Besselink GAJ*, Heideman RG, Schreuder E, Wevers LS, Falke F and Van den Vlekkert HH
Integrated-optical (bio) chemical sensors are more and more commercialized, mainly because of their high intrinsic sensitivity in combination with the possibilities they offer for integration in optofluidic devices. The microring resonator (MRR), for example, is a very feasible structure to be used as microarray sensor element for multiplex biosensing. Fabrication of MRRs has been described in the case of the TriPleX platform employing well-defined stacks of stoichiometric Si3N4 and SiO2 material. This platform allows for a wide variety of applications, due to its intrinsic low loss and its transparency for the VIS/NIR wavelength range. In the present paper, we describe the recent achievements in the characterization of arrays of these MRRs regarding temperature sensitivity, refractive index sensitivity and protein immobilization performance. Furthermore, the use of a reference channel/reference MRR is demonstrated in order to show the advantage of compensation of unintended change in temperature or sample composition. The refractive index sensitivity was determined to be 104 nm/RIU and the limit of detection was about 2 × 10-6 RIU. MRRs appeared to behave very comparable (expressed as the coefficient of (intra-array) variation (CV)) regarding the response to temperature (CV≈0.3%) as well as refractive index (CV<0.1%). Furthermore, it is shown that protein immobilization onto the different MRRs of the same arrays can be realized in a comparable way (CV<3%). A good comparability (i.e., a low variation) in these aspects allows for the use of internal referencing in order to compensate for unintended change in temperature or refractive index and also helps to attain a high assay precision in the ultimate biosensing application. Ongoing research is focused on the integration of more functionality on chip and further miniaturization in order to allow for fabrication of complex, though affordable, sensor devices.
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