A DEVELOPMENT OF MICRO. SHEATH FLOW CHAMBER
`
`Rye Miyake , Hiroshi Ohki
`and Ryohei Yabe
`
`I sao Yamazaki
`
`Mechanical Engineering Research Lab..
`Hitachi.Ltd.
`502 Kandatsu, Tsuchiura 300 JAPAN
`*Naka Works, Hitachi.Ltd.
`882 Ichigc, Katsuta 312 JAPAN
`
`ABSTRACT
`
`1.1NTRODUCTION
`
`is developed using
`sheath flow chamber
`A
`micro-machining.
`Sheath flow geometry is
`formed
`in
`the two—dimensional passage configuration.
`A
`viscous
`flow analysis using
`FEM(Finite Element
`Method)
`helps
`to examine the inside
`flow of
`a
`small
`passage
`and
`design
`the
`passage
`configuration.
`sheath flow chamber consists of
`The micro
`for sheath Fluid.
`a constricted
`passages
`bent
`a capillary tube.
`The height of
`passage.
`and
`is
`300 gm.
`The
`viscous
`flow
`these passages
`analysis
`reveals that swirl
`flow is generated at
`the
`constricted passage.
`thus causing the
`sample
`flow to
`scatter. This result
`suggests
`that
`a
`sample flow guide plate is needed to eliminate the
`swirl
`flow and
`induce a flow to
`envelope
`the
`sample
`fluid.
`Experimental mesurement
`of
`the
`sample flow using a guide plate shows a the smooth
`constricted sheath
`Flow is obtained and
`the
`velocity reaches
`3.0 m/s. nearly the same
`speed
`as the value obtained by the viscous analysis.
`
`bufier
`(sheath fluid}
`
`
`\\sampb
`
`
`
`
`Failicles
`
`capmaw
`tube
`
`scatterd
`fight
`detector
`
`Fig.1 Schematic Diagram
`of Flow cytometer
`(Emphasis on Flow Chamber)
`
`Recent advancement of micro—machining aids in
`the development of portable particle analyzer as a
`fluid integrated micro system.
`a capability of
`A particle analyzer
`has
`measuring
`and
`displaying multiple
`spectro-
`photometoric properties of particles
`at
`rates
`exceeding 5,000 particles per second due to
`high—
`speed particle
`flow. This
`instrument
`commonly
`employs
`a
`fluid dynamic Focusing
`flow chamber
`which allows
`one by one examination of the sample
`particles.
`The flow is called "sheath flow"
`as
`illustrated in Fig.1. Particles
`in
`suspension.
`entering the
`chamber via an
`axial
`nozzle.
`are
`enveloped in a coaxial buffer sheath. The
`coaxial
`stream is
`accelerated and constricted in
`the
`chamber
`and led to a capillary tube.
`Suspended
`particles
`flow along the center of the capillary
`tube one bye one.
`sheath flow
`Crossland-Taylor made the first
`performance
`chambertl). considering fluid dynamic
`are
`several
`of
`the
`chamber (2),[3).(4). There
`types of flow chambers for different uses, most of
`which
`are made of glass.
`The
`flow
`chamber
`conventionally used for particle counting is shown
`in Fig.2.
`To obtain a
`high
`resolution.
`the
`objective has bigger numerical aperture(NA).
`that
`is.
`a short working distance.
`To
`avoid
`contact
`between the objective and the cone,
`the
`capillary
`tube must
`be at least as long as
`the objective
`diameter.
`In
`this
`case. NA=U.4,
`the
`working
`distance
`is 1.63mm and the objective diameter
`is
`30mm. Consequently.
`this chamber should be
`150mm
`long. This length is larger for the micro system.
`to
`apply
`a
`and
`it
`is difficult
`glass-made
`
`
`
`sampm
`
`Fig-2 Conventional Flow Chamber
`
`CH2957—9l91!0000-0265$01.00
`
`© 1991 IEEE
`
`265
`
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`
`
`

`

`a micro particle
`flow chamber to
`conventional
`analyzer made by micro—machining.
`In this study,
`as the first step of the development of the micro
`system.
`attention is paid to the
`development of
`the sheath flow chamber using micro-machining.
`
`2.HICRO BREATH FLO“ CHAMBER
`
`is made
`A micro sheath flow chamber, which
`To
`form
`using photo-etching,
`is shown in Fig.3.
`the sheath flow geometry.
