Practice question

In non-contact mode, AFM cantilever oscillates near its resonance slightly above surface, experiencing attractive van der Waals forces without touching. Frequency and amplitude shifts are detected to map topography, avoiding tip-induced deformation or damage to soft biological samples like DNA, proteins, and lipid membranes. Contact mode drags tip, generating high lateral forces that can displace molecules, while tapping mode intermittently contacts. Non-contact preserves delicate structures and extends tip life, though resolution may slightly reduce in liquid, making it valuable for non-invasive imaging of hydrated biomolecules.