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Self-Assembled Monolayers and Soft Lithography in High School Chemistry

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Self-Assembled Monolayers and Soft Lithography in High School Chemistry

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    1. Self-Assembled Monolayers and Soft Lithography in High School Chemistry Jen Ehrlich UW-MRSEC RET Summer 2007

    2. Water Polar Hydrogen bonding (very strong!)

    3. Water’s Unique Properties

    4. Surface Tension

    5. Surface tension is the enhancement of the intermolecular attractive forces at the surface

    6. Have You Ever Seen a Square Water Droplet? Why Not?

    8. How is surface tension affected by soap?

    9. Hydrophobic

    10. Hydro phobic

    11. Hydrophobic materials

    12. What makes something hydrophobic?

    13. Hydrophilic

    14. Hydro philic

    15. Hydrophilic materials

    16. What makes something hydrophilic?

    17. Soap— Hydrophobic or Hydrophilic?

    18. Soap is a surface acting agent

    19. Surfaces

    20. WWWD? – What would water do?

    22. Student Lab Self Assembled Monolayer Role Play Silver Petri Dishes and Test Water on monolayers of Alkane Thiol, Acid Thiol, & Ag Prepare PDMS Stamp Play-doh Analogy Stamp Ag with Alkane Thiol

    23. Classroom Role Play—Part 1 Rules: Your right hand can only touch someone’s back Your left hand can only touch someone’s right shoulder Teacher should limit space to a small enough area to get a “mass” of students Self Assembly

    24. Self Assembly Students will “self-assemble” themselves into a mono-layer

    25. Self Assembly Classroom Role Play—Part 2 Rules are the Same: Your right hand can only touch someone’s back Your left hand can only touch someone’s right shoulder This time, the teacher should limit the space students can take up (i.e. they can only stand in “these three rows” or cover some tiles with chairs/colored paper so they are not accessible to students)

    27. What Is Self Assembly? When molecules organize themselves into patterns without any outside intervention Examples: Formation of crystals Cell membrane formation (lipid bilayers) Schools of fish Self assembled monolayers

    28. What Self Assembly Is Not

    29. Self Assembled Monolayers (SAMs) Molecules arrange themselves spontaneously onto certain surfaces in a layer that is one molecule thick Surface properties of the material are changed, while bulk properties remain the same

    30. WWWD? – what would water do?

    31. Student Lab Self Assembled Monolayer Role Play Silver Petri Dishes and Test Water on monolayers of Alkane Thiol, Acid Thiol, & Ag Prepare PDMS Stamp Play-doh Analogy Stamp Ag with Alkane Thiol

    32. Prepare Petri Dishes for Silvering Wash plastic Petri dishes with dish washing detergent or laboratory detergent Add dilute tin (II) chloride solution to each Petri dish for 30 seconds. Rinse each Petri dish with distilled water.

    33. Preparation of Tollens’ Solution To 0.1 M silver nitrate, add concentrated aqueous ammonia dropwise, while stirring. At first, brown precipitate will form. Continue adding ammonia until the precipitate dissolves.

    34. Silvering Plastic Petri Dish Add Tollens’ solution to the Petri dish Add about 1 ml of 0.5 M glucose solution to the Petri dish. Rinse with distilled water, and dry with a blow dryer.

    35. Chemical reaction to form the silver? 2 Ag+ + (aq) 2 OH- (aq) ? Ag2O (s) + H2O (l) Ag2O (s) + 4NH3 (aq) + H2O (l) ? 2[Ag(NH3)2]+ (aq) + 2 OH- (aq) Glucose is oxidized/Ag ion is reduced C6 H12 O6 + Ag(NH3 )2+ + OH- ?

    36. Self Assembled Monolayers On the back of one Petri dish, use a permanent maker to divide it into three sections. Use tape to label the front of the Petri dish as shown. Add a few drops of HDT and Acid Thiol to their respective thirds and let dry

    37. WWWD? – what would water do?

    38. Tilt the Petri dish to almost a 90o angle and, from your pipet, let one drop of water fall onto a dry spot of each surface. Release as small a drop of water as possible. Record your observations

    39. Student Lab Self Assembled Monolayer Role Play Silver Petri Dishes and Test Water on monolayers of Alkane Thiol, Acid Thiol, & Ag Prepare PDMS Stamp Play-doh Analogy Stamp Ag with Alkane Thiol

    40. Making the PDMS Stamp Mix 10 parts Sylgard polymer base to 1 part curing agent crosslinker. Place an overhead transparency, with the patterned grid facing up, onto a metal plate and place the square metal tubing on top of the transparency. Pour the uncured PDMS mix over the transparency. Place the whole assembly in a toaster oven set at 250oF for 20 minutes.

    41. Student Lab Self Assembled Monolayer Role Play Silver Petri Dishes and Test Water on monolayers of Alkane Thiol, Acid Thiol, & Ag Prepare PDMS Stamp Play-doh Analogy Stamp Ag with Alkane Thiol

    42. Macroscopic Model Station 1: Printing a Pattern

    43. Macroscopic Model Station 2: Making the PDMS Mold

    44. Macroscopic Model Station 3: Coating stamp with alkanethiol

    45. Macroscopic Model Station 4: Stamping the metallic surface

    46. Macroscopic Model Station 5: Applying water to stamped image

    47. Student Lab Self Assembled Monolayer Role Play Silver Petri Dishes and Test Water on monolayers of Alkane Thiol, Acid Thiol, & Ag Prepare PDMS Stamp Play-doh Analogy Stamp Ag with Alkane Thiol

    48. WWWD? – what would water do?

    49. Stamping Use a cotton swab to spread HDT on the surface of the PDMS stamp. Dry it with a blow dryer or wave it in the air. Repeat. Invert the stamp onto the surface of your silvered Petri dish. Cover the stamp with a 1kg mass or the equivalent for 2 minutes. Peel the stamp away from the silver.

    51. Alternative: Use a 20uL micropette

    52. How is this Nanotechnology? We stamped nanometer sized molecules onto silver in such a way that the molecules cause water to form into shapes that they would not naturally form.

    53. Recall… Floor ? Silver Surface Feet ? Sulfur atom Body ? Hydrophobic Carbon Chain 2 nm tall Arm to Back/Arm to Shoulder Connections ? Van der Waals Forces

    54. Steps of Soft Lithography

    55. Why Use Microcontact Printing? Simple Quick Cost effective for making small high –quality structures Can form a pattern on a non-planar surface Can be performed in a conventional chemistry lab (no clean room necessary) Stamps can be re-used and are durable

    56. Applications Surface Chemistry: Study different surface characteristics i.e. roughness, wettability, reactivity Microelectronics SAMs can be used as nm size resists Protein Research SAMs used to control the adsorption of proteins onto a surface Patterns of proteins used for biosensors, cell biology research, tissue engineering Cell Biology How cells interact with different surfaces, how cell shape affects cell division DNA arrays—faster and less DNA needed Microfluidic Channels used to flow small volumes of protein solutions along a certain path

    57. Something to Look Into…

    58. Acknowledgements

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