`two glass plates (A) and
`(E).
`and three thin metal plates {SUS 316, 100 pm
`thick) (E),(C) and (D) are used.
`The sample
`flow
`passage
`is
`carved only in plate
`(C),
`so
`the
`sample
`flow is expected to be enveloped
`by
`the
`sheath fluid.
`The five plates are bonded together
`and equipped with a sample fluid tube.
`two
`sheath
`fluid tubes and an outlet tubeI as shown in Fig.4.
`Here, fluid dynamic focusing flow of sample
`fluid
`from the nozzle is illustrated.
`is
`chamber
`Because
`the
`top surface of the
`with
`absolutely flat,
`there is no
`interference
`length
`objective.
`Therefore,
`the capillary tube
`can
`be
`shortened as necessary,
`as
`examined
`in
`chapter 3.
`The micro sheath flow chamber is
`15mm
`long.
`1/10 the length of a conventional
`chamber.
`In addition. photo-etching remarkably improves the
`flow passage accuracy of the flat
`flow chamber.
`Therefore
`mass production of
`chambers
`with
`easier'
`'homogeneous
`fluid dynamic performance
`is
`than that of conventional chambers.
`0n
`the other hand. closer
`investigation of
`fluid
`dynamic
`focusing
`performance
`is
`the
`necessary because the flow passage is now almost
`two-dimensional.
`
`3.DESiGN 0F PASSAGE CONFIGURATION
`
`3.1 Examination using viscous flow analysis
`
`As shown in Figure 4, each plate has the same
`passage configuration.
`Therefore.
`the
`sample
`
`
`
`Fig.3 Fabrication
`of Flow Chamber
`
`
`
`Ianpla fluid
`s eath<3
`“€9::::::::::ZZZ::
`Nozzle Area in detail
`
`
`
`sheath
`flow
`Fig.4 Micro Flow-Chamber
`
`and
`both sheath fluids
`between
`put
`fluid is
`constricted only in one direction as
`the
`sheath
`fluid flows.
`To check whether or not
`the
`sample
`fluid is Focused 3-dimensionally,
`investigation
`of
`the inside flow is necessary.
`A viscous
`flow
`analysis using a Finite Element Method(5)
`is
`employed
`to examine
`the
`inside
`flow.
`Flow
`analysis
`is effective for the chamber because
`it
`is
`too
`small
`to
`investigate using only
`an
`experimental approach.
`It has been confirmed that
`FEM simulates the actual
`flow well.cspecially
`in.
`the small passage with laminar flou(6).
`the
`The 3-dimensional mesh configuration for
`FEM is
`shown in Fig.5. The passage
`is divided
`into 48in
`elements. This model has
`three
`inlet
`ports and an ouLlet port.
`Two of the inlet ports
`are for sheath fluid. and the other is for
`sample
`fluid.
`As
`a
`expedient,
`the
`conordinatcs
`are
`adopted as shown in the same figure. The velocity
`at
`the
`sample fluid port is given for
`a
`sample
`flow rate of lfll/s. and the velocity at the sheath
`fluid port is given For a flow rate of
`120 #1/3.
`The
`conventional chamber
`is usually adopts
`these
`same flow rates.
`
`sheath fluid
`
`100nm
`
`_ boundary
` sample fluid
`boundary
`
`sample fluid
`
`mum
`
`masses;
`
`
`
`
`
`boundary 1”“
`
`
`outlet
`
`300nm
`
`Fig.5
`
`3—Dimensiona1 Mesh Configuration
`
`
`
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`
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`

`

`passage
`
`
` bent
`
`
`constricted
`passage
`
`_
`
`capillary
`tube
`
`
`,
`Serl flu"
`_
`.
`.'
`'
`'
`Fig.5 Velocity giggiiiégedCEZEEaEECtlon
`‘
`L
`total flow rate 1 QtZlZlnl/s
`sample flow rate : Qs=
`lulfs
`
`'in
`shown
`result of this calculation is
`A
`the
`in
`This
`shows the V9109it¥ vector
`Fig.5.
`the
`cross-section at
`the constricted nae-Bagel
`IL
`position of
`0mm
`in
`the X-coordinates
`}.
`reveals four swirl
`flows around its axis,
`which,
`judging from their symmetrical pattern. may
`be
`caused by the upper two passages for sheath fluid.
`in fact. further examination of this upper
`stream
`indicates the generation of strong secondary flow.
