Piotr Garstecki

advertisement
Reversibility of droplet trains
in microfluidic networks
Piotr Garstecki1, Michael J. Fuerstman2,
George M. Whitesides2
1 Institute
of Physical Chemistry, PAS, Warsaw, Poland
2 Department of Chemistry and Chemical Biology, Harvard University
Kenis, Science (1999)
the simplest network – a single loop
amplification and feedback:
• drop flows into the arm characterized by lower resistance
(higher pressure gradient)
• once the drop enters a channel it increases its resistance
the simplest network – a single loop
period-1
period-2
ffeed / fflow
period-3
irregular
Phys. Rev. E (2006)
nonlinear dynamics embedded in a linear flow
invariant under: x  - x,
(or, equivalently V  - V, and p  -p)
period 1
period N
??? period 1
period N
The “operation” of the system
is stable against small differences
in the incoming signal
Science (2007)
there is amplification and feedback, but:
• the nonlinear events are isolated (very short)
• the long-range interactions are instantaneous (information is
transmitted much faster than the flow proceeds)
• it is all embedded in a linear, dissipative flow
formation of bubbles – a single nozzle
water
gas
water
height = 30 mm
1 mm
Appl. Phys. Lett. 85, 2649 (2004)
formation of bubbles – a single nozzle
water
gas
water
height = 30 mm
Appl. Phys. Lett. 85, 2649 (2004)
fraction of the area of the orifice occupied by gas
1
fraction
1 mm
0.8
0.6
0.4
0.2
0
0
5
10
15
20
time [ms]
nitrogen (p=8 psi) / 2% Tween20 in water (Q=3 mL/h), orifice width/length/height: 60/150/30 mm.
liquid
gas
liquid
50 mm
end of the gas
Inlet channel
equilibrium shape
for a given volume
enclosed by the
gas-liquid interface
end of the orifice
surface evolver
• rate of collapse linear in the of inflow of the
continuous phase
• only the very last (and short) stage is driven
by interfacial tension
Phys. Rev. Lett. 94, 164501 (2005)
coupled flow-focusing oscillators
information
(fast)
final break-up takes ‘no’ time
evolution
(slow)
+ dissipative dynamics (low to mod Re)
coupled flow-focusing oscillators
period-29
Nature Phys. 1, 168 (2005)
coupled flow-focusing oscillators
Nature Phys. 1, 168 (2005)
160 kfps –
– 6.25 ms
The observed dynamics is (again) stable.
Nature Phys. 1, 168 (2005)
dynamics of flow through networks:
• complicated (complex)
 it is possible to design complex,
automated protocols
• stable
 the protocols can be executed in practice
Download
Related flashcards

Physical chemistry

44 cards

Catalysts

34 cards

Physical chemistry

44 cards

Gases

45 cards

Speed skating venues

16 cards

Create Flashcards