Abstract

We demonstrate a three-dimensional scanning probe microscope in which the extremely soft spring of an optical tweezers trap is used. Feedback control of the instrument based on backscattered light levels allows three-dimensional imaging of microscopic samples in an aqueous environment. Preliminary results with a 2-µm-diameter spherical probe indicate that features of approximately 200 nm can be resolved, with a sensitivity of 5 nm in the height measurement. The theoretical resolution is limited by the probe dimensions.

© 1999 Optical Society of America

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References

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  1. D. W. Pohl, W. Denk, M. Lanz, “Optical stethoscopy: image recording with resolution λ/20,” Appl. Phys. Lett. 44, 651–653 (1984).
    [CrossRef]
  2. G. Binnig, C. Quate, C. Gerber, “Atomic force microscope,” Phys. Rev. Lett. 56, 930–932 (1986).
    [CrossRef] [PubMed]
  3. L. Malmqvist, H. M. Hertz, “Trapped particle optical microscopy,” Opt. Commun. 94, 19–24 (1992).
    [CrossRef]
  4. L. Malmqvist, H. M. Hertz, “Two-color trapped-particle optical microscopy,” Opt. Lett. 19, 853–855 (1994).
    [CrossRef] [PubMed]
  5. S. Kawata, Y. Inouye, T. Sugiura, “Near-field scanning optical microscope with a laser trapped probe,” Jpn. J. Appl. Phys. 33, L1725–L1727 (1994).
    [CrossRef]
  6. L. P. Ghislain, W. W. Webb, “Scanning-force microscope based on an optical trap,” Opt. Lett. 18, 1678–1681 (1993).
    [CrossRef] [PubMed]
  7. A. L. Stout, W. W. Webb, “Optical force microscopy,” in Methods in Cell Biology, M. P. Sheetz, ed. (Academic, San Diego, Calif., 1998), pp. 99–116.
  8. M. E. J. Friese, H. Rubinsztein-Dunlop, N. R. Heckenberg, E. W. Dearden, “Determination of the force constant of a single-beam gradient trap by measurement of backscattered light,” Appl. Opt. 35, 7112–7117 (1996).
    [CrossRef] [PubMed]
  9. W. H. Wright, G. J. Sonek, M. W. Berns, “Parametric study of the forces on microspheres held by optical tweezers,” Appl. Opt. 33, 1735–1748 (1994).
    [CrossRef] [PubMed]
  10. J. Gold, B. Nilsson, B. Kasemo, “Microfabricated metal and oxide fibers for biological applications,” J. Vac. Sci. Technol. A 13, 2638–2644 (1995).
    [CrossRef]

1996 (1)

1995 (1)

J. Gold, B. Nilsson, B. Kasemo, “Microfabricated metal and oxide fibers for biological applications,” J. Vac. Sci. Technol. A 13, 2638–2644 (1995).
[CrossRef]

1994 (3)

1993 (1)

1992 (1)

L. Malmqvist, H. M. Hertz, “Trapped particle optical microscopy,” Opt. Commun. 94, 19–24 (1992).
[CrossRef]

1986 (1)

G. Binnig, C. Quate, C. Gerber, “Atomic force microscope,” Phys. Rev. Lett. 56, 930–932 (1986).
[CrossRef] [PubMed]

1984 (1)

D. W. Pohl, W. Denk, M. Lanz, “Optical stethoscopy: image recording with resolution λ/20,” Appl. Phys. Lett. 44, 651–653 (1984).
[CrossRef]

Berns, M. W.

Binnig, G.

G. Binnig, C. Quate, C. Gerber, “Atomic force microscope,” Phys. Rev. Lett. 56, 930–932 (1986).
[CrossRef] [PubMed]

Dearden, E. W.

Denk, W.

D. W. Pohl, W. Denk, M. Lanz, “Optical stethoscopy: image recording with resolution λ/20,” Appl. Phys. Lett. 44, 651–653 (1984).
[CrossRef]

Friese, M. E. J.

