A Microfluidic System for Controlling Reaction Networks In Time Presented By Wenjia Pan

A Microfluidic System for Controlling Reaction Networks In

Time

Presented By Wenjia Pan

A Microfluidic System for Controlling Reaction Networks

• It allows to control

– When each reaction begins

– For how long each reaction evolves

– When each reaction is analyzed or quenched

A Microfluidic System for Controlling Reaction Networks

• 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

A Microfluidic System for Controlling Reaction Networks

• Applications– Parallel combinational

chemical reactions• No impurity• No cross-contamination

– nanomaterial synthesis• Allow user to synthesize

species of specific yet variable characteristics.

– Integrated microfluidic bioprocessor

• thermal cycling• sample purification• capillary electrophoresis

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

• 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

A Microfluidic System for Controlling Reaction Networks

A Microfluidic System for Controlling Reaction Networks

• 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

• 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–

A Microfluidic System for Controlling Reaction Networks

0

Re spV L VsL InertialForces

V ViscousForces

0

0Vp

A Microfluidic System for Controlling Reaction Networks

• 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

A Microfluidic System for Controlling Reaction Networks

• 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

A Microfluidic System for Controlling Reaction Networks

• A comparison:– Top: Re = 150– Bottom: Re =105

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

A Microfluidic System for Controlling Reaction Networks

• 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

A Microfluidic System for Controlling Reaction Networks

• Practical model described here– Mixing is faster– Dispersion eliminated

ANGEWAND Edition 42(7): 768 – 772, 2003

A Microfluidic System for Controlling Reaction Networks

• 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

A Microfluidic System for Controlling Reaction Networks

• 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

A Microfluidic System for Controlling Reaction Networks

• Plug Forming:– Mixes left and right, NOT top and the bottom– Laminar flow preserved

A Microfluidic System for Controlling Reaction Networks

• Chaotic advection: rapid mixing– Fluid cavity experiments

• Simultaneous motion• Time-periodic, alternating motion

ANGEWAND Edition 42(7) : 768 – 772, 2003

A Microfluidic System for Controlling Reaction Networks

• Microfluidic system– Similar situation– Different frame of reference

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

ANGEWAND Edition 42(7) : 768 – 772, 2003

A Microfluidic System for Controlling Reaction Networks

ANGEWAND Edition 42(7) : 768 – 772, 2003

A Microfluidic System for Controlling Reaction Networks

ANGEWAND Edition 42(7): 768 – 772, 2003

A Microfluidic System for Controlling Reaction Networks

• Splitting and merging– Merging:

• Merging channel: wide main channel• Small droplets move more slowly• Driven with pressure

ANGEWAND Edition 42(7) : 768 – 772, 2003

A Microfluidic System for Controlling Reaction Networks

• Splitting– Constricting the channel at the branching points– Be subjected to pressure gradients

ANGEWAND Edition 42(7) : 768 – 772, 2003

A Microfluidic System for Controlling Reaction Networks

• Conclusion– Advantages

• Planar• Trivia to fabricate• Disposable plastic chip• Available equipment

– Applications• High-throughout screening• Combinational synthesis• Analysis• diagnostics

A Microfluidic System for Controlling Reaction Networks

• 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