Thermal Optofluidics: Principles and Applications

Thermal optofluidics is an emerging field that promises to create numerous research and application opportunities in biophysics, biochemistry, and clinical biology. Innovation in plasmonic optics has led to the development of various invaluable tools in the fields of biosensing and microfluidic manipulation. The optothermal effect originates from light-matter interactions during photon-phonon conversion, which can lead to micro- or nanoscale inhomogeneities in the thermal distribution. This further induces a series of hydrodynamic phenomena such as natural convection, Marangoni convection, thermophoresis, the electrolyte Seebeck effect, depletion forces, and interfacial effects in colloidal particles. Light-matter interactions are particularly important for three aspects of microfluidics, namely the motion of colloidal particles, fluidic actuation, and biochemical reactions. This review first systematically elucidates the role of both nanoscale plasmonic thermal generation and heat-induced fluidic motion in optofluidic microsystems. Then, recent state-of-the-art thermal optofluidic applications of the above-listed three aspects are presented. The paper aims to provide an insightful reference for future research in optofluidic biochemical systems.