Basic Silicone Chemistry (II)

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Basic Silicone Chemistry (II)
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Silicone Classifications by Physical Form

• (1) Fluids (hydraulic, release agents, cosmetics,
  heat transfer media, polishes, lubricants,
  damping, dry cleaning)
• Polymer chains of difunctional units (D)
  terminated with monofunctional (M) units OR
  cyclics (Dx)
• (2) Gums (high temperature heat transfer fluids,
  lubricants, greases, cosmetic and health care
  additives)
• Same structure as PDMS fluids, but much higher
  molecular weight (viscosities gt1,000,000 cSt).
• (3) Resins (varnishes, protective coatings,
  release coatings, molding compounds, electronic
  insulation)
• Rigid solids based on trifunctional (T) and
  tetrafunctional (Q) units. Surface modification
  with (M) units
• (4) Elastomers (Heat cured and RTVs tubing and
  hoses, medical implants, sealants, adhesives,
  surgical aids, electrical insulation, fuel
  resistant rubber parts, rollers, etc)
• Soft solids based on crosslinked SiH Fluids

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Elastomers
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Elastomers
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Elastomers RTV
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Sylgard 184 PDMSElastomer
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Microfluidics Technology

• Applications
• Genome Mapping
• Rapid Separations
• Novel Sensors
• Nano-scale Reactions
• Ink-Jet Printing
• Drug Screening

http//www.fluidigm.com/about.htm
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Microfluidics Technology
A microfabricated cell sorter with integrated
valves and pumps. This is a two-layer device the
bottom layer is a T-shaped fluidic channel, and
the top layer contains pneumatic control lines
for pumps and valves, as well as cavities to
smooth out oscillations. Scale bar, 1 mm.
Photograph courtesy of Felice Frankel/Steve
Quake Caltech
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Microfluidics Technology
Optical image showing beadsorting in action. A
red bead is being sorted to the collection
channel.
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Device Fabrication
Thin Layer
Thick Layer
100 mm
Photoresist
100 mm
50 mm
12 mm

1. Cast into Mold
2. Partial Cure

Si Wafer

• Spin Coat
• Partial Cure

100 mm
PDMS
5 mm
PDMS
20 mm
50 mm
12 mm
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Device Fabrication Continued

1. Peel off thick layer, rotate 90o, Place onto top
   of thin layer
2. Cure completely (adheres two layers while
   maintaining features)

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Valve Actuation
Cross sectional view of valve actuation
Thick layer
Thick layer
Air 20 psi
Thin Layer
Thin Layer
Open Valve
Closed Valve
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Challenges

• Dow Cornings Sylgard 184 PDMS Elastomer
• Currently the most widely used material
• in microfluidic device fabrication
• Flexible, non-toxic, easily cured, low surface
  energy

• Chemical Nature of PDMS allows for significant
• swelling in common organic solvents
• Swelling greatly disrupts micron-scale features
  of
• microfluidic devices
• Severely limits the versatility of microfluidics
  
• technology!

Strong Demand for solvent-resistant
materials with mechanical properties of PDMS
Elastomers !
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PFPE Elastomers
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CH2Cl2 Swelling Data
Immersion Time (h) Swelling Sylgard 184 Swelling PFPE
48 74 1
72 103 3
94 109 3
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Two-Layer PFPEDevice
Top-down view of PFPE Device
Thin Channel
Thick Channel
100 mm
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Organic Solvents in DevicesPFPE vs. PDMS
Dye Solution of Methylene Chloride, Acetonitrile,
Methanol

• PFPE channel
• Solvent moves into channel

• PDMS channel
• Solvent swells material,
• cannot get into channel

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Entropy Driven Ring Opening Polymerization
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Ring Opening Metathesis Polymerization
Metathesis Greek meta meaning change and
titheme meaning place
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Ring Opening Metathesis Polymerization
Metallocyclobutane 4-membered intermediate
Transition metal catalyzed process
No polymer formation.
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Ring Opening Metathesis Polymerization
But what if.
Polymer formation
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Ring Opening Metathesis Polymerization
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Ring Opening Metathesis Polymerization
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Ring Opening Metathesis Polymerization