title: Optical trapping of a spherically symmetric sphere in the ray-optics regime: a model for optical tweezers upon cells.
abstract: Since their invention in 1986, optical tweezers have become a popular manipulation and force measurement tool in cellular and molecular biology. However, until recently there has not been a sophisticated model for optical tweezers on trapping cells in the ray-optics regime. We present a model for optical tweezers to calculate the optical force upon a spherically symmetric multilayer sphere representing a common biological cell. A numerical simulation of this model shows that not only is the magnitude of the optical force upon a Chinese hamster ovary cell significantly three times smaller than that upon a polystyrene bead of the same size, but the distribution of the optical force upon a cell is also much different from that upon a uniform particle, and there is a 30% difference in the optical trapping stiffness of these two cases. Furthermore, under a small variant condition for the refractive indices of any adjacent layers of the sphere, this model provides a simple approximation to calculate the optical force and the stiffness of an optical tweezers system.
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu, Taiwan. YRChang.eo91g@nctu.edu.tw
authors.forename: Yi-Ren
authors.initials: YR
authors.lastname: Chang
authors.forename: Long
authors.initials: L
authors.lastname: Hsu
authors.forename: Sien
authors.initials: S
authors.lastname: Chi
mesh_terms: D000818:Animals; D016466:CHO Cells; D018929:Cell Culture Techniques / Q000379:methods*; D002465:Cell Movement / Q000528:radiation effects; D002468:Cell Physiological Phenomena / Q000528:radiation effects*; D003198:Computer Simulation; D006224:Cricetinae; D003412:Cricetulus; D005434:Flow Cytometry / Q000379:methods*; D007834:Lasers; D008846:Micromanipulation / Q000379:methods*; D008954:Models, Biological; D011829:Radiation Dosage; D013314:Stress, Mechanical