Optical manipulation of micro/nanoscale objects is of importance in life sciences, colloidal science, and nanotechnology. Optothermal tweezers exhibit superior manipulation capability at low optical intensity. However, our implicit understanding of the working mechanism has limited the further applications and innovations of optothermal tweezers. Herein, we present an atomistic view of opto-thermo-electro-mechanic coupling in optothermal tweezers, which enables us to rationally design the tweezers for optimum performance in targeted applications. Specifically, we have revealed that the non-uniform temperature distribution induces water polarization and charge separation, which creates the thermoelectric field dominating the optothermal trapping. We further design experiments to systematically verify our atomistic simulations. Guided by our new model, we develop new types of optothermal tweezers of high performance using low-concentrated electrolytes. Moreover, we demonstrate the use of new tweezers in opto-thermophoretic separation of colloidal particles of the same size based on the difference in their surface charge, which has been challenging for conventional optical tweezers. With the atomistic understanding that enables the performance optimization and function expansion, optothermal tweezers will further their impacts.

微/纳米级物体的光学操纵在生命科学、胶体科学和纳米技术中具有重要意义。光热镊子在低光强度下表现出卓越的操作能力。然而，我们对工作机制的隐含理解限制了光热镊子的进一步应用和创新。在这里，我们提出了光热镊子中光热机电耦合的原子视图，这使我们能够合理地设计镊子以在目标应用中实现最佳性能。具体来说，我们揭示了不均匀的温度分布会导致水极化和电荷分离，从而产生主导光热捕获的热电场。我们进一步设计实验以系统地验证我们的原子模拟。以我们的新模型为指导，我们开发了使用低浓度电解质的新型高性能光热镊子。此外，我们展示了使用新型镊子根据表面电荷的差异对相同尺寸的胶体颗粒进行光热分离，这对于传统的光学镊子来说是一个挑战。凭借能够实现性能优化和功能扩展的原子理解，光热镊子将进一步发挥其影响力。