`The upper passage for sheath fluid is
`the
`bent
`passage with an axis radius of about 2mm
`and
`a
`height
`is
`0.3mm.
`In
`this
`small passage.
`the
`boundary layer of the stream is filled because the
`viscosity by the wall exerts to the center of
`the
`stream.
`The Velocity
`distribution
`becomes
`the
`?arflbOIiC.
`that
`is.
`the Velocity of
`center
`becomes much larger than that close to the wall,
`as shown in Fig.?. At
`the bent passage,
`there
`is
`centrifugal
`force
`upon
`the
`stream,
`and
`it
`increases
`as the velocity increases.
`Since
`the
`pressure
`is almost
`the same in
`the
`s-direction.
`the
`center stream under large
`centrifugal
`force
`beats the pressure gradient and flow outward.
`On
`the other hand,
`the stream close to the wall
`is
`beaten by the pressure gradient and flows
`inward.
`
`layer
`boundary
`skewed
`the
`T describes
`Figure
`the
`caused by the above mentioned phenomenon and
`generation of
`the secondary flow in
`the
`cross-
`section of the passage.
`The center stream flows
`outward toward both the upper and lower parts near
`the outer side-wall and returns to the inner side-
`wall.
`This causes two paths of circulation that
`are symmetrical
`from the center and become 4 swirl
`flows at the constricted passage.
`small
`the
`It may
`be
`noted that in
`passage
`the stream is remarkably subject
`to
`viscosity,
`thus, causing secondary flow.
`flow
`According to this calculation,
`the swirl
`axial
`velocity
`is 5%~10% of the velocity in
`the
`swirl
`1f
`flow.
`the sample fluid flows into this
`flow, it expands to both the upper and lower walls
`of
`the passage,
`and
`scatters
`to
`the whole-
`capfllary regkm.
`To
`nmke
`the
`samfle
`fluid
`constrict 3—dimensionally, further improvement of
`the passage configuration is necessary.
`
`bent
`the
`
`3.2 Modification of sample nozzle
`
`the
`at
`flow
`swirl
`the
`eliminate
`To
`it is necessary to weaken the
`constricted passage,
`secondary
`flow at the upper bent passage.
`One
`effective method would be to install a flow guide,
`for letting the center stream of the bent passage
`flow inward,
`in the constricted passage.
`The flow
`guide is shown in Fig.3. This flow guide prevents
`the
`sample
`fluid
`From
`scattering
`at
`the
`constricted passage. We call it a
`”sample
`flow
`guide plate".
`This plate is
`also useful
`for
`making the sample fluid constrict from all
`sides.
`This effect is discussed later.
`the
`Further calculation for the passage with
`in
`sample
`flow guide plate has been carried out
`order
`to check its
`effectiveness.
`The
`result
`shows
`that
`the velocity vector
`in
`the
`cross-
`section or the constricted passage is less than 1%
`of
`the velocity in
`the
`axial
`flow.
`This
`indicates
`that
`thc
`swirl
`flow
`is
`almost
`eliminated.
`Next. another effect of the sample flow guide
`is disscussed.
`The viscous
`flow analysis
`plate
`also shows that this guide plate induces the
`flow
`which
`envelopes the sample fluid from all
`sides.
`
`direction
`of
`pressure
`gradient
`
`growth of laminar
`boundary layer
`
`
`
`skewed
`boundary
`layer
`
`'
`
`
`secondary
`2
`flow
`
`\§\ rm
`58 ‘
`swirl
`flows
`
`centrifugal
`force
`
`Fig-7 Secondary Flow at Bent Passage
`
`£18422
`
`Fig.8 Sheath Flow Chamber
`with Sample Flow Guide Plate
`
`Width of sample channel
`Thickness of plate :
`
`: 300nm
`100 in
`
`267
`
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`

`

`
`
`Fig.9
`
`Velocity Distribution of Z—directiOn
`in
`Cross-section at 66in
`from Upper Wall
`
`the
`distribution in
`The z-direction velocity
`cross section at Baum from the upper wall is shown
`in Fig.9. This indicates that the sheath stream
`from the bend passage goes over the front of
`the
`guide plate E
`the region with a positive velocity
`)
`and down between the plates(the region with a
`negative
`velocity).
`Similarly.
`there
`is
`a
`symmetrical
`sheath stream below the plates which
`goes
`under
`the plates
`and
`up
`between
`them.
