Issue 4, 2007
From the journal:

Lab on a Chip

Concentration and binary separation of micro particles for droplet-based digital microfluidics†

Sung Kwon Cho,*a   Yuejun Zhaoa  and  Chang-Jin “CJ” Kimb  

* Corresponding authors

a Department of Mechanical Engineering and Materials Science, University of Pittsburgh, 3700 O'Hara St., Pittsburgh, USA
E-mail: skc@engr.pitt.edu, yuz21+@pitt.edu
Fax: +1 412-624-4846
Tel: +1 412-624-9798

b Mechanical and Aerospace Engineering Dept., University of California, Los Angeles (UCLA), 420 Westwood Plaza, Los Angeles, CA, USA
E-mail: cjkim@ucla.edu
Fax: +1 310-206-2302
Tel: +1 310- 825-0267

Abstract

This paper describes a concept of concentration and binary separation of particles and its experimental confirmations for digital microfluidics where droplets are driven by the mechanism of electrowetting-on-dielectric (EWOD). As a fundamental separation unit, a binary separation scheme is developed, separating two different types of particles in one droplet into two droplets, one type each. The separation scheme consists of three distinctive steps, each with their own challenges: (1) isolate two different types of particles by electrophoresis into two regions inside a mother droplet, (2) physically split the mother droplet into two daughter droplets by EWOD actuation so that each type of particle is concentrated in each daughter droplet, and (3) free the daughter droplets from the separation site by EWOD to ready them for follow-up microfluidic operations. By applying a similar procedure to a droplet containing only one type of particle, two daughter droplets of different particle concentrations can be created. Using negatively charged carboxylate modified latex (CML) particles, 83% of the total particles are concentrated in a daughter droplet. Successful binary separation is also demonstrated using negatively charged CML particles and no-charge-treated polystyrene particles. Despite the undesired vortex developed inside the mother droplet, about 70% of the total CML particles are concentrated in one daughter droplet while about 70% of the total polystyrene particles are concentrated in the other daughter droplet.

Graphical abstract: Concentration and binary separation of micro particles for droplet-based digital microfluidics

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Article information

DOI
https://doi.org/10.1039/B615665G
Article type
Paper
Submitted
31 Oct 2006
Accepted
22 Jan 2007
First published
12 Feb 2007

Lab Chip, 2007,7, 490-498

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Concentration and binary separation of micro particles for droplet-based digital microfluidics

S. K. Cho, Y. Zhao and C. “. Kim, Lab Chip, 2007, 7, 490 DOI: 10.1039/B615665G

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