Encased Cantilevers for Gentle Atomic forceMicroscopy and low noise Force Spectroscopy InLiquids    Keep Cantilever Dry   ...
Imaging Soft Samples          Deformation Limits Resolution    AFM measurements require force between the tip and sample. ...
Damping of Cantilevers in viscous Media           4k BTk      Fn =        = 4k BTb           ω0Qi  Force noise: “Smallest ...
Damping of Cantilevers in viscous Media           4k BTk      Fn =        = 4k BTb           ω0Qi         b = 6πRη        ...
Damping of Cantilevers in viscous Media         4k BTk    Fn =        = 4k BTb         ω0Qi        b = 6πRη        Size of...
Damping of Cantilevers in viscous Media        4k BTk   Fn =        = 4k BTb        ω0Qi    b = 6πRη    Size of       Visc...
Let`s go Scuba Diving!
Fabrication of Encased Cantilevers       SiO2 / ParyleneLength of levers can be tuned              short is ideal for high...
Fabrication of Encased Cantilevers    SiO2 / Parylene                      TEM shows that tip radius <10nm is maintained  ...
Performance in WaterHigh Q factor and high resonance frequency while submerged in waterHydrophobic encasement prevents wat...
Gentle Imaging OF Lipid BiLayers  Measured height of supported DPPC bilayer on mica  (softest possible tapping mode).     ...
Contact Mode - Force Spectroscopy                        Regular cantilever in liquid                        (Silicon, 350...
Cantilever with integrated Interferometer                                                Fabry-Pérot Etalon               ...
Fabrication Defects Reduce Effective Finesse                                                         White Light Spectrosc...
Optical Setup (Home-Built AFM)                                                         Finesse ~3                 Copyrigh...
Optical Setup (Home-Built AFM)             k=45N/m             f0=320kHz                                                  ...
Summary• Encased cantilevers perform up to              •First prototypes of interferometric  10x better in liquid than re...
AcknowledgementsPaul Ashby PhDSee his talk tomorrow 2:00 PM, UU5.02. Breaking the Raster Scan Paradigm.Interferometric Can...
Acknowledgements Want to become a beta tester of encased cantilevers? Contact us, and become a user of the Molecular Found...
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2012 fallmrs encasedlevers_dominikziegler_summary

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  • Add spectra in water… Ugly. Thermal might be ok.
  • (L-α-dipalmitoyl-phosphatidylcholine)
  • worm like chain model with a change in contour length of 33nm repeat and a persistence length of 0.28nm Examples where thermal noise of the cantilevers dominates the measurements Bandwidth 2kHz
  • 2012 fallmrs encasedlevers_dominikziegler_summary

