An Ultrasensitive Microfluidic Biosensor Based on Vertically-Aligned MoS2 Nanolayers

利用高灵敏度二维（2D）纳米材料的下一代生物传感器可以提供卓越的分析性能，从而为分子诊断、环境监测和食品安全检查等领域的各种应用提供快速、超灵敏的测试。原子薄单层二硫化钼（MoS2）作为一种新兴的类石墨烯二维纳米材料，引起了生物传感器界的广泛关注。尽管最近在开发高性能单层MoS2生物传感器方面取得了进展，但先前报道的设备存在制造成本率低、生物功能化具有挑战性和可重复性低的问题；这些问题很大程度上是由于单层二硫化钼的一些固有性质和制备工艺不利于生物传感器的发展。在这个项目中，我们首次提出将一种新型的二硫化钼纳米结构——垂直排列的二硫化钼纳米层（VAMNs）集成到微流控场效应晶体管（FET）生物传感器中。由于其独特的纳米结构，VAMNs具有以前的MoS2生物传感器所不具备的一些新特征，包括在其垂直排列的活性边缘位置上方便可靠的共价固定生物分子，以及批量微加工的良好计算能力。同时，所提出的fet生物传感器还保留了单层MoS2的直接带隙、对表面分子结合的超高灵敏度和快速响应等物理特性；因此，它可以提供显著增强的生物传感性能，包括超高灵敏度和高稳定性/重复性。我们的生物传感器的微流体设计也允许简单的设备操作，多路分析和低样品消耗。作为第一个演示，我们将应用我们的fet生物传感器快速、超灵敏地检测脑损伤蛋白标志物，以持续监测心脏手术期间患者的大脑状况。这项研究将提供一个强大的基于vamn的生物传感平台，可以找到许多需要超高灵敏度和极短阵列时间的重要应用。

Next-generation biosensors that exploit highly-sensitive, two-dimensional (2D) nanomaterials could provide superior analytical performance and thus enable rapid, ultrasensitive tests for a variety of applications in areas such as molecular diagnosis, environmental monitoring, and food safety inspection. Atomically-thin monolayer molybdenum disulfide (MoS2), as an emerging graphene-like 2D nanomaterial, has attracted significant attention from the biosensor community. Despite the recent advancement in developing high-performance monolayer MoS2 biosensors, previously reported devices suffer from low fabrication yield, challenging biofunctionalization, and low reproducibility; these issues can be largely attributed to some inherent property and preparation process of monolayer MoS2 that are not favorable in biosensor development. In this project, we propose, for the first time, to integrate a novel form of MoS2 nanostructure, vertically-aligned MoS2 nanolayers (VAMNs), into microfluidic field-effect-transistor (FET) biosensors. Because of its unique nanostructures, the VAMNs enable a few new features that do not exist in previous MoS2 biosensors, including facile and reliable covalent immobilization of biomolecules on its vertically-aligned, populated active edge sites and good computability with batch microfabrication. In the meanwhile, the proposed FET-biosensor will also retain the advantageous physical properties of monolayer MoS2 such as its direct bandgap, ultrahigh sensitivity to surface molecule binding, and fast response; therefore, it could provide significantly-enhanced biosensing performance including ultrahigh sensitivity and high stability/reproducibility. The microfluidic design of our biosensor also allows easy device operation, multiplexed assay, and low sample consumption. As the first demonstration, we will apply our FET-biosensor to rapid, ultrasensitive detection of brain injury protein markers for constant monitoring of patient brain conditions during cardiac surgery. This research will offer a powerful VAMN-based biosensing platform, which could find many important applications where ultrahigh sensitivity and very short array time are desired.