Tetsuro Tsuji (Kyoto University, Japan)
The 33rd International Symposium on Rarefied Gas Dynamics (hosted by the German Aerospace Center (DLR))
July 15 - 19 (2024) @ Tagungs- und Veranstaltungshaus Alte Mensa, Göttingen, Germany �(presentation on July 16 13:30-14:10, Micro- and Nanoscale Flows I)
T. Tsuji, S. Mei & S. Taguchi, “Thermo-osmotic slip flows around a thermophoretic microparticle characterized by optical trapping of tracers”, Phys. Rev. Appl. 20, 054061 (2023) Featured in Physics @ APS
Thermally-induced Microflows and
Microparticle Migration
initial state
heating @ 0 s
thermo-osmotic slip flow
Table of contents
thermal flows
speaker: Tetsuro Tsuji (Kyoto University)
title: Thermally-induced Microflows and Microparticle Migration
Phys. Rev. Appl. (2023)
Phys. Rev. Appl. (2018)
×15
50 µm
mean
flow
Physica A (2018)
Introduction
What is thermally-induced microflows ( = thermal flows)?
advection
decoupled
flow
NS system
heat
energy eq.
downsizing…
huge resistance
low efficiency
1
characteristic length
surface effect
is important
small scale
/ 4
Introduction
What is thermally-induced microflows ( = thermal flows)?
characteristic length
surface effect
is important
characteristic length
mean free path
Kn =
ℓ
L
= O(1)
Knudsen number (Kn) is a good indicator of
the significance of surface properties
case of gases
gas-surface interaction
rarefied gas
(or molecular gas)
1
large Kn → collision with surfaces > collision with gas molecules
small scale
cf. Boltzmann equation
/ 4
Introduction
Sone, Phys. Fluids (1991) http://hdl.handle.net/2433/120983
heated plate
heated plate
ambient pressure
LOW pressure
thermal convection
thermal creep
vacuum
heater
What is thermally-induced microflows ( = thermal flows)?
低温
高温
no-slip b.c. for ordinary viscous fluids
flow over a boundary with
a temperature gradient
thermal creep for rarefied gases
Maxwell (1879)
thermal-stress slip flow
nonlinear-thermal-stress flow
thermal edge flow
other types of
thermal flows
Sone (2007)
2
evidence of
thermal creep
windmill-type flow indicator
/ 4
Introduction
vacuum
What is thermally-induced microflows ( = thermal flows)?
低温
高温
no-slip b.c. for ordinary viscous fluids
flow over a boundary with
a temperature gradient
thermal creep for rarefied gases
Maxwell (1879)
thermal-stress slip flow
nonlinear-thermal-stress flow
thermal edge flow
other types of
thermal flows
Sone (2007)
2
applications ?
/ 4
Introduction
Sugimoto & Sone (2005)
Taguchi & Tsuji (2022)
(thermally-driven pump without mechanically moving parts)
X. Wang, et al. Knudsen Pumps: a Review. Microsystems Nanoeng. (2020)
application (ex. 1)
What is thermally-induced microflows ( = thermal flows)?
低温
高温
no-slip b.c. for ordinary viscous fluids
flow over a boundary with
a temperature gradient
thermal creep for rarefied gases
Maxwell (1879)
one-way flow
thermal-stress slip flow
nonlinear-thermal-stress flow
thermal edge flow
other types of
thermal flows
Sone (2007)
thermal-edge flow
one-way flow
2
/ 4
Introduction
flow over a boundary with
a temperature gradient
What is thermally-induced microflows ( = thermal flows)?
no-slip b.c. for ordinary viscous fluids
thermal creep for rarefied gases
Maxwell (1879)
thermal-stress slip flow
nonlinear-thermal-stress flow
thermal edge flow
other types of
thermal flows
Sone (2007)
S. Takata & Y. Sone (1995)
force
≈ Kn
force
force toward
cold side
application (ex. 2)
2
/ 4
Introduction
flow over a boundary with
a temperature gradient
What is thermally-induced microflows ( = thermal flows)?
no-slip b.c. for ordinary viscous fluids
thermal creep for rarefied gases
Maxwell (1879)
thermal-stress slip flow
nonlinear-thermal-stress flow
thermal edge flow
other types of
thermal flows
Sone (2007)
S. Takata & Y. Sone (1995)
force
≈ Kn
force
force toward
cold side
application (ex. 2)
focus of the talk
deeper understanding of thermophoresis
me hoping to
understand
thermophoresis
2
/ 4
Introduction
What is thermally-induced microflows ( = thermal flows)?
