Advances in Nanophotonic Sensing Technologies During Three International Label-Free Lab-On-Chip Projects

We review the results from the use of various integrated nanophotonic sensors for label-free biosensing developed in three recent European biosensor collaborations: SABIO, INTOPSENS, and POSITIVE. Nanophotonic transducers are attractive for label-free biosensing due to their small footprint, high Q-factors, and compatibility with on-chip optics and microfluidics. This enables integrated sensor arrays for compact labs-on-chip. One application of label-free sensor arrays is for point-of-care medical diagnostics. Bringing such powerful tools to the single medical practitioner is an important step towards personalized medicine, but requires addressing a number of issues: improving limit of detection, managing the influence of temperature, parallelization of the measurement for higher throughput and on-chip referencing, efficient light-coupling strategies to simplify alignment, and packaging of the nanophotonics chip and integration with microfluidics. From SABIO, we report a volume sensing sensitivity of 240 nm/RIU and detection limit of 5 × 10 ^-6 RIU, and a surface sensing limit of detection (LOD) of 0.9 pg/mm ² for at 1.3 μm for an eight-channel slot-waveguide ring resonator sensor array, within a microfluidics integrated compact cartridge. In INTOPSENS, ongoing efforts have so far resulted in various nanophotonic transducer designs with volume sensing sensitivities as great as 2,169 nm/RIU and LODs down to 8.3 × 10 ^-6 RIU at 1.5 μm. Early experiments from the POSITIVE project have demonstrated volumetric sensitivities as high as 1,247 nm/RIU at 1.5 μm.