Nanotools for Materials Science

1. Nanotools for Materials Science Nicholas D. Spencer Dept. Of Materials, ETH-Zürich Animations by Marc Duseiller

2. Outline • STM and AFM • AFM as a chemical probe: Oxides • AFM as a chemical probe: Polymers • Designer molecules for Biosensors

3. Outline • STM and AFM • AFM as a chemical probe: Oxides • AFM as a chemical probe: Polymers • Designer molecules for Biosensors

4. Scanning Tunneling Microscopy Binnig and Rohrer: Nobel Prize for Physics, 1986

5. Scanning Tunneling Microscopy

6. STM: Constant-Height Mode

7. STM: Constant-Current Mode

12. Atomic Force Microscopy

13. AFM: Photodiode detection

14. AFM: Attractive and Repulsive Force Curves

15. AFM: TappingModeTM

16. The compound eye of a housefly (Musca domestica), seen by TappingMode AFM. The detail image reveals channel-like features on the surface. 60µm scan courtesy P. Gorostiza, I. Diez, F. Sanz, Universitat de Barcelona, Spain.

17. AFM: Phase-Contrast Mode

18. TappingMode AFM Phase image of a PMMA-b-polybutylacrylate-b-PMMA symmetric triblock copolymer partly covering a mica substrate. The PMMA component forms cylindrial microdomains (located 40 nm apart) that appear as cones on the phase image. 1.5µm scan courtesy P. LeClere and R. Lazzaroni, Universite de Mons-Hainaut, Belgium.

19. AFM: Lateral Mode (LFM)

20. AFM as Nanoindenter

21. "The world's smallest turbine." Densely packed assembly of proton driven rotors of the chloroplast ATP synthase imaged in buffer solution. Rotors are incorporated in both orientations with respect to the membrane plane. At a lateral resolution better than 1nm, the fourteen subunits of the wide connector end (diameter ~7.6nm) can be seen. 70nm scan courtesy of H. Seelert, A. Poetsch, N. Dencher, A. Engel, H. Stahlbert and D.J. Müller, Max-Planck-Institute of Molecular Cell Biology and Genetics, Dresden, Germany.

22. TappingModeTM AFM image of CD surface

23. Contact mode AFM of cholera toxin oligomers bound to lipid bilayer under buffer. Note that a clear pentameric structure is resolved for many of the cholera toxin oligomers, while others appear hexameric or unstructured. 80 nm scan size. Courtesy of Shao lab, University of Virginia.

24. Normal and sickled human red blood cells. Sample preparation consisted of a standard smear on a glass slide. The rigid contour of the sickled cell (center) contrasts with the normal red blood cells; note the sickled cell has indented the softer red blood cell. Three spicules (top left of cell), approximately 0.5 to 1.0µm long, project out from the sickled cell, denoting rearrangement of intracellular hemoglobin molecules. Sample courtesy of Sansum Medical Clinic, Santa Barbara, CA.

25. Outline • STM and AFM • AFM as a chemical probe: Oxides • AFM as a chemical probe: Polymers • Designer molecules for Biosensors

26. Spatial Resolution Range of Imaging Surface Methods for Insulating Samples Chemical iXPS Information SAM Gap ToF-SIMS Morphological SEM STM AFM 1Å 1nm 10nm 100nm 1µm 10µm 100µm SpatialResolution

27. Experimental Setup

28. 10 a) 5 pH 4 pH 8.5 Normal Force [nN] 0 -5 40 0 20 20 40 0 Tip-Sample Separation [nm] Effect of pH on Force Curves Si3N4 tip, Si/SiO2 Sample A. Marti, G. Hähner, and N.D. Spencer, Langmuir11 (1995) 4632-5

29. Lateral Force for Si3N4/SiO2 and Si3N4/Al2O3 tip Si N 3 4 Al O 2 3 Si O 2 Lateral Force [arb. units] 3 4 6 8 9 11 5 7 10 pH G. Hähner, A. Marti, and N.D. Spencer, Tribology Letters 3 (1997) 359-65

30. Chemical Imaging with pH-Dependent AFM/LFM—1 G. Hähner, A. Marti, and N.D. Spencer, Tribology Letters 3 (1997) 359-65

31. Chemical Imaging with pH-Dependent AFM/LFM Self-assembled Monolayers µCP-generated thiol pattern No height difference observable A. Marti G.Hähner ETH-LSST Chemical (frictional) contrast in the lateral force image can be changed by modifying pH, due to a pKa value of 4-5 of the -COOH groups.

