Optically-controlled platforms for transfection and single- and sub-cellular surgery

Nanometer optical trap based on stimulated emission in evanescence of a totally reflected Arago spot : Nanometer optical trap for fluorescent nanoparticles

Optical tweezers have paved the way towards the manipulation of particles and living cells at the micrometer range. Its extension towards the nanometer world may create unprecedented potentialities in many areas of science. Following a letter (O. Emile, J. Emile, H. Tabuteau, EPL 129, 58001 (2020)) that reported the observation of the trapping of a single 200nm diameter fluorescent particle in a nanometric volume, we detail here our experimental findings. In particular, the trapping mechanism is shown to be based on the radiation pressure of light in one direction and on the stimulated emission of the particle in the evanescent wave of a nanometer Arago spot on a glass/liquid interface on the other directions. The trapping volume is a 200nm height cylinder whose radius varies with the spreading of the evanescent wave near the spot and can reach 50nm. The calculation of the force and the parameters limiting the lifetime are detailed. Applications to laser trapping of atoms and molecules are also discussed.

Laser-assisted optoporation of cells and tissues - a mini-review

Laser microbeam techniques are presented, which permit the introduction of molecules or small particles into living cells. Possible mechanisms - including photochemical, photothermal and opto-mechanical interactions (ablations) - are induced by continuous wave (cw) or pulsed lasers of different wavelength, power, and mode of operation. Laser-assisted optoporation permits the uptake of fluorescent dyes as well as DNA plasmids for cell transfection, and, in addition to its broad application to cultivated cells, may have some clinical potential.

Micro-gun based on laser pulse propulsion

This paper proposes a novel "micro-gun" structure for laser pulse propulsion. The "micro-bullets" (glass microspheres) are irradiated by a laser pulse with a 10 ns duration in a dynamic process. Experimental parameters such as the microsphere diameter and the laser pulse energy are varied to investigate their influence on laser pulse propulsion. The energy field and spatial intensity distribution in the capillary tube were simulated using a three-dimensional finite-difference time-domain method. The experimental results demonstrate that the propulsion efficiency is dependent on the laser pulse energy and the microsphere size. The propulsion modes and sources of the propelling force were confirmed through direct observation and theoretical calculation. Waves also generated by light-pressure and thermal expansions assisted the propulsion.

Light-driven micro-tool equipped with a syringe function

Leveraging developments in microfabrication open new possibilities for optical manipulation. With the structural design freedom from three-dimensional printing capabilities of two-photon polymerization, we are starting to see the emergence of cleverly shaped 'light robots' or optically actuated micro-tools that closely resemble their macroscopic counterparts in function and sometimes even in form. In this work, we have fabricated a new type of light robot that is capable of loading and unloading cargo using photothermally induced convection currents within the body of the tool. We have demonstrated this using silica and polystyrene beads as cargo. The flow speeds of the cargo during loading and unloading are significantly larger than when using optical forces alone. This new type of light robot presents a mode of material transport that may have a significant impact on targeted drug delivery and nanofluidics injection.