IIM.tech Seminar I

8/2/2019 IIM.tech Seminar I

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Presented by,Anusree Unnikrishnan

II M.Tech

CB.EN.P2CHE10001

Novel Microreactors for FunctionalNovel Microreactors for Functional

Polymer BeadsPolymer Beads.T . Nisisako et al. , Dept of Precision Engineering ,Graduate School of

Engineering, University of Tokyo, Chemical Engineering Journal ,2004.


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IntroductionPolymeric microspheres of uniform size in the diameter

range 10100 m have a great many applications in diverse

fields.

In liquid chromatography, mono-sized particles packed

optimally in columns provide significant improvement in

separation efficiency .

Regular-sized beads in liquid crystal displays give a clear

and uniform image.


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Introduction Cont.

Many other applications arise in science and technology

which includes:

y Particle-based bioassays

y Flow measurement : Particle image velocimetry (PIV)

y Microparticle - based displays


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Introduction Cont.Therefore studies have been carried out in engineering of

polymeric microspheres of the requisite diameter having a

tight distribution of sizes.


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Classical Methods

1m dia

a.)Dispersion Polymerization

b.)Seed Polymerization

10-100m dia

a.) Suspension

Polymerization

Microspheres


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Recent Techniques

Membrane Emulsification

Omi et al. successfully manufactured polystyrene

microspheres of 29m with a CV of close to 10% by

suspension polymerization of relatively uniform oil/water

emulsion produced by sirasu porous glass (SPG) membrane

emulsification.

Microfabricated channel arrays on silicon have been used

for preparing suspensions for polymerization and polymericdivinylbenzene beads of over 50 m with a CV below 5%

.


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Current Approach

Preparation of monodispersed droplets :

In this technique we make use of a microfluidic

systems in which two immiscible liquids areintroduced into separate microchannels , and then one

liquid is forced into the second liquid at a junction to

form microdroplets one by one.

Droplet formation a the junction is both rapid and

reproducible.


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Objective

To produce monodisperse polymeric microspheres of

diameter 30120 m by polymerization of a monomer

suspension, using a simple T-shaped channel

configuration.

We also engineer bicolored beads using another

microfluidic device


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Experimental Setup

1.) Generation of single-phase microdroplets :

T-shaped channel employed

Grooves and holes for supply ports and drain ports,

were machined into quartz chipsCovered by Fusion bonding with another quartz chip.

The channels were machined deeper and wider near

the drain port in order to measure the size of the

droplets as spheres are formed there.

The channel widens gradually so that the flow speed

changes only slowly.


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T-junction device

.

The organic phase

(monomer) flow channel

is at right angles to theaqueous phase flow

channel

This T-junction is

positioned at 3mm fromthe organic phase supply

port and 8mm from the

aqueous phase supply

port

Schematic of the T-shaped channel

(Channel sizes are written as width depth).


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Equipments Required

Glass microsyringes (1000 series, Hamilton Company,NV,

Syringe pumps (KDS200, KD Scientific Inc., PA, USA)

[ The pumps were tested in advance to confirm constant supply of liquids

by using pressure sensors ]

The glass microchip was assembled in a stainless jig(40mm

30mm8mm) and linked to syringes through polytetrafluoroethylene(PTFE) tubes and connectors.

An optical microscope (BX-51, OLYMPUS OPTICAL CO. Ltd., Japan)

A high-speed video camera (Fastcam-max, PHOTRON LIMITED,

Japan) :These were used to observe and record the microfluidic behavior

of the two immiscible liquids [so as to capture such phenomena as the

formation of microdroplets at junctions].

Images were downloaded digitally to an IBM-compatible PC, and the

droplet size was calculated from the images.


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The resulting droplets were collected in a beaker andcured either by UV light radiation (for 12 min) or ahot water bath (7080 C for 45 min).

To prevent clogging in the microchannels , allequipment was placed in a clean room.

The room was air-conditioned to a constant

temperature (293 K) to prevent thermally drivenfluctuations in the viscosity, surface tension and other

physical properties of the fluids.


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Results & Discussion


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Conclusion

We have reported here the production of polymeric

microspheres using confluent microflow systems.

Monomer droplets of uniform size were rapidly and

reproducibly formed in the crossflow junction, and polymerparticles with a CV below 2% were successfully prepared

by subsequent polymerization.

The particle size was reliably chosen in the range of 30

120m by controlling flow conditions.A flow diagram focusing on droplet breakup phenomena

was obtained.


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Conclusion Cont . . .

This simple technique will be applicable to a variety of

functional spheres: porous particles, magnetized beads,

microcapsules, and many others.

We showed a further functionality by preparinghemispherically colored droplets and microspheres that

were cured subsequently. These functional particles could

find application as materials in electric displays, as Gyricon

balls have done .The possibility of active control of the internal design of

particles now arises. This method shows great promise and

we believe that it will open up a new field of research in the

microfluidic synthesis of pioneering materials


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THANK YOUTHANK YOU

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IIM.tech Seminar I