Ultrahigh Sensitivity Parametric Sensing with Nanotube

由于光刻工艺的局限性，通过微机械加工制造纳米级结构非常困难，并且通常由于蚀刻和氧化过程而在纳米结构上引入大量的表面损伤。这种损伤的影响在纳米级结构中更为突出，因为表面体积比与r成反比，例如，对于半径为r的棒。这成为将这种制造的纳米结构用于超高频率和超高质量因数谐振器应用的限制因素。在机械共振系统中，表面损伤是能量耗散的散射中心，从而起到阻尼的作用。此外，即使对于最先进的光刻设备，制造直径约为数十纳米的均匀悬浮梁结构仍然是一项具有挑战性的任务。新型纳米结构，如氮化硼和碳纳米管，由于其优异的力学、电学和结构性能，在传感、材料增强、真空微电子和微纳机电系统（MEMS/ NEMS）等领域具有广泛的应用前景。这种纳米结构的极小物理尺寸意味着理论上对外部扰动具有很高的灵敏度，因此有利于飞克质量测量、生物分子和气体传感。我们打算将这种纳米结构与MEMS结合，并探索独特的谐振原理，以实现超高频和超高灵敏度的传感。本课题的研究目标是研究独特纳米材料的共振传感行为，并将研究发现应用于超高灵敏度传感器的开发。该研究基于先进的研究能力、原位自由空间纳米操作和电子显微镜表征，允许在纳米尺度上对多功能材料进行有效和灵活的研究和器件原型设计；研究的基础是基于参数共振原理，其共振行为具有不稳定性，可用于放大极小的扰动。总体而言，本研究旨在通过纳米操作在扫描电镜和透射电镜下实现和表征单个纳米管的参数共振；研制了集成激励和传感机构的参数谐振传感器样机，并开发了纳米管参数谐振传感器的微加工装置。该研究将有助于解决纳米材料在高灵敏度共振传感中应用所面临的纳米尺度机电响应的电子传感和NEMS中纳米材料的器件集成等长期存在的实验难题。拟议研究的更广泛影响：拟议研究吸收了先进研究能力发展和新型纳米材料研究的前沿成果，通过应用先进的物理，力学，电子和微加工技术实现独特的NEMS设备。该研究旨在推动机械共振研究的当前状态，以实现极高的灵敏度传感。该研究将机电传感的应用扩展到一个新的水平和新的维度，并最终导致用于单分子水平质量传感和单电荷机电传感的纳米级传感器的发展。本研究中开发的方法和技术可广泛应用于许多涉及纳米级传感和表征的其他研究。与这一创新和多学科研究项目紧密结合的是一项教育倡议，它将自然地将本科生引入科学研究，积极促进妇女和少数民族学生的参与，并有效地吸引和传播科学知识给公众。

Owing to the limitation associated with lithography based processes, fabrication of nanoscale structure by micromachining has been very difficult, and usually involves introducing large amount of surface damages onto the nanostructure due to the etching and oxidation processes. The effect of such damages is more prominent in the nanoscale structure as the surface to volume ratio is inversely proportional to r, for example, for a rod having a radius of r. This becomes the limiting factor in using such fabricated nanostructures for ultrahigh frequency and ultrahigh quality factor resonator applications. Surface damages serve as scattering centers for energy dissipation, thus the damping, in mechanical resonance system. In addition, the fabrication of uniform, suspended beam structure having a diameter around tens of nanometer is still a challenging task even for most advanced lithography facilities. Novel nanostructures, such as BN and C nanotubes, have attracted great attention recently due to their excellent mechanical, electrical and structural properties, which promises their applications in sensing, materials reinforcement, vacuum microelectronics, and micro- or nano- electromechanical systems (MEMS/ NEMS). The extremely small physical dimensions of such nanostructures imply theoretically high sensitivity to external perturbation, which is thus advantageous for femto-gram mass measurement, and bio-molecule and gas sensing. We intend to integrate such nanostructures with MEMS and to explore unique resonance principles to achieve ultrahigh frequency and ultrahigh sensitivity sensing. The intellectual merits of the proposed research: The research objective of the proposed research is to study the resonance sensing behavior of unique nanomaterials and apply the discovery for the development of ultrahigh sensitivity sensor. The research implementation is based on the advanced research capability, the in situ free space nanomanipulation and characterization with electron microscopy, which allows the effective and flexible investigation and device-prototyping of multifunctional materials at the nanoscale; and the research fundamental is based on the principle of parametric resonance, which exhibits instability in its resonance behavior that will be utilized for amplifying extremely small perturbation. Overall, the research aims to realize and characterize the parametric resonance of individual nanotubes with nanomanipulation inside scanning electron microscope and transmission electron microscope; to prototype parametric resonance sensor integrated with excitation and sensing mechanisms, and to develop device with microfabrication of parametric resonance sensor incorporating nanotubes. The study will help to resolve the long standing experimental challenges, such as electronic sensing of electromechanical response at the nanoscale and device integration of nanomaterials for NEMS, facing the application of nanomaterials for high sensitivity resonance sensing. The broader impact of the proposed research: The proposed study assimilates the forefront results in the development of advanced research capabilities and the study of novel nanomaterials to realize unique NEMS devices by applying advanced physics, mechanics, electronics and micromachining technology. The study aims to advance the current state of the art in mechanical resonance research to achieve extremely high sensitivity sensing. The research will extend the application of electromechanical sensing to a new level and to a new dimension never explored before, and will ultimately lead to the development of nanoscale sensor useful for single molecule level mass sensing and single charge electromechanical sensing. The methods and technologies developed in this study are broadly translatable to many other studies involving sensing and characterization at the nanoscale. Strongly coupled with this innovative and multidisciplinary research program is an educational initiative that will naturally introduce undergraduate students into scientific research, proactively promote the participation of woman and minority students, and effectively engage and disseminate scientific knowledge to the general public.