Abstract

Manipulation of micro- or nano-objects, such as particles or fluids is of significant importance for cutting-edge technologies in biomedical or physical applications. In the past few decades, different kinds of methods have been developed to meet the requirement of all kinds of scenarios depending on mechanical, electrokinetic, magnetic, hydrodynamic, and optical forces et al. As a contactless method with high spatial and temporal resolution, the optical based method has drawn much attention very recently. However, its application is also limited since extremely high fluence is required for the irradiated light to generate adequate powers to control the movement of fluids or particles, which may damage the microfluidic chip or the bio-samples in the micro-channels such as cells or biomarkers. To solve this problem, plasmonics was introduced to the field of microfluidics, especially optofluidcis. Due to the near-field interaction of plasmonic structures, when illustrated light with certain wavelength, a very high and localized electromagnetic field will be generated. The intensity of the focused electromagnetic field can be hundred or even thousand times higher than the original intensity of the laser. Since the optical force is proportional to the light intensity and gradient, the laser intensity can be reduced significantly, which will improve the feasibility of this technique. In addition, the enhanced electromagnetic field will also increase the local temperature of the plasmonic structures induced by Joule heat, which may induce local thermal convection of surrounding fluid. This is a double-edged sword which may affect the precision of fluid control. However, with accurate prediction, this could also be used to improve the application of this technique. Here, we will review the recent development of thermoplasmonics in the application of microfluidics. Also, we will demonstrate our most recently works in using the plasmonic induced thermal effect to control microfluids and particles