低温
高温
flow over a boundary with
a temperature gradient
no-slip b.c. for ordinary viscous fluids
thermal creep for rarefied gases
Maxwell (1879)
thermal-stress slip flow
nonlinear-thermal-stress flow
thermal edge flow
other types of
thermal flows
Sone (2007)
fluid-dynamic limit
Kn = ≪ 1
ℓ
L
small
generalized slip flow theory (Sone, 2007)
fluid-dynamic-type system (e.g. Stokes set) + slip b.c.
How is thermally-induced microflows analyzed?
flow velocity
unit tangent
slip coef.
temperature
2
/ 4
Motivation
~ difficulties & challenges ~
me hoping to
understand
thermophoresis
Motivation
低温
高温
case of gas
flow velocity
unit tangent
slip coef.
temperature
generalized slip flow theory
~ difficulties & challenges ~
& various computational tools
3
e.g., DSMC
thermal flows
/ 4
Motivation
低温
高温
Arkilic, et al., (2001) Colin, et al., (2004) Graur, et al., (2009) Yamaguchi, et al., (2011) Silva, et al., (2018)
Perrier, et al., (2019) Zhang et al., (2023), etc. .
slip coef. measurement
(NO flow profile)
case of gas
mass-flow rate measurements
flow velocity
unit tangent
slip coef.
temperature
generalized slip flow theory
~ difficulties & challenges ~
3
Rojas Cardenas, et al., (2011, 2013), Yamaguchi, et al., (2014, 2016)
thermal slip
shear slip
/ 4
Motivation
低温
高温
Fratantonio et al., (2018, 2020)
laser-induced fluorescence
case of gas
mass-flow rate measurements
molecular tagging velocimetry
flow velocity
unit tangent
slip coef.
temperature
generalized slip flow theory
~ difficulties & challenges ~
3
flow profile measurement
(NOT for thermal flow)
/ 4
Motivation
低温
高温
case of gas
flow velocity
unit tangent
slip coef.
temperature
generalized slip flow theory
mass-flow rate measurements
molecular tagging velocimetry
~ difficulties & challenges ~
me hoping to
understand
thermophoresis
challenges
me hoping to
understand
thermophoresis
me hoping to
understand
thermophoresis
3
So far, NO observation of thermal flow profile is made…,
force
and so do thermal flows around thermophoretic particle!!!
naïve question: what is the situation for liquids?
/ 4
Motivation
低温
高温
case of gas
flow velocity
unit tangent
slip coef.
temperature
generalized slip flow theory
mass-flow rate measurements
molecular tagging velocimetry
~ difficulties & challenges ~
me hoping to
understand
thermophoresis
challenges
me hoping to
understand
thermophoresis
me hoping to
understand
thermophoresis
3
Kavokine, Netz, Bocquet,
Fluids at the Nanoscale: From Continuum to Subcontinuum Transport
Ann. Rev. Fluid. Mech. (2021)
NS system seems to be valid much smaller scale than gas,
but still there is a threshold.
naïve question: what is the situation for liquids?
/ 4
Motivation
低温
高温
case of liquid
case of gas
flow velocity
unit tangent
slip coef.
temperature
generalized slip flow theory
mass-flow rate measurements
molecular tagging velocimetry
~ difficulties & challenges ~
various parameters
4
treatment of
fluid and surface
are different
collision law
(molecular beam experiment)
Kinefuchi, et al., (2017)
/ 4
Motivation
case of liquid
case of gas
flow velocity
unit tangent
slip coef.
temperature
generalized slip flow theory
mass-flow rate measurements
molecular tagging velocimetry
~ difficulties & challenges ~
various parameters
thermal slip coef. K
∝ excess enthalpy in B.L.
Churaev, Derjaguin, Muller
Surface Forces (1987)
same
(formally)
local excess enthalpy
slip coef.
distance from the boundary surface
difficult to measure…
cf.
4
collision law
(molecular beam experiment)
Kinefuchi, et al., (2017)
viscosity
/ 4
Motivation
低温
高温
case of liquid
case of gas
flow velocity
unit tangent
slip coef.
temperature
generalized slip flow theory
mass-flow rate measurements
molecular tagging velocimetry
~ difficulties & challenges ~
various parameters
thermal slip coef. K
∝ excess enthalpy in B.L.
