Whispering Gallery Mode Carousel: A means for Enhanced Detection in Biosensing and Surface-Force Probing

0933531阿诺德病毒颗粒是人类疾病的主要原因，其早期检测和识别越来越重要，因为航空旅行使这些传染性病原体迅速传播到地球仪的人群中。通过确定病毒粒子的种类和大小对单个病毒粒子敏感的快速检测器将满足早期检测的需求。目前的建议是继续调查微球回音壁模式（WGM）的生物传感器，用于早期检测人体体液中的病毒，因为我们利用最近发现的现象的光捕获的纳米粒子内的WGM倏逝体积。传感是基于微球的极窄光子共振，由于环境变化而改变其频率。在WGM的范围内？s倏逝场（~ 200 nm）纳米颗粒通过梯度力被拉向表面，类似于光镊中存在的那些。捕获势阱由吸引的倏逝极化势、排斥的静电势和货车范德华势形成。在结合亲和力低或结合位点密度低的情况下，纳米颗粒通过辐射压力在轨道上推进。这种捕获机制（WGM Carbohydrate）沿着受控的结合亲和力增加了额外的功能，并确保了WGM生物传感器的高灵敏度和特异性。最终目标是建立对单个病毒颗粒敏感的微流控生物传感器，并可以根据其大小/质量和对特定抗体的亲和力区分病毒体。这些生物颗粒的小尺寸需要微米尺寸的传感器3。然而，超低浓度分析物穿过边界层的布朗扩散被认为是微型传感器的主要障碍4。初步结果表明，与其他微型传感器相比，WGM Carbide传感器可以显著提高颗粒到传感区域的传输速率（50倍）。此外，转盘机构提供了一种用于调查在表面附近产生的力的手段。了解这些力对于微流控器件的设计和微加工具有重要意义。在WGM转盘中捕获的纳米颗粒可用于定量测量来自其随机径向运动的表面相互作用。通过适当地选择相互作用表面和液体介质，将有可能屏蔽静电排斥并揭示短程相互作用，例如货车德瓦尔斯相互作用。对于DLVO（胶体稳定性理论）来说，要正确描述各种水溶液在非常短的距离（5 nm）下的相互作用存在挑战，其中观察到排斥溶剂化力。WGM Carnival将帮助应对这些挑战。

0933531ArnoldVirus particles are a major cause for human disease, and their early detection and identification is of increasing importance as air travel allows these infectious agents to spread rapidly to populations across the globe. A fast detector that is sensitive to a single virus particle by determining its genus and size would answer the demand for early detection. The present proposal is to continues the investigation into microsphere whispering gallery mode (WGM) biosensors for early detection of viruses in human fluids as we utilize a recently discovered phenomenon of light trapping of nanoparticles within the WGM evanescent volume. The sensing is based on the extremely narrow photonic resonances of microspheres that shift their frequencies as a result of an environmental change. Within the reach of the WGM?s evanescent field (~ 200 nm) nanoparticles are drawn toward the surface by gradient forces, similar to those present in optical tweezers. A trapping potential-well is formed by an attractive evanescent polarization potential, repulsive electrostatic potential, and van der Waals potential. In the case of a low binding-affinity or a low density of binding sites, nanoparticles are propelled around in orbit by radiation pressure. This trapping mechanism (WGM Carousel) along with controlled binding-affinity adds additional functionality and assures high sensitivity and specificity to the WGM biosensor. The ultimate goal is to build microfluidic biosensors that are sensitive to a single viral particle and can differentiate virions according to their size/mass and affinity to specific antibodies. The small size of these bio-particles demands micrometer-size sensors3. However Brownian diffusion of ultra-low concentration analytes crossing the boundary layer is considered a major hurdle4 for miniature sensors. Preliminary results show that the WGM Carousel sensor can have significantly enhanced transport rates ( 50×) of particles to the sensing region, compared to other miniature sensors. In addition the carousel mechanism provides a means for investigating forces arising near the surface. Understanding these forces is of great importance for the design of microfluidic devices and micro-fabrication. Nanoparticles trapped in a WGM carousel can be used to quantitatively measure surface interactions from their stochastic radial motion. By proper choice of the interacting surfaces and the liquid medium it will be possible to screen the electrostatic repulsion and reveal short range interactions such as van der Waals. There are challenges for the DLVO (the theory of colloidal stability) to properly describe the interactions at very short range (5nm) for various aqueous solutions, where repulsive solvation forces are observed. WGM Carousel will help address these challenges.