A numerical model was established for photothermal detection of non-fluorescent molecules confined in micro/nanofluidic channels. Recently, nanofluidics has been accepted as a methodology to analyze the behavior of single molecules. The extremely high surface-to-volume ratio of the nanospace is also promising for biochemical reactors. However, detection of the solute molecules confined in the nanospace is still difficult unless the molecules are fluorescently labeled. To date, our group has studied photothermal spectroscopy, which can detect non-fluorescent molecules using thermal relaxation, and developed photothermal optical phase shift (POPS) detection. The POPS detector has realized a detection limit of 30 protein molecules, but heat transfer from the sample solution to the glass nanochannel is a barrier to achieve single-molecule sensitivity. In this study, a finite element method (FEM) analysis was performed to simulate the photothermal effect and heat transfer in the nanochannels. The POPS signal calculated from the temperature distribution was compared with experimental values to validate the numerical model. The influences of the detection parameters, including channel depth, modulation frequency, and misalignment of laser beams, are all discussed for improvement of the sensitivity.

建立了微/纳米流体通道中非荧光分子的光热检测数值模型。最近，纳米流体学已被接受为一种分析单分子行为的方法。纳米空间极高的表面积与体积比也有望用于生化反应器。然而，除非分子被荧光标记，否则检测限制在纳米空间中的溶质分子仍然很困难。迄今为止，我们小组已经研究了光热光谱，它可以使用热弛豫检测非荧光分子，并开发了光热光学相移 (POPS) 检测。POPS 检测器实现了 30 个蛋白质分子的检测限，但从样品溶液到玻璃纳米通道的热传递是实现单分子灵敏度的障碍。在这项研究中，进行了有限元方法 (FEM) 分析来模拟纳米通道中的光热效应和热传递。将根据温度分布计算的 POPS 信号与实验值进行比较以验证数值模型。讨论了通道深度、调制频率和激光束错位等检测参数的影响，以提高灵敏度。