纳米通道中的热气泡成核机理研究

The sensing technologies based on thermal bubbles are still limited in micro-scale recently because of the complexities of the design and the processing technologies and the extremely strict requirements of the precision for the fabrication. The fundamental theory study of nano-scale thermal bubble are suggested in this proposal. The nucleation mechanisms of nano-scale thermal bubble and the characters of thermal bubble confined in nanochannels will be systemically investigated, through which the theoretical and technical supports are expected to be provided for the development of sensing technologies based on nano-scale thermal bubble. For theoretical research, based on the recent phenomenological simulation results, the computer simulation will be used to investigate the fundamental nucleation mechanisms (e.g. activation energy) of nano-scale thermal bubble in both homogeneous and nanochannel systems. For experimental research, the Micro/nanofabrication technologies are suggested to design and fabricate the experimental devices for investigating the nano-scale thermal bubble confined in nanochannels. The behavior of the thermal bubble in the nanochannel will be indirectly studied by detecting the ionic current through the nanochannel of the device based on the principle of the Coulter Counter. Through this project, we expect that the trans-scale thermal bubble nucleation theoretical system can be established gradually. And we also expect to obtain some theoretical and technical supports for the development of sensing technologies based on nano-scale thermal bubble.

由于器件设计与加工工艺的复杂性，以及对精度的极高要求，基于热气泡成核的传感技术目前仅在微米尺度上得到应用。本项目开展纳米通道中的热气泡成核问题的基础理论与实验研究，探索纳尺度热气泡的成核机理及纳通道中的热气泡成核特点, 以期为发展纳尺度热气泡传感技术提供理论依据与技术支持。在理论研究方面，期望利用分子动力学模拟，在现有唯像的模拟结果基础上，从活化能等更为本质的层面系统考察均质体系及纳通道中的热气泡成核机理，建立描述跨尺度的热气泡成核理论模型；实验研究方面，利用微纳加工技术，设计、制作研究纳通道中热气泡特性的试验器件，提出基于库尔特计数器原理，通过考察流经纳通道两端的电流来间接地研究纳通道中的热气泡成核特点。通过本项目的研究，有望逐步构建跨尺度的热气泡成核理论体系，并为功能性纳尺度热气泡传感器的设计及应用提供一定的理论依据与技术支持。

本项目在原有基本研究的基础上进一步研究了较大规模氩体系，观察到的现象与前期工作一致；在氩体系的基础上，进一步考察了具有不同壁面性质，不同壁面结构的纳通道中受限水体系的热气泡成核过程以及通道高度与成核温度之间的关系；在实验中运用目前的观测设备可清晰地观察到通道中热气泡的成核现象，当尺度下降到几十纳米甚至更小时，直接观察通道中的热气泡成核将会变得相当困难，库尔特计数器可有效用于检测溶液中的生物细胞及其他颗粒的数量及大小，利用库尔特计数器原理，通过考察通道中的电流随时间变化情况可以间接考察通道中的热气泡行为。目前，我们已经完成了实验芯片及实验测试平台的设计。测试试验结果显示，随着通道高度下降，水系统成核温度将剧烈提高，这些结果在微纳尺度传热等领域具有重要的工程应用意义。