Monolithic integration of planar waveguide technology and microfluidics

LioniX announces a technological breakthrough with the succesfull integration of planar waveguide technology for microfluidic applications. Microfluidics and integrated optics, are LioniX' two core competences. By combining both disciplines LioniX takes a leading position in the area of optical detection technologies for microfluidic applications. The monolithic integration of them has been a real challenge and has not been seen elsewhere. The development took several years and was carried out within a program financed by the Netherlands Agency for Aerospace Programmes (NIVR). Applications are not restricted to space. LioniX expects to apply the technology for custom developments in life science and environmental markets.

Technology

The technology development involves the transfer of integrated optical technology from silicon substrates to fused silica substrates, while maintaining the optical properties of the silicon nitride / silicon oxide waveguide and controlling the mechanical stress. The optical wafer is directly bonded on a fluidic channel wafer. The direct bonding technology involves no glue or other strange materials and requires nanometer flatness of both surfaces.

Applications

The new technology enables a whole new range of optical detection techniques in micrometer sized channels without disturbing the flow profile. Therefore it is very suitable for measurements with high spatial resolution as needed for example in separation techniques. The use of fused silica substrates further allows for analysis techniques based on electroosmotic flow (e.g. capillary electrophoresis) and the combination with microscopic detection techniques downto UV wavelengths.

A typical application is the use of a refractive index detector based on the interaction of the evanescent field with the sample in a Young-interferometer configuration. Such a detector could be used for label-free detection of biomolecules in CE applications.

The figure below shows the stepresponse to a 1% sugar solution (Delta R.I. 0.003). The step response was induced by electroosmotic pumping and switching between 2 different reservoirs. The measured phase change was approx. 0.2 of a fringe, which is in very good agreement with the expected value based on a wavelength of 633 nm and a sensing window length of 250 microns.