Churaev, Derjaguin, Muller
Surface Forces (1987)
same
(formally)
Continuum theory, Fayolle, Bickel, Würger (2008)
effect of surface charge
effect of hydrophilicity
MD simulation, Fu, Merabia, Joly (2017)
4
collision law
(molecular beam experiment)
Kinefuchi, et al., (2017)
/ 4
Motivation
低温
高温
case of liquid
case of gas
flow velocity
unit tangent
slip coef.
temperature
generalized slip flow theory
mass-flow rate measurements
molecular tagging velocimetry
~ difficulties & challenges ~
various parameters
thermal slip coef. K
∝ excess enthalpy in B.L.
Churaev, Derjaguin, Muller
Surface Forces (1987)
Continuum theory, Fayolle, Bickel, Würger (2008)
effect of surface charge
effect of hydrophilicity
MD simulation, Fu, Merabia, Joly (2017)
same
(formally)
4
collision law
(molecular beam experiment)
Kinefuchi, et al., (2017)
observation of slip flow in thermophoresis
no information on thermal flow profile
/ 4
Motivation
低温
高温
case of liquid
case of gas
flow velocity
unit tangent
slip coef.
temperature
generalized slip flow theory
mass-flow rate measurements
molecular tagging velocimetry
~ difficulties & challenges ~
various parameters
thermal slip coef. K
∝ excess enthalpy in B.L.
Churaev, Derjaguin, Muller
Surface Forces (1987)
Continuum theory, Fayolle, Bickel, Würger (2008)
effect of surface charge
effect of hydrophilicity
MD simulation, Fu, Merabia, Joly (2017)
same
(formally)
4
collision law
(molecular beam experiment)
Kinefuchi, et al., (2017)
observation of slip flow in thermophoresis
thermal flow profile
Fränzl & Cichos (2022)
heated by laser
thermal creep (or thermo-osmosis) on flat surface
Bregulla, et al. (2016)
Fränzl & Cichos (2022)
/ 4
Motivation
低温
高温
case of liquid
~ difficulties & challenges ~
various parameters
thermal slip coef. K
∝ excess enthalpy in B.L.
Churaev, Derjaguin, Muller
Surface Forces (1987)
Continuum theory, Fayolle, Bickel, Würger (2008)
effect of surface charge
effect of hydrophilicity
MD simulation, Fu, Merabia, Joly (2017)
same
(formally)
4
observation of slip flow in thermophoresis
thermal flow profile
Fränzl & Cichos (2022)
heated by laser
thermal creep (or thermo-osmosis) on flat surface
Bregulla, et al. (2016)
Fränzl & Cichos (2022)
me hoping to
understand
thermophoresis
challenges
force
but still NO thermal flows profile around thermophoretic particle!!!
Thermal flow profile can be investigated in liquid.
This situation is better than the case of gas …,
/ 4
Motivation
~ difficulties & challenges ~
me hoping to
understand
thermophoresis
Let’s observe thermal flow around thermophoretic particle and check if thermal flow is indeed the origin of thermophoresis
Table of contents
speaker: Tetsuro Tsuji (Kyoto University)
title: Thermally-induced Microflows and Microparticle Migration
Phys. Rev. Appl. (2023)
Phys. Rev. Appl. (2018)
×15
50 µm
mean
flow
Physica A (2018)
Introduction
Thermophoresis → Motion along temperature gradient
ions, biomolecules, nano- & microparticles
thermophoretic mobility
T: fluid temperature
100 μm
hot
cold
cold
hot
Tsuji, et al. Micro & Nano Lett., (2017)
in Water
in NaOH
Piazza, Soft Matter (2008)
Wurger, Rep. Prog. Phys. (2010)
Mechanism…?
1
/ 7
Phys. Rev. Appl. (2023)
Introduction
thermo-osmotic
slip flow
counteraction
particle motion
(thermophoresis)
Thermophoresis of colloids
gas Takata, et al (1995), Sone (2007) etc.
liquid Ruckenstein (1981), Fayolle, et al (2008) etc.
theory
slip flow
Piazza, Soft Matter (2008)
Wurger, Rep. Prog. Phys. (2010)
Molecular gas dynamics
Macroscopic, Ionic, Electric force
Mechanism…?
