2D-Material Heterostructure NEMS Sensors

微型和纳米机电系统(NEMS)传感器，如压力传感器、加速计和陀螺仪，对于各种应用都很重要，包括用于活动水平监测的可穿戴电子设备、患者恢复监测、用于心力衰竭监测的植入式系统和物联网(IoT)。对于大多数这样的应用，NEMS传感器进一步小型化是至关重要的。这是由于应用程序的要求，超出了降低每台设备成本的明显优势。最近，我们的团队展示了悬浮石墨烯薄膜作为超小型压阻式NEMS传感器的优秀机电换能器元件。然而，石墨烯NEMS传感器的压阻率相对较低，导致典型的测量系数仅为2-4。与石墨烯和六方氮化硼(h-BN)相比，具有较高规范因子的2D材料(如二硫化钼(MoS2))的稳定性较差。为了解决这些限制，我们将探索由堆叠的二维(2D)材料制成的新型异质结构，目的是探索新型NEMS换能器的基本物理原理，其规范系数至少比现有的NEMS换能器高10倍。为了实现这一目标，我们将探索2D材料的悬浮异质结构，包括石墨烯、h-BN、MoS_2和其他2D过渡金属二卤化物(例如WS_2、MoSe_2、WSe_2)。我们还将利用我们团队最近开发的基于粘结剂晶片粘合技术的2D材料堆叠的新方法。为了评估新型异质结作为压阻式换能器的实用性，我们将开发三种NEMS演示器：(1)基于2D材料异质结的应变片，用于执行与应变相关的输运测量；(2)基于悬置2D材料异质结薄膜的压阻式NEMS压力传感器；(3)基于悬置2D材料异质结带的压阻式NEMS加速度计。如果成功，这项工作将有助于更好地理解二维材料异质结构中的材料性质和转换机制。这将为大幅缩小尺寸和提高性能的新型NEMS传感器铺平道路。这类传感器将有广泛的潜在应用，跨越几个重要的科技领域，包括生物医学植入物、纳米机器人、可穿戴电子设备和材料表征。

Micro and nanoelectromechanical system (NEMS) sensors such as pressure sensors, accelerometers and gyroscopes are important for a variety of applications, including wearable electronics for activity level monitoring, patient recovery monitoring, implantable systems for heart failure monitoring, and the Internet of Things (IoT). For most of these applications, it is of critical importance that the NEMS sensors are further miniaturized. This is due to application requirements and goes beyond the obvious advantage of reduced cost per device. Recently our teams have demonstrated suspended graphene membranes as excellent electromechanical transducer elements for ultra-miniaturized piezoresistive NEMS sensors. However, graphene NEMS sensors suffer from the comparably low piezoresistivity of graphene, which leads to typical gauge factors of only 2-4. 2D materials with higher gauge factors, such as molybdenum disulfide (MoS2) suffer from less stability compared to graphene and hexagonal boron nitride (h-BN). To address these limitations, we will explore novel heterostructures made of stacked two-dimensional (2D) materials, with the aim to explore the underlying physics of novel NEMS transducers with gauge factors that are at least a factor of ten higher than those of existing NEMS transducers. To achieve this goal, we will explore suspended heterostructures of 2D materials, including graphene, h-BN, MoS2, and other 2D transition metal dichalcogenides (e.g. WS2, MoSe2, WSe2). We will also leverage a new method for 2D material stacking based on an adhesive wafer bonding technique, recently developed by our teams. To evaluate the utility of the novel heterostructures as piezoresistive transducers, we will develop three NEMS demonstrators: (1) Strain gauges based on 2D material heterostructures to perform strain-dependent transport measurements; (2) piezoresistive NEMS pressure sensors based on suspended 2D material heterostructure membranes; (3) piezoresistive NEMS accelerometers based on suspended 2D material heterostructure ribbons with attached proof masses. If successful, this work will contribute to an improved understanding of the material properties and the transduction mechanisms in 2D material heterostructures. This will pave the way for novel NEMS sensors with dramatically reduced size and improved performance. Such sensors will have wide-ranging potential applications, spanning several important scientific and technological areas, including biomedical implants, nanoscale robotics, wearable electronics and material characterization.