Electroosmotic flow analysis of a branched U-turn nanofluidic device

Abstract

In this paper, we present the analysis of electroosmotic flow in a branched U-turn nanofluidic device, which we developed for detection and sorting of single molecules. The device, where the channel depth is only 150 nm, is designed to optically detect fluorescence from a volume as small as 270 attolitres (al) with a common wide-field fluorescent setup. We use distilled water as the liquid, in which we dilute 110 nm fluorescent beads employed as tracer-particles. Quantitative imaging is used to characterize the pathlines and velocity distribution of the electroosmotic flow in the device. Due to the device's complex geometry, the electroosmotic flow cannot be solved analytically. Therefore we use numerical flow simulation to model our device. Our results show that the deviation between measured and simulated data can be explained by the measured Brownian motion of the tracer-particles, which was not incorporated in the simulation.

Size-dependent trajectories of DNA macromolecules due to insulative dielectrophoresis in submicrometer-deep fluidic channels

“…12 We therefore focus our observations in this study on the same region, which is also shown as the red rectangle in Fig. 1.…”

“…However, in channels with a low Reynolds number ͑in our case: in the order of 10 −3 ͒, these inertia forces become negligibly small, such that particles and molecules can turn around sharp corners without exhibiting a significant momentum. 12 Therefore, after considering all the forces above, it is valid for us to assume that the observed size-dependent trajectories in our experiments are solely due to dielectrophoresis. Nevertheless, the discussion above highlights how complex the physical system in the experiment is, such that the list of forces we provided above might be not entirely complete.…”

Simulation and experimental characterization of plug distortion in hybrid microchannels

“…Sikanen et al 2005 determined the f-potential via a conductivity increase of the fluid between sample and waste reservoir, at which a higher buffer concentration displaced the lower one by EOF of the fluid and electrophoretic migration of the buffer molecules. Other methods observe the absolute velocity of the carrier fluid with microbeads (Parikesit et al 2005;Lee et al 2004). Nonnegligible electrophoretic mobilities and nonspecific charging of the microbeads during the measurement causes a measurement error.…”

Measuring Nanoparticle Polarizability Using Fluorescence Microscopy

“…28,32 While studies of particles are limited, measurements of the polarizability of biomolecules have proceeded over the past decades and have resulted in approaches that could potentially provide measurements of polarizability of abiotic nanoscale objects. [33][34][35][36][37][38][39][40][41][42][43][44][45] However, measurements of DNA and other biomolecules have revealed puzzling behavior regarding the interaction between salt concentration and polarizability that has not yet been reconciled, likely due to the difficulty in accurately modeling biomolecules as simple structures. 42,44,46,47 Here, we develop a method to measure the polarizability of photoluminescent nanoparticles and use it to quantify the polarizability of semiconductor quantum dots (QDs), which is found to dramatically increase at low salt concentrations (Figure 1B).…”

“…6-10, 13, 14, 48 This, together with individual particles being optically resolvable, enables indirect quantification of α through measurements of velocity resulting from a competition between drag and DEP, 6,11,13,15 the external flow speed needed to dislodge a particle from a stationary DEP trap, 7,39 or the trajectory of particles through curving fluid flows. 41 In interpreting such measurements, material properties are typically estimated using analytical models such as the expression for a spherical particle,…”