Research Summary

Although today’s technologies have produced significant achievements using the miniaturized electronic devices, future revolutions in sensing, energy, and even information technology will require hybrid machines that integrate small biological, electronic, optical, and mechanical components. The current conventional lithographical fabrication techniques can build such functional devices on a two-dimensional (2D) planar wafer for a variety of industrial and consumer product applications. However, the size of current multifunctional devices/machines is typically at micron scale, which is significantly larger than the atoms and molecules that make up matter. This size makes it difficult to observe new physical characteristics and phenomena like quantum and plasmonic behaviors. On the other hand, for biomedical applications and building a seamless human-machine interface, multi-dimensional (0D, 1D, 2D, and 3D) architectures can precisely manipulate matters and enhance interaction with molecular and cellular structures for critical insights when compared to solely 2D planar configurations. Therefore, my approach to create a better interaction between artificial functional systems and matters in nature is to develop advanced manufacturing techniques for building hybrid and hyper-dimensional nanomachines. Such system would significantly advance the capability to control matters and communicate with organic and inorganic systems in nature, promising radical applications in sensing, energy, and information technology. I am particularly interested in using Origami/Kirigami technqiue, an ancient oriental art, to fabricate intricate architectures through morphology and topology evolution. Novel optical, electrical, and mechanical properties that cannot be achieved in planar structures and devices could arise from such unique structures, which would significantly extend the boundary of science and engineering.

Area 1: Kirigami Engineering of Graphene Mechanical Transducer

Nanoscale electro/optomechanical systems are emerging platforms for realizing next generation technologies such as advanced sensors, nanorobotics, and reconfigurable quantum states. Due to their unparalleled mechanical strength and stability, sp2-bonded materials including graphene and hexagonal boron nitride (hBN) represent the ultimate limit in size of both mechanical atomic membranes and molecular electronics. Understanding and tailoring the mechanical properties of the nanomaterials is crucial for exploring interesting properties of 2D materials and developing applications with new functionalities. I developed a strategy to tune the resonant frequency of a graphene optomechanical resonator by utilizing kirigami patterns. These kirigami patterns allows precise tune of the device's in-plane stress and further its vibrational mode. As a result, the resonators' behavior could be programmed for various applications.

Publication:

  1. C. Dai, Y. Rho, B. McCormick, K. Pham, W. Zhao, F. Wang, M. Crommie, C. P. Grigoropoulos, and A. Zettl, “Kirigami Engineering of Graphene Mechanical Transducer,” Nano Letters, 22, 5301-5206, 2022. Link

Area 2: Origami Engineering of 3D Functional Nanostructures

Project 2.1: In Situ Monitored Origami-Like Nanoscale Self-Assembly

3D nanostructures are promising platforms for developing next generation nanodevices and further exploring novel phenomena. Nanoscale self-assembly, as a technique to transform two-dimensional (2D) planar patterns into three-dimensional (3D) nanoscale architectures, has achieved tremendous success in the past decade. However, an assembly process at nanoscale is easily affected by small unavoidable variations in sample conditions and reaction environment, resulting in a low yield. In order to overcome this issue, I have developed in-situ monitored self-assembly processes using ion and electron beams that achieve stress generation and real-time observation simultaneously, which significantly enhances the controllability of self-assembly. This enables the realization of intricate 3D nanostructures with sub-10 nanometer precision and a high yield of nearly 100%.

Publication:

  1. C. Dai, J. H. Cho, “Electron beam maneuvering of a single polymer layer for reversible 3D self-assembly,” Nano Letters, 21, 2066–2073, 2021. Link

  2. C. Dai, L. Li, D. Wratkowski, J. H. Cho, “Electron Irradiation Driven Nanohands for Sequential Origami,” Nano Letters, 20, 4975-4984, 2020. Link

  3. C. Dai, K. Agarwal, J. H. Cho, “Ion-Induced Localized Nanoscale Polymer Reflow for Three-Dimensional Self-Assembly,” ACS Nano, 12, 10251-10261, 2018. Link

  4. D. Joung, D. Wratkowski, C. Dai, S. Lee, and J. H. Cho, “Fabrication of Three-Dimensional Graphene-Based Polyhedrons via Origami-Like Self-Folding,” Journal of Visualized Experiment (JoVE), 139, e58500, 2018. Link

  5. C. Dai and J. H. Cho, “In situ Monitored Self-Assembly of Three-Dimensional Polyhedral Nanostructures,” Nano Letters, 16, 3655-3660, 2016. Link

Project 2.2: 3D Graphene Plasmonics

The limited spatial coverage of the plasmon enhanced near-field in 2D graphene ribbons presents a major hurdle in practical applications. To overcome the limited coverage, we built diverse self-assembled 3D graphene architectures and explored their hybridized plasmon modes by simultaneous in-plane and out-of-plane coupling. While 2D graphene can only demonstrate in-plane, bidirectional coupling through the edges, 3D architectures benefit from fully symmetric 360° coupling at the apex of pyramidal graphene, orthogonal four-directional coupling in cubic graphene, and uniform cross-sectional radial coupling in tubular graphene. The 3D coupled vertices, edges, surfaces, and volume induce corresponding enhancement modes that are highly dependent on the shape and dimensions comprising the 3D geometries. The hybridized modes introduced through the 3D coupling amplify the limited plasmon response in 2D ribbons to deliver nondiffusion limited sensors, high efficiency fuel cells, and extreme propagation length optical interconnects.

Publication:

  1. C. Dai, K. Agarwal, H.A. Bechtel, C. Liu, D. Joung, A. Neilstuman, Q. Su, T. Low, S. Koester, and J.H. Cho, “Hybridized Radial and Edge Coupled 3D Plasmon Modes in Self-Assembled Graphene Nanocylinders,” Small, 17(14), 2100079. [Selected for the Inside Back Cover]. Link

  2. K. Agarwal, C. Dai, A. D. Joung, J.H. Cho, “Nano-Architecture Driven Plasmonic Field Enhancement in 3D Graphene Structures,” ACS Nano, 13, 1050-1059, 2019. Link

  3. D. Joung, A. Nemilentsau, K. Agarwal, C. Dai, C. Liu, Q. Su, J. Li, T. Low, S. J. Koester, J. H. Cho, “Self-Assembled Three-Dimensional Graphene Based Polyhedrons Inducing Volumetric Light Confinement,” Nano Letters, 17, 1987-1994, 2017. Link

Project 2.3: 3D Optofluidic Biosensor for Bodily Fluid Detection

Bodily fluids, such as blood, urine, and sweat, are often involved in various physiological activities, which are rich with information related to health status. A bodily fluid test is a common method for disease diagnosis. However, most of the current test techniques are highly time, labor, and cost intensive and therefore are not suitable for resource limited settings. To overcome these limitations, I developed a 3D plasmonic nanofluidic biosensor, which allows highly sensitive and selective, one-shot diagnosis of biomolecules, such as hemoglobin.


Publication:

  1. C. Dai, Z. Lin, K. Agarwal, C. Mikheal, A. Aich, K. Gupta, J. H. Cho, “Self-Assembled 3D Nano-Split Rings for Plasmon-Enhanced Optofluidic Sensing,” Nano Letters, 20, 6697-6705, 2020. Link


Area 3: Atomic Engineering of Solid State Nanopore Sensor for DNA Storage

Coming Soon!!!