Optothermal pulling, trapping, and assembly of colloids using nanowire plasmons

Area of Science:

• Soft matter physics
• Nanophotonics
• Colloid science

Background:

• Optical excitation of colloids enables non-equilibrium soft matter systems.
• Surface plasmon polaritons (SPPs) on silver nanowires interact with light.
• Optothermal effects can influence colloidal particle dynamics.

Purpose of the Study:

• Investigate the dynamics of silica colloids near SPP-propagating silver nanowires.
• Explore optothermal pulling, trapping, and assembly mechanisms.
• Determine the role of excitation polarization in these phenomena.

Main Methods:

• Experimental studies of silica colloid behavior near silver nanowires.
• Optical excitation and manipulation of SPPs.
• Observation of particle dynamics and assembly.
• Numerical simulations of temperature distribution.

Main Results:

• Colloids were directionally pulled towards the excitation point on the nanowire.
• Spatio-temporal trapping of colloids occurred at the excitation location.
• Multi-particle assembly was observed with increased colloid concentration, driven by thermophoresis and SPPs.
• Colloid assembly showed sensitivity to excitation polarization.

Conclusions:

• SPPs on silver nanowires can drive optothermal pulling, trapping, and assembly of colloids.
• The observed phenomena are sensitive to excitation polarization.
• This system serves as a test-bed for plasmon-driven active matter and SPP-assisted manipulation.