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

Abstract

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.

Cooperative transport by flocking phototactic micromotors

“…Controllable capturing and transporting cargoes such as drug molecules, proteins, capsules, and cells in microenvironments is the pivotal nanotechnology that is extensively studied. [1][2][3][4][5][6] Synthetic micro/nanomotors can extract various energies from the surrounding environment, and convert them into mechanical output allowing for autonomous motions. 7- 15 Thus, the micro/nanomotors are endowed with the undeniable capability to serve as micro/nanocarriers to realize micromanipulation by establishing physical/chemical interactions between the motors and cargoes.…”

Progress of Microfluidic Continuous Separation Techniques for Micro-/Nanoscale Bioparticles

“…Migration of suspended colloidal particles due to a concentration gradient of solute molecules is basically the same mechanism as the diffusiophoresis performed by the gas concentration gradient. Based on concentration gradients of ionic solutions (e.g., NaCl), many previous studies have verified diffusiophoresis for separation of charged particles in a microfluidic chip in both theoretical and experimental manners [ 41 , 114 , 115 , 116 , 117 , 118 , 119 , 120 ]. Several representative cases are described as schematic diagrams shown in Figure 3 C(i) [ 108 ].…”

Diffusiophoresis driven colloidal manipulation and shortcuts to adiabaticity

“…We next combine optical and diffusiophoretic drivings to establish our ESE protocol. The colloidal system is subject to optical confinement that can be timedependent, and is furthermore in an electrolyte that can be controlled through the boundaries of the system, as performed in [53,55]. It might be thought that such a surface driving through the boundary concentration φ(t) does not provide enough command over the system, since salt invariably diffuses in the bulk of the solution, but we will see below that the present setting nevertheless offers interesting means to shape shortcutting protocols.…”

“…In this paper, we propose an ESE strategy that takes advantage of diffusiophoresis. As the phoretic force direction depends on both the solute gradient direction and the solute-surface interaction, creating a repulsive potential is achievable by appropriately tuning the solute concentration on the boundaries of the system as a function of time [54,55]. Accordingly, our approach allows for both an accelerated expansion or an accelerated compression of a colloid state in harmonic or non-harmonic confinement.…”