| 研究実績の概要 |
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.
|
