Saczek Joshua, Murphy Koren, Zivkovic Vladimir, Putranto Aditya, Pramana Stevin S
School of Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
School of Chemistry and Chemical Engineering, University of Surrey, Guildford GU2 7XH, UK.
Soft Matter. 2024 Jul 24;20(29):5822-5835. doi: 10.1039/d4sm00478g.
Liquid marbles are soft matter objects characterised by a liquid droplet enclosed within a hydrophobic particle coating, preventing wetting. This distinctive structure serves as active sites for solid-liquid-gas reactions. However, the impact the chosen coating material has on liquid marble stability, particularly regarding the number of coating layers and material wetting, remains uncertain. There is a need for a modelling approach to predict the overall lifetime considering these coating characteristics. This study reveals that for PTFE liquid marbles evaporating at ambient temperature, smaller coating particles (250 nm) extend their lifetime by forming a multilayered coating. Conversely, using larger particle sizes (200 μm) results in the formation of monolayer liquid marbles with shorter lifetimes than their equivalent naked droplets. Additionally, a higher number of particle layers and a larger contact angle generally enhance the liquid marble's lifetime. For multilayered liquid marbles comprised of smaller particles (250 nm), the particle contact angle is found to have a more significant impact than the number of layers on lifetime extension, whereas the opposite holds true for larger particle sizes (20 μm). A modelling approach using the reactor engineering method for liquid marble evaporation demonstrates excellent agreement with experimental results, yielding an of 0.996. The implementation of this specific model, capable of assessing lifetime across various physical modifications, will enhance our understanding of liquid marble properties before their application in biomedical, microreactor, and green technologies.
液滴弹是一种软物质物体，其特征是液滴被包裹在疏水颗粒涂层内，防止液体浸湿。这种独特的结构是固-液-气反应的活性位点。然而，所选涂层材料对液滴弹稳定性的影响，特别是关于涂层层数和材料润湿性的影响，仍然不确定。需要一种建模方法来预测考虑这些涂层特性的整体寿命。本研究表明，对于在环境温度下蒸发的聚四氟乙烯液滴弹，较小的涂层颗粒（250纳米）通过形成多层涂层来延长其寿命。相反，使用较大的粒径（200微米）会导致形成单层液滴弹，其寿命比同等的裸液滴短。此外，更高的颗粒层数和更大的接触角通常会延长液滴弹的寿命。对于由较小颗粒（250纳米）组成 的多层液滴弹，发现颗粒接触角对寿命延长的影响比层数更大，而对于较大粒径（20微米）则相反。使用反应器工程方法对液滴弹蒸发进行建模的方法与实验结果显示出极佳的一致性，相关系数为0.996。这种能够评估各种物理变化下寿命的特定模型的实施，将增进我们在液滴弹应用于生物医学、微反应器和绿色技术之前对其性质的理解。
