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Microfluidics Could Open the Door to Graphene Opto-electronics

The aim is to exploit flakes of graphene and other 2D materials suspended in microfluidic structures which can be coupled to CMOS photonic circuits.

The fluids in the micro-channels are liquid crystals, which can be controlled to physically hold optically-active graphene oxide flakes in position to form 2D-fluid composite materials which provide appropriate optical responses for the CMOS.

 Key to holding them is place is measuring how the flakes are dispersed and aligned, for which the team is using Raman spectroscopy among other optical techniques.

However, due to the sparse distribution of the particles involved, standard optical techniques are not sensitive enough, said the university.

To improve sensitivity for the Raman spectroscope, which is fixed above the chip, the fluid channels (shown within the lower transparent layer in the diagram) have been designed to enhance sensitivity at certain wavelengths.

“We discovered an ultra-high signal sensitivity to the xyz alignment of 2D flakes within the optofluidic waveguide. This in turn enables precise in-situ alignment detection, for the first practicable realisation of 3D photonic microstructure shaping based on 2D-fluid composites and CMOS photonics platform,” said the research team in ‘Dynamic in-situ sensing of fluid-dispersed 2D materials integrated on microfluidic Si chip‘, a paper in Nature Scientific Reports.

There are two ways to use the technology, said the team, the main one is to keep the flakes in liquid suspension, manipulating them on-the-fly to form tuneable photonic crystals – variable optical filter components over the silicon. The second possibility is to use microfluidics to build solid-state structures by control flake deposition from liquid suspension.

This is an international team. Exeter worked with: Skolkovo Institute of Science and Technology, Moscow; University of Dublin; École Nationale Supérieure de Mécanique et des Microtechniques, Besançon, France; and ITMO University, St Petersburg.

Source: Electronics Weekly

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