Pressure-driven laminar flow switching for rapid exchange of solution environment around surface adhered biological particles

Abstract

This paper describes a technique for rapidly exchanging the solution environment near a surface by displacing laminar flow fluid streams using sudden changes in applied pressure. The method employs off-chip solenoid valves to induce pressure changes, which is important in keeping the microfluidic design simple and the operation of the system robust. The performance of this technique is characterized using simulation and validated with experiments. This technique adds to the microfluidic tool box that is currently available for manipulating the solution environment around biological particles and molecules.

Tuning the performance of an artificial protein motor

“…(1), namely, τ ligand (to avoid misstepping) and τ bound (to avoid unbinding from the track) [12]. Given that, for perfect stepping, the motor speed is given by x L /τ ligand , and it may be possible to operate TW with τ ligand as short as 0.1 s, it is desirable to keep τ diff as short as possible, and below about 100 μs.…”

“…Each repressor protein "foot" binds with high affinity to a unique double-stranded DNA (dsDNA) recognition sequence only when it has bound a specific ligand (a, b, and c, respectively) with a concentration in solution that can be controlled externally. Thus, by using a dsDNA "track" with cyclic, equally spaced repeats of the three unique repressor motifs, motor stepping can be achieved as follows: by cyclically changing the buffer around the motor, the ligand concentration is cycled in the order [ [12]. When the ligand concentration is changed, one foot loses its ligand as its concentration drops in solution and the foot releases from the DNA, while the other foot remains tightly bound.…”

Controlling Mass Transport in Microfluidic Devices

“…When fluid is emitted from parallel microchannels that are close to one another, the unconstrained streams remain unmixed for up to several millimeters or even centimeters (44–47). In this case, the streams remain parallel and segregated in the absence of any physical partitions between them, which gives rise to virtual containers (44–47).…”

“…In this case, the streams remain parallel and segregated in the absence of any physical partitions between them, which gives rise to virtual containers (44–47). …”

Accelerating microfluidic immunoassays on filter membranes by applying vacuum

“…Over the past few years, tremendous efforts have improved the performance of immunoassays, e.g. optimizing reaction temperature, decreasing diffusion time and enlarging contact surface of reactions Allen et al 2010). Notably, microfluidics has proven to be a promising approach for optimizing immunoassays.…”