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Metamaterials

Metamaterials. Zaven Kalfayan Lindsay Hunting Phyllis Xu Joy Perkinson . Presentation Outline. Motivation of project Project goals Processing and materials Results Cost analysis TechWatch and future work. What is a Metamaterial?.

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Metamaterials

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  1. Metamaterials Zaven Kalfayan Lindsay Hunting Phyllis Xu Joy Perkinson

  2. Presentation Outline • Motivation of project • Project goals • Processing and materials • Results • Cost analysis • TechWatch and future work

  3. What is a Metamaterial? A periodic material that derives its properties from its structure rather than its components. *Taken From 3.042 handout & Physics Worlds 2005 “Sound Ideas”

  4. Project Motivation • Developing field of research • Applications in wide range of sectors, such as communications, optics, energy • Currently used for wave manipulation

  5. Project Goals • Design a process using lithography to fabricate a 3D structure • Create macroscale models of 2D structure, phase mask, and 3D structure • Create a 3D metamaterial and image using SEM

  6. Process Design Interference lithography 2-D photoresist pattern 3-D pattern Phase mask Titania structure Sol-gel infiltration

  7. 2D Structure Fabrication Coat soft bake @95° to evaporate solvent and cut into pieces coat with SU-8 20xx photoresist using spin coater coat with HMDS to promote adhesion plain Si wafer post bake at first 65° then 95° to promote crosslink formation Exposure UV exposure for xx seconds flip 90° and expose again submerge in isopropanol to wash away all remnants—final structure submerge in PM acetate to dissolve unexposed photoresist (20 min） Develop

  8. Phase Mask Fabrication Vacuum sample with open bottle of fluorosilane so that it evaporates onto sample. Step 1 Step 2 Layer with PDMS and heat at 65°to 75°for at least three hours. Step 3 Gently peel off PDMSlayer as phase mask.

  9. 3D Structure Fabrication Coat soft bake @95° to evaporate solvent and cut into pieces plain glass slide coat with SU-8 2005 photoresist using spin coater coat with HMDS to promote adhesion post bake at first 65° then 95° to promote crosslink formation Exposure Place phase mask on top of slide Expose for xx seconds and remove phase mask submerge in isopropanol to wash away all remnants—final structure submerge in PM acetate to dissolve unexposed photoresist (5-10 min) Develop

  10. Process Tuning • Exposure times (contact lithography): • SU8-2002: 0.5-25 seconds • SU8-2005: 5-40 seconds • SU8-2015: 1-45 seconds • Exposure times (interference lithography): • 3-20 seconds for all samples

  11. Prototype Functionality Problems for 2D & 3D patterns 15s SU-8 2015 Top Overexposure Unwashed monomer Adhesion problems Inconsistent results 15s SU-8 2015 Cross

  12. Design Functionality 2-D Patterns • 5s exposure of SU-8 2015 • Coated with HMDS • Broadband laser filtered at 365nm • Top down • Hole spacing - 3.38 um • Hole length ~1.5um 5s SU-8 2015 Cross 5s SU-8 2015 Top

  13. Design Functionality Phase mask • PDMS on SU-8 2015 2D pattern • Coated with flourosilane • Baked overnight 65C • Column • Spacing ~ 4 um • Height ~15 um PDMS on 10s SU-8 2015 PM of 10s SU-8 2015

  14. Design Functionality 3-D Patterns 3s SU-8 2005Top • 3s exposure of SU-8 2005 • Coated with HMDS • Thickness ~ 5um • 355 YAG pulse laser • Used in continues mode

  15. 2-D Pattern Phase Mask 3-D Pattern CAD Model 3-D Printing Model Actual Sample

  16. Cost Analysis • Fixed cost: • Spin coater, lasers, SEM • General lab equipment, facilities • Variable cost: • SU-8 20xx and HMDS ($300/1L $30/500mL ) • Trifluoroacetic acid and TiO2 ($60/100mL, $117/50mL) • Si wafers ($15/piece) • Glass wafers ($240/2500 slides) • Total costs/sample: $6/sample

  17. Future Work • Optimize process • Explore new thicknesses and exposure times • Adhesion promoters • Create more complicated 3D structures • Characterize 3D structure properties

  18. TechWatch • 2004: • Miniaturized antennas based on negative permittivity materials—Lucent Technologies • Metamaterial scanning lens antenna systems and methods—The Boeing Company • 2003: • Metamaterials employing photonic crystal—MIT • Methods of fabricating electromagnetic metamaterials—The Boeing Company • 2002: • Resonant antennas—Lucent Technologies

  19. Questions?

  20. Design Functionality Thick Film Photoresist Calculation: Sin (70) = 58 / t Thickness (t) ~ 61 microns Success! 45s SU-8 2050

  21. Design Functionality Problems in 2-D patterns Un-washed monomer Over exposure Non-uniform columns 15s SU-8 2015 Top Width of top ~ 1.81 um Width of bottom ~ 1.00 um 15s SU-8 2015 Cross

  22. TiO2 Sol Gel Infiltration Dip sample in TiO2 solution (trifluoroacetic acid, titanium oxide, and deionized water) for about 30 seconds. Step 1 Step 2 Dry the sample for at least 2 hours. Step 3 Heat sample up to 600°C in 8 hours and cool down to room temperature in 6 hours to evaporate photoresist.

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