Exploring the thermal effect of far-infrared therapy on the kinetics of blood cells by optical tweezers

Cold and heat are two types of non-invasive and non-addictive treatments, which induce therapeutic effects including temperature modulation, muscle relaxation, pain relief, and hemostasis. In this study, we explored the bio-physical mechanism of the effects of cold and heat therapies on blood physiology. Optical tweezers are powerful tools used in the application of micro-manipulation and the quantification of micro-interaction. We evaluated the interaction between RBCs by measuring the required trapping power and estimated the average kinetic energy of RBCs by optical tweezers. Through investigation of RBCs' mobility in coagulation process, we found cold therapy reduced the intercellular interaction and suppressed the blood circulation, thus suppressed the blood flow, reduced local congestion and stopped bleeding; whereas heat application could intensify RBCs' interaction, inspire their activity, and therefore promote the circulation system and enhance the metabolism physiology.