Institute of Aerospace Thermodynamics, University of Stuttgart, 70569 Stuttgart, Germany.
Department of Engineering and Applied Science, California Institute of Technology, 91125 Pasadena, USA; Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland.
J Colloid Interface Sci. 2017 Oct 15;504:751-757. doi: 10.1016/j.jcis.2017.06.027. Epub 2017 Jun 8.
Spontaneous imbibition in cellulosic materials is an expanding field of research due to the direct applicability in paper-based microfluidics. Here, we show experimentally, using simultaneous thermal and optical imaging that the temperature at the wetting front during capillary filling of paper is temporarily increased, even if the imbibed fluid and the cellulosic substrate are initially at isothermal conditions. Several liquids and two types of filter paper, characterised by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis, were investigated demonstrating a significant temperature rise at the wetting front that cannot be neglected form the process. The temperature rise is found to be related to the energetics of imbibition compounds, including acid-base contributions, that result in electrostatic attractions as the liquid molecules are adhered on the fiber surfaces upon capillary contact.
由于在基于纸张的微流控中具有直接的适用性，纤维素材料的自发浸润是一个不断发展的研究领域。在这里，我们通过同时进行的热和光学成像实验表明，即使在毛细填充过程中浸润液体和纤维素基底最初处于等温条件下，纸张润湿前沿处的温度也会暂时升高。我们研究了几种液体和两种类型的滤纸，通过扫描电子显微镜 (SEM) 和 X 射线衍射 (XRD) 分析进行了表征，结果表明在润湿前沿处会发生显著的升温，这一升温在过程中不容忽视。发现升温与浸润化合物的能量学有关，包括酸碱贡献，当液体分子在毛细接触时附着在纤维表面上时，这些贡献会导致静电吸引力。