Gerber, C.

G. Binnig, C. Quate, C. Gerber, “Atomic force microscope,” Phys. Rev. Lett. 56, 930–932 (1986).
[CrossRef] [PubMed]

Ghislain, L. P.

Gold, J.

J. Gold, B. Nilsson, B. Kasemo, “Microfabricated metal and oxide fibers for biological applications,” J. Vac. Sci. Technol. A 13, 2638–2644 (1995).
[CrossRef]

Heckenberg, N. R.

Hertz, H. M.

L. Malmqvist, H. M. Hertz, “Two-color trapped-particle optical microscopy,” Opt. Lett. 19, 853–855 (1994).
[CrossRef] [PubMed]

L. Malmqvist, H. M. Hertz, “Trapped particle optical microscopy,” Opt. Commun. 94, 19–24 (1992).
[CrossRef]

Inouye, Y.

S. Kawata, Y. Inouye, T. Sugiura, “Near-field scanning optical microscope with a laser trapped probe,” Jpn. J. Appl. Phys. 33, L1725–L1727 (1994).
[CrossRef]

Kasemo, B.

J. Gold, B. Nilsson, B. Kasemo, “Microfabricated metal and oxide fibers for biological applications,” J. Vac. Sci. Technol. A 13, 2638–2644 (1995).
[CrossRef]

Kawata, S.

S. Kawata, Y. Inouye, T. Sugiura, “Near-field scanning optical microscope with a laser trapped probe,” Jpn. J. Appl. Phys. 33, L1725–L1727 (1994).
[CrossRef]

Lanz, M.

D. W. Pohl, W. Denk, M. Lanz, “Optical stethoscopy: image recording with resolution λ/20,” Appl. Phys. Lett. 44, 651–653 (1984).
[CrossRef]

Malmqvist, L.

L. Malmqvist, H. M. Hertz, “Two-color trapped-particle optical microscopy,” Opt. Lett. 19, 853–855 (1994).
[CrossRef] [PubMed]

L. Malmqvist, H. M. Hertz, “Trapped particle optical microscopy,” Opt. Commun. 94, 19–24 (1992).
[CrossRef]

Nilsson, B.

J. Gold, B. Nilsson, B. Kasemo, “Microfabricated metal and oxide fibers for biological applications,” J. Vac. Sci. Technol. A 13, 2638–2644 (1995).
[CrossRef]

Pohl, D. W.

D. W. Pohl, W. Denk, M. Lanz, “Optical stethoscopy: image recording with resolution λ/20,” Appl. Phys. Lett. 44, 651–653 (1984).
[CrossRef]

Quate, C.

G. Binnig, C. Quate, C. Gerber, “Atomic force microscope,” Phys. Rev. Lett. 56, 930–932 (1986).
[CrossRef] [PubMed]

Rubinsztein-Dunlop, H.

Sonek, G. J.

Stout, A. L.

A. L. Stout, W. W. Webb, “Optical force microscopy,” in Methods in Cell Biology, M. P. Sheetz, ed. (Academic, San Diego, Calif., 1998), pp. 99–116.

Sugiura, T.

S. Kawata, Y. Inouye, T. Sugiura, “Near-field scanning optical microscope with a laser trapped probe,” Jpn. J. Appl. Phys. 33, L1725–L1727 (1994).
[CrossRef]

Webb, W. W.

L. P. Ghislain, W. W. Webb, “Scanning-force microscope based on an optical trap,” Opt. Lett. 18, 1678–1681 (1993).
[CrossRef] [PubMed]

A. L. Stout, W. W. Webb, “Optical force microscopy,” in Methods in Cell Biology, M. P. Sheetz, ed. (Academic, San Diego, Calif., 1998), pp. 99–116.

Wright, W. H.

