. and Sun Y. (2009) Physical Review E, 79, 066703 Self-Similar Evaporation (Moving Contact Line) Acknowledgments: Support for this work was provided by the National Science Foundation (Grant No. CAREER-0846825) and the American Chemical Society Petroleum Research Fund (Grant No. 47731-G9). The lattice Boltzmann method (LBM) is a useful computational tool to investigate the fundamental physical processes during deposition of functional materials using inkjet printing. Experimentally observed processes like contact line pinning can be modeled with ease. The final particle deposits can be studied as a function of process parameters in order to optimize the process and obtain repeatable results. Future work will consist of experimental validation of the model and extension to simulate deposition of non-spherical (ellipsoidal) particles. x z Periodic boundary Periodic boundary z y x z y x This type of evaporation is observed for smooth substrates with no physical or chemical heterogeneities. Most of our results so far have been obtained for such an “ideal” substrate. The contact angle remains unchanged throughout the evaporation process. L x L Y D Number of suspended particles Suspended particle radius Initial liquid drop diameter Initial spacing between adjacent (periodic) liquid drops Evaporation rate (suction velocity at the top of the domain) Equilibrium contact angle L Y D R P N P U Z θ eq LBM Parameters for Obtaining Line Deposits x y 87 particles / drop 44 particles / drop Contact line
Transcript of Colloidal Drop Spreading, Evaporation and Particle Deposition...
Colloidal Drop Spreading, Evaporation and Particle Deposition – A Lattice Boltzmann StudyAbhijit S. Joshi and Ying Sun, Complex Fluids and Multiphase Transport Lab
Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia PA 19104
Evaporation with a “Pinned” Contact Line
For rough surfaces, experiments reveal that the contact line can remain pinnedduring drop evaporation until the receding contact angle is reached. The LBMsimulation above demonstrates this effect for a receding contact angle of 15°. Likeexperiments, suspended particles inside the liquid are observed to flow towardsthe contact line in the LBM.
Isothermal Evaporation Model
Effect of Drop Spacing on Deposit Morphology
A large spacing between successive drops (top row) leads to isolated deposits.When the spacing between the drops is reduced (bottom row), the spreadingcontact lines of adjacent drops connect with each other and the final depositshows continuity. Reducing spacing between drops can lead to line deposits.
Inkjet printer nozzle
FlexibleSubstrate
Liquid drop with suspended material
Functional material deposit
z
yx
Motivation: Functional Material Deposition using Inkjet Printing
0.70 1.04 1.40
Drop spacing / Drop diameter
Initi
al p
artic
le v
olum
e fr
actio
n
Morphology Map: Final Particle Deposition
10%
5%
Conclusions & Future WorkVapor outflow boundary
condition induces isothermal evaporation of the liquid drop
Fixed solid substrate
Suspended solid particles
Vapor
Liquid
Lattice Boltzmann Method
SUBSTRATE
1
3
2
LIQUIDVAPOR
A three-dimensional (3D), multi-phase (liquid + vapor) particle suspension model has been developed based on the 2D model of Joshi and Sun (2009)*. The computer code has been developed using FORTRAN 90 and runs on a parallel supercomputer.
Suspended particles are spherical in shape and their motion is coupled to the fluid flow.
Inter-particle forces prevent particles from overlapping with each other, or with the solid substrate at the bottom.
Particles can be trapped by the liquid-vapor interface.
* Joshi A. S. and Sun Y. (2009) Physical Review E, 79, 066703
Self-Similar Evaporation (Moving Contact Line)
Acknowledgments: Support for this work was provided by the National ScienceFoundation (Grant No. CAREER-0846825) and the American Chemical SocietyPetroleum Research Fund (Grant No. 47731-G9).
The lattice Boltzmann method (LBM) is a useful computational tool to investigatethe fundamental physical processes during deposition of functional materialsusing inkjet printing.
Experimentally observed processes like contact line pinning can be modeled withease.
The final particle deposits can be studied as a function of process parameters inorder to optimize the process and obtain repeatable results.
Future work will consist of experimental validation of the model and extension tosimulate deposition of non-spherical (ellipsoidal) particles.
x
z
Peri
odic
bou
ndar
y
Peri
odic
bou
ndar
y
z
yx
z
y x
This type of evaporation is observed for smooth substrates with no physical orchemical heterogeneities. Most of our results so far have been obtained for suchan “ideal” substrate. The contact angle remains unchanged throughout theevaporation process.
Lx
L Y
D
Number of suspended particles
Suspended particle radius
Initial liquid drop diameter
Initial spacing between adjacent (periodic) liquid drops
Evaporation rate (suction velocity at the top of the domain)
Equilibrium contact angle
L Y
D
RP
NP
U Z
θeq
LBM Parameters for Obtaining Line Deposits
x
y
87 particles / drop
44 particles / drop
Contact line
