Realization of pitch-rotational torque wrench in two-beam optical tweezers

Abstract

3D Pitch (out-of-plane) rotational motion has been generated in spherical particles by maneuvering the laser spots of holographic optical tweezers. However, since the spherical particles, which are required to minimise drag are perfectly isotropic, a controllable torque cannot be applied with it. It remains free to spin about any axis even after moving the tweezers beams. It is here that we trap birefringent particles of about 3 μm diameter in two tweezers beams and then change the depth of one of the beam foci controllably to generate a pitch rotational torque-wrench and avoid the free spinning of the particle. We also detect the rotation with newly developed pitch motion detection technique and apply controlled torques on the particle.

Simultaneous Optical Trapping and Electromagnetic Micromanipulation of Ferromagnetically Doped NaYF4 Microparticles

“…However, for the first time, the magnetic properties of these NYFs through co-doping with Fe are being explored. We show that this co-doped particle can be held in optical tweezers while the magnetic field could be used to turn the particle in all three degrees of freedom, namely, yaw, pitch, ,− and roll, in airline nomenclature. Controlled in-plane rotations of single ferromagnetic magnetite nanowires using external magnetic fields were reported, but the detection of the rotations lacks the high spatiotemporal resolution that our system offers.…”

A hydro-thermophoretic trap for microparticles near a gold-coated substrate

“…The particle is spatially confined in all three dimensions but also observed to be executing different out-of-plane rotations, namely roll 34 and pitch [40][41][42][43] due to the thermoplasmonic fluid flow. It is not exactly clear why the particle executes this rotation but it could arise from minor differences in fluid velocities in the local neighborhood of the equilibrium location.…”

Roadmap for optical tweezers

“…Here, the anisotropy in the scatter pattern is detected using the difference in halves of a split photodiode. The technique of determining the pitch angle to high resolution can be used in combination with a two-beam rotation generation method on a birefringent particle to realise the optical pitch torque wrench [162]. Using this, one can think of applying controlled pitch torques on surfaces like membranes, which is relevant during situations like cell endocytosis.…”