Towards non-blind optical tweezing by finding 3D refractive index changes through off-focus interferometric tracking

Abstract

In modern 3D microscopy, holding and orienting arbitrary biological objects with optical forces instead of using coverslips and gel cylinders is still a vision. Although optical trapping forces are strong enough and related photodamage is acceptable, the precise (re-) orientation of large specimen with multiple optical traps is difficult, since they grab blindly at the object and often slip off. Here, we present an approach to localize and track regions with increased refractive index using several holographic optical traps with a single camera in an off-focus position. We estimate the 3D grabbing positions around several trapping foci in parallel through analysis of the beam deformations, which are continuously measured by defocused camera images of cellular structures inside cell clusters. Although non-blind optical trapping is still a vision, this is an important step towards fully computer-controlled orientation and feature-optimized laser scanning of sub-mm sized biological specimen for future 3D light microscopy.

Photon-efficient optical tweezers via wavefront shaping

“…Our concept is fundamentally different; we aim to optimize trapping stiffness, which entails shaping light fields to create high intensity gradients on the boundaries of a homogeneous particle rather than projecting uniform intensity throughout its volume. Recent work has also begun to explore ways to identify regions of high–refractive index gradients within large inhomogeneous particles to exert higher optical forces by focusing light onto these areas ( 78 ).…”

Dual-Arm Visuo-Haptic Optical Tweezers for Bimanual Cooperative Micromanipulation of Nonspherical Objects

“…Although we attempted to realize the cooperative indirect micromanipulation for only two types of single samples in a limited (that is, in a 2D and not 3D) workspace because of the insufficient performance of the used PC, it was demonstrated that the system could help to realize highly robust indirect micromanipulation (that is, ensuring the continuous locking of microbeads as end-effectors in the optical tweezers) during cooperative manipulation involving visuo-haptic information. A possible application based on the straightforward implementation of 3D cell rotation by multi-fingers (namely, multiple traps) in a 3D workspace is tomographic imaging and 3D microscopy for nonspherical cells [30]. As future work, we plan to expand the performance of image processing and multiple traps from 2D to 3D traps by replacing the PC.…”

Shining Light in Mechanobiology: Optical Tweezers, Scissors, and Beyond

“…Other related techniques can be used to greatly increase optical trapping strength by choosing ideal phase patterns to transform the optical potential restraining dielectric particleswhich could potentially be used on cellswithout retro-reflection. Recently, impressive demonstrations of precise positioning and rotation of groups of cells using feedback to control a structured optical potential has been demonstrated …”

“…Recently, impressive demonstrations of precise positioning and rotation of groups of cells using feedback to control a structured optical potential has been demonstrated. 154 ■ LIGHT-BASED NEUROSCIENCE Innovation in light-based technologies has recently made it possible to observe the neural mechanical properties, behavior, and growth of neurons as well as neuronal networks across small intact brains (e.g. : mice, Drosophila, zebrafish, C. elegans) while perception and behavior occur.…”