This work presents a novel flow switch for centrifugal microfluidic platforms which is solely controlled by the Coriolis pseudo force. This Coriolis switch consists of an inverse Y-structure with one common upstream channel and two symmetric outlets on a rotating disk. Above a certain threshold frequency, the Coriolis force becomes dominant that the entire flow is diverted into one of the outlets which is selected by the direction of rotation. The threshold frequency has been measured to be 350 rad s(-1)(approximately 55.7 Hz) for a channel width of 360 microm and a depth of 125 microm. The results are supported by extensive CFD simulations.

No abstract

We demonstrate how the speed of mixing under laminar conditions can be appreciably enhanced in concurrent centrifugal flows through straight, low-aspect-ratio microchannels pointing in radial direction in the plane of rotation. The convective mixing is driven by the inhomogeneous distribution of the velocity-dependent Coriolis pseudo force and the interaction of the soinduced transverse currents with the side walls. By investigating the key impact parameters, which are the geometry of the channels and the speed of rotation, it is shown that the contact surface between two laminar flows can be folded to shorten mixing times by up to two orders of magnitude!

We demonstrate that Multi-Body Dissipative Particle Dynamics (MDPD) can be used as an efficient computational tool for the investigation of nanoscale capillary impregnation of confined geometries. As an essential prerequisite, a novel model for a solid-liquid interface in the framework of MDPD is introduced, with tunable wetting behaviour and thermal roughening to reduce artificial density-and temperature oscillations. Within this model, the impregnation dynamics of a water-like fluid into a nanoscale slit pore has been studied. Despite the coarse graining implied with the model fluid, a sufficient amount of non-equilibrium averaging can be achieved allowing for the extraction of useful information even from transient simulations, such as the dynamic apparent contact angle. Although it is found to determine the capillary driving completely, it cannot be intepreted as a simple function of the capillary number.Introduction. Over the last decade, continuous, mesoscale particle simulation methods such as Dissipative Particle Dynamics (DPD)[1, 2] and many variants thereof [3,4,5] have received considerable attention. Originally invented to include hydrodynamic effects in meso scale simulations of simple and complex fluids [1,6], it also has successfully been employed for studying polymeric systems or melts [7,8,9] or lipid membranes [10], and for colloidal suspensions [11,12]. As a model for solvents, one of the most important recent developments is the introduction of cohesive properties [13,14,15], extending the simple quadratic dependance on density in the equation of state (EOS) in early formulations [2]. The approach of Warren [15] leads to particularly stable liquidvapor interfaces and could be of great value in studying free-surface fluid dynamics problems where thermal capillary fluctuations are important, such as the intriguing phenomena related to the nanoscale Rayleigh instability (e.g. the break-up of liquid nano jets [16]). In most numerical studies involving fluid particle (FP) [17] methods, the investigations have largely been kept generic. Specific interactions, e.g., between solid-liquid interfaces, have only been accounted for in crude ways, since in the majority of cases, the FP-interactions do not arise from a systematic coarse graining procedure starting at the atomistic scale. We nevertheless suggest that a FP method can still be suitable for studying the aforementioned phenomena, provided that adhesive and interfacial properties are introduced carfully and with respect to the

We describe a new multilamination technique to accelerated mixing of centrifugally pumped flows through a simple network of preferentially radial, lowaspect-ratio microchannels. Mixing by multilamination is enforced by planar split-and-recombine structures, consisting of a common inlet for two concurrent centrifugal flows, and a transient region of parallel microchannels which merge again into one common outlet. A repatterning of flow is observed in each parallel channel which is induced by the Coriolis pseudo force. In a distinct regime of the parameter space spanned by the speed of rotation, the channel geometry as the viscosity (and density) of the liquids, a multilamination of flow is achieved at the entrance of the common outlet channel. We also present parallelization and cascading strategies to further enhance the homogeneity and throughput of mixing by multilamination.