Abstract Objective: Flexible Electrocorticography (ECoG) electrode arrays that conform to the cortical surface and record surface field potentials from multiple brain regions provide unique insights into how computations occurring in distributed brain regions mediate behavior. Specialized microfabrication methods are required to produce flexible ECoG devices with high-density electrode arrays. However, these fabrication methods are challenging for scientists without access to cleanroom fabrication equipment. Results: Here we present a fully desktop fabricated flexible graphene ECoG array. First, we synthesized a stable, conductive ink via liquid exfoliation of Graphene in Cyrene. Next, we established a stencil-printing process for patterning the graphene ink via laser-cut stencils on flexible polyimide substrates. Benchtop tests indicate that the graphene electrodes have good conductivity of ∼1.1 × 10 3 S cm −1 , flexibility to maintain their electrical connection under static bending, and electrochemical stability in a 15 d accelerated corrosion test. Chronically implanted graphene ECoG devices remain fully functional for up to 180 d, with average in vivo impedances of 24.72 ± 95.23 kΩ at 1 kHz. The ECoG device can measure spontaneous surface field potentials from mice under awake and anesthetized states and sensory stimulus-evoked responses. Significance: The stencil-printing fabrication process can be used to create Graphene ECoG devices with customized electrode layouts within 24 h using commonly available laboratory equipment.
more »
« less
On-Wafer Graphene Devices for THz Applications Using a High-Yield Fabrication Process
We characterize a novel fabrication procedure for the implementation of large arrays of subwavelength graphene devices. With the proposed process, we can now integrate graphene layers on large substrate areas (> 4 cm2) and implement thousands of devices with high-yield (> 90 %). Examples of such systems include broadband THz phased arrays and metasurfaces that can be used in THz imaging and sensing. Current nano-fabrication processes hinder the proliferation of large arrays due to the fragile nature of graphene. Conversely, we use titanium sacrificial layers to protect the delicate graphene throughout the fabrication process. Thus, we minimize graphene delamination and enable multiple devices on large-area substrates with high-yield. In addition, we present a series of on-wafer measurement results in the 220-330 GHz band, verifying the robustness of our fabrication process.
more »
« less
- Award ID(s):
- 1847138
- NSF-PAR ID:
- 10135990
- Date Published:
- Journal Name:
- 2019 IEEE MTT-S International Microwave Symposium (IMS)
- Page Range / eLocation ID:
- 1107 to 1110
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
We present a novel fabrication technique for large-scale, on-wafer graphene devices. With the proposed technique, large-area graphene apertures can be fabricated, enabling the proliferation of graphene-based reconfigurable devices, including metasurfaces. Such topologies require large-area high yield fabrication processes. To avoid graphene delamination during the chemical processes of the fabrication, we use a titanium sacrificial layer to protect the graphene monolayer. To evaluate the fabrication method, we present broadband in-plane graphene measurements in the 220-330 GHz band for the first time and compare the measured resistance sheet with previous works.more » « less
-
more » « less
Abstract The proliferation of van der Waals (vdW) heterostructures formed by stacking layered materials can accelerate scientific and technological advances. Here, we report a strategy for constructing vdW heterostructures through the interface engineering of the exfoliation substrate using a sub-5 nm polymeric film. Our construction method has two main features that distinguish it from existing techniques. First is the consistency of its exfoliation process in increasing the yield and in producing large (>10,000 μm2) monolayer graphene. Second is the applicability of its layer transfer process to different layered materials without requiring a specialized stamp—a feature useful for generalizing the assembly process. We demonstrate vdW graphene devices with peak carrier mobility of 200,000 and 800,000 cm2V−1s−1at room temperature and 9 K, respectively. The simplicity of our construction method and its versatility to different layered materials may open doors for automating the fabrication process of vdW heterostructures.
-
more » « less
Abstract The advancement of nanoenabled wafer‐based devices requires the establishment of core competencies related to the deterministic positioning of nanometric building blocks over large areas. Within this realm, plasmonic single‐crystal gold nanotriangles represent one of the most attractive nanoscale components but where the formation of addressable arrays at scale has heretofore proven impracticable. Herein, a benchtop process is presented for the formation of large‐area periodic arrays of gold nanotriangles. The devised growth pathway sees the formation of an array of defect‐laden seeds using lithographic and vapor‐phase assembly processes followed by their placement in a growth solution promoting planar growth and threefold symmetric side‐faceting. The nanotriangles formed in this high‐yield synthesis distinguish themselves in that they are epitaxially aligned with the underlying substrate, grown to thicknesses that are not readily obtainable in colloidal syntheses, and present atomically flat pristine surfaces exhibiting gold atoms with a close‐packed structure. As such, they express crisp and unambiguous plasmonic modes and form photoactive surfaces with highly tunable and readily modeled plasmon resonances. The devised methods, hence, advance the integration of single‐crystal gold nanotriangles into device platforms and provide an overall fabrication strategy that is adaptable to other nanomaterials.
-
more » « less
Abstract Terahertz waves spanning over the 0.1 to 10 THz region of the electromagnetic spectrum have attracted significant attention owing to a variety of potential applications such as short‐range high‐speed data transmission, noninvasive screening and detection, materials characterization, spectroscopy, etc. This has resulted in massive strides in the development of essential system components such as broadband terahertz sources, detector arrays with high responsivity, as well as modulators. In parallel to this, spurred by the isolation of graphene in 2004, a tremendous interest in 2D systems has led to the rapid exploration and development of a library of atomically thin materials. These can exhibit a myriad of electrical and optical functionalities stemming from semiconducting, insulating, semi‐metallic, or superconducting behavior. In this context, since the early 2010s, 2D materials have been actively explored for active control of terahertz electromagnetic radiation. This paper aims to provide a concise overview of the pioneering efforts as well as the latest progress in these two overlapping research areas. In particular, the discussion is focused on the application of graphene and transition metal dichalcogenides in optically and electrically actuated terahertz amplitude and phase modulators. Furthermore, it provides an outlook on the technological prospects and challenges in these devices.
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/MWSYM.2019.8701093
