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Electric-field-controlled Droplet Sorting in a Bifurcating Channel


To study the electric-field-controlled droplet sorting in the microfluidic chip, an unsteady numerical model of droplet sorting controlled by a nonuniform electric field is developed based on the coupled phase-field method and electric current model. The results indicate that both the shape and trajectory of the droplet are dependent on the permittivity ratio (S = εoi) and electric conductivity ratio (R = κio) between the fluids when flowing through the electric field. The behaviors of the droplet are summarized in a sorting regime diagram according to the droplet size (r*) and electric Euler number (Eue). In the case of RS < 1, a small droplet (r* ≤ 0.25) flowing through the horizontal channel is observed under the condition of weak electric intensity (Eue ≥ 1 × 10–4). As Eue decreases, the sorting regime of the droplet transits to downward deflection. Pinning on the grounded channel wall occurs when Eue ≤ 7.21 × 10–5. Eventually, droplet breakup is triggered (r* ≥ 0.3, Eue ≤ 1.17 × 10–4). In the case of RS > 1, droplets are observed flowing through the horizontal channel in the sorting process of both small and large droplets at large Eue (r* ≤ 0.25, Eue ≥ 4.9 × 10–4 and r* ≥ 0.3, Eue ≥ 2.44 × 10–4). A strong electric intensity (Eue ≤ 2.44 × 10–4) contributes to the breakup regime of large droplets (r* ≥ 0.3).

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Data Availability

Data available on request from the authors.


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The authors gratefully acknowledge the supports provided by National Natural Science Foundation of China (No. 52036006 and 51725602).

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Correspondence to Liangyu Wu.

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Hao, G., Li, L., Wu, L. et al. Electric-field-controlled Droplet Sorting in a Bifurcating Channel. Microgravity Sci. Technol. 34, 25 (2022).

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  • Microfluidic
  • Electric control
  • Droplet sorting
  • Bifurcating channel