Jae-Woo Kim

Bio: Jae-Woo Kim is an academic researcher from Government of the United States of America. The author has contributed to research in topics: Carbon nanotube & Ferritin. The author has an hindex of 8, co-authored 25 publications receiving 265 citations. Previous affiliations of Jae-Woo Kim include Langley Research Center.

Method for the free form fabrication of articles out of electrically conductive filaments using localized heating

Abstract: A method of fabricating composite articles includes supplying electrical current to an electrically conductive filament. The electrically conductive filament may include a first material that is electrically conductive and a polymer second material. The polymer second material comprises at least one of a thermoplastic polymer and a partially cured thermosetting polymer. The heated filament is deposited according to a predefined pattern in successive layers to adhere the polymer material of the layers together and build up a three dimensional article. The article includes strands of the first material embedded in a substantially continuous polymer matrix of the second material.

Devices and methods for additive manufacturing using flexible filaments

Abstract: A method of fabricating (printing) parts utilizing flexible filaments includes anchoring a portion of a flexible filament to a substrate. A length of flexible filament is extended over the substrate while the flexible filament is in tension to thereby avoid buckling of the flexible filament. The flexible filament may comprise a thermoplastic material and fibers or other reinforcing materials whereby composite 3D parts can be fabricated.

Cutting mechanism for carbon nanotube yarns, tapes, sheets and polymer composites thereof

Abstract: A cutting mechanism includes electrodes that are utilized to cut or score a non-conductive outer material of a filament or sheet. The electrodes contact a conductive reinforcing material of the filament or sheet to complete an electric circuit. Electric current flows through and heats the conductive material to oxidize or otherwise separate/cut the conductive material and any remaining non-conductive material.

High altitude airship configuration and power technology and method for operation of same

Abstract: A new High Altitude Airship (HAA) capable of various extended applications and mission scenarios utilizing inventive onboard energy harvesting and power distribution systems. The power technology comprises an advanced thermoelectric (ATE) thermal energy conversion system. The high efficiency of multiple stages of ATE materials in a tandem mode, each suited for best performance within a particular temperature range, permits the ATE system to generate a high quantity of harvested energy for the extended mission scenarios. When the figure of merit 5 is considered, the cascaded efficiency of the three-stage ATE system approaches an efficiency greater than 60 percent.

New insights into subsurface imaging of carbon nanotubes in polymer composites via scanning electron microscopy

Abstract: Despite many studies of subsurface imaging of carbon nanotube (CNT)-polymer composites via scanning electron microscopy (SEM), significant controversy exists concerning the imaging depth and contrast mechanisms. We studied CNT-polyimide composites and, by three-dimensional reconstructions of captured stereo-pair images, determined that the maximum SEM imaging depth was typically hundreds of nanometers. The contrast mechanisms were investigated over a broad range of beam accelerating voltages from 0.3 to 30 kV, and ascribed to modulation by embedded CNTs of the effective secondary electron (SE) emission yield at the polymer surface. This modulation of the SE yield is due to non-uniform surface potential distribution resulting from current flows due to leakage and electron beam induced current. The importance of an external electric field on SEM subsurface imaging was also demonstrated. The insights gained from this study can be generally applied to SEM nondestructive subsurface imaging of conducting nanostructures embedded in dielectric matrices such as graphene-polymer composites, silicon-based single electron transistors, high resolution SEM overlay metrology or e-beam lithography, and have significant implications in nanotechnology.

Progress towards biocompatible intracortical microelectrodes for neural interfacing applications

Abstract: To ensure long-term consistent neural recordings, next-generation intracortical microelectrodes are being developed with an increased emphasis on reducing the neuro-inflammatory response. The increased emphasis stems from the improved understanding of the multifaceted role that inflammation may play in disrupting both biologic and abiologic components of the overall neural interface circuit. To combat neuro-inflammation and improve recording quality, the field is actively progressing from traditional inorganic materials towards approaches that either minimizes the microelectrode footprint or that incorporate compliant materials, bioactive molecules, conducting polymers or nanomaterials. However, the immune-privileged cortical tissue introduces an added complexity compared to other biomedical applications that remains to be fully understood. This review provides a comprehensive reflection on the current understanding of the key failure modes that may impact intracortical microelectrode performance. In addition, a detailed overview of the current status of various materials-based approaches that have gained interest for neural interfacing applications is presented, and key challenges that remain to be overcome are discussed. Finally, we present our vision on the future directions of materials-based treatments to improve intracortical microelectrodes for neural interfacing.

Dispersing carbon nanotubes using surfactants

Abstract: We review the recent advances in dispersing single-wall carbon nanotubes (SWNTs) using amphiphilic surfactants in aqueous solutions. Three aspects are discussed. (1) On the organization of surfactant molecules with SWNTs, new insights at the microscopic level arise from electron microscopy and detailed computer simulation studies. (2) Quantitative measurements, such as molecular interactions between functional groups and SWNTs, the coverage of surfactant on SWNTs in solution, the charge state of the SWNT/surfactant complex, and the degree of dispersion are critical for better understanding dispersion mechanisms and for the further development of dispersion strategies. (3) The thermodynamic driving forces and the role of metastability in the structure of surfactant dispersed SWNT suspensions are analyzed. An outlook on practical and fundamental issues is also presented.

Airborne fulfillment center utilizing unmanned aerial vehicles for item delivery

Abstract: Described is an airborne fulfillment center (“AFC”) and the use of unmanned aerial vehicles (“UAV”) to deliver items from the AFC to users. For example, the AFC may be an airship that remains at a high altitude (e.g., 45,000 feet) and UAVs with ordered items may be deployed from the AFC to deliver ordered items to user designated delivery locations. As the UAVs descend, they can navigate horizontally toward a user specified delivery location using little to no power, other than to stabilize the UAV and/or guide the direction of descent. Shuttles (smaller airships) may be used to replenish the AFC with inventory, UAVs, supplies, fuel, etc. Likewise, the shuttles may be utilized to transport workers to and from the AFC.

Multilayer fiber reinforcement design for 3D printing

Abstract: A three-dimensional geometry is received, and sliced into layers. A first anisotropic fill tool path for controlling a three dimensional printer to deposit a substantially anisotropic fill material is generated defining at least part of an interior of a first layer. A second anisotropic fill tool path for controlling a three dimensional printer to deposit the substantially anisotropic fill material defines at least part of an interior of a second layer. A generated isotropic fill material tool path defines at least part of a perimeter and at least part of an interior of a third layer intervening between the first and second layers.