Diffusiophoresis Research Articles

Simultaneous PM2.5 and moisture removal from wet flue gas by a gas-liquid cross flow array

A gas-liquid cross-flow array (GLCA) system is proposed as the direct condensing technique for PM2.5 and moisture simultaneous removal from the wet flue gas. Such a GLCA with huge surface area is formed by numerous vertically down-flowing wastewater films along a number of wires through a perforated distributor. And each falling film acts as an independent sink to remove PM2.5 and moisture. Analytical models are developed to predict PM2.5 and moisture removal efficiency of a GLCA, based on the differential equation of convection diffusion with diffusiophoresis (DP), the only considering mechanism of PM2.5 removal. The models indicate that PM2.5 removal efficiency is proportional to the moisture removal amount, and PM2.5 removal efficiency can be increased sharply due to moisture condensation. Experiments with a lab-scale GLCA are carried out with variable humidity of inlet gas, and a constant gas (60℃) and water (20℃) temperature. The experimental measurements for PM2.5 and moisture removal generally compare satisfactorily with the model predictions.

Design strategies for engineering soluto-inertial suspension interactions

Soluto-inertial (SI) suspension interactions allow colloidal particles to be driven large distances over sustained periods of time. These interactions involve soluto-inertial "beacons" that establish and maintain solute fluxes over long times by slowly absorbing or emitting solutes in response to changes in the surrounding solution. Suspended particles then migrate in response to solute fluxes via diffusiophoresis (DP). Beacon materials must be chosen to maintain these solute fluxes, with range and duration in mind. Here we present a general strategy to facilitate qualitative design and quantitative prediction of SI interactions for a given beacon-solute pair. Specifically, we look at two classes of SI beacons: those that partition solute and those that associate with solute. We identify the design parameters for these systems to construct a parameter space map, calculate characteristic timescales over which SI fluxes persist, and generate approximate analytical expressions for solute concentration profiles. Further, we use these expressions to predict the DP velocity of colloids interacting with beacons, noting qualitative differences between beacon sources that release solute and beacon sinks that absorb solute. Proof-of-principle experiments of beacon sources and sinks, of partitioning, and associating types highlight the basic findings. More broadly, the conceptual approach outlined here can be adapted to treat SI interactions mediated by other materials such as dissolving solids, gases, evaporating liquids, ion-exchange resins, and others.

Dynamic Transport Control of Colloidal Particles by Repeatable Active Switching of Solute Gradients.

Diffusiophoresis (DP) is described as typically being divided into chemiphoresis (CP) and electrophoresis (EP), and the related theory is well-established. However, not only the individual effect of CP and EP but also the size dependency on the resulting DP of colloidal particles has not yet been comprehensively demonstrated in an experimental manner. In this paper, we present a dynamic transport control mechanism for colloidal particles by developing a micro-/nanofluidic DP platform (MNDP). We demonstrate that the MNDP can generate transient and/or steady-state concentration gradients, making it possible to control the direction and rate of transport of colloidal particles through the individual manipulation of CP and EP by simply and rapidly switching solutions. In addition, the MNDP allows the size-dependent separation as well as fractionation of submicron particles through the individual manipulation of CP and EP, thus empirically validating the classic theoretical model for DP under the influence of electrical double layer (EDL) thickness. Furthermore, we provide theoretical analysis and simulation results that will enable the development of a versatile separation and/or fractionation technique for various colloidal particles, including biosamples, according to their size or electrical feature.

Simulation of diffusiophoresis force and the confinement effect of Janus particles with the continuum method

The Janus particle is a special class of colloidal particle that has different surface characteristics on its two hemispheres. In the microsystem field, an interesting application is the Janus particle's self-propulsion. Diffusiophoresis (DFP) provides one possible mechanism to explain this phenomenon. In this paper, we used the continuum model to simulate DFP and to study the confinement effect of Janus particles travelling on the substrate. In the experiment, we noticed a special quasi-1D motion, in which the DFP force is dominant and particles move at a constant velocity within a short interval approximately along a straight line. This enables us to adopt a reference frame to numerically study the distributions of the flow field and concentration field and hence to evaluate the different forces. Because the confinement effect has a great influence on the magnitude of forces, the gaps were calculated accurately according to the force balance principle. Meanwhile, the fitting coefficients to match the experimental and numerical results were suggested. This result may help us to get a better understanding of self-propulsion and is also beneficial for designing a DFP-based micro-device.

Diffusiophoresis caused by gradients of strongly adsorbing solutes

Diffusiophoresis caused by gradients of strongly adsorbing solutes