The atomic force microscope sees surfaces by touch, not by light
Ordinary microscopes are limited by how light bends. The atomic force microscope sidesteps that entirely: it drags a tiny sharp tip across a surface and feels its bumps, resolving detail finer than a nanometre, over 1,000 times beyond the optical limit. It can even push individual atoms around.
An atomic force microscope, or AFM, is a kind of scanning probe microscope. Instead of lenses or beams, it uses a sharp tip on the free end of a small, springy cantilever. As the tip meets the forces of a sample, the cantilever bends; a detector, often an optical lever or interferometer, converts that deflection into an electrical signal. Piezoelectric elements shift the sample by minute, precise amounts, so an atomic-scale interaction becomes a measurable, macro-scale motion. Despite the name, it has nothing to do with nuclear forces.
It does three jobs. It can measure forces between tip and sample to gauge properties such as stiffness. It can image topography by scanning back and forth across a grid while a feedback loop keeps the force constant, recording height at each point and rendering it as a false-colour map. And it can manipulate, moving atoms, drawing patterns in lithography or stimulating individual cells. Alongside height it can map adhesion, conductivity or surface potential, and most other scanning probe techniques are variants of it.
Because no light or electron beam is involved, it escapes diffraction and aberration and needs neither a vacuum nor sample staining. That lets it work on specimens in air or liquid, which is why it serves fields from semiconductors and polymer chemistry to cell biology and medicine.
The instrument grew out of IBM Research in Zurich, where Gerd Binnig and Heinrich Rohrer built the scanning tunnelling microscope in the early 1980s and shared the 1986 Nobel Prize in Physics. Binnig invented the AFM in 1985, and he, Calvin Quate and Christoph Gerber published the first working version in 1986. Commercial machines followed in 1989. Atomic resolution proved hard: Ohnesorge and Binnig showed atomic-scale defects in liquid in 1993, and Franz Giessibl later achieved true atomic resolution of the silicon 7x7 surface.
Source: Atomic force microscopy
