Chaudhuri Joydip, Timung Seim, Dandamudi Chola Bhargava, Mandal Tapas Kumar, Bandyopadhyay Dipankar
Department of Chemical Engineering, Indian Institute of Technology, Guwahati, India.
Centre for Nanotechnology, Indian Institute of Technology, Guwahati, India.
Electrophoresis. 2017 Jan;38(2):278-286. doi: 10.1002/elps.201600276. Epub 2016 Aug 29.
Numerical simulations supplemented by experiments together uncovered that strategic integration of discrete electric fields in a non-invasive manner could substantially miniaturize the droplets into smaller parts in a pressure driven oil-water flow inside microchannels. The Maxwell's stress generated from the electric field at the oil-water interface could deform, stretch, neck, pin, and disintegrate a droplet into many miniaturized daughter droplets, which eventually ushered a one-step method to form water-in-oil microemulsion employing microchannels. The interplay between electrostatic, inertial, capillary, and viscous forces led to various pathways of droplet breaking, namely, fission, cascade, or Rayleigh modes. While a localized electric field in the fission mode could split a droplet into a number of daughter droplets of smaller size, the cascade or the Rayleigh mode led to the formation of an array of miniaturized droplets when multiple electrodes generating different field intensities were ingeniously assembled around the microchannel. The droplets size and frequency could be tuned by varying the field intensity, channel diameter, electrode locations, interfacial tension, and flow ratio. The proposed methodology shows a simple methodology to transform a microdroplet into an array of miniaturized ones inside a straight microchannel for enhanced mass, energy, and momentum transfer, and higher throughput.
数值模拟与实验相结合发现，以非侵入性方式对离散电场进行策略性整合，能够在微通道内压力驱动的油水流动中，将液滴大幅微缩成更小的部分。油水界面处电场产生的麦克斯韦应力可使液滴变形、拉伸、变细、钉扎并分解成许多微缩的子液滴，这最终开创了一种利用微通道形成油包水微乳液的一步法。静电、惯性、毛细和粘性力之间的相互作用导致了液滴破碎的各种途径，即裂变、级联或瑞利模式。在裂变模式下，局部电场可将液滴分裂成多个较小尺寸的子液滴，而当围绕微通道巧妙组装多个产生不同场强的电极时，级联或瑞利模式会导致形成一系列微缩液滴。通过改变场强、通道直径、电极位置、界面张力和流量比，可以调节液滴的大小和频率。所提出的方法展示了一种简单的方法，可在直微通道内将微滴转化为一系列微缩微滴，以增强质量、能量和动量传递，并提高通量。
