Characterization of the evanescent field profile and bound mass sensitivity of a label-free silicon photonic microring resonator biosensing platform

Abstract

Silicon photonic microring resonators have emerged as a sensitive and highly multiplexed platform for real-time biomolecule detection. Herein, we profile the evanescent decay of device sensitivity towards molecular binding as a function of distance from the microring surface. By growing multilayers of electrostatically bound polymers extending from the sensor surface, we are able to empirically determine that the evanescent field intensity is characterized by a 1/e response decay distance of 63 nm. We then applied this knowledge to study the growth of biomolecular assemblies consisting of alternating layers of biotinylated antibody and streptavidin, which follow a more complex growth pattern. Additionally, by monitoring the shift in microring resonance wavelength upon the deposition of a radioactively labeled protein, the mass sensitivity of the ring resonator platform was determined to be 14.7 ± 6.7 [pg/mm 2 ]/Δpm. By extrapolating to the instrument noise baseline, the absolute mass limit of detection is found to be 1.5 ± 0.7 pg/mm 2 . Taking the small surface area of the microring sensor into consideration, this value corresponds to an absolute mass detection limit of 97 ag (i.e. 0.6 zmol of IgG), demonstrating the remarkable sensitivity of this promising label-free biomolecular sensing platform.

Performance of Arrayed Microring Resonator Sensors with the TriPleX Platform

“…In practice, a measurement rate of 10 Hz is used. This is very fast compared to measurement rates described for other systems such as once per 8 s (5 MRRs [16], or 32 MRRs [14]) or once per minute (12 MRRs [21]). This measurement rate is sufficient enough to monitor drastic changes in refractive index, for example, when regeneration is carried out with high salt solutions.…”

“…Fabrication of integrated MRRs has been described in the case of all three main IO main platforms, especially SOI [10,13,14] but also InP [15] and Si 3 N 4 [12,16,17] while realization was also reported for polymer systems [18,19]. The SOI platform offers a large refractive index contrast and therewith a small allowable bend radius and thus footprint.…”

“…The resonators in series differ by 30 nm in circumference to avoid spectral overlap of resonances [21]. Luchansky et al [14] also employ vertical grating couplers but with a separate input for each individual MRR and, instead of the drop port, the intensity of the through port signals is monitored by means of an infrared camera. Ghasemi et al [16] employ end-fire coupling of tunable laser light (λ≈655 nm) into a common bus coupled to an array of 5 SiN MRRs.…”

Improved Sensitivity of Microring Resonator-Loaded Mach–Zehnder Interferometer Biosensor

“…(4)(5)(6)(7)(8)(9)(10)(11) In addition, microring resonator (MRR)-based biosensors have also been intensively developed because of their compactness, high sensitivity, and low cost. (12)(13)(14)(15)(16)(17)(18)(19)(20) We have also proposed and developed a biosensor based on an MRR-loaded Mach-Zehnder interferometer (MRR-MZI) (21) that has a higher sensitivity than conventional MRR sensors. Although avidin at a concentration as low as 20 pM was detected as a change in light transmittance with the MRR-MZI sensor, a sufficient change in transmittance has not yet been obtained.…”

Measurement of small molecule diffusion with an optofluidic silicon chip

“…We take advantage of the successful micro-ring resonator platform that brought about various demonstrations of real-time sample analysis with concentration accuracies down to 10 ng mL −1 and as low as 60 fM when receptor molecules are used. 5,6 A micro-ring resonator is a resonant device in which the resonant optical frequencies depend on the refractive index of the surrounding fluid. The refractive index of the fluid alters with changing concentration of its solutes and their refractive indices.…”