3D and Aerosol Printed Conductor Dielectric Full- 3D RF Metamaterials

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1 3D and Aerosol Printed Conductor Dielectric Full- 3D RF Metamaterials June 22, 2017 Jimmy Hester, Evan Nguyen, Jesse Tice, and Vesna Radisic Approved for Public Release: NG , 6/2/17

2 Outline Introduction Metamaterials and additive manufacturing technologies Approach and results Process and materials characterization A novel, AM enabled electromagnetic bandgap (EBG) transmission line Conclusion and outlook 2 Approved for Public Release: NG , 6/2/17

3 Metamaterials Overview Metamaterials are engineered to have electromagnetic properties that are not easily found in nature. Some examples include: negative or low value of permittivity (ε), permeability (µ), index of refraction (n), as well as RF magnetism and certain types of anisotropy Metamaterials obtain their properties not from the natural molecular properties of the base materials, but from an artificially designed structure Metamaterial structures are made up of artificially constructed EM resonant unit cells that are arranged in a 1, 2 or 3D lattice Unit cells are small compared to the EM wavelength Metasurfaces are 2D versions of metamaterials nn = ± ε<0, µ>0, n=im Metals at optical freq Evanescent wave µ ε<0, µ<0, n<0 Double negative materials Backward-wave propagation ε>0, µ>0, n>0 Isotropic dielectrics Forward-wave propagation ε>0, µ<0, n=im Ferrites Evanescent wave ε

4 Metamaterials Impact on Aerospace Platforms Components Filters Antennas Lenses Beamforming Beamsteering Limiters Isolators Circulators Waveguides & transmission lines Low density structures Light weight components Aqua Earth-Observing Satellite Transceivers Nonlinear optics & RF Switches and modulators Lasers and detectors Reconfigurable transceivers Ref. NASA 4 Engineered electromagnetic materials are a powerful enabling technology that impacts many diverse applications Approved for Public Release: NG , 6/2/17

5 The Appeal of Additive Manufacturing Technologies The metamaterial designer s ideal fabrication process: Source: Vossman, Wikimedia ommons/archive/b/bc/ %21Voxels.svg 5 This would enable the emergence of novel RF metamaterial structures, with unprecedented performance Approved for Public Release: NG , 6/2/17

6 NGAS Approach Combine: Dielectric 3D printing (SLA, DLP, FDM) Conformal aerosol printing of: Conductors (nanoparticle inks) Active materials (phase-changing, etc.) Electroless plating techniques (not used here) Goals: Fully 3D-printed RF metamaterials 3D structures significantly exceeding performance of 2D counterparts Demonstrating unique properties Invent new 3D AMT-enabled RF metamaterials 6 Approved for Public Release: NG , 6/2/17

7 Tools Used for This Work Optomec Printer Formlabs Printer Aerosol jet printer Can print interconnects on both 2D and 3D substrates Can print on curved surfaces DC and RF conductor performance needs to be evaluated Stereolithography (SLA) 3D printer High resolution patterning Can print 3D objects out of dielectrics Polymers and (soon) ceramics Limited selection of dielectric Dielectric losses not well evaluated 7 Source: Formlabs 2 Approved for Public Release: NG , 6/2/17

8 Aerosol Jet Printed Silver Ink Evaluation Fabrication: Print set of 100 µm-wide lines with varying printing parameters on Si wafer 1-3 layers, (5,10,20,30) µm spacing between passes Oven thermal sintering Short and long lines used for measurement fixture de-embedding Characterization Measurement of the resistivity of the lines Two-line differential method Measurements taken with DC probes, on probe station Cross-section measurements using optical profilometry on Keyence microscope Processing Extraction of the conductivity Extraction of the linear mass deposition rate 8 Approved for Public Release: NG , 6/2/17

9 Calculated Bulk Conductivity on Si Wafer Processing comments: 100% density was assumed for the silver traces Comments Good conductivity was achieved: 2.4e7 S/m 5 µm-spaced passes stand out: Resistance is higher than expected 6.3 x 10 7 S/m 1.7 x 10 7 S/m 2.4 x 10 7 S/m 9 Approved for Public Release: NG , 6/2/17

10 Calculated Mass Deposition Rate on Si Wafer Comments Visible anomaly for 1- layer samples This effect has been reliably reproduced 10 Approved for Public Release: NG , 6/2/17

11 3D Printed Dielectric Characterization Evaluated SLA printed epoxy resin from FormLabs Two transmission line method was used ε r =3.65 to 3.95, tan δ=0.06 Surface Topological Scan Extracted Permittivity 2 µm 11 Surface roughness ~2 µm, dielectric permittivity 3.95 to 3.65 Approved for Public Release: NG , 6/2/17

12 Aerosol Jet Printed Conductor on SLA substrate High-resolution metallization deposition and patterning process done with the Optomec aerosol jet printing system Silver nanoparticle ink on dielectric substrate printed with the FormLabs SLA printer Metallization thickness ~ 2 µm, DC sheet resistance ~ 0.2 Ω/ 12 Approved for Public Release: NG , 6/2/17

13 A Bright Future for Full 3D RF Metamaterials The combination of SLA dielectrics and aerosol conductors provides unique capabilities for RF MM fabrication Nevertheless, more work needs to be done from the materials perspective: Lower dielectric loss SLA or DLP dielectrics need to be used Surface roughness mitigation techniques need to be developed SLA substrate/aerosol SNP ink interaction and optimal sintering techniques need to be explored Additional inks need to be developed for increased functionality This work demonstrates that orders-of-magnitude RF metamaterials performance improvements can be achieved through the use of additive manufacturing technologies 13 Approved for Public Release: NG , 6/2/17

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