Thermophoresis → Motion along temperature gradient
ions, biomolecules, nano- & microparticles
COLD
HOT
flow velocity
unit tangential vector
slip coef.
temperature
SLIP BOUNDARY CONDITION
1
/ 7
Phys. Rev. Appl. (2023)
Introduction
thermo-osmotic
slip flow
counteraction
particle motion
(thermophoresis)
Thermophoresis of colloids
gas Takata, et al (1995), Sone (2007) etc.
liquid Ruckenstein (1981), Fayolle, et al (2008) etc.
theory
Piazza, Soft Matter (2008)
Wurger, Rep. Prog. Phys. (2010)
Mechanism…?
Thermophoresis → Motion along temperature gradient
ions, biomolecules, nano- & microparticles
Weinert & Braun, PRL (2008)
exp
Evaluation of thermo-osmotic slip flows around thermophoretic particles
slip flow
COLD
HOT
challenge
1
Fränzl & Cichos,
Nature Commun. (2022)
difficulty
to suppress thermal convection
e.g., near surface
(thermophoresis & Brownian motion of tracers)
Optical trapping
of TRACERS� (flow indicators)
This study
laser
tracer
/ 7
Phys. Rev. Appl. (2023)
CONCEPT OF EXPERIMENT
Trap on a circular path
Trap on a circular path
CONCEPT OF EXPERIMENT
Experiment
target
optical trap on
circular path
dia.
2
/ 7
Phys. Rev. Appl. (2023)
Control experiment
Tracer
thermophoresis
20 μm
laser heating
no trapping laser
no target particle
laser heating
20 μm
Thermophoresis
of target particle�(d = 7 µm)
no trapping laser
with target particle
(freely movable)
with trapping laser
no target particle
target particle
hot
cold
heating start
t = 0 s
3
/ 7
Phys. Rev. Appl. (2023)
Main result
target particle
(target particle is fixed)
Hypothesis
If the slip flow exists, the tracers are directed to hotter side
4
/ 7
Phys. Rev. Appl. (2023)
Main result
R = 4.4 μm
R = 5.4 μm
R = 6.5 μm
hot
cold
start heating
t = 0 s
target particle
Hypothesis
If the slip flow exists, the tracers are directed to hotter side
(target particle is fixed)
4
/ 7
Phys. Rev. Appl. (2023)
Main result
R = 4.4 µm
R = 5.4 µm
R = 6.5 µm
HOT
intensity distribution
t = 25 s
θ/π
target particle
Hypothesis
If the slip flow exists, the tracers are directed to hotter side
(target particle is fixed)
COLD
COLD
symbol: experiment
curve: model fitting
4
/ 7
Phys. Rev. Appl. (2023)
Slip coefficient
R = 4.4 µm
R = 5.4 µm
R = 6.5 µm
intensity distribution
t = 25 s
θ/π
Curve fitting model
HOT
COLD
COLD
symbol: experiment
curve: model fitting
estimation of slip coef.
from experimental data
slip B.C.
slip coef.
5
/ 7
Phys. Rev. Appl. (2023)
Slip coefficient
R = 4.4 µm
R = 5.4 µm
R = 6.5 µm
intensity distribution
t = 25 s
θ/π
Curve fitting model
HOT
COLD
COLD
symbol: experiment
curve: model fitting
5
/ 7
Phys. Rev. Appl. (2023)
Slip coefficient
R = 4.4 µm
R = 5.4 µm
R = 6.5 µm
intensity distribution
t = 25 s
θ/π
Curve fitting model
HOT
COLD
COLD
symbol: experiment
curve: model fitting
slip B.C.
5
/ 7
Phys. Rev. Appl. (2023)
Slip coefficient
R = 4.4 µm
R = 5.4 µm
R = 6.5 µm
intensity distribution
t = 25 s
θ/π
Curve fitting model
HOT
COLD
COLD
symbol: experiment
curve: model fitting
tracer density
diffusion coef.
drift
thermophoretic velocity
flow velocity
5
/ 7
Phys. Rev. Appl. (2023)
Slip coefficient
intensity distribution
t = 25 s
θ/π
Curve fitting model
HOT
COLD
COLD
tracer density
diffusion coef.
drift
thermophoretic velocity
flow velocity
flow speed − thermophoretic speed
diffusion
=
related to slip coef.
