Towards Stable Trapping of Single Macromolecules in Solution.

Area of Science:

• Optical trapping
• Nanoparticle manipulation
• Femtosecond laser applications

Background:

• Continuous wave (CW) lasers are typically used for optical trapping.
• High instantaneous peak power from femtosecond lasers offers potential for trapping nanoparticles.
• Previous studies demonstrated stable optical trapping of latex nanoparticles using femtosecond laser pulses.

Purpose of the Study:

• To investigate the trapping of latex nanoparticles using high instantaneous peak power femtosecond laser pulses.
• To explore the feasibility of trapping quantum dots with dimensions similar to macromolecules.
• To address the challenges in directly measuring instantaneous trapping forces due to the short pulse duration.

Main Methods:

• Utilizing femtosecond laser pulses with high instantaneous peak power but moderate time-averaged power (~10 mW).
• Demonstrating stable optical trapping of latex nanoparticles.
• Showcasing the trapping of quantum dots.

Main Results:

• Successful stable optical trapping of latex nanoparticles was achieved, which is not possible with CW illumination at similar power levels.
• Trapping of quantum dots, comparable in size to macromolecules, was demonstrated.
• Direct measurement of instantaneous trapping force/stiffness was found to be unsuccessful due to the ultrashort pulse duration (~100 fs).

Conclusions:

• Femtosecond laser pulses provide a viable method for stable optical trapping of nanoparticles and quantum dots.
• The ultrashort nature of femtosecond pulses complicates direct measurement of instantaneous trapping forces using current calibration techniques.
• This technique expands the possibilities for manipulating nanoscale objects, including those with dimensions similar to macromolecules.