Optical trapping of sub-millimeter sized particles and microorganisms

Area of Science:

• Optics and Photonics
• Biophysics
• Microscopy

Background:

• Optical tweezers (OT) typically confine small particles.
• Counter-propagating (CP) dual-beam traps handle larger specimens but are complex and have low stiffness.
• Existing CP traps are limited to particles around 100 μm.

Purpose of the Study:

• To develop and demonstrate a new class of counter-propagating optical tweezers with broken symmetry.
• To enable the trapping and manipulation of larger particles (>100 μm) and biological specimens.
• To simplify the setup, improve robustness, and enhance trapping stiffness.

Main Methods:

• Utilizing a single Gaussian beam folded back retro-reflectively in an asymmetrical manner.
• Creating a broken-symmetry CP trap capable of trapping particles from 1 μm up to 250 μm.
• Demonstrating simultaneous 3D trapping and light-sheet microscopy of C. elegans worms (up to 450 μm).

Main Results:

• Successfully trapped and manipulated particles significantly larger than 100 μm, up to 250 μm in diameter.
• Achieved a simplified and robust system, less sensitive to misalignments compared to traditional CP traps.
• Demonstrated versatility in trapping various particle sizes and shapes, including microorganisms, using low laser power and NA optics.

Conclusions:

• The novel broken-symmetry CP optical tweezers offer a versatile and robust method for trapping and manipulating large particles and biological specimens.
• This technique overcomes limitations of traditional CP traps, enabling new possibilities for imaging and spectroscopic studies.
• The method facilitates advanced applications like simultaneous 3D trapping and light-sheet microscopy of extended biological samples.