Optical tweezers

Optical tweezers use a tightly focused laser beam to trap and manipulate microscopic particles through forces exerted by light. They can measure forces and displacements at microscopic scales.

Optical gradient force: A force that draws dielectric particles toward regions of stronger light intensity. It pulls a trapped particle toward the laser focus when the particle is displaced.
Single-molecule biophysics: The study of the structure, dynamics, and interactions of individual biological molecules. Optical tweezers can apply controlled loads to individual molecules and measure their responses.
Arthur Ashkin: American physicist who pioneered optical trapping and shared the 2018 Nobel Prize in Physics. Ashkin demonstrated optical trapping and developed the technique that became optical tweezers.
Magnetic tweezers: A technique that applies forces to magnetic beads using controlled magnetic fields. Unlike optical tweezers, magnetic tweezers exert force without relying on a focused laser.
Radiation pressure: Force exerted on matter when electromagnetic radiation transfers momentum to it. It pushes particles along the beam and helps determine whether a stable trap forms.
DNA stretching: Experimental extension of DNA under applied force to study its mechanical properties and interactions. Trapping beads attached to DNA reveals how the molecule extends under force.
Optical levitation: Suspension of particles against gravity using forces exerted by light. Early levitation experiments established that light could exert controllable forces on small particles.
Atomic force microscopy: A scanning-probe method that maps surfaces by measuring forces on a sharp tip. Both measure microscopic forces, but atomic force microscopy uses a mechanical probe rather than light.
Rayleigh scattering: Scattering of light by particles much smaller than its wavelength. Its dipole approximation explains optical forces on particles far smaller than the laser wavelength.
Molecular motor: A protein that converts chemical energy into directed movement or mechanical work in a cell. Tweezers can track the steps and forces generated by individual molecular motors.

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