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Splitting dynamics of ferrofluid droplets inside a microfluidic T-junction using a pulse-width modulated magnetic field in micro-magnetofluidics

Bijarchi, M. A ; Sharif University of Technology | 2021

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  1. Type of Document: Article
  2. DOI: 10.1039/d0sm01764g
  3. Publisher: Royal Society of Chemistry , 2021
  4. Abstract:
  5. Micro-magnetofluidics offers a promising tool for better control over the ferrofluid droplet manipulation which has been vastly utilized in biomedical applications in recent years. In this study, the ferrofluid droplet splitting under an asymmetric Pulse-Width-Modulated (PWM) magnetic field in a T-junction is numerically investigated using a finite volume method and VOF two-phase model. By utilizing the PWM magnetic field, two novel regimes of ferrofluid droplet splitting named as Flowing through the Same Branch (FSB) and Double Splitting (DS) have been observed for the first time. In the FSB regime, the daughter droplets move out of the same microchannel outlet, and in the DS regime, the droplet splitting occurs two times which results in generating three daughter droplets. The main problem related to the asymmetric droplet splitting under a steady magnetic field is daughter droplet trapping. By using a PWM magnetic field, this issue is resolved and the trapped/escaped regions are obtained in terms of the duty cycle and dimensionless magnetic field frequency. The effects of six important dimensionless parameters on the splitting ratio, including magnetic Bond number, duty cycle, dimensionless magnetic field frequency, capillary number, dimensionless mother droplet length, and dimensionless dipole position are investigated. The results showed that the splitting ratio increases with increasing magnetic Bond number or duty cycle, or decreasing the dimensionless magnetic field frequency. Eventually, a correlation is offered for the splitting ratio based on the dimensionless variables with an average relative error of 2.67%. © The Royal Society of Chemistry 2020
  6. Keywords:
  7. Drops ; Finite volume method ; Medical applications ; Pulse width modulation ; Average relative error ; Biomedical applications ; Dimensionless parameters ; Dimensionless variables ; Magnetic field frequency ; Microfluidic T junctions ; Pulse-width-modulated ; Steady magnetic fields ; Magnetic field effects ; Adult ; Controlled study ; Dipole ; Female ; Human ; Magnetic field
  8. Source: Soft Matter ; Volume 17, Issue 5 , 2021 , Pages 1317-1329 ; 1744683X (ISSN)
  9. URL: https://pubs.rsc.org/en/content/articlelanding/2021/sm/d0sm01764g