EAGER: Two-Dimensional Material-Based Epidermal Active Sensors for Brain Monitoring.

脑电(EEG)测量由大脑神经元内离子电流流动引起的沿头皮的微妙电压波动。脑电作为一种低成本、便携和非侵入性的手段被广泛使用，不仅可以捕捉认知和记忆表现，还可以捕捉癫痫和中风等大脑疾病。传统的脑电记录是通过在皮肤磨损后用导电凝胶在头皮上放置单独的厚而硬的电极来获得的，这加强了电极与皮肤的接触。几十年来，脑电技术一直存在空间分辨率低、信噪比低、没有适当的信号放大、电极连接费时且受阻、凝胶干燥测量时间短等局限性。这样的限制部分是由于柔软、曲线和可变形的人体皮肤与硬、平面和刚性电极和电子设备之间的不兼容性。原子厚度二维材料的超薄、高电子性能和透明性在神经电子学中提供了明显的机械、电子和光学优势。这项研究提出用二维材料制成的纹身状超薄、超柔软、干燥的电极和信号放大器来取代传统的刚性脑电电极的想法。初步结果表明这一想法是可行的，进一步的研究将证明纹身般的、持久的、高性能的神经电子学造福社会的可行性和未来前景。此外，从事这项研究的研究生和博士后研究人员将获得成为工业、学术界或政府研究生职业技术领袖所需的高级科学和工程技能。此外，还将招募不同背景的本科生参与这项促进高等科学和工程事业的研究。这项建议的目标是开展一项可行性研究，将石墨烯和原子稀薄的二硫化钼等二维材料用作非侵入性、长期、高保真的脑电传感的电极和放大器材料。基于二维材料的表皮活性脑电传感器的主要技术障碍在于器件设计、异质制造和可靠的生物集成，最终目标是增强脑电传感。提出了一种新颖的有源电极结构，该结构采用石墨烯作为传感电极和栅极，将二硫化钼与超薄聚合物介质和石墨烯源漏集成在一起作为现场信号放大器。为了完成可行性研究，提出了两个研究方向：i)制备和验证基于石墨烯的无源表皮脑电电极；ii)在石墨烯电极上垂直集成二硫化钼与超薄聚合物介质和石墨烯源漏作为晶体管放大器用于有源脑电记录。预期的结果是对集成神经电子学的可行性做出肯定的决定，这种集成神经电子学可以在没有导电凝胶的情况下共形叠层在人体皮肤上，但仍然能够记录长期、高保真的脑电，并具有数量级的信号放大。对于数百的目标增益，有源电极使外部噪声最小化，并允许大幅减少电极阵列。

Electroencephalographic (EEG) measures subtle voltage fluctuations along the scalp resulting from ionic current flows within the neurons of the brain. EEG is widely used as a low cost, portable, and noninvasive means to capture not only cognitive and memory performance, but also brain disorders like epilepsy and stroke. Conventional EEG recording is obtained by placing individual thick and stiff electrodes on the scalp with conductive gel after skin abrasion which enhances electrode-skin contact. For many decades, EEG technology has suffered from limitations such as low spatial resolution, poor signal-to-noise ratio without proper signal amplification, time consuming and obstructive electrode connections, and short measurement time as gel dries out. Such limitations are partially due to the incompatibility between the soft, curvilinear, and deformable human skin and the hard, planar, and rigid electrodes and electronics. The ultrathin, high electronic performance, and transparency of atomically thick two-dimensional materials offer clear mechanical, electronic, and optical advantages over silicon in the neuroelectronics. This research proposes to explore the idea of replacing conventional rigid EEG electrodes by tattoo-like ultrathin, ultrasoft, dry electrodes and signal amplifiers fabricated from two-dimensional materials. Preliminary results indicate this idea is feasible and further research will prove the feasibility and future prospects for tattoo-like, long lasting, and high performance neuroelectronics to benefit society. In addition, the graduate student and post-doctoral researchers working on this research effort will gain advanced scientific and engineering skills needed to be technical leaders in industry, academia or government post-graduate careers. Moreover, undergraduate students from diverse backgrounds will be recruited to participate in the research effort to promote advanced science and engineering careers.The objective of this proposal is to carry out a feasibility study that two-dimensional materials such as graphene and atomically thin molybdenum disulfide can be applied as the electrode and amplifier materials for noninvasive, long-term, high fidelity Electroencephalographic sensing. The major technical barrier towards two-dimensional materials based epidermal active EEG sensor lies in the device design, heterogeneous fabrication, and reliable bio-integration with the final goal of enhanced EEG sensing. An innovative active electrode architecture is proposed in which graphene is employed as both the sensing and gate electrodes, and molybdenum disulfide integrated with ultrathin polymer dielectrics and graphene source/drain as the on-site signal amplifier. Two research thrusts are proposed to accomplish the feasibility study: i) fabricating and validating graphene based passive epidermal EEG electrodes, and ii) integrating molybdenum disulfide vertically on top of the graphene electrode with ultrathin polymer dielectrics and graphene source/drain as a transistor amplifier for active EEG recording. The expected outcome is an affirmative decision on the feasibility of an integrated neuroelectronics that can be conformally laminated on human skin without conductive gel but still able to record long term, high fidelity EEG with orders of magnitude signal amplification. For the targeted gain of several hundreds the active electrode minimizes both the extrinsic noise and allows substantial reduction of the electrode arrays.