a microfluidic system for controlling reaction networks in time presented by wenjia pan
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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