Three-dimensional thermal noise imaging

We present a scanning probe microscope based on optical tweezers for three- dimensional imaging of the topology of transparent material in the nanomete r range. A spherical nanoparticle serves as a probe. An optical trap moves it through the sample (e.g., a polymer network), while the position of the particle center is recorded by three-dimensional interferometry. Accessible volumes are reconstructed from the histogram of thermal position fluctuati ons of the particle. The resolution in determining the position of surfaces in three dimensions is about 20 nm. (C) 2001 American Institute of Physics .