Low-temperature optothermal nanotweezers

Optical tweezers that rely on laser irradiation to capture and manipulate nanoparticles have provided powerful tools for biological and biochemistry studies. However, the existence of optical diffraction-limit and the thermal damage caused by high laser power hinder the wider application of optical tweezers in the biological field. For the past decade, the emergence of optothermal tweezers has solved the above problems to a certain extent, while the auxiliary agents used in optothermal tweezers still limit their biocompatibility. Here, 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 °C in the microfluidic cell, we can control a single nanoparticle at lower laser power without adding additional agent solute in the solution. This novel optical tweezering scheme has provided a new path for the manipulation of inorganic nanoparticles as well as biological particles.