Benefits of using our optofluidic Young Interferometer (YI): Majority of the YIs reported in literature allow refractive index measurement at a point. In contrast, our optofluidic YI allows real-time imaging of refractive index changes along the length of microchannels. In our optofluidic YI, light interacts with the with the entire depth of the solutions in the microchannels of microfluidic devices, resulting in at least comparable refractive index resolution to current point-based YIs.

How our optofluidic YI works: When light from two point sources interacts, it undergoes constructive and destructive interference, resulting in peaks and troughs in light intensity as shown below. If refractive index difference between the two point sources changes, positions of peaks and troughs shift. A video can be downloaded from here. Refractive index can change because of analyte binding to recognition elements immobilised on one of the point sources. The change in refractive index and hence position of interference fringes because of analyte binding forms the basis of sensing using interferometry.

We built on the concept described above, and replaced the point sources with hydrogel pillars to amplify the shifts in the positions of peaks and troughs because of refractive index changes. We subsequently replaced hydrogel pillars with hydrogel filled channels to obtain a stack of fringes in the third dimension for real-time imaging of refractive index changes along the length of microchannels.

Sample solutions are transported in hydrogel filled channels by applying electric field. The use of electric field also allow us to do in-situ sample processing (i.e. preconcentration and clean-up).

We are working to immobilise arrays of antibodies with specificity towards different analytes in the hydrogel filled channels, which when combined with electrophoresis integrated YI, will allow rapid, sensitive and multiplexed analysis.

Related publications:
We have integrated electrophoresis with our optofluidic YI to transport proteins in hydrogel filled microchannels while monitoring the movement of proteins in real-time.