Fraunhofer Institute for Photonic Microsystems
Fraunhofer Institute for Photonic Microsystems

Photonic Biosensors

based on microring resonators

Photonic Biosensors

Optical Ring Resonator

© Fraunhofer IPMS
Functional principle of a biosensor based on a optical ring resonator.
© Fraunhofer IPMS
Image of a silicon wafer with processed oprical ring resonator biosensors.

Photonic biosensors are very well suited for rapid and accurate molecular analysis in point-of-care applications for early detection of diseases, as an alternative to the standard method of detecting microorganisms by blood cultures, for food analysis or for environmental monitoring.

We are developing photonic biosensors with silicon nitride microring resonators as transducer elements. In detail, the microring resonator-based biosensor works as follows: Target bioproteins that bind to the surface of the functionalised microring structure cause a change in the effective refractive index of the mode entering the structure and thus a shift in the resonance wavelength, which is detected when monitoring the spectrum at the output port. The narrower the resonance peaks of the transmission spectrum, the higher the sensitivity of the resonator.

Furthermore, a suitable functionalisation of the microring surface enables the detection of a binding between a specific bioactive receptor (antibody, DNA) and the analyte (e.g. biomarker protein) that takes place on the modified surface. Micro-ring resonator-based biosensors could be used to detect biomarker proteins down to very low concentrations of about 10 pg/ml.

We are developing a highly sensitive, cost-effective, reliable and scalable on-chip biosensor platform with multiplex architecture and optimised light coupling to the chip.

Early disease detection in body fluids with photonic biosensors

© Fraunhofer IPMS
Silicon wafer with processed microring resonator biosensors.

Standard medical procedures are time-consuming and often do not take into account individual differences between patients, leading to potential consequences for treatment outcomes and quality of life. To address this problem, Fraunhofer IPMS, in collaboration with partner institutes Fraunhofer IZI and Fraunhofer IOF at the Fraunhofer Center Erfurt, is developing disposable biosensors with extensive multiplexing capabilities that deliver rapid results. These biosensors enable early disease detection, personalized medicine and precision medicine, which has the potential to significantly improve healthcare outcomes. The photonic biosensor chips are developed at Fraunhofer IPMS on a silicon nitride waveguide platform technology. These biosensors consist of specially designed, scalable on-chip multi-channel microring resonator architectures of currently up to 16 sensors operating at a wavelength of 1550nm. Further designs are currently being developed towards the visible range based on microring resonators and Mach-Zehnder interferometers. The detection method is based on special bioassays developed by the partner institute Fraunhofer IZI, in which antigen molecules bind specifically to functionalized sensor surfaces. If binding is successful, a resonance wavelength shift is read out in the transmission spectra of the device. These biosensors are highly sensitive in detecting biomolecules in liquids, which makes them useful for the early detection of diseases in body fluids. The research team's approach is multidisciplinary. This approach includes the development of sensor chips, bioassays, biocomponents, surface functionalization, microfluidics and system integration. By considering all these aspects, the team strives for optimal performance and reliability of the biosensor system. The research team has successfully developed a demonstrator based on a multi-channel silicon nitride microring resonator biosensor system. This system enables the multiplex detection of specific miRNA biomarkers associated with neurodegenerative diseases in liquids. The detection is performed via DNA-based capture molecules immobilized on the sensor surface. The developed sensors and the integrated system are versatile and can be adapted for the detection of nucleic acids, various pathogenic biomarkers, viruses or bacteria in different liquids.The next development phase involves collaboration with diagnostics companies and clinics to further advance the development of biosensors for relevant biomedical applications. The aim is to realize the practical implementation of these biosensors in healthcare facilities.

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