ABSTRACT
The paper presents theoretical analyses and experimental investigations of broadband differential interference in planar gradient waveguides made via K+-Na+ ion exchange in BK-7 glass. This technology, due to its large polarimetric dispersion, is especially useful for applications in differential interferometry. We discuss the influence of technological parameters on the operation characteristics of the structure in terms of sensor applications. The refractive index variation in the measured external surroundings affects the modal properties of TE and TM modes and the spectral distribution at the output of the differential interferometer. The optical system described in this work has been designed specifically for use in biological systems where variations in the index of refraction need to be measured.
Subject(s)
Optical Devices , Refractometry , Ion Exchange , Spectrum Analysis , InterferometryABSTRACT
Microfluidic technology is a powerful tool to precisely establish artificial microenvironments and has been used to generate numerous biomimetic devices. Here, we present a combined microenvironment platform, which consists of microchamber microfluidics filled with thermoresponsive glycomicrogels, and enables live-cell immobilization and continuous observation. Poly(N-isopropylacrylamide) microgels containing trehalose has been selected from our previous study to possess adequate physicochemical characteristics and provide potential multivalent interactions with cell surfaces. We show that the designed microplatform enables small population of cells to be trapped in individual parallel microchambers and further immobilized in an artificial extracellular matrix. We applied our platform to long-term imaging experiments and studied HeLa cell growth dynamics under continuous, diffusion-dominated medium exchange. The mathematical modeling revealed that regardless of the initial number of cells, the growth dynamic follows the exponential growth pattern over the analyzed timespan (one week). These results confirm that the presented microsystem facilitates the long-term cell culture in a cellular-mimicking microenvironment without reaching environmental constraints.
Subject(s)
Cellular Microenvironment , Microfluidics , Cell Culture Techniques , Cell Proliferation , HeLa Cells , HumansABSTRACT
A model and the waveguide parameters of a broadband, polymer-based slab waveguide difference interferometer is presented in this paper. The parameters were determined based on knowledge of the dispersion in the structure materials used to fabricate the waveguide. The impact of the waveguide layer thickness, propagation path length, and change in the waveguide cover refractive index on the output signal from the system was determined. It has been shown that the direction of the maximum shifting is determined by the thickness of the waveguide layer. A relationship describing the shift in the signal extrema for a change in the waveguide cover refractive index was derived. The results show that the use of a propagation constant simplifies the description of the interferometer. Polymer waveguides, although they have a small contrast in refractive indices, allow for large shifts in the maxima of the signal. The determined shifts in the output signal extrema for polymer waveguides are comparable, and these shifts are larger for some waveguide thicknesses compared to waveguides based on Si3N4.
ABSTRACT
Integrated Optical Broad-Band Difference Interferometer (IO BB DI) is introduced as an alternative and economical measurement method to integrated optical label-free affinity sensors. A detailed theoretical analysis of the method is presented and the effects of the waveguide layer on the operation of the system are shown. A very short operating distance of less than 0.5 mm allows miniaturization of the interferometer. The analysis was performed for Si3N4/SiO2 layers that can be obtained in standard microelectronics technological processes.
