Measurement of forces in optical tweezers with applications in biological systems

Abstract

Optical tweezers, a tool for contactless manipulation of micro-and nano-particles, are widely used to apply and measure forces. This thesis investigates various force measurement methods and their applications for force measurements in biological systems. Unlike position-based methods, the direct optical force measurement technique does not require calibration of the trap stiffness. The direct force measurement method utilises the determination of the change in the momentum of the trapping light to measure the optical forces acting on a trapped object. This thesis has developed a method for the measurement of the calibration constant for the force detector based on simultaneous detection of the position of the trapped particle and the optical force. Rigorous tests of the calibration technique and the direct force measurement method using different particles (red blood cell, vaterite, silica spheres), a variety of trapping media (water, plasma, ethanol), and trapping beams (HG 00 and HG 01) have shown Financial support

Optical trapping in vivo: theory, practice, and applications

“…This precise cell characterization and its linkage with health and survivability are therefore of great importance for medicine. In Kashchuk's work [167], dual OTs were used to controllably stretch blood cells of different ages and measure their stiffness. Measurements were done by holding one trap at a constant position and stretching the cell by moving the other trap away from the first trap.…”