`Therefore,
`the sample fluid is enveloped by
`both
`sheath streams.
`The locus of the
`sample
`fluid
`using computational simulation is shown in Fig.10.
`This
`shows
`that the sample fluid is
`constricted
`into a 2Dym diameter at the capillary tube.
`This
`value
`is almost equal
`to the width of the
`sample
`flow,
`given
`by the flow visualization that
`is
`mentioned in the next chapter.
`
`sample flow guide plate
`
`
`
`capillary tube
`width:300ym
`
`Fig.10 Computational SimulatiOn
`of Sample Fluid
`
`Only half the region is simulated
`because the flow from each side
`is
`symmetrical.
`
`3.3 Length of capillary tube
`
`the
`flow analysis also gives
`The viscous
`appropriate length for the capillary tube.
`most
`The capillary tube accelerates the
`sample
`flow.
`After the fluid enters the the capillary tube,
`the
`velocity distribution becomes parabolic due to the
`shear
`stress caused by the wall.
`The capillary
`tube
`has such an inlet region, which varies with
`the velocity distribution. Generally.
`this
`is
`known as the "inlet length"(?). At
`the lower part
`of
`this
`region,
`the pressure loss
`increases
`in
`vain
`with
`the
`length or
`the
`capillary(7}.
`Therefore,
`it may
`be thought
`that
`this
`inlet
`length is the minimum acceleration length.
`center
`Figure 11
`shows
`the growth of
`the
`velocity in the capillary tube obtained from the
`analysis.
`It is normalized by the mean velocity
`(=l.6m/s).
`In a square tube,
`the center velocity
`is close to 2.1 times the mean velocity along
`the
`inlet
`length. This figure shows that
`the center
`velocity is almost 2.1 times the mean velocity for
`a distance of only 2mm. This result suggests that
`a distance or 2mm is enough for the acceleration.
`Therefore,
`the length of the capillary is fixed at
`4mm, with 2 of the 4 provided for detection.
`
`
`
`1.5
`
`distance from inlet(x=0) (mm)
`
`Fig.ll Growth of Center Velocity
`in Capillary Tube(calcu1ated)
`
`mean velocity :
`total flow rate
`
`vw=1.6m/s
`Qt=133fllfs
`
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`

`
`
`d.INVESTIGATION USING FLOH VISUALIZATION
`
`4.1 Check of sheath flow
`
`formed
`check whether the sheath flow is
`To
`and how narrowly the sample flow is constricted in
`the micro
`sheath
`flow
`chamber,
`a
`flow
`visualization
`technique,
`which
`employs
`a
`microscope,
`is used.
`The experimental setup for flow visualization
`consists of a flow system. a lighting system and a
`microscope-TV camera system.
`by
`The
`sample
`and sheath fluid is driven
`The
`pressurized air
`and regulated by valves.
`flow
`sheath flow rate is measured by a float-type
`meter, and a laminar flow meter is used to measure
`the
`sample Flow rate. The flow rate ranges
`from
`30—300 nl/s for the sheath flow rate and
`0.1—3.0
`nlfs for the sample flow rate.
`The
`laminar
`flow
`meter was manufactured
`specifically for
`this
`eXperiment as there was no equipment available
`to
`measure
`such
`a
`small
`flow rate.
`It has
`a
`capillary tube(l40um in diameter,
`100mm long) with
`pressure transducers at each ends, and shows
`good
`linearity.
`A light source with optical fibers is used to
`came I‘fl."
`the
`light
`sample
`flow.
`A
`colour
`1W
`microscope system makes it possible to observe the
`sample
`flow.
`To observe the sample Flow,
`sample
`water is dyed by the uraninc( C20H1005Na2), which
`is diluted with water 1.000 times by weight.
`The
`sheath
`fluid is filtered water.
`Uranine
`emits
`green fluorescence undcr lighting.
`
`sample feminine“;
`
`
`
`
`
`
`
`
`(bJWith Sample Flow Guide Plate
`
`Fig.12
`
`Sample Flow near Nozzle
`
`total flow rate . Qt:12lfllls
`sample flow rate : Qs=
`1 His
`dye : uranine
`
`
`
`is
`sample flow observed near the nozzle
`The
`in Fig.12. Figure 12(a) shows the flow of
`shown
`chamber without the Sample flow guide plate.
