Optical tweezers for trapping in a microfluidic environment

Abstract

Optical tweezers use the force from a light beam to implement a precise gripping tool. Based purely on an optical principle, it works without any bodily contact with the object. In this paper we describe an optical tweezers that targets an application within the framework of nuclear magnetic resonance (NMR) spectroscopy of small objects, which are embedded inside a microfluidic channel that will be integrated in a micro-NMR detector. In the project's final stages, the whole system will be installed within the wide bore of a superconducting magnet. The aim is to precisely maintain the position of the object to be measured, without the use of susceptibility disturbing materials or geometries. In this contribution we focus on the design and construction of the tweezers. For the optical force simulation of the system we used a geometrical optics approach, which we combined with a ray fan description of the output beam of an optical system. By embedding both techniques within an iterative design process, we were able to design efficient optical tweezers that met the numerous constraints. Based on details of the constraints and requirements given by the application, different system concepts were derived and studied. Next, a highly adapted and efficient optical trapping system was designed and manufactured. After the components were characterized using vertical scanning interferometry, the system was assembled to achieve a monolithic optical component. The proper function of the optical tweezers was successfully tested by optical trapping of fused silica particles.

Optofluidic Particle Manipulation: Optical Trapping in a Thin-Membrane Microchannel

“…Another optical trapping method is optical tweezers. A focused laser uses scattering and gradient forces acting in unison to confine the particle in the beam waist or focal point [ 10 ]. This method is advantageous as it is easy to manipulate and move the particle by translation of the laser [ 11 ].…”

Statistic estimation of cell compressibility based on acoustophoretic separation data

“…The field of cell manipulation in microfluidic systems has grown tremendously in recent years producing multiple technical solutions to perform unit operations such as concentration, trapping, washing, alignment, stretching, sorting and separation (Lee et al 2017;Nilsson et al 2009). To perform these operations, various physical principles, such as dielectrophoresis, magnetophoresis, acoustophoresis, deterministic lateral displacement, optical and inertial focusing among others, have been utilized (Pethig et al 2010;Pethig 2017;Alnaimat et al 2018;Zhao et al 2016;Antfolk and Laurell 2017;McGrath et al 2014;Kampmann et al 2018;Martel and Toner 2014;Lenshof et al 2017). These techniques commonly rely on the physical properties of the manipulated cells such as size, density, shape, deformability, compressibility, polarizability, magnetic susceptibility and refractive index.…”

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

“…There have been various methods developed to assemble two-dimensional colloidal crystals [1][2][3]. Since the discovery of optical tweezers [4], optical tweezers have been used in various applications [5][6][7][8], and widely used for the assembly and reconfiguration of particles. In the liquid environment, each optical trap can only manipulate one or very few particles three-dimensionally.…”