Slip coef. K
-0.50 μm2/s K
-0.45 μm2/s K
-0.44 μm2/s K
Experiments with different laser power
(78 mW)
(47 mW)
(30 mW)
5
/ 7
Phys. Rev. Appl. (2023)
Slip coefficient
intensity distribution
t = 25 s
θ/π
Curve fitting model
HOT
COLD
COLD
tracer density
diffusion coef.
drift
thermophoretic velocity
flow velocity
Slip coef. K
-0.50 μm2/s K
-0.45 μm2/s K
-0.44 μm2/s K
Experiments with different laser power
(78 mW)
(47 mW)
(30 mW)
-0.58 μm2/s K
K obtained from
thermophoresis
good agreement
control experiment
5
/ 7
Phys. Rev. Appl. (2023)
Effect of surface modification
SO FAR
carboxylate-modified
amine-modified
Effect of
surface modification?
ζ = - 46.0 mV
ζ = - 23.7 mV
target particle
Hypothesis
If the slip flow exists, the tracers are directed to hotter side
6
/ 7
Phys. Rev. Appl. (2023)
Effect of surface modification
θ/π
hot
ζ = - 46.0 mV
ζ = - 23.7 mV
Weak zeta potential ⇒ weak flow
Qualitatively consistent
hot
hot
cold
cold
heating
t = 0 s
7 µm
Fayolle, Bickel, Wurger, PRE (2008)
thin EDL (electric double layer) limit, weak surface charge (Debye-Hückel approx.)
surface potential
Slip velocity
viscosity
electric permittivity
thermal conductivity
heating
t = 0 s
6
/ 7
Phys. Rev. Appl. (2023)
Short summary
7
T. Tsuji, S. Mei & S. Taguchi, �“Thermo-osmotic slip flows around a thermophoretic microparticle characterized by optical trapping of tracers”, �Phys. Rev. Appl. 20, 054061 (2023) �Featured in Physics @ APS
/ 7
Phys. Rev. Appl. (2023)
Table of contents
speaker: Tetsuro Tsuji (Kyoto University)
title: Thermally-induced Microflows and Microparticle Migration
Phys. Rev. Appl. (2023)
Phys. Rev. Appl. (2018)
×15
50 µm
mean
flow
Physica A (2018)
Effect of mass in thermophoresis
mechanism based on thermal flows neglects the effect of mass
force
Epstein (1929), Brock (1962),
Takata & Sone (1995), Sone (2007) etc.
Stadelmaier & Kohler (2009)
DT(Mw) – DT(∞) (normalized)
molecular weight
different mechanism other than thermal flow?
1
/ 5
Physica A (2018)
Effect of mass in thermophoresis
■Adiabatic piston problem Gruber & Piasecki (1999)
toward hotter side
2
/ 5
Physica A (2018)
Effect of mass in thermophoresis
■Adiabatic piston problem Gruber & Piasecki (1999)
toward hotter side
“asymmetry of fluctuation”
negative thermophoresis?
2
/ 5
Physica A (2018)
Effect of mass in thermophoresis
■Adiabatic piston problem Gruber & Piasecki (1999)
“asymmetry of fluctuation”
negative thermophoresis?
COLD
HOT
HOT
COLD
HOT
HOT
COLD
COLD
analogy
2
/ 5
Physica A (2018)
Linear Boltzmann equation
HOT
HOT
COLD
COLD
mixture with large mass difference
velocity distribution function of nanoparticles
nanoparticle
collision term between nanoparticles and gas molecules
gain
loss
nanoparticle
velocity of nanoparticles
gain
loss
velocity of gas molecules
direction of relative position
linear
Boltzmann-type
equation
3
velocity distribution function of gas molecules
/ 5
Physica A (2018)
Linear Boltzmann equation
HOT
HOT
COLD
COLD
mixture with large mass difference
given function (gas is not disturbed by the nanoparticle)
linear
Boltzmann-type
equation
velocity distribution function of nanoparticles
nanoparticle
gain
loss
nanoparticle
(non-local collision)
“grazing” collision (due to large mass difference)
velocity of nanoparticles
gain
loss
collision term between nanoparticles and gas molecules
3
/ 5
Physica A (2018)
Linear Boltzmann equation
velocity of nanoparticles
given function (gas is not disturbed by the nanoparticle)
linear
Boltzmann-type
equation
velocity distribution function of nanoparticles
gain
loss
(non-local collision)
“grazing” collision (due to large mass difference)
gain
loss
collision term between nanoparticles and gas molecules
mass ratio (small)
(non-dimensional) temperature gradient (small)
asymptotic analysis
3
/ 5
Physica A (2018)
Asymptotic analysis
set of linear PDEs for Φi,j
…
diffusion scaling
4
/ 5
Physica A (2018)
Asymptotic analysis
…
: differential operators
is a Maxwellian
set of linear PDEs for Φi,j
κ
λ
4
/ 5
Physica A (2018)
Asymptotic analysis
…
density ratio
set of linear PDEs for Φi,j
mass of a nanoparticle
mass of gas molecules in the same volume as nanoparticle
4
/ 5
Physica A (2018)
Asymptotic analysis
integration 2nd order eqs. by velocity space
Drift-diffusion Eq.
