We present the design, fabrication, and characterisation of an array of optical slot-waveguide ring resonator sensors, integrated with microfluidic sample handling in a compact cartridge, for multiplexed real-time label-free biosensing. Multiplexing not only enables high throughput, but also provides reference channels for drift compensation and control experiments. Our use of alignment tolerant surface gratings to couple light into the optical chip enables quick replacement of cartridges in the read-out instrument. Furthermore, our novel use of a dual surface-energy adhesive film to bond a hard plastic shell directly to the PDMS microfluidic network allows for fast and leak-tight assembly of compact cartridges with tightly spaced fluidic interconnects. The high sensitivity of the slot-waveguide resonators, combined with on-chip referencing and physical modelling, yields a volume refractive index detection limit of 5 x 10(-6) refractive index units (RIUs) and a surface mass density detection limit of 0.9 pg mm(-2), to our knowledge the best reported values for integrated planar ring resonators.

QC 20100715

We demonstrate label-free molecule detection by using an integrated biosensor based on a Si 3 N4/Si0 2 slotwaveguide microring resonator. Bovine serum albumin (BSA) and anti-BSA molecular binding events on the sensor surface are monitored through the measurement of resonant wavelength shifts with varying biomolecule concentrations. The biosensor exhibited sensitivities of 1.8 and 3.2 nm/(ng/mm 2 ) for the detection of anti-BSA and BSA, respectively. The estimated detection limits are 28 and 16 pg/mm 2 for anti-BSA and BSA, respectively, limited by wavelength resolution.Label-free biomolecule optical sensing technologies are of great interest because of their flexibility to analyze biomolecular interactions without using fluorescence, absorptive, or radio-labels. This simplifies the assay and allows time-resolved study of the kinetics of biomolecular interactions. Integrated photonic devices used as biosensors present important advantages, such as high sensitivity, small size, and high scale integration. Thus, label-free integrated optical biosensors based on Mach-Zehnder interferometers , directional couplers , microring , and disk resonators have been demonstrated to be very sensitive label-free biosensors.Recently, we have reported an integrated photonic sensor based on a slot-waveguide resonator . This photonic structure takes advantage of the remarkable property of slot-waveguides to provide high optical intensity in a subwavelength-size low refractive index region (slot-region) sandwiched between two high refractive index strips (rails) . This permits a very high interaction between the slot-waveguide mode probe and a liquid analyte. As a result, the reported slot-waveguide sensor exhibited a bulk ambient sensitivity as high as 212.1 nm/refractive index unit (RIU), which is more than twice as large as that exhibited by ring resonator optical sensors based on conventional strip waveguides. In this Letter we demonstrate the detection of label-free molecular binding reactions on the surface of a slot-waveguide ring resonator. Bovine serum albumin (BSA) protein and anti-BSA are used to study the biosensor performance.The device consists of a 70 /mm radius slotwaveguide ring resonator made of Si 3 N 4 on Si0 2 The Si 3 N4 rails of the slot-waveguide ring are separated by 200 nm (w sht ), and their widths are 400 and 550 nm for the outer and inner rails, respectively, as illustrated in Fig. 1(a). A beam propagation method calculation of the quasi-TE optical mode of the ring slot-waveguide at 1.3 /mm operation wavelength is

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We report experimental results of label-free anti-bovine serum albumin (anti-BSA) antibody detection using a SOI planar photonic crystal waveguide previously bio-functionalized with complementary BSA antigen probes. Sharp fringes appearing in the slow-light regime near the edge of the guided band are used to perform the sensing. We have modeled the presence of these band edge fringes and demonstrated the possibility of using them for sensing purposes by performing refractive index variations detection, achieving a sensitivity of 174.8 nm/RIU. Then, label-free anti-BSA biosensing experiments have been carried out, estimating a surface mass density detection limit below 2.1 pg/mm2 and a total mass detection limit below 0.2 fg.