Leaky Waveguides

Benefits of using our leaky waveguides (LWs): Our LWs offer significant benefits – (1) closely-coupled referencing for reliable measurements in complex samples under uncontrolled environmental conditions, (2) ease of integration with electric field driven sample processing for speed and sensitivity, and (3) broad wavelength range of operation for information rich data. Additionally, our waveguides are fabricated using solution-processing methods and widely available materials for affordability.

How our LWs work: LWs are slab waveguides comprising a few microns thick hydrogel film on a glass or plastic substrate. The refractive index of the hydrogel waveguides is in between the substrate and sample. Thus, light in these waveguides is confined via Fresnel reflection and total internal reflection (TIR) at the substrate/ waveguide and waveguide/ sample interfaces respectively. This implies that light is only partially confined in our waveguides and hence they are also called leaky waveguides.

Partial confinement of light is beneficial because light can be coupled in and out of our waveguides easily using a prism. As shown in the figure below, we can record reflected light, scattering and fluorescence emission to obtain complementary information.

Leaky waveguide

Instrumentation (reflected light)

Instrumentation (scattering or fluorescence)

Sensing modalities: We can operate our LWs in the following configurations to obtain a range of information.

Related publications:
We have studied and reported a novel manifestation for the visualisation of the resonance angle of LWs.

Analyte concentration – We have applied this to measure the concentration of thrombin.

Absorption spectroscopy – We showed that we can use this information to perform enzyme assays with high sensitivity using small sample volumes.

Optical dispersion – We showed we can use this information to determine the average iron content of Ferritin in a single step, which is not possible using state-of-art methods.

A picture showing the application of our waveguides to image particles by recording the scattered light. As particles reach the vicinity of the waveguide surface, they appear as peaks in the picture. We can count the number of peaks at a fixed time to determine the concentration of particles in the sample. A video can be downloaded from here.