217 / 2024-07-21 13:44:37

Nanorefrigerative tweezers for optofluidic manipulation

Plasmonic,Thermal conductivity,Natural convection,Thermophoresis,Anti-Stokes fluorescence,Nanocrystals,Nanoparticle,Optical tweezers

Plasmonic optical tweezers with the ability to manipulate nano-sized particles or molecules that are beyond the diffraction limit have been developed rapidly in recent years. However, plasmonic heat generation always limits its applications in capturing particles or biomacromolecules that are vulnerable to high temperatures. Here, we propose nanorefrigerative tweezers based on a single refrigerative nanocrystal, which can form a nanometer-sized cold-spot via anti-Stokes fluorescence. Numerical simulations are performed to compute the temperature and velocity fields. The results show that thermo-osmosis and thermophoresis play major roles in nanoparticle manipulation, while natural convection in the nanoscale is negligible. This tweezing scheme not only offers a sub-diffraction-limit way to manipulate nano-objects but also avoids possible thermal damage to the trapped targets. Besides, we report a kind of nanotweezers based on the sign transformation of the thermophoresis coefficient of colloidal particles in low-temperature environment. Using a self-made microfluidic refrigerator to reduce the ambient temperature to around 0℃ in the microfluidic cell, we can control a single nanoparticle at lower laser power without adding additional agent solute in the solution. Therefore, it will potentially become a powerful tool in biomedical and biosensing research studies.