Lekshmi Bindhu Sunilkumar, Yadav Ajeet Singh, Ranganathan Panneerselvam, Varanakkottu Subramanyan Namboodiri
Optofluidics and Interface Science Laboratory, Department of Physics, National Institute of Technology Calicut, Kozhikode 673601, India.
Department of Chemical Engineering, National Institute of Technology Calicut, Kozhikode 673601, India.
Langmuir. 2020 Dec 22;36(50):15396-15402. doi: 10.1021/acs.langmuir.0c02988. Epub 2020 Dec 11.
Liquid marbles are gaining increased attention because of their added advantages such as low evaporation rates, less friction, and ease of manipulation over the pristine liquid drop. Their functionalities could be further enhanced by incorporating different types of particles (size, hydrophobicity, chemical properties, etc.), commonly called Janus liquid marbles (JLMs). However, their fabrication process remains a challenge, especially when we require continuous production. Here, we present a simple and fast approach for the fabrication of JLMs covered with nano- and microparticles in an additive-free environment based on the controlled impact of a water drop over the particle beds. The fabrication process involves collection of polyvinylidene difluoride particles (PVDF, particle type 1) by a water drop followed by its impact over an uncompressed bed of black toner particles (BTP, particle type 2). The whole process takes a time of approximately 30 ms only. The drop impact and the condition of the JLM formation were explained based on the Weber number () and maximum spread (β) analysis. A theoretical model based on the energy balance analysis is performed to calculate the maximum spreading (β), and the experimental and theoretical analyses are found to be in good agreement. Tunability in particle coverage is demonstrated by varying the droplet volume in the range of 5-15 μL. We further extend this strategy for the fast and continuous production of nearly identical JLMs, which could enhance the capabilities of open-surface microfluidic applications.
液态弹珠因其具有诸如低蒸发率、低摩擦力以及相较于原始液滴更易于操控等附加优势而受到越来越多的关注。通过加入不同类型的颗粒（尺寸、疏水性、化学性质等），其功能可进一步增强，这些颗粒通常被称为双面液态弹珠（JLM）。然而，它们的制造过程仍然是一个挑战，尤其是当我们需要连续生产时。在此，我们提出一种简单快速的方法，用于在无添加剂的环境中基于水滴对颗粒床的可控撞击来制造覆盖有纳米和微米颗粒的JLM。制造过程包括水滴收集聚偏二氟乙烯颗粒（PVDF，颗粒类型1），随后水滴撞击未压缩的黑色碳粉颗粒床（BTP，颗粒类型2）。整个过程仅需约30毫秒。基于韦伯数（）和最大铺展度（β）分析对水滴撞击和JLM形成条件进行了解释。基于能量平衡分析进行了理论模型构建以计算最大铺展度（β），实验分析与理论分析结果吻合良好。通过在5 - 15 μL范围内改变液滴体积展示了颗粒覆盖率的可调性。我们进一步扩展了这一策略，用于快速连续生产几乎相同的JLM，这可以增强开放式表面微流体应用的能力。