2nd order:
conservation of mass
0
set of linear PDEs for Φi,j
4
/ 5
Physica A (2018)
Drift-diffusion equation
number density
drift velocity
(DT >0 → motion toward colder side)
heavy-mass limit
Duhr & Braun, Proc. Natl. Acad. Sci. USA (2006)
thermophoretic mobility
5
mass of gas molecules in
the same volume as nanoparticle
/ 5
Physica A (2018)
Drift-diffusion equation
5
HOT
HOT
COLD
COLD
?
?
/ 5
Physica A (2018)
Drift-diffusion equation
toward cold
toward hot
5
unit vector�in x1 direction
center of nanopartice
vector pointing
to surface
temperature gradient
nanoparticle diameter R → ∞
equivalent
toward hotter side
/ 5
Physica A (2018)
Drift-diffusion equation
toward cold
toward hot
Mw:molecular weight
weight dependence for macromolecules:
Stadelmaier & Kohler, (2008, 2009)
DT(Mw) – DT(∞) (normalized)
molecular weight
same functional form
5
unit vector�in x1 direction
center of nanopartice
vector pointing
to surface
temperature gradient
/ 5
Physica A (2018)
Table of contents
speaker: Tetsuro Tsuji (Kyoto University)
title: Thermally-induced Microflows and Microparticle Migration
Phys. Rev. Appl. (2023)
Phys. Rev. Appl. (2018)
×15
50 µm
mean
flow
Physica A (2018)
Application of thermophoresis
thermophoresis in on-chip microfluidic devices
detection of nano/micro particles (cell, biomolecules, virus, etc.)
Kawaguchi, et al (2012) J. Phys.: Condense. Matter
1
/ 7
Phys. Rev. Appl. (2018)
Application of thermophoresis
thermophoresis in on-chip microfluidic devices
microfluidic device
microchannel
local heating
concept of selective transport by thermophoresis
DT > 0
DT < 0
Kawaguchi, et al (2012) J. Phys.: Condense. Matter
detection of nano/micro particles (cell, biomolecules, virus, etc.)
1
/ 7
Phys. Rev. Appl. (2018)
Microfluidic device
test section
(bottom view)
channel height ≈ 17 μm
2
/ 7
Phys. Rev. Appl. (2018)
Observation of thermophoresis
×15 speed
50µm
electrode
themophobic
PS beads are
repelled from
hot region
Test section
electric current (0.34 W)
3
/ 7
Phys. Rev. Appl. (2018)
Thermophoretic filtration
×15 speed
50µm
pressure-
driven flow
local concentration of PS beads
thermophoretic velocity
mean flow
100-fold concentration
4
/ 7
Phys. Rev. Appl. (2018)
Particle-flow control
electrode
×15 speed
electrode
×15 speed
microparticle
(Φ=1 µm)
nanoparticle
(Φ=100 nm)
Current OFF
Tsuji et al., Micromachines (2019)
5
/ 7
Phys. Rev. Appl. (2018)
Thermophoresis of silica beads
×15 speed
50µm
Thermophilic
Attraction
to hot region
×15 speed
50µm
Thermophobic
Repulsion�from hot region
6
/ 7
Phys. Rev. Appl. (2018)
Selective filtration
PS & silica
d = 1 μm
locally heated
pressure-driven flow
same experiment with different optical filter
PS & silica
d = 1 μm
invisible
PS
silica
Tsuji, et al., Phys. Rev. Appl. (2018a)
Tsuji, et al., Phys. Rev. Appl. (2018b)
PS
100 nm
laser heating
7
/ 7
Phys. Rev. Appl. (2018)
Table of contents
Thank you for your attention
speaker: Tetsuro Tsuji (Kyoto University)
title: Thermally-induced Microflows and Microparticle Migration
Phys. Rev. Appl. (2023)
Phys. Rev. Appl. (2018)
×15
50 µm
mean
flow
Physica A (2018)