Optofluidics is a research and technology area that combines the advantages of optics together with fluids. On one hand, the high sensitivity of photonic devices enables the development of effective analyte sensors with applications ranging from biosensing to environmental monitoring. On the other hand, the exploitation of fluid properties with optical devices offers a plethora of possibilities ranging from adaptive optics to the precise study of single biomolecules. Accordingly, our research group focuses on nano-optics and nanofluidics with a drive towards their integration.

Our optics research considers a variety of nano-scale approaches (e.g. distributed feedback lasers, gratings, photonic crystals and disordered media, plasmonics, liquid crystals, random lasers) to address numerous challenges in today’s society. Some of our key focus areas include the development of affordable lab-on-a-chip bio-molecular sensors and manipulators, pigment-free plastic devices with structurally induced color and smart windows for solar harvesting and improved interior daylighting.

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Left: Dye-doped polymer photonic crystal lasers enable high resolution sensing of biological and other organic compounds via refractive-index-based detection. Right: Plasmonic V-grooves offer controlled sub-wavelength confinement of light with favorable characteristics for photonic circuit miniaturization and lab-on-a-chip type applications. 

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Left: Color based on surface scattering from randomized structures (rather than using dyes or other pigments) can be achieved inexpensively in plastic materials by replication of a master stamp.  Right: Enhanced control of diffracted light through smart windows can improve the distribution of interior daylighting or partially redirect light to solar cells at the glass edges. 

We use nanofluidic devices, fabricated by direct nanoimprint or reactive-ion etching, as a platform for analysis of single DNA molecules in solution. By confining the DNA in nanochannels, the molecules may unwind and stretch such that their inherent information is more readily accessible. For the experiments, the DNA molecules are stained and visualized by fluorescence microscopy. This technique is used together with nanofluidic channels to develop a next generation of DNA sequencers based on single molecules. 

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Extracting the DNA from separated cancer cells may lead to effective cancer diagnostic tools. Left: Pinched flow fractionation allows separation of e.g. cancer cells from blood cells. Right: Multiple displacement amplification of DNA in a micro- and nanofluidic polymer device allows for single cell genomic sequencing.

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Left: Single Lambda-phage DNA molecules moving in an entropic trap array. Right: Circular DNA trapped in a 100 nm slit.

Our nano-optics and nanofluidics research is supported by technology development in nanofabrication based on electron beam and nanoimprint lithography in the DANCHIP clean room at DTU. Our research in nanofabrication is focused on up-scalablability of devices for large-scale production.

Select materials, such as sol-gels and organically modified ceramics (ORMOCER™), are used to create devices by adding functionality via nanostructuring thin-films using nanoimprint lithography. For some applications we also modify the thin-film materials by introducing organic dyes to provide optical gain and energy conversion, or nanocrystals to achieve nanoporosity. In this regard, some example devices include nanoimprinted plastic photonic crystal dye microlasers, all-silica nanofluidic devices fabricated by direct nanoimprint in sol-gel, and structured metal plasmonic V-grooves.

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Left: SEM image showing the nanoprotrusions of a λ/4-phase-shifted photonic crystal fused silica stamp. Right: AFM image of an imprint formed by the stamp seen above in an ORMOCORE film.