Dragonflies are four-winged insects that have the ability to control aerodynamic performance by modulating the phase lag (phi) between forewings and hindwings. We film the wing motion of a tethered dragonfly and compute the aerodynamic force and power as a function of the phase. We find that the out-of-phase motion as seen in steady hovering uses nearly minimal power to generate the required fo...

The behavior of DNA molecules is observed in a nanofluidic device near the interface of two regions that produce different configuration entropies. An electric field is applied to drive the molecules partway across the interface. Upon removal of the field, the molecules recoil to the higher-entropy region with a profile characteristic of a force localized to the interface and independent of len...

We present a first-principles theory for the active nonlinear microrheology of colloidal model system; for a constant external force on a spherical probe particle embedded in a dense host dispersion, neglecting hydrodynamic interactions, we derive an exact expression for the friction. Within mode-coupling theory, we discuss the threshold external force needed to delocalize the probe from a host...

The capture of solid particles by air bubbles is a complex process influenced by hydrodynamic and surface forces. Computer simulation provides an alternative way to experimental approaches to give an insight into the phenomenon of particle capture. In this paper, the threedimensional Discrete Element Method (DEM) has been applied to simulate the interactions between fine particles and a central...

We have investigated the hydrodynamic drag force between charged particles in electrolyte solutions, specifically the electroviscous force that arises from the distortion of the electrical double layers by the flow field. We report an improvement on the thin-double-layer theory (S.G. Bike, D.C. Prieve, J. Colloid Interface Sci. 136 (1990) 95-112), using a more accurate boundary condition for th...

In the recent years microfluidic technology has affirmed itself as a powerful tool in medical and biological research. Among the different applications, cell manipulation has been widely investigated. Micro-flowcytometers, micromixers, cell sorters and analyzers are only few examples of the developed devices. Various methods for cell manipulation have been proposed, such as hydrodynamic, magnet...

Solvent plays an important role in the relative motion of nanoscopic bodies, and the study of such phenomena can help elucidate the mechanism of hydrophobic assembly, as well as the influence of solvent-mediated effects on in vivo motion in crowded cellular environments. Here we study important aspects of this problem within the framework of Brownian dynamics. We compute the free energy surface...

We discuss the hydrodynamic collective effects due to active protein molecules that are immersed in lipid bilayer membranes and modeled as stochastic force dipoles. We specifically take into account the presence of the bulk solvent that surrounds the two-dimensional fluid membrane. Two membrane geometries are considered: the free membrane case and the confined membrane case. Using the generaliz...

We report an integrated microfluidic device for fine-scale manipulation and confinement of micro- and nanoscale particles in free-solution. Using this device, single particles are trapped in a stagnation point flow at the junction of two intersecting microchannels. The hydrodynamic trap is based on active flow control at a fluid stagnation point using an integrated on-chip valve in a monolithic...