Speckle tweezers for manipulation of high and low refractive index micro-particles and nano-particle loaded vesicles

Abstract

Several fundamental research and applications in biomedicine and microfluidics often require controlled manipulation of suspended micro- and nanoscale particles. Speckle tweezers (ST) by incorporating randomly distributed light fields have been used to control micro-particles with refractive indices higher than their medium and to perform manipulation tasks such as guiding and sorting. Indeed, compared to periodic potentials, ST represents a wider possibility to be operated for such tasks. Here, we extend the usefulness of ST into micro-particles of low index with respect to the surrounding. Repelling of such particles by high intensity regions into lower intensity regions makes them to be locally confined, and the confinement can be tuned by changing the average grain intensity and size of the speckle patterns. Experiments on polystyrenes and liposomes validate the procedure. Moreover, we show that ST can also manipulate the nano-particle (NP)-loaded liposomes. Interestingly, the different interactions of NP-loaded and empty liposomes with ST enable collective manipulation of their mixture using the same speckle pattern, which may be explained by inclusion of the photophoretic forces on NPs. Our results on the different behaviors between empty and non-empty vesicles may open a new window on controlling collective transportation of drug micro-containers along with its wide applications in soft matter.

Sorting of mesoporous silica derivatives by random optical fields

“…As explained in the Introduction the ST applies local intensity gradients which are the reasons of optical local forces. The mechanism of ST as an extension for optical trapping is explained in detail in 43 . The effect of ST is assessed visually by the microscopic image sequences and then in a more quantitative fashion by trajectory analysis and particle velocimetry.…”

“…On the other hand, low refractive index particles are rippled by positive intensity gradients and need to be trapped, for example, by Laguerre-Gaussian beams which contain central dark regions. Given this, ST has been used for manipulation of several high and low refractive index particles simultaneously 43 .…”

Ultrastable Three-Dimensional Photophoretic Trap in Air Facilitated by a Single Multimode Fiber

“…Recently, speckle optical tweezers (STs) have been developed where a speckle pattern, generated using an MM fiber, has been used for performing collective optical manipulation of high-refractive-index particles 26 and even controlled manipulation of high-and low-refractive index microparticles and nanoparticle-loaded vesicles. 27 In addition, a holographic optical tweezer system has been developed by fabricating a high-NA soft-glass step-index MM fiber. 28 Besides, opto-thermoelectric speckle tweezers have been developed very recently where an optical speckle field was fed into a thermal speckle field through interaction with plasmonic substrates, thus converting the high-intensity speckle grains into the corresponding thermal speckle grains.…”

“…The speckle pattern can be generated in various ways, such as the scattering of laser light from a rough surface or transverse mode mixing in a multimode (MM) fiber. Recently, speckle optical tweezers (STs) have been developed where a speckle pattern, generated using an MM fiber, has been used for performing collective optical manipulation of high-refractive-index particles and even controlled manipulation of high- and low-refractive index microparticles and nanoparticle-loaded vesicles . In addition, a holographic optical tweezer system has been developed by fabricating a high-NA soft-glass step-index MM fiber .…”

Evaluation of pitting corrosion by dynamic speckle pattern analysis

“…For instance, blood flow monitoring using speckle pattern is announced and characterization of polymer surface is investigated by means of dynamic speckle pattern 12,13 .The procedure is applicable for different biological phenomena like seed analysis 14 and fruits 15 , parasite activities 16 , activity of bone scaffold 17 to name a few. A part from, the examination of the paints drying 18 by dynamic speckle pattern, detecting imperfections of the subsurface in multilayer composites is suggested 19 and various applications in 20,21 . Besides, in the corrosion field, a number of studies have been conducted in this field.…”