Dielectrophoretically tuneable optical waveguides using nanoparticles in microfluidics

We present a tuneable optical waveguide using dielectrophoretically controlled nanoparticles in microfluidics. Silicon dioxide nanoparticles of different sizes in de-ionized water are channelled through a microfluidic system. An array of microelectrodes generates the dielectrophoretic force to funnel nanoparticles, forming narrowbands at the center of the microfluidics at different applied voltages and frequencies. It is observed that these narrowbands either scatter or guide the coupled light under selected conditions. The realization of such a system offers exciting possibilities for the development of a new class of optofluidics, which are tuned by the positioning of nanoparticles on demand.

Dielectrophoretically assembled particles : feasibility for optofluidic systems

This work presents the dielectrophoretic manipulation of sub-micron particles suspended in water and the investigation of their optical responses using a microfluidic system. The particles are made of silica and have different diameters of 600, 450, and 250 nm. Experiments show a very interesting feature of the curved microelectrodes, in which the particles are pushed toward or away from the microchannel centerline depending on their levitation heights, which is further analyzed by numerical simulations. In doing so, applying an AC signal of 12 V_p-p and 5 MHz across the microelectrodes along with a flow rate of 1 μl/min within the microchannel leads to the formation of a tunable band of particles along the centerline. Experiments show that the 250 nm particles guide the longitudinal light along the microchannel due to their small scattering. This arrangement is employed to study the feasibility of developing an optofluidic system, which can be potentially used for the formation of particles-core/liquid-cladding optical waveguides.

Investigating strain transfer in polymer coated structures for the health monitoring of aerospace vehicles using polymer photonic waveguides

In this work, we present the concept of planar polymer photonic waveguides for the health monitoring of aerospace structures. Here a polymer layer is deposited onto the material/structure to be monitored. Within the polymer layer, waveguides are created after deposition. These waveguides can then be used as 'optical fibres' for optical fibre sensing methodologies. In investigating the use of polymer photonic waveguides the question to be answered is: does the strain in the test material transfer to the polymer layer, such that the value to be measured optically is reliable and indicative of the true strain in the test structure? To answer this question we have conducted a preliminary structural analysis with finite element analysis, utilising ANSYS. A simple aluminium cantilever was used as the test structure, and layers of polyethylene with different thicknesses were added to this. Result show that the thinner the layer of polymer, the more accurate the measured strain will be. For a 100um coating, the difference is strain was observed to be on the order of 3.3%. © 2014 IEEE.

Generalized characteristics of photo-elastic birefringence in polymer strip waveguides

This work investigates the material birefringence in a polymer strip waveguide which originates from thermal stress during the fabrication process. The stress is estimated through a comprehensive numerical study based on a realistic finite element model. The characteristics of birefringence are obtained in a generalized form and expressed by an empirical formula, which is applicable to various polymer materials. The developed formula can be employed to specify the photo-elastic birefringence of a polymer strip channel only by knowing the birefringence in its planar film. This will eliminate the necessity of extensive numerical analysis of thermal stress in such polymer waveguides, and accordingly help the management of stress-induced effects efficiently.