National Institute for Standards (NIS, Egypt), Nanotechnology lab, Tersa Street, El Haram Giza, Egypt P. O. Box: 136 Giza, Code No. 12211 E-mail: rsayed.nis@gmail.com, phone: 002 01005567106

Abstract. An optical tweezers technique is used for ultraprecise micromanipulation to measure positions of micrometer scale objects with a precision down to the nanometer scale. It consists of a high performance research microscope with motorized scanning stage and sensitive position detection system. Up to 10 traps can be used quasi-simultaneously. Non photodamage optical trapping of Escherichia coli (E. coli) bacteria cells of 2 µm in length, as an example of motile bacteria, has been shown in this paper. Also, efficient optical trapping and rotation of polystyrene latex particles of 3 µm in diameter have been studied, as an optical handle for the pick and place of other tiny objects. A fast galvoscanner is used to produce multiple optical traps for manipulation of micro-sized objects and optical forces of these trapped objects quantified and measured according to explanation of ray optics regime. The diameter of trapped particle is bigger than the wavelength of the trapping laser light. The force constant (k) has been determined in real time from the positional time series recorded from the trapped object that is monitored by a CCD camera through a personal computer.

Keywords: optical tweezers, multiple traps, force calibration, nanometer displacement, E. coli bacteria.

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