FIGURE 3.

Optical cell stretching technique. (A) Single non-adhesive cells are transported by flow in a microfluidic system that is placed perpendicular to two opposite divergent non-focused laser-beams and can trap and stretch individual cells one after another. (B) A standard protocol for a cell stretching experiment is as follows: Firstly, a cell is trapped for 1 s with 100 mW laser power at each laser. Secondly, the cell is stretched with 800 mW laser powers for 2 s. Thirdly, the cell is relaxed by switching the high laser powers to 100 mW (trapping laser powers) for 2 s. The black line shows the laser power profile and the blue line the deformation of the cell. (C) During the stretching phase, the cell is stretched at its major axis (parallel to the laser beam axis) and compressed at its minor axis (perpendicular to the laser beam axis). (D) The momentum of two rays with different intensities show how these forces propagate through a cell. The intensity profile of the laser is given in the diagram. For simplicity, the second laser in the opposite direction is omitted. The blue spherical object represents a single cell.