32. Outline • STM and AFM • AFM as a chemical probe: Oxides • AFM as a chemical probe: Polymers • Designer molecules for Biosensors

33. AFM of Polyesterurethane Block Copolymer Spin-Coated from a 1% NMP Soln. onto a Si-Wafer K. Feldman - ETH-LSST

34. PS PAN iPP Polystyrene PMMA Isotactic Polypropylene Avg. MW=250,000 Polyacrylonitrile Avg. MW=250,000 Tg = 100°C PVDF Avg. MW=200,000 Tg = 22°C Tg = 87°C Poly(vinylidene fluoride) PAA Poly(methyl methacrylate) Avg. MW=534,000 Avg. MW=150,000 FEP Tg = 38°C Tg = 102°C Poly(acrylic acid) FEP Avg. MW=150,000 Avg. MW=50,000 Tg = 102°C Polymers used in this Study Increasing H-bonding Interaction Non-Polar Polar

35. Comparison of Force Curves, Pull-On, and Pull-Off Forces Between a SiOx Probe and a PMMA Surface in Different Media

36. Hamaker Constant dipole-dipole and dipole-induced-dipole components (from dielectric constants) dispersion (London) component (from refractive indices) Israelachvili’s Approximation to Lifshitz’ Theory for Calculation of the Non-Retarded Hamaker Constant = + Work of Adhesion, W, calculated from W≈ATotal / (12Do2), where Do=0.165nm is the commonly used value for the cut-off separation

37. Non-Polar Polymer Adhesion is Due to London Interaction Only (all measurements under perfluorodecalin) PS Yields tip radius of 50 nm, assuming JKR Theory holds (confirmed by FESEM) iPP PVDF FEP (Lifshitz Theory) K. Feldman, T. Tervoort, P. Smith, N.D. Spencer, Langmuir14(1998)372

38. Towards a Force Spectroscopy of Polymers Silica Tip Gold Tip K. Feldman, T. Tervoort, P. Smith, N.D. Spencer, Langmuir14(1998)372

39. Chemical Imaging of PS:PMMA Blend (1:10) (Spin-coated from toluene, 2 wt.% total) Plasma-Cleaned Si3N4 Tip Plasma-Cleaned Au Tip K. Feldman, T. Tervoort, P. Smith, N.D. Spencer, Langmuir14(1998)372

40. Outline • STM and AFM • AFM as a chemical probe: Oxides • AFM as a chemical probe: Polymers • Designer molecules for Biosensors

41. Analyte/Antigen Active site Protein Denaturing Interactions Linker species Biosensors, Proteomics Challenge: How to immobilize proteins in an active, well-defined state?

42. PLL backbone MW: 20,000 to 350,000 Positively charged at pH<10 (R= –NH3+) Approximate length of backbone: 90 to 1000 nm PEG side chain MW: 2000 to 5000 Adsorbs water and has properties similar to water Protein resistant Approximate length of side chain:20 nm PLL backbone PEG side chain Poly-l-lysine (PLL)-g-polyethylene glycol (PEG) J. Hubbell, D. Elbert, Chem Biol 5: (3) 177-183 (1998)

43. Attachment of the Comb-like Co-Polymer to a Negatively Charged Surface Hydrophilic Uncharged Flexible chains High water content Steric repulsion Biocompatible PEG side chains PLL back-bone Positive charge High coverage Kinetic inertness pH dependence Oxide surface

45. Buffer 1.6076 1.5742 1.5738 Buffer Antibody 1.6072 Effective refractive index TE 1.5734 Effective refractive index TM 1.5730 1.6068 Antigen 1.5726 1.6064 1.5722 0 100 200 Time [min] MONITORING BIOMOLECULE ADSORPTION • refractive index and thickness of adlayer can be calculated • highly sensitive (~1 ng/cm2) • 3-second time resolution

46. Surface Modification with PLL-PEG – Effect on Serum Adsorption Optical grating coupler SiO2/TiO2 waveguide Full human serum HEPES buffer Without (bare oxide) and with adlayer of PLL-PEG G.L.Kenausis,J.Vörös,D.L.Elbert,N.Huang,R.Hofer,L.Ruiz,M.Textor J.A.Hubbell, and N.D.Spencer, J.Phys.Chem.B104 (2000)3298-3309

47. Cell Attachment on PLL-PEG-coated Optical Waveguides Osteoblast attachment to SiO2/TiO2surface treated with PLL-g-PEG Osteoblast attachment to untreated SiO2/TiO2 surface J. Vörös, G. Kenausis - ETH-LSST

48. INITIAL SENSOR SURFACE RECEPTOR IMMOBILIZATION ANALYTE DETECTION Biosensor surface Biosensor surface Biosensor surface Passive: resistant to non-specific binding Controlled orientation and concentration Optimum sensitivity, low non-specific adsorption OUR APPROACHTO BIOAFFINITY SENSING

49. B i o s e n s o r s u r f a c e B i o s e n s o r s u r f a c e STARTING SENSOR SURFACE TODAY OUR APPROACH Bioactive: nonspecific binding Passive: resistant to nonspecific binding

50. B i o s e n s o r s u r f a c e IMMOBILIZATIONOF RECEPTOR MOLECULES Controlled orientation and concentration