Controlled rotation of biological microscopic objects using optical line tweezers

Area of Science:

• Biophysics
• Optical trapping
• Cell biology

Background:

• Microscopic object manipulation requires precise control.
• Existing optical tweezer techniques for rotation can be complex and inefficient.

Purpose of the Study:

• To develop a simpler and more efficient method for controlled rotation of cells and intracellular objects using optical tweezers.
• To demonstrate the capability of rotating biological samples of varying sizes.

Main Methods:

• Generated an elliptic beam profile (line tweezers) by inserting a cylindrical lens into the optical path of the trapping beam.
• Rotated the cylindrical lens to control the orientation of the line tweezers and thus the trapped object.
• Applied the technique to rotate E. coli bacteria and an intracellular crystal within a plant cell.

Main Results:

• Achieved controlled, continuous rotation of microscopic objects from 2 to 40 micrometers.
• Rotated E. coli bacteria at speeds up to 10 Hz with 25 mW trapping beam power.
• Successfully rotated an intracellular object (calcium oxalate crystal) within a plant cell at speeds up to 4 Hz.

Conclusions:

• The line tweezers method offers a simpler, more efficient approach for rotating microscopic objects compared to previous techniques.
• This technique allows for better utilization of laser power and easier control over the trap beam profile.
• This is the first reported instance of rotating an intracellular object using optical tweezers.