ABSTRACT
This chapter provides an introduction to the theory and design of optical tweezers. It describes the optical tweezers apparatus, including instrument design considerations, position detection schemes, and calibration techniques. The chapter reviews some important progresses in single-molecule manipulation by the use of optical tweezers and finally, and provides a detailed protocol to study folding of DNA hairpin using optical tweezers. Force is the basis of a fundamental and regulatory mechanism of biomolecular interactions, which drive many cellular processes. Optical tweezers were immediately found to be useful in biological research, due to their ability to trap and move microorganisms without physical contact, which can even allow manipulation of organelles in live cells. The origin of optical forces is from the exchange of momentum between the incident photons and an optically trapped object.
