microfluidic_wenjia_two-phas

8/7/2019 microfluidic_wenjia_two-phas

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A Microfluidic System for

Controlling Reaction Networks In

Time

Presented By Wenjia Pan


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Controlling Reaction Networks

It allows to control

When each reaction

begins

For how long eachreaction evolves

When each reaction is

analyzed or quenched


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Why microscopic chemical reactions?

Traditionally, macroscopic

Labs, using test tubes and etc.

Advantages to perform chemical reactions in

microscopic:

To manipulate, process and analyze molecular

reaction on the micrometer to nanometre scale


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Applications Parallel combinational

chemical reactions No impurity

No cross-contamination

nanomaterial synthesis Allow user to synthesizespecies of specific yetvariable characteristics.

Integrated microfluidicbioprocessor

thermal cycling

sample purification

capillary electrophoresis

http://www.nature.com/nature/journal/v442/n7101/full/nature05062.html


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Linear transform: t = d/u

t: time used for reaction [s]

d: distance traveled [m] u: flow rate [m/s]

Setup:

Initial: d = 0 t = 0

At constant velocity: t = d/u




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3 Types of behavior in fluid dynamics

Laminar flow (Re < 2100)

Transition flow (2100 < Re < 3000) Turbulent flow (Re > 3000)

Microfluidic system: laminar flow

Re: Reynolds number


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Reynolds Number

Vs: the velocity of the flow [m/s]

P : the density [kg/m3]

L : the diameter of the capillary [m]

: the viscosity of the fluid [kg/ms] V : the kinetic fluid viscosity



0

RespV L VsL InertialForces

V ViscousForcesQ! ! !

0Q

0V

p

Q!


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Reynolds number

To quantify the relative importance of the inertial forces and the

viscous forces

To identify if it is laminar/turbulent flow

http://www.daviddarling.info/encyclopedia/L/laminar_flow.html


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From left top corner, clockwise: Re = 1.54,(9.6, 13.1, 26), 105

http://www.media.mit.edu/physics/pedagogy/nmm/student/95/aries/mas864/obstacles.html


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A comparison: Top: Re = 150

Bottom: Re =105

http://www.media.mit.edu/physics/pedagogy/nmm/student/95/aries/mas864/obstacles.html


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Challenges Mixing is slow

d = 0 NOT => t=0

Dispersion is large Velocity is not consistent.

t = d/u is a range.

ANGEWAND Edition 42(7) : 768 772, 2003


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Practical model described here

Mixing is faster

Dispersion eliminated

ANGEWAND Edition 42(7): 768 772, 2003


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Methods described

For forming plugs of multiple solutions of

reagents

For using chaotic advection to achieve rapid

mixing

For splitting and merging these plugs in order

to create microfluidic networks


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Plugs of solutions of reagent A and B A, B: 2 laminar streams

Separating stream: inert center stream Diffusion will be slow

Water immiscible perfluorodecaline (PFD) Inert

Immiscible with water

Organic solvents

Does not swell PDMS

http://en.wikipedia.org/wiki/Polydimethylsiloxane


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Plug Forming:

Mixes left and right, NOT top and the bottom

Laminar flow preserved


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Chaotic advection: rapid mixing

Fluid cavity experiments

Simultaneous motion

Time-periodic, alternating motion



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Microfluidic system Similar situation

Different frame of reference

Flow cavity experiment: reference = the fluid Microfluidic system: reference = walls



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ANGEWAND Edition 42(7):768 772, 2003


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Splitting and merging Merging:

Merging channel: wide main channel

Small droplets move more slowly

Driven with pressure



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Splitting

Constricting the channel at the branching points

Be subjected to pressure gradients



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Conclusion

Advantages

Planar

Trivia to fabricate Disposable plastic chip

Available equipment

Applications

High-throughout screening Combinational synthesis

Analysis

diagnostics


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Summary Strengths:

Controllable and rapid mixing

Able to build complex microfluidic networks

Weakness: Hard to extract the vast amount of information produced in a complex networks

http://www.nature.com/nature/journal/v442/n7101/fig_tab/nature05062_F6.html

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microfluidic_wenjia_two-phas