Collaborative Research: IDBR: Metamaterial Enhanced Spectrometer for Terahertz Hyperspectral Imaging of Biological Specimens

项目概述合作研究：IDBR：用于生物标本高光谱太赫兹成像的超材料增强型光谱仪拟议研究的目标是开发新型仪器，以促进生物标本的高灵敏度高光谱成像，在很少探索但信息丰富的太赫兹频率电磁频谱。由于分子间振动、旋转和扭转模式的存在，该光谱具有广泛的光谱可能性，为生物分子识别提供了独特的宽带分子指纹和内在对比。然而，现有的太赫兹成像方法的灵敏度有限，因为(1)缺乏进出生物样品的太赫兹辐射的有效耦合，(2)由于样品/光谱仪界面上不必要的散射而导致的更高水平的信号损失，以及(3)在太赫兹频率范围内缺乏有效的探测器，从而限制了它们的性能。此外，探测器通常是单像素探测器，需要扫描才能获得二维图像，并且它们无法捕捉生物分子动力学的时空演变。为了解决这些问题，该仪器引入了两项新兴技术：(1)超材料（mm）和(2)GaAs pHEMT器件的等离子体波操作。超材料是具有亚波长金属夹杂物的人工结构，可以设计成具有奇异的电磁响应，如负介电常数和磁导率、负折射率和理想的吸收或透射率。GaAs pHEMT装置的等离子体波操作使太赫兹辐射的共振检测具有无与伦比的灵敏度。智力优势：该计划将导致超材料增强反射（或透射）成像太赫兹光谱仪（Merit /METIT）的发展，作为细胞和组织太赫兹成像的超灵敏平台。这些光谱仪将揭示超高速构象蛋白动力学（蛋白质折叠）和其他与许多人类疾病发病机制有关的生物分子过程，主要是癌症。该光谱仪的关键技术创新是：(1)实现了完美的阻抗匹配光谱共轭层，消除了杂散反射，减轻了水分吸收的影响；(2)利用GaAs pHEMT器件实现了高速（106帧/秒）、基于共振等离子体波探测太赫兹辐射的大型二维太赫兹焦平面阵列（TFPA）。多个机构（波士顿学院和塔夫茨大学）的pi之间的跨学科合作，在超材料理论，模拟和实验，HEMT晶体管器件建模和制造以及成像实践知识方面取得了成就，证明了成功开展研究和教育计划的潜力。更广泛的影响：除了为基础研究提供丰富的生物细胞和组织的光谱图像外，该仪器在医学诊断和药物发现方面具有潜力。pi计划通过生物学家经常光顾的印刷文章和在线杂志来接触生物学界。该仪器将提供给波士顿地区的研究人员进行评估。该仪器开发项目将在波士顿学院和塔夫茨大学建立一个研究和教学实验室，研究超材料和太赫兹成像设备。它将培养未来一代的科学和工程专业的实验技术，如极宽带频域光谱、超材料制造、砷化镓III-V技术以及计算机模拟技术。通过参与(1)夏季学者和本科研究项目（BEND），以及(2)麦克奈尔奖学金项目（McNair scholarship program，一个面向弱势群体学生的研究生院准备项目），pi对本科生研究有着坚定的承诺。通过正在进行的学生教师外展导师计划（STOMP），旨在K©\12外展的活动成为可能。pi计划通过在当地高中©\学校的讲座和网络教程的开发来分享他们的研究和发现的兴奋。

Project SummaryCollaborative Research: IDBR: Metamaterial Enhanced Spectrometer for Hyperspectral Terahertz Imaging of Biological Specimens The objective of the proposed research is the development of novel instrumentation to facilitate highly sensitive, hyperspectral imaging of biological specimens, in the minimally explored yet information-rich electromagnetic spectrum of terahertz frequencies. This spectrum is broad in spectroscopic possibilities due to presence of the intermolecular vibrational, rotational and torsional modes, providing a distinct broadband molecular fingerprint and intrinsic contrast for biomolecular identification. However existing terahertz imaging approaches have limited sensitivity due to (1) Lack of efficient coupling of terahertz radiation in and out of the biological sample, (2) Higher level of signal loss due to unwanted scattering at sample/spectrometer interface, and (3) Lack of efficient detectors in the terahertz frequency range, thus limiting their performance. Moreover the detectors are typically single pixel detectors that require scanning to obtain a 2D image and they fail to capture the spatiotemporal evolution of biomolecular dynamics.To solve these issues, the proposed instrument brings two emergent technologies ¨C (1) Metamaterials (MMs) and (2) Plasma wave operation of GaAs pHEMT device. Metamaterials are artificial structures with subwavelength metallic inclusions that can be designed to exhibit exotic electromagnetic response such as negative permittivity and permeability, negative index, and ideal absorption or transmittance. Plasma wave operation of GaAs pHEMT device facilitates resonant detection of terahertz radiation with unparalleled sensitivity. Intellectual Merit: The proposed program will result in the development of a Metamaterial Enhanced Reflectance (or Transmittance) Imaging Terahertz (MERIT/METIT) spectrometer as an ultrasensitive platform for terahertz imaging of cells and tissues. These spectrometers will shed new light on ultra-fast conformational protein dynamics (protein folding) and other biomolecular processes responsible for pathogenesis in many human diseases, primarily cancer. Key technical innovations of the proposed spectrometer are (1) Realization of perfect impedance matched spectral conjugate layers to eliminate spurious reflections and to mitigate effects of water absorption, and (2) Realization of a high speed (106 frames/sec), large 2D terahertz focal plane array (TFPA) based on resonant plasma wave detection of terahertz radiation by a GaAs pHEMT device. An interdisciplinary collaboration between PIs at multiple institutions (Boston College and Tufts University) with records of achievement in metamaterials theory, simulation and experiment, HEMT transistor device modeling and fabrication, and practical knowledge in imaging, evince the potential for carrying out a successful research and educational program. Broader Impact: Beyond providing rich spectroscopic images of biological cells and tissues for fundamental studies, the instrument has potential in medical diagnostics and drug discovery. The PIs plan to reach out to the biology community through articles in print and online magazines frequented by biologists. The instrument will be made accessible to Boston area researchers for evaluation purposes. The instrument development project will establish a research and teaching laboratory at Boston College and Tufts University in the area of metamaterials and THz imaging devices. It will train the future generation of science and engineering majors in experimental techniques, such as extremely broadband frequency domain spectroscopy, fabrication of metamaterials, GaAs III-V technology as well as computer simulation techniques. The PIs have a strong commitment to undergraduate research through involvement in (1) summer scholars and BEND program for undergraduate research, and (2) the McNair scholarship program, a graduate school preparation program for students from underrepresented groups. Activities aimed at K©\12 outreach is made possible through the ongoing Student Teacher Outreach Mentor Program (STOMP). The PIs plan to share the excitement of their research and discovery through lectures at local high©\schools and development of web-based tutorials.