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

ArnoldVirus粒子是人类疾病的主要原因，随着航空旅行使这些传染病病原体迅速传播到全球各地的人群中，它们的早期检测和识别变得越来越重要。一种通过确定单个病毒颗粒的种类和大小来对其敏感的快速检测器将满足早期检测的需求。目前的建议是继续研究微球耳廊模式(WGM)生物传感器，以早期检测人体体液中的病毒，因为我们利用最近发现的WGM消逝体积内纳米颗粒的光捕获现象。这种传感是基于微球的极窄光子共振，这些微球的频率会因环境变化而发生变化。在WGM？S逝去场(~200 nm)的范围内，纳米粒子被梯度力吸引到表面，类似于光镊子中的情况。俘获势垒是由吸引的消逝极化势、排斥静电势和范德华势能形成的。在低结合亲和力或低结合部位密度的情况下，纳米颗粒在辐射压力的推动下在轨道上四处移动。这种捕获机制(WGM Carousel)与受控的结合亲和力一起增加了额外的功能，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，并可以根据病毒粒子的大小/质量和对特定抗体的亲和力来区分病毒粒子。这些生物颗粒的小尺寸需要微米级的传感器。然而，超低浓度分析物跨越边界层的布朗扩散被认为是微型传感器的一个主要障碍。初步结果表明，与其他微型传感器相比，WGM Carousel传感器可以显著提高颗粒到传感区域的传输率(50倍)。此外，旋转木马机制提供了一种调查在地表附近产生的力的方法。了解这些力对于微流控器件的设计和微细加工具有重要意义。捕获在WGM旋转木马中的纳米颗粒可以用来根据其随机的径向运动来定量测量表面相互作用。通过适当选择相互作用面和液体介质，可以屏蔽静电斥力，揭示短程相互作用，如范德华作用。对于DLVO(胶体稳定性理论)来说，要恰当地描述在很短的范围(5 Nm)内观察到排斥溶剂化力的各种水溶液的相互作用是很困难的。WGM Carousel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.