DNA-based highly tunable particle focuser

Abstract

DNA is distinguished by both long length and structural rigidity. Classical polymer theories predict that DNA enhances the non-Newtonian elastic properties of its dilute solution more significantly than common synthetic flexible polymers because of its larger size and longer relaxation time. Here we exploit this property to report that under Poiseuille microflow, rigid spherical particles laterally migrate and form a tightly focused stream in an extremely dilute DNA solution (0.0005 (w/v)%). By the use of the DNA solution, we achieve highly efficient focusing (499.5%) over an unprecedented wide range of flow rates (ratio of maximum to minimum flow rates B400). This highly tunable particle-focusing technique can be used in the design of cost-effective portable flow cytometers, high-throughput cell analysis and also for cell sorting by size. We demonstrate that DNA is an efficient elasticity enhancer, which originates from its unique structural properties.

Dynamics of particle migration in channel flow of viscoelastic fluids

“…Under the assumption of zero Reynolds number and small blockage ratio, Ho & Leal (1976) showed that a lateral force, originating from the normal stress differences, drives the particle towards the lower-shear region in a second-order fluid. This conclusion has been verified in other experiments and simulations, where particles move to the central axis of a circular tube (Tehrani 1996;D'Avino et al 2012;Romeo et al 2013;Kang et al 2014) and to both centreline and corners in a rectangular channel (Yang et al 2011;Leshansky et al 2007). Based on simulations of the Giesekus and Phan Thien-Tanner constitutive equations, Villone et al (2011, 2013) and D'Avino et al (2012 observed bistable dynamics of particles in shear-thinning fluids, i.e.…”

“…The migration velocity of the particle is the most important measure of particle focusing, and its dependence on the particle size has been used for particle separation applications (Nam et al 2012;Kang et al 2014;Lim et al 2014b). In figures 5 (a) and (b), we plot the particle migration velocity V p as a function of particle position Y p in Oldroyd-B and Giesekus fluids, respectively.…”

“…For example, even in a weakly inertial regime in a rectangular channel of viscoelastic fluid, the equilibrium positions at the corners become unstable and particles focus only at the channel centreline (Yang et al 2011). This elasto-inertial particle focusing in the range of low Reynolds number (Re ∼ 10 −2 − 10 −1 ) and high elasticity number (El ∼ 10 1 − 10 2 ) is destabilized as the channel Reynolds number increases beyond order unity (Yang et al 2011;Kang et al 2014). Conversely, a recent study by Lim et al (2014a) shows that stable particle focusing at the channel centreline can be achieved in weakly viscoelastic flows at a high Reynolds number (El ∼ 0.1, Re ∼ 2000).…”

Particle manipulations in non-Newtonian microfluidics: A review

“…Such a 3D focusing effect was first observed by Karnis et al for sub-millimeter particles in circular pipes of millimeter-diameter in 1960s [94,95]. It has been demonstrated effective for both micro particles [96] and submicron-sized Brownian particles [27] in cylindrical microchannels. It has also been recently utilized by Dannhauser et al [97] to align erythrocytes for a continuous characterization of the morphological property of every individual cell.…”

“…This phenomenon was also attributed to the substantial shear thinning effects of the suspending solution. In addition, Kang et al [96] demonstrated an efficient particle focusing phenomenon in an extremely dilute DNA solution (0.0005 (w/v)% or 5 ppm) ( Fig. 2d), which arises from the large size and long relaxation time of DNA molecules [52,53].…”