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PhD students Brian Blankenship and Timon Meier, have developed a non-destructive confocal microscopy technique to image internal defects in complex metamaterial structures with micro- and nanoscale architectures. Metamaterials often exhibit enhanced and unconventional properties compared to their bulk counterparts. By carefully incorporating defects into the microstructures of these materials, unique, and sometimes enhanced properties can be achieved. However, manufacturing defects can be problematic when their specific, uncontrolled incorporation is paramount to a material's functional properties. The team demonstrated the ability of confocal microscopy to non-destructively precisely locate and visualize a range of intentional incorporated defects inside of metamaterial lattices. This method not only enhances the existing array of diagnostic techniques but also opens the door for adapting and applying similar strategies during the fabrication process itself, enabling the in situ detection and characterization of defects. The work has been published in ACS Applied Engineering Materials, https://pubs.acs.org/doi/10.1021/acsaenm.4c00160
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Exciton dynamics plays a critical role in the functionality of two-dimensional (2D) materials and devices; however, the measurement of nanoscale excitonic behaviors remains challenging. Postdoctoral fellow Jingang Li and PhD student Rundi Yang reported a near-field transient nanoscopy to probe exciton dynamics beyond the diffraction limit. Exciton recombination and exciton-exciton annihilation processes in monolayer and bilayer MoS2 are studied as the proof-of-concept demonstration. Moreover, with the capability to access local sites, intriguing exciton dynamics near the monolayer-bilayer interface and at the MoS2 nano-wrinkles are resolved. Such nanoscale resolution highlights the potential for fundamental investigation of exciton physics and further optimization of functional devices. This work was published in Advanced Materials, https://doi.org/10.1002/adma.202311568
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Transition metal dichalcogenides (TMDCs) with high refractive index at the near-infrared wavelengths are predicted to have superior performances in photonic devices compared with conventional semiconductors. Postdoctoral fellow Jingang Li and PhD student Rundi Yang investigated the optical waveguiding properties of colloidal MoS2 nanowires by scattering-type scanning near-field optical microscopy (s-SNOM). The combined experiments and simulations showed highly tunable waveguide modes, which can be modulated by nanowire thickness, incident wavelength, and environmental temperature, highlighting the potential for active optical components and integrated photonic devices. This work was published in Advanced Functional Materials
https://onlinelibrary.wiley.com/doi/10.1002/adfm.202312127 |
PhD students Brian Blankenship and Timon Meier, along with undergraduate Naichen Zhao, have developed a technique to image internal deformations in polymeric metamaterials using confocal microscopy. Many metamaterials are composed of complex micro- and nanoscale architectures that give these materials enhanced, and often unnatural material properties over their bulk counterparts. While SEM is commonly used for high-resolution imaging of such small-scale features, its limitations in probing deep within these materials hinders our ability to understand their internal behavior. In turn, we demonstrate an optical confocal microscopy-based approach that allows for high-resolution optical imaging of internal features, deformations and fracture processes in microscale metamaterials under mechanical load. The work has been published in Nano Letters, doi.org/10.1021/acs.nanolett.3c04421
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PhD students Timon Meier, Jacky Li, Stefanos Mavrikos and Brian Blankenship, in collaboration with former LTL PhD student Zacharias Vangelatos and Dr. Erden Yildizdag from Instabul Technical University, have demonstrated new ways to inverse design metamaterials with tailored elastic properties. The research introduces a methododology that combines automated modeling, FEA, multi-objective optimization, 2PP fabrication and experimental validation. Utilizing their flexible framework, they successfully developed metamaterials featuring both isotropic and auxetic properties, offering new potential in material science and engineering applications.
The work was published in npj Computational Materials, https://doi.org/10.1038/s41524-023-01186-2 |
The quantitative analysis of s-SNOM experiments usually relies on analytical models, whose accuracy can be impaired by simplifications made on the system. PhD student Rundi Yang and postdoctoral fellow Jingang Li developed a numerical approach to study the carrier dynamics in pump-probe near-field nanoscopy, which could directly simulate the time-resolved near-field response and bypass the limitations of the analytical models. This method provides a validated and versatile framework to investigate the carrier behaviors in a broad range of semiconductor materials. The work was published in Journal of Physical Chemistry C,
https://pubs.acs.org/doi/10.1021/acs.jpcc.3c06824 |
PhD Student Brian Blankenship develops a method for incorporating and imaging nanodiamonds containing NV centers into two photon polymerization structures. He then demonstrates how these particles can be used for taking precise measurements of temperature and magnetic field in microscale environments. This has significant applications in the field of quantum information science for building practical sensors that work at room temperature. The work has been published to Nano Letters,
https://pubs.acs.org/doi/epdf/10.1021/acs.nanolett.3c02251 |
PhD Students Brian Blankenship and Jacky Li develop a novel, neuromorphic sensor that relies on heating a substrate made out of the phase change material, vanadium dioxide. This sensor is shown to have several neuromorphic functionalities and capabilities such as memory, non-linear thresholding, and the potential for sending information via spike-encoding. This work has been published to Nano Letters, https://doi.org/10.1021/acs.nanolett.3c02681
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Biomimetic and Bioinspired designs have been investigated due to the advances in modeling, mechanics and experimental characterization of structural features of living organisms. The deep sea sponge Euplectella Aspergillum has been of interest due to its complex and hierarchical lattice structure. Former LTL PhD student Zacharias Vangelatos characterized and modeled the mechanical behavior of this sponge from a structural standpoint. Dr. Erden Yildizdag of Instabul Technical University and University of L'Aquila, Italy contributed on the FEA modeling. The research enabled a deeper understanding of Nature’s tailored hierarchy and the design of metamaterials. The work was reported in Extreme Mechanics Letters, https://doi.org/10.1016/j.eml.2023.102013.
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The Laser Thermal Lab is directed by Prof. Costas P Grigoropoulos of the Mechanical Engineering Department, UC Berkeley. Current research interests are focused on laser materials interactions, nanomanufacturing and the fundamental study of microscale and nanoscale transport phenomena.
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For a full list go to the Publications/Journals
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