Abstract

We consider sedimented at a solid wall particles that are immersed in water containing small additives of photosensitive ionic surfactants. It is shown that illumination with an appropriate wavelength, a beam intensity profile, shape and size could lead to a variety of dynamic, both unsteady and steady state, configurations of particles. These dynamic, well-controlled and switchable particle patterns at the wall are due to an emerging diffusio-osmotic flow that takes its origin in the adjacent to the wall electrostatic diffuse layer, where the concentration gradients of surfactant are induced by light. The conventional nonporous particles are passive and can move only with already generated flow. However, porous colloids actively participate themselves in the flow generation mechanism at the wall, which also sets their interactions that can be very long ranged. This light-induced diffusio-osmosis opens novel avenues to manipulate colloidal particles and assemble them to various patterns. We show in particular how to create and split optically the confined regions of particles of tunable size and shape, where well-controlled flow-induced forces on the colloids could result in their crystalline packing, formation of dilute lattices of well-separated particles, and other states.

Graphic Abstract

中文翻译：

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被动和主动微粒的光诱导操纵

摘要

我们考虑沉积在固体壁上的颗粒，该颗粒浸入含有少量光敏离子表面活性剂添加剂的水中。结果表明，具有适当波长、光束强度分布、形状和尺寸的照明可以产生各种动态、非稳态和稳态的粒子配置。壁上这些动态、控制良好且可切换的颗粒图案是由于新兴的扩散渗透流所致，该扩散渗透流起源于壁静电扩散层附近，其中表面活性剂的浓度梯度是由光引起的。传统的无孔颗粒是被动的，只能随着已经产生的流动而移动。然而，多孔胶体积极参与壁上的流动生成机制，这也使得它们的相互作用可以是非常长范围的。这种光诱导的扩散渗透开辟了操纵胶体颗粒并将其组装成各种图案的新途径。我们特别展示了如何以光学方式创建和分割尺寸和形状可调的颗粒的受限区域，其中胶体上受良好控制的流动诱导力可能会导致其结晶堆积，形成良好分离的颗粒的稀晶格，以及其他州。

图文摘要