Ratcheted electrophoresis for rapid particle transport

Abstract

Ratcheted electrophoresis of contact-charged particles allows for high speed transport through microfluidic channels over large distances and even against fluid flows. Using a set of predictive design heuristics, we demonstrate an extension of this microfluidic ratchet to separate conductive particles from a particle suspension.

Identification of two mechanisms for current production in a biharmonic flashing electron ratchet

“…A ratchet is a non-equilibrium scheme that rectifies the motion of randomly moving particles without a net applied force in the direction of transport, by breaking symmetries of the particle motion in space and time. Ratcheting is the operative mechanism of biological enzymes, pumps, and motors [1,2], and has been experimentally realized in particle separators and sorters [3][4][5][6][7][8]. In particular, a "flashing" ratchet works by switching, continuously or instantaneously, between two states of the potential surface on which the particle travels ( Figure 1a): (i) a surface with periodic features that are asymmetric in the direction of transport, and (ii) a surface that allows random, isotropic diffusion of a particle (i.e., a flat potential).…”

Next generation digital microfluidic technology: Electrophoresis of charged droplets

“…Zhou and Yao demonstrated non-contact electrostatic charging of droplets by polarizing a neutral droplet and splitting it into two oppositely charged daughter droplets in a T-junction microchannel [86]. Recently, Bishop et al reported a series of works for contact charge electrophoresis (CCEP) of particles [20,75,106,107]. They focused on the rapid transport of particles or mixing by particle motion in microchannels.…”

“…Modeling of drop/particle motion experiencing the contact charging phenomenon is one of the key subjects in this field [4][5][6]66,[74][75][76][77][78][79][80][81][82]. In microfluidics field, the direct contact charging is used to manipulate droplet [38,[83][84][85][86] or particle motions [20,75] in microchannels in addition to digital microfluidic approaches [6,23,70,77,[87][88][89]. The details of each category will be covered in the following fundamentals and applications section.…”

Motion in microfluidic ratchets

“…Drews et al demonstrated that this oscillatory motion can be rectified to obtain directed transport of micron sized particles in a microfluidic channel. 7 In order to achieve this, they fabricated a microfluidic channel containing inclined PDMS barriers at alternative positions and flanked by gallium electrodes (Fig.2b). In a medium of a dielectric liquid (mineral oil), they suspended the conductive micro-particles (silver electrodes, the particles acquire a net charge corresponding to the charge of the electrode and begin to translate in the opposite direction.…”