Optical binding of nanoparticles outside the photon beam: creation of primeval optical matter. OptoMat

Since the pioneering work of Ashkin in1986, optical trapping has been used in various research fields (e.g., biology, chemistry, physics, and material sciences) for three-dimensional trapping and manipulation of micro- and nano-scale objects (e.g., nanoparticles (NPs), live cells, proteins, DNA, or small molecules). Inside an optical field, three different optical (scattering, gradient, and absorption) forces are imposed on particles. While inside bulk solution, a stable trapping spot is only generated at the laser focus when the gradient force is larger than the scattering force, completely different phenomena occur at an interface, where all the optical forces contribute to stably trapping and gathering the objects.As result, so called “dynamic evolving assemblies” have been recently reported using different types of objects (metallic and polymeric particles, polymers, and proteins).These assemblies can gather more than hundreds of objects outside the irradiated area, which can only be explained by an expansion of the optical potential, most likely through multiple scattering processes. In the OptoMat project, we will further investigate the unexplored phenomenon of optical binding outside of the irradiated area, which has a unique potential to develop sub-millimeter-sized optical matter. Our initial working hypothesis considers that the NPs are optically bound outside the focal spot by the back-scattered light and multi-channel light scattering, forming a dynamic optical binding network. We will explore the different experimental conditions which yield optical binding outside the irradiated area, from both optical (e.g., laser beam mode and pattern, laser polarization, number of laser beams, etc.) and material (e.g., size, shape, metallic vs dielectric vs hybrid materials, surface decoration, etc.) points of view.

Keywords:Optical trapping, Optical binding, Nanoparticles, Surface plasmon resonance, Optical microscopy, Electron microscopy

Disciplines:Nanochemistry, Physical chemistry of materials, Chemistry of clusters, colloids and nanomaterials