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

项目摘要合作研究：IDBR：生物样品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的仪器，以促进在太赫兹频率的最小探索但信息丰富的电磁频谱中对生物样品进行高灵敏度的高光谱成像。由于分子间振动、转动和扭转模式的存在，这种光谱具有广泛的光谱可能性，为生物分子鉴定提供了明显的宽带分子指纹和内在对比度。然而，现有的太赫兹成像方法由于(1)太赫兹辐射在生物样品内外缺乏有效的耦合，(2)由于样品/光谱仪界面处的不想要的散射而导致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，因此具有有限的灵敏度。针对这些问题，该仪器引入了两种新兴技术--(1)超材料(MMS)和(2)GaAsPHEMT器件的等离子体波操作。超材料是一种含有亚波长金属夹杂物的人造结构，可以设计成表现出奇特的电磁响应，如负介电常数和磁导率、负折射率和理想的吸收或透过率。GaAsPHEMT器件的等离子体波工作有助于太赫兹辐射的共振检测，具有无与伦比的灵敏度。智力优势：拟议的计划将导致开发超材料增强反射(或透射率)成像太赫兹(MERIT/METIT)光谱仪，作为细胞和组织太赫兹成像的超灵敏平台。这些光谱仪将为超快速构象蛋白质动力学(蛋白质折叠)和其他生物分子过程提供新的线索，这些生物分子过程与许多人类疾病的发病机制有关，主要是癌症。该光谱仪的关键技术创新是：(1)实现了完全阻抗匹配的光谱共轭层，以消除杂散反射和抑制水吸收的影响；(2)利用GaAsPHEMT器件实现了基于共振等离子体波检测太赫兹辐射的高速(106帧/秒)大型2D太赫兹焦平面阵列(TFPA)。多个机构(波士顿学院和塔夫茨大学)的专业人员之间的跨学科合作，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方面的实践知识方面取得了成就，表明了开展成功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也具有潜力。PI计划通过生物学家经常访问的印刷和在线杂志上的文章来接触生物界。该仪器将向波士顿地区的研究人员提供，用于评估目的。仪器开发项目将在波士顿学院和塔夫茨大学建立一个超材料和太赫兹成像设备领域的研究和教学实验室。它将培训未来一代理工科专业的实验技术，如极宽带频域光谱、超材料制造、GaAsIII-V技术以及计算机模拟技术。PIs通过参与(1)暑期学者和Bend本科研究计划，以及(2)McNair奖学金计划，这是一个为代表性不足群体的学生提供的研究生院准备计划，坚定地致力于本科生研究。通过正在进行的学生教师外展导师计划(STOMP)，可以开展针对K©12外展的活动。PI计划通过在当地高中的讲座和开发基于网络的教程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.