Hollow waveguide-based full-field absorbance biosensor

This paper presents the design, simulation, fabrication and characterization of a silicon hollow waveguide-based full-field absorbance biosensor and its application for the detection of hydrogen peroxidase (H₂O₂) using a peroxidase enzyme as a model recognition element. Such a system merges into one single microstructure the transducer (waveguide) and the bioreactor (recognition element), achieving a high degree of integration with only one photolithographic step. Moreover, this configuration allows the interaction between the light confined into the hollow waveguide with the analyte. Hence, high sensitivities or small interaction lengths can be easily achieved. Numerical simulations and experimental results show a good agreement, with a linear behaviour ranging from 0.01 mM to 0.3 mM and sensitivities of 2.7 AU/mM and 3.0 ± 0.2 AU/mM, respectively. Furthermore, the experimental characterization shows a limit of detection of 0.020 ± 0.001 mM and a signal-to-noise ratio ranging from 20 dB to 14 dB on the linear range. These results, the simple design and technology proposed, together with the potential capability of the hollow waveguides to integrate microfluidic and microelectronics, present these structures as excellent candidates for the fabrication of ultra-compact, low-cost, micro total analysis systems (μTAS).