Which scanning probe technique maps surface using van der Waals and electrostatic forces?
AFM operates by sensing interatomic forces between sharp tip and sample surface. Cantilever deflection reflects van der Waals attraction, Pauli repulsion, and electrostatic contributions, enabling topographic mapping without light or electrons. Unlike SEM and TEM using electron beams, PALM using photoactivation, AFM measures mechanical interactions directly in air or liquid, achieving sub-nanometer vertical resolution. Force spectroscopy extends capability to measure adhesion and elasticity. Van der Waals forces dominate at short range, providing sensitivity to surface chemistry and molecular contours, making AFM invaluable for studying protein-DNA complexes, lipid phases, and polymer surfaces at nanoscale.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.