Appl. Opt. (2)

Appl. Phys. Lett. (1)

D. W. Pohl, W. Denk, M. Lanz, “Optical stethoscopy: image recording with resolution λ/20,” Appl. Phys. Lett. 44, 651–653 (1984).
[CrossRef]

J. Vac. Sci. Technol. A (1)

J. Gold, B. Nilsson, B. Kasemo, “Microfabricated metal and oxide fibers for biological applications,” J. Vac. Sci. Technol. A 13, 2638–2644 (1995).
[CrossRef]

Jpn. J. Appl. Phys. (1)

S. Kawata, Y. Inouye, T. Sugiura, “Near-field scanning optical microscope with a laser trapped probe,” Jpn. J. Appl. Phys. 33, L1725–L1727 (1994).
[CrossRef]

Opt. Commun. (1)

L. Malmqvist, H. M. Hertz, “Trapped particle optical microscopy,” Opt. Commun. 94, 19–24 (1992).
[CrossRef]

Opt. Lett. (2)

Phys. Rev. Lett. (1)

G. Binnig, C. Quate, C. Gerber, “Atomic force microscope,” Phys. Rev. Lett. 56, 930–932 (1986).
[CrossRef] [PubMed]

Other (1)

A. L. Stout, W. W. Webb, “Optical force microscopy,” in Methods in Cell Biology, M. P. Sheetz, ed. (Academic, San Diego, Calif., 1998), pp. 99–116.

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Figures (7)

Fig. 1
Fig. 1

Schematic diagram of a particle in a strongly focused laser beam. Vertical particle motion is monitored by detection of the backscattered light. D is the distance between the imaging optics and the detector; Z is the distance from the imaging optics to the image plane; z is the position of the particle below the objective; and dz is the small change in the vertical position of the trapped particle.

Fig. 2
Fig. 2

Flow diagram of feedback control based on backscattered light. The servo maintains the height of the specimen so that the probe remains in the same vertical position in the optical trap.

Fig. 3
Fig. 3

Schematic diagram of a spherical probe scanning a surface. (a) When the probe diameter is smaller than the width of a well, the dimensions of the feature are detectable. The depth of the feature is correctly determined, whereas the edges are distorted. (b) When the sphere diameter is larger than the width of the well, it is still possible to detect the existence of the well, but its real dimensions are not clearly resolved. The detection of the depth of the well is compromised. (c) and (d) When a particle is scanned over a protrusion, the height can always be determined. The measured width of the feature is larger than the true width owing to the circular path traveled by the probe.

Fig. 4
Fig. 4

Limit of height resolution by this method is determined by the signal to noise of the backscattered light detection. The 30-mV peak-to-peak signal shows the voltage applied to the z-axis piezoactuator of the stage, and the smaller signal shows the resulting backscattered light signal from a 1-µm-radius polystyrene sphere attached to a glass slide mounted on the stage.

Fig. 5
Fig. 5

Images of SiO2 structures. (a) and (b) are images produced by use of scanning with an optically trapped stylus. (c) Same structure imaged with a 100× objective. (d) Scanning electron microscope picture of a SiO2 structure from the same batch.

Fig. 6
Fig. 6

(a) Single linear scan across the SiO2 structure, confirming that the measured height is in agreement with the known height of the sample (0.5 ± 0.05 µm). (b) Linear scans of a small part of the surface (offset by 300 nm for convenience) show that although the signal contains high-frequency noise, features of 200 nm in size are present in consecutive scans.

Fig. 7
Fig. 7

Scans of a polystyrene surface with a polystyrene probe. (a) Two consecutive scans, both exhibiting steplike features that probably represent the probe response to frictionlike forces. (b) and (c) Full scans of the polystyrene surface.

Equations (6)

Equations on this page are rendered with MathJax. Learn more.

Pav=PRdet/Rim2,
ΔZ=MlΔz=Mt2Δz,
ΔPzdPav/dzΔz2PavMt2/D-ZΔz.
zR=πω02/λ,
y=-r+r2-x21/2.
d=r-r2-w2/41/2.

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