Laser-accelerated self-assembly of colloidal particles at the water–air interface

Abstract

We experimentally demonstrate that optical tweezers can be used to accelerate the self-assembly of colloidal particles at a water-air interface in this Letter. The thermal flow induced by optical tweezers dominates the growth acceleration at the interface. Furthermore, optical tweezers are used to create a local growth peak at the growing front, which is used to study the preferential incorporation positions of incoming particles. The results show that the particles surfed with a strong Marangoni flow tend to fill the gap and smoothen the steep peaks. When the peak is smooth, the incoming particles incorporate the crystal homogeneously at the growing front.

Formation of Two-Dimensional Magnetically Responsive Clusters Using Hematite Particles Self-Assembled via Particle-Induced Heating at an Interface

“…Optical confinement, − a noncontact technique widely applied in various disciplines of science and technology (i.e., physics, chemistry, and biology like single molecule biophysics and cell biology − ), is advantageous for trapping and manipulating objects such as organelles inside cells, − colloidal particles, − and nanoparticles. − When laser light is illuminated on an interface, it generates a local hotspot that induces convection currents, which assist in the aggregation of microparticles. − This confinement technique facilitates the creation and manipulation of assemblies of nano- and microcolloidal particles − and is thus employed in analyzing the characteristics of various interfacial systems, like liquid–solid, liquid–liquid, − and air–liquid . The properties of such assemblies are vastly different from their constituent particles, because of which the phenomena can alter the interfacial properties in different systems …”

“…16−20 This confinement technique facilitates the creation and manipulation of assemblies of nano-and microcolloidal particles 21−23 and is thus employed in analyzing the characteristics of various interfacial systems, like liquid−solid, 22 liquid−liquid, 24−26 and air−liquid. 17 The properties of such assemblies are vastly different from their constituent particles, because of which the phenomena can alter the interfacial properties in different systems. 27 Colloidal particle assemblies can be induced by various phenomena, such as the fluid flow generated by thermal, 28 concentration, 29 and surface tension gradients, 30 which cause Marangoni convection, 17 thermal convection, 31 and thermophoresis 32 resulting in particle migration and thus selfassembly.…”

“…17 The properties of such assemblies are vastly different from their constituent particles, because of which the phenomena can alter the interfacial properties in different systems. 27 Colloidal particle assemblies can be induced by various phenomena, such as the fluid flow generated by thermal, 28 concentration, 29 and surface tension gradients, 30 which cause Marangoni convection, 17 thermal convection, 31 and thermophoresis 32 resulting in particle migration and thus selfassembly. 33−37 To date, several studies have been conducted on ordered colloidal assemblies 18,23,38−40 and has applications.…”

“…Colloidal particle assemblies can be induced by various phenomena, such as the fluid flow generated by thermal, concentration, and surface tension gradients, which cause Marangoni convection, thermal convection, and thermophoresis resulting in particle migration and thus self-assembly. − To date, several studies have been conducted on ordered colloidal assemblies ,,− and has applications. For example, heating a solid–liquid interface using thermo-optical tweezers leads to the formation of a continuous mesoscopic pattern, which is used in lithography; similarly, focused laser-induced heating by focused laser of a liquid–air interface results in the formation of particle assemblies owing to the fluid flow phenomenon. , In this study, we designed a method to induce self-assembly of colloidal hematite particles at an air–water interface using an upconverting particle (UCP).…”

Optical Assembling of Micro-Particles at a Glass–Water Interface with Diffraction Patterns Caused by the Limited Aperture of Objective

“…It is generally believed that the particles are trapped only in an irradiated diffraction limited spot where optical force is exerted on the particles by a laser beam. However, in recent years, it has been demonstrated that single beam optical tweezers can gather lots of colloidal particles outside the focus of trapping laser at the glass-solution interfaces [16][17][18][19][20][21][22]. The mechanism of the above phenomenon is complicated.…”