`the
`The photograph confirms that the sample
`flow is
`scattered at the capillary tube as was
`indicated
`by
`the flow analysis.
`On the other hand,
`figure
`12(b]
`shows that smooth fluid dynamic focusing of
`the
`sample flow are obtained in the chamber with
`the
`guide plate.
`In the capillary tube,
`the
`sample flow is constricted to about 20pm in width.
`This is almost
`the same as the value given by
`the
`simulation in Chapter 3.
`
`4.2 Speed of sample flow
`
`source with optical
`the light
`Instead of
`fibers.
`a couple of double pulse lamps ( under
`1 useo pulse width, 50Hz) are equipped to measure
`the
`speed of the sample flow. Pulse light
`from
`each
`lamp radiates at intervals of 20usec to
`the
`sample flow containing particles(3um in diameter).
`A
`TV
`camera catches the two images of
`the
`same
`particle
`in the same video frame. The two
`images
`at the capillary(x=3mm] are shown in Fig.13.
`The
`length between these two images is
`the distance
`that the particle flows during a 20nsec
`interval.
`Therefore,
`the speed is obtained by dividing the
`length by the distance travelled in one
`interval.
`That is,
`the velocity is 3.0m/s when x=3mm.
`This
`value
`is
`clcse to the result of
`the
`calculated
`sample velocity.
`It
`is
`experimentally confirmed
`capillary length of
`4mm
`is
`enough
`adequate acceleration.
`
`a
`that
`to obtain
`
`flow direction
`—..
`
`
`
`Fig.13 Video Image of Particles
`in Capillary Tube
`
`Sequential double pulse lights
`shows the distance that
`the
`particle flows during one interval.
`The distance is 60pm in this case.
`Interval of pulse lights : Zflysec
`Center velocity :
`3.0m/s
`Diameter of particles :
`3am
`
`
`
`
`
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`

`5.CONCLUDING REMARKS
`
`a particle
`for
`Flow chamber
`sheath
`A micro
`analyzer was developed using micro-machining.
`Sheath
`flow geometry
`is
`formed
`in
`the
`two-
`dimensional
`passage configuration. Viscous
`Flow
`analysis using FEM effectively investigates
`the
`flow of
`the
`small
`region,
`and
`reveals
`the
`influences of viscosity, such as the
`growth of
`secondary
`flow at the small bent
`passage.
`The
`speed of the sample is experimctally confirmed
`to
`be 3m/s in the micro sheath flow chamber.
`
`REFFERENCES
`
`a
`
`(l) Crossiand—Tayier,P.J.; A Device for Counting
`Small Particles
`suspended in a Fluid
`through
`Tube: Nature Vol.171. No.4340. pp 37-38, 1953.
`[2) Eisert,W.G.. Ostertag,R.
`and Niemann,E.-G.;
`Simple
`Flow Hicrophotomcter
`for
`Rapid
`Celi
`Population Analysis: Rev. Sci.
`Inst., Vol
`46,
`No.8, pp.lU2i-1024 .19?5.
`(3) Kachel,V., Kordwig,E. and Glossner,E.; Uniform
`Lateral Orientation, Caused by Flow Forces.
`of
`Flat Particles
`in Flow-Through Systems:
`J.
`of
`Histochemistry and Cytochemistry: Vol.25, No.?,
`pp.774-730 ,lS'i'i'.
`(4} Eisert,N.G.. Dcnnenloehr.M.; Nozzle Design for
`the
`Generation
`of
`Plane
`Liquid
`Surfaces:
`Cytometry, Vol.1, No.4, pp.249-253. 1931.
`and
`(5)
`lkegawa,M.,
`Shikano,Y.,
`Katoh.C.
`Symposium
`Nakano.S.:
`Proceedings of the lst Int.
`on
`Supercomputer
`for Mechanical
`Engineering.
`JASME, pp.58-55, March, 1988.
`(E) 0hki,H., Miyake.R., Yamazaki.l., and Kancko.T.
`: Proceedings of the 2nd int.
`Symposium on Fluid
`Control
`Measurement
`Mechanics
`and
`Flow
`Visualization,
`pp.245-249, 5-9
`September
`1988.
`Sheffield England.
`(T) Hermann,Sehlighting : Boundary-Layer Theory:
`McGRAH~HiLL,lnc.,NewYork US, 1979.
`
`270
`
`ABS Global, Inc. and Genus plc - Ex. 1010, p. 270
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`
`