Speed enhancement of multi-particle chain in a traveling standing wave

Abstract

A moving array of optical traps created by interference of two counter-propagating evanescent waves has been used for delivery of particle chains up to 18 micro-particles long immersed in water. The particles were optically self-arranged into a linear chain with well-separated distances between them. We observed a significant increase in the delivery speed of the whole structure as the number of particles in the chain increased. This could provide faster sample delivery in microfluidic systems. We quantified the contributions to the speed enhancement caused by the optical and hydrodynamic interactions between the particles.

Speckle optical tweezers: micromanipulation with random light fields

“…In fact, the required optical intensities are comparable to those reported in similar studies where the force field was generated either with holographic optical traps or with periodic potentials [3,[7][8][9][10][11][12][13][14][15][16][17]32,33]. Our technique, beyond demonstrating that random potentials are a valid alternative to more regular potentials for the purpose of optical manipulation, offers some additional advantages to current optical manipulation techniques [3,[7][8][9][10][11][12][13][14][15][16][17]32,33], such as intrinsic robustness to noise and aberrations from the optics and the environment. Moreover, an additional advantage of speckle patterns is that they are also intrinsically widefield so that they have the potential of sorting many particles in parallel in a broader microfluidic chamber, where flow speed is strongly reduced.…”

“…Although a carefully engineered periodic potential or array of traps optimized for a given application can perform better than a speckle field, this technique expands the set of tools that researchers and engineers can adopt to perform optical manipulation tasks. As it is the case for alternative optofluidic devices based on periodic optical potentials or holographic optical tweezers [3,[7][8][9][10][11][12][13][14][15][16][17]32,33], our approach can also be scaled to achieve the high throughput or sensitivity needed in microfluidics by increasing the flow speed and laser power. In fact, the required optical intensities are comparable to those reported in similar studies where the force field was generated either with holographic optical traps or with periodic potentials [3,[7][8][9][10][11][12][13][14][15][16][17]32,33].…”

“…As it is the case for alternative optofluidic devices based on periodic optical potentials or holographic optical tweezers [3,[7][8][9][10][11][12][13][14][15][16][17]32,33], our approach can also be scaled to achieve the high throughput or sensitivity needed in microfluidics by increasing the flow speed and laser power. In fact, the required optical intensities are comparable to those reported in similar studies where the force field was generated either with holographic optical traps or with periodic potentials [3,[7][8][9][10][11][12][13][14][15][16][17]32,33]. Our technique, beyond demonstrating that random potentials are a valid alternative to more regular potentials for the purpose of optical manipulation, offers some additional advantages to current optical manipulation techniques [3,[7][8][9][10][11][12][13][14][15][16][17]32,33], such as intrinsic robustness to noise and aberrations from the optics and the environment.…”

“…However, apart from these previous studies, the intrinsic randomness of speckle patterns is largely considered a nuisance to be minimized for most purposes in optical manipulation [30,31]. In fact, similar and even more complex effects have been extensively studied using periodic potentials rather than random potentials: these studies include the demonstration of guiding and sorting particles using either moving periodic potentials [16,17], static periodic potentials in microfluidic flows [7,11,12], or optical ratchets based on spatially symmetric energy landscapes [32,33].…”

“…They have, therefore, gained increasing importance as tools in microbiology and biophysics both for fundamental studies [6] and for more advanced applications such as optical sorting and optical delivery [3,7,8]. In particular, the development of techniques based on reconfigurable spatially extended patterns of light, such as multiple traps [3,[9][10][11][12] or periodic potentials [13][14][15][16][17], offers the promise of high throughput optical methods to be applied both in static and moving fluids. Also, particles' delivery, trapping and manipulation over extended areas was demonstrated near a surface employing the evanescent fields associated, for example, to surface plasmons [18] or to optical waveguides [19].…”