    1. 1. Encased Cantilevers for Gentle Atomic forceMicroscopy and low noise Force Spectroscopy InLiquids Keep Cantilever Dry Interferometric Detection Reduce Force Noise Reduce Position Sensing Noise Dominik Ziegler PhD Molecular Foundry Lawrence Berkeley National Lab
    2. 2. Imaging Soft Samples Deformation Limits Resolution AFM measurements require force between the tip and sample. This force can cause deformation and damage.
    3. 3. Damping of Cantilevers in viscous Media 4k BTk Fn = = 4k BTb ω0Qi Force noise: “Smallest force one can measure in a given bandwidth”Viscous damping defines force resolution. ω0≈150 kHz Fn≈20fN/√Hz Q≈200 ω0≈50 kHz Fn≈200fN/√Hz Q≈4 In water AFM cantilevers are about 10100 µm long, 30 µm wide times less sensitive than in air! Copyrighted Material dziegler@lbl.gov
    4. 4. Damping of Cantilevers in viscous Media 4k BTk Fn = = 4k BTb ω0Qi b = 6πRη Size of Viscosity object ω0≈150 kHz Fn≈20fN/√Hz Q≈200 ω0≈50 kHz Fn≈200fN/√Hz Q≈4 In water AFM cantilevers are about 10100 µm long, 30 µm wide times less sensitive than in air! Copyrighted Material dziegler@lbl.gov
    5. 5. Damping of Cantilevers in viscous Media 4k BTk Fn = = 4k BTb ω0Qi b = 6πRη Size of Viscosity object Force Noise Fn=23fN/√Hz Requires special 2um instrument 2 µm Olympus BioleverFAST Detection limits size Viani et. al. JAP v86 p2258 (1999) Copyrighted Material dziegler@lbl.gov
    6. 6. Damping of Cantilevers in viscous Media 4k BTk Fn = = 4k BTb ω0Qi b = 6πRη Size of Viscosity object Keeping the cantilever dry (reduce viscosity). Copyrighted Material dziegler@lbl.gov
    7. 7. Let`s go Scuba Diving!
    8. 8. Fabrication of Encased Cantilevers SiO2 / ParyleneLength of levers can be tuned short is ideal for high speed imaging long and soft for contact mode force spectroscopy Copyrighted Material dziegler@lbl.gov
    9. 9. Fabrication of Encased Cantilevers SiO2 / Parylene TEM shows that tip radius <10nm is maintained Copyrighted Material dziegler@lbl.gov
    10. 10. Performance in WaterHigh Q factor and high resonance frequency while submerged in waterHydrophobic encasement prevents water from entering (>2 days) Copyrighted Material dziegler@lbl.gov
    11. 11. Gentle Imaging OF Lipid BiLayers Measured height of supported DPPC bilayer on mica (softest possible tapping mode). 5.34nm 2000 1500 Number of events 1000 500 0 0 2 4 6 8 10 12 Topography [nm] Height Histograms “Hydra Levers” by AppNano 12x12 µm2 Cantilever Length: 200 µm 6.32nm Res. Frequency: 17 kHz Number of events 3000 2500 2000 1500 1000 500 0 0 5 10 15 20 Topography [nm] Height HistogramsEncased silicon lever (Mikromasch Thicker measured heightNSC36 A) etched back 110 µm, 12x12 µm2  Less deformation by tipstiffness of 0.95N/m and frequency85kHz. Copyrighted Material dziegler@lbl.gov
    12. 12. Contact Mode - Force Spectroscopy Regular cantilever in liquid (Silicon, 350 µm long, 1µm thick, 35 µm wide) Same cantilever with encasementEncasement also lowers noise in DCmeasurements. worm like chain modelProtein Pulling (unfolding) experimentsSimulation for worm like chain modelAt bandwidth of 2kHz noise of thecantilevers dominates the measurements Copyrighted Material dziegler@lbl.gov
    13. 13. Cantilever with integrated Interferometer Fabry-Pérot Etalon (Reflectance Mode) Destructive interference for gap size g = n λ/2 Finesse: Copyrighted Material dziegler@lbl.gov
    14. 14. Fabrication Defects Reduce Effective Finesse White Light Spectroscopy Finesse ~ 1 Non uniform gap size along lever! Finesse ~3 Copyrighted Material dziegler@lbl.gov
    15. 15. Optical Setup (Home-Built AFM) Finesse ~3 Copyrighted Material dziegler@lbl.gov
    16. 16. Optical Setup (Home-Built AFM) k=45N/m f0=320kHz 70nm Network of Carbon NanotubesOptical Beam Deflection Interferometric Cantilevers,(Measured before deposition of gold layer on encasement) Home-built AFMMultimode Bruker ~6fm/ √ Hz! (@ 10.6mW,~770nm)~25fm/ √ Hz (@ ~1mW,680nm) Copyrighted Material dziegler@lbl.gov
    17. 17. Summary• Encased cantilevers perform up to •First prototypes of interferometric 10x better in liquid than regular cantilevers outperform position noise in cantilevers with similar dimensions state-of-the-art commercial AFMs! Force Noise of 12fN/ √ Hz Position Noise of 6fm/ √ Hz• Work in any commercial instruments achieved with optical beam deflection •Successfully used for imaging• Tunable length of cantilever for different applications Copyrighted Material dziegler@lbl.gov
    18. 18. AcknowledgementsPaul Ashby PhDSee his talk tomorrow 2:00 PM, UU5.02. Breaking the Raster Scan Paradigm.Interferometric Cantilevers:Adrian Nievergelt Mechanical Engineering, ETH Zurich, SwitzerlandPreparation of Lipid Bilayers:David Chmielewski LBNL, BerkeleyCNT Samples provided byAminy Ostfeld, LBNL, BerkeleyALL MEMBERS OF NANOFABRICATION AND NANOIMAGING GROUPS dziegler@lbl.gov #DE-AC02-05CH11231
    19. 19. Acknowledgements Want to become a beta tester of encased cantilevers? Contact us, and become a user of the Molecular Foundry.dziegler@lbl.gov www.foundry.lbl.gov

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