Analysis and control of bubble generation in solid state nanopores

尽管沸腾具有多尺度的性质，但由于使用传统成像技术捕获低于阿贝衍射极限的纳秒分辨率动力学固有的困难，人们对纳米尺度的沸腾知之甚少。为了解决这一根本问题，我们通过焦耳加热来研究纳米孔内的沸腾，使用阻性脉冲传感和声波传感来检测兆赫频段的汽泡，基于电流和声波信号，我们表征了固态纳米孔内的成核、转变和膜沸腾。成核沸腾包括均匀的蒸汽纳米气泡的周期性成核，这些气泡最终从纳米孔中释放出来。随着电压的升高，焦耳散热增强，孔表面覆盖着一层纳米环状蒸汽膜。在纳米孔沸腾曲线中总结了沸腾区域(分叉)随偏压的变化，对于一定的孔尺寸，我们还发现了一种新的从膜沸腾到核沸腾的反向转变，当电压增加到一个临界值以上时。这些结果归因于来自接触线钉扎、扩散-弹道热传输和聚焦焦耳加热的限制效应。这些发现被总结在一篇期刊论文中(Paul等人)。2022个物理量。Rev Research 4,043110)和候选人的博士论文，并于2022年8月5日成功答辩。

Despite the multi-scale nature of boiling, much less is known about nanoscale boiling due to the inherent difficulty of capturing the nanosecond resolution dynamics below the Abbe diffraction limit using traditional imaging techniques. To address this fundamental problem, we studied boiling inside nanopore through Joule heating, using resistive pulse sensing and acoustic sensing for vapor bubble detection at megahertz bandwidth.Based on current and acoustic signals, we characterized nucleate, transition and film boiling inside solid-state nanopores. Nucleate boiling comprised of periodic nucleation of homogeneous vapor nanobubbles, which were ultimately emitted from the nanopore. When the Joule heat dissipation was intensified with voltage increase, a nano-torus vapor film blanketed the pore surface. The variation in boiling regimes (bifurcations) with increasing bias voltages was summarized in a nanopore boiling curve.For certain pore sizes, we also found a novel reverse transition from film to nucleate boiling, when the voltage was increased beyond a critical value. These results were attributed to confinement effects originating from contact-line pinning, diffusion-ballistic heat transport and focused Joule heating. These findings were summarized in a journal paper (Paul et al. 2022 Phys. Rev. Research 4, 043110) and the candidate’s doctoral dissertation, which was successfully defended on August 5, 2022.