Silicon microring resonators are widely used as optical biosensors because of their high sensitivity and promise of low-cost mass-manufacturing. Typically, they only measure the adsorbed molecular mass via the refractive index change they detect. Here, we propose and demonstrate a silicon microring biosensor that can measure molecular thickness and density as well as electrochemical activity simultaneously, thereby enabling quantification of the conformation of surface-immobilized biological and molecular layers in real time. Insight into the molecular conformation is obtained by recording the resonance shift from two geometrically distinct ring-resonators connected to a single access waveguide. The resonant cavities both support a single TE polarized optical mode but have different widths (480 and 580 nm); the extent of their evanescent fields is thus very different, providing different depth-resolution of the interaction with a molecular layer on the sensor surface. By combining the optical shift from these two measurements, we demonstrate unambiguous quantification of the thickness and the refractive index of a molecular layer assembled on the waveguide. The precision of the technique is 0.05 nm and 0.005 RIU in the molecular layer thickness and refractive index, respectively. We demonstrate the cascaded electrophotonic ring resonator system using two exemplar systems, namely, (a) physisorption of a bovine serum albumin monolayer and (b) an electroactive DNA oligonucleotide hairpin, where we uniquely show the ability to monitor electrochemical activity and conformational change with the same device. This novel sensor geometry provides a new approach for monitoring the conformation and conformational changes in an inexpensive and miniaturized platform that is amenable to multiplexed, high-throughput measurements.

中文翻译：

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使用硅电子光子生物传感器的分子构象的实时分析

硅微环谐振器因其高灵敏度和低成本制造的前景而被广泛用作光学生物传感器。通常，它们仅通过检测到的折射率变化来测量吸附的分子质量。在这里，我们提出并证明了一种硅微环生物传感器，它可以同时测量分子的厚度和密度以及电化学活性，从而能够实时量化表面固定的生物和分子层的构象。通过记录来自连接到单个访问波导的两个几何上不同的环形谐振器的谐振位移，可以洞悉分子的构象。谐振腔均支持单个TE偏振光学模式，但具有不同的宽度（480和580 nm）；因此，它们的e逝场的范围非常不同，从而提供了与传感器表面上的分子层相互作用的不同深度分辨率。通过结合这两个测量的光学位移，我们证明了组装在波导上的分子层的厚度和折射率的明确量化。该技术的精度在分子层厚度和折射率上分别为0.05 nm和0.005 RIU。我们展示了使用两个示例系统的级联电光环共振器系统，即（a）牛血清白蛋白单层的物理吸附和（b）电活性DNA寡核苷酸发夹，其中我们独特地展示了监测电化学活性和构象变化的能力。同一台设备。