Using a laser to heat microfluid has the advantages of non-contact local operation, high accuracy, and good adjustability. In this study, a focused infrared laser with a 1550-nm wavelength was applied to heat an oil–water-oil double-emulsion droplet in a microchannel. The Finite Volume Method was used to numerically study the thermocapillary flow and heat transfer of this laser-heating process. In the simulation, the laser energy distribution was modeled using a volumetric Gaussian heat source. The attention was focused on the heat transfer and thermocapillary flow of the double-emulsion droplet. The influences of laser parameters (power and beam diameter) and the temperature coefficient of interfacial tension were studied. We found that the intensity of the thermocapillary flow and the temperature linearly increased with input power; they first decreased and then increased as the size of the input beam increased because of the combined effect of absorbing energy and energy concentration. Moreover, there were four and two thermocapillary vortices inside the middle water phase when the sign of the temperature coefficient of interfacial tension in the double interfaces was the same and different, respectively. In all cases, the uneven temperature coefficient of the inner droplet was lower than that of the middle water phase, but the average temperatures of both regions were extremely close. These results can prove useful in the future operation of double-emulsion droplet-based microfluidics using a laser as a precise and sensitive heating source for drug discovery and delivery, cell analyses, and micro/nanoparticle synthesis.

采用激光加热微流体具有非接触局部操作、精度高、可调性好等优点。在这项研究中，使用波长为 1550 nm 的聚焦红外激光加热微通道中的油-水-油双乳液液滴。有限体积法用于数值研究该激光加热过程的热毛细流动和传热。在模拟中，使用体积高斯热源对激光能量分布进行建模。注意力集中在双乳液液滴的传热和热毛细流动上。研究了激光参数（功率和光束直径）和界面张力温度系数的影响。我们发现热毛细管流的强度和温度随输入功率线性增加；由于吸收能量和能量集中的共同作用，它们随着输入光束尺寸的增加而先减少然后增加。此外，当双界面界面张力温度系数符号相同和不同时，中间水相内部分别存在四个和两个热毛细涡流。在所有情况下，内部液滴的不均匀温度系数都低于中间水相的温度系数，但两个区域的平均温度非常接近。这些结果可以证明在未来使用激光作为精确和灵敏的加热源进行药物发现和递送、细胞分析和微/纳米粒子合成的基于双乳液液滴的微流体的操作中是有用的。