1. Basic Silicone Chemistry (II)

2. 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 >1,000,000 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

3. Elastomers

4. Elastomers

5. Elastomers: RTV

6. Sylgard 184® PDMS Elastomer

7. Microfluidics Technology
Applications:
Genome Mapping
Rapid Separations
Novel Sensors
Nano-scale Reactions
Ink-Jet Printing
Drug Screening

8. 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]

9. Microfluidics Technology
Optical image showing bead sorting in action. A red bead is
being sorted to the collection
channel.

10. Device Fabrication Thin Layer Thick Layer Cast into Mold Partial Cure
100 mm
Photoresist
100 mm
50 mm
12 mm
Cast into Mold
Partial Cure
Si Wafer
Spin Coat
Partial Cure
100 mm
PDMS
5 mm
PDMS
12 mm
20 mm
50 mm

11. Device Fabrication Continued…
Peel off thick layer, rotate 90o, Place onto top of thin layer
Cure completely (adheres two layers while maintaining features)

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

13. Challenges Currently the most widely used material
Dow Corning’s 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 !

14. PFPE Elastomers

15. CH2Cl2 Swelling Data Immersion Time (h) % Swelling Sylgard 184 PFPE 48
74 %
1 % 72
103 %
3 % 94
109 %

16. Two-Layer PFPE Device “Top-down view of PFPE Device” 100 mm
Thin Channel
Thick Channel
100 mm

17. Organic Solvents in Devices: PFPE vs. PDMS
Dye Solution of Methylene Chloride, Acetonitrile, Methanol
PFPE channel
Solvent moves into channel
PDMS channel
Solvent swells material,
cannot get into channel

18. Entropy Driven Ring Opening Polymerization

19. Ring Opening Metathesis Polymerization
Metathesis: Greek “meta” meaning “change” and “titheme” meaning “place”

20. Ring Opening Metathesis Polymerization
Metallocyclobutane
4-membered intermediate
Transition metal catalyzed process
No polymer formation….

21. Ring Opening Metathesis Polymerization
But what if….
Polymer formation…

22. Ring Opening Metathesis Polymerization

23. Ring Opening Metathesis Polymerization

24. Ring Opening Metathesis Polymerization