Pohang University of Science and Technology

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    106947 research outputs found

    A transfer method for embedding conductive fillers on the surface of multi-scale structures for 3D flexible conductors

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    Analysis and Design of Multi-Stacked FET Power Amplifier With Phase-Compensation Inductors in Millimeter-Wave Band

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    Stacked-FET topology is analyzed to increase the output power of a power amplifier (PA) in the millimeter-wave (mm-wave) band. In the mm-wave band, parasitic capacitances of the transistor severely degrade stacking efficiency due to the phase mismatch between stacked FETs. The phase-compensation (PC) inductances, including the losses of the inductor for the best stacking efficiency, are presented in both series and shunt connections. From this analysis, a triple-stacked-FET PA is designed in the F -band. Proper PC series or shunt inductor types are used between the first and second stacked FETs and between the second and third stacked FETs in consideration of the core layout and inductor size. The PA is fabricated in the 28-nm CMOS fully depleted silicon-on-insulator (FD-SOI) process. With a compact core area of 0.054 mm 2 , the PA achieves peak PSAT and PAE MAX of 15.1 dBm and 18.6%, respectively.11Nsciescopu

    Development of Dual-Unit Ceiling Adhesion Robot System With Passive Hinge for Obstacle Traversal Under Kinodynamic Constraints

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    The inspection of high ceilings or surfaces is important to ensure the quality and safety of infrastructure; however, the approach adopted by people or conventional robots is rather limited. Kinodynamic constraints (simultaneous kinematic and dynamic constraints) are presented by obstacles in real-life scenarios, such as suspended piping and wiring, which further limits the usability of robots. Therefore, this paper proposed an adhesion robot system that is attached to and maneuvers on flat and curved ceilings while traversing obstructions. To traverse obstacles, the robot comprises two units connected by a passive hinge mechanism. Traversal motion is achieved under adhesion force control with preexisting electric ducted fans without using separate hinge motors; thus, no additional weight is included. In addition to robot hardware, this study investigated the development of a control method based on dynamic analysis under the aforementioned kinodynamic constraints. Specifically, the proposed control algorithm considers the slipping and rollover conditions of the robot caused by the external force and moment applied to the unit during the obstacle traversal, respectively. The algorithm was systematically analyzed by conducting simulations to prevent the robot from experiencing adhesion failure, and the results were verified experimentally. The use of the robot in real-life scenarios was determined by performing feasibility tests in real-life applications. © 2013 IEEE.11Ysciescopu

    Human iPS-derived blood-brain barrier model exhibiting enhanced barrier properties empowered by engineered basement membrane

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    © 2022 Elsevier LtdThe basement membrane (BM) of the blood-brain barrier (BBB), a thin extracellular matrix (ECM) sheet underneath the brain microvascular endothelial cells (BMECs), plays crucial roles in regulating the unique physiological barrier function of the BBB, which represents a major obstacle for brain drug delivery. Owing to the difficulty in mimicking the unique biophysical and chemical features of BM in in vitro systems, current in vitro BBB models have suffered from poor physiological relevance. Here, we describe a highly ameliorated human BBB model accomplished by an ultra-thin ECM hydrogel-based engineered basement membrane (nEBM), which is supported by a sparse electrospun nanofiber scaffold that offers in vivo BM-like microenvironment to BMECs. BBB model reconstituted on a nEBM recapitulates the physical barrier function of the in vivo human BBB through ECM mechano-response to physiological relevant stiffness (∼500 kPa) and exhibits high efflux pump activity. These features of the proposed BBB model enable modelling of ischemic stroke, reproducing the dynamic changes of BBB, immune cell infiltration, and drug response. Therefore, the proposed BBB model represents a powerful tool for predicting the BBB permeation of drugs and developing therapeutic strategies for brain diseases.11Nsciescopu

    3d Printed Multi-Growth Factors Delivery Patches with Decellularized Extracellular Matrix-Based Hybrid Inks Via Aza-Michael Addition for Promoting Cerebral Angiogenesis

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    Generally, brain angiogenesis is a tightly regulated process, which scarcely occurred in the absence of specific pathological conditions. Delivery of exogenous angiogenic factors enables the induction of de-sired angiogenesis by stimulating neovasculature formation. However, effective strategies of mimicking the angiogenesis process with exogenous factors have not yet been fully explored. Herein, we develop a 3D printed spatiotemporally compartmentalized cerebral angiogenesis inducing (SCAI) hydrogel patch, releasing dual angiogenic growth factors (GFs), using extracellular matrix-based hybrid inks. We intro -duce a new hybrid biomaterial-based ink for printing patches through dual crosslinking mechanisms: Chemical crosslinking with aza-Michael addition reaction with combining methacrylated hyaluronic acid (HAMA) and vascular-tissue-derived decellularized extracellular matrix (VdECM), and thermal crosslink-ing of VdECM. 3D printing technology, a useful approach with fabrication versatility with customizable systems and multiple biomaterials, is adopted to print three-layered hydrogel patch with spatially sepa-rated dual GFs as outer-and inner-layers that provide tunable release profiles of multiple GFs and fabrica-tion versatility. Consequently, these layers of the patch spatiotemporally separated with dual GFs induce excellent neovascularization in the brain area, monitored by label-free photoacoustic microscopy in vivo . The developed multi-GFs releasing patch may offer a promising therapeutic approach of spatiotemporal drugs releasing such as cerebral ischemia, ischemic heart diseases, diabetes, and even use as vaccines.11Nsciescopu

    POSTECH as the Hub of Innovative Materials Research in South Korea over the last 35 Years

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    Layering Charged Polymers Enable Highly Integrated High-Capacity Battery Anodes

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    High-capacity anode materials are promising candidates for increasing the energy density of lithium (Li)-ion batteries due to their high theoretical capacities. However, a rapid capacity fading due to the huge volume changes during charge-discharge cycles limits practical applications. Herein, a layering-charged polymeric binder is introduced that can effectively integrate high-capacity anodes using a strong yet reversible Coulomb interaction and enriched hydrogen bonding. The charged polymeric binder builds a dynamically charge-directed network on the active materials with high versatility and efficiently dissipates the electrode stress with its excellent mechanical properties. In addition, poly(ethylene glycol) (PEG) moieties of the charged binder offer a fast Li-ion conduction pathway that can form an ultra-thick silicon oxide (SiOx)-based electrode (≈10.2 mAh cm−2) without compromising the reversible specific capacity and promote effective charge interaction as a mechanical modulator. Such an unprecedented charge-directed binder provides insights into the rational design of a binder for high-capacity anodes.11Nsciescopu

    Disordered plasmonic nanoparticle-driven etalon for colorimetric gas sensor

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    A sticky carbohydrate meets a mussel adhesive: Catechol-conjugated levan for hemostatic and wound healing applications

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    The stickiest natural polysaccharide, levan, plays a role in metalloproteinase activation, which is an important step involved in the healing of injured tissue. However, levan is easily diluted, washed away, and loses adhesion in wet environments, which limits its biomedical applications. Herein, we demonstrate a strategy for fabricating a levan-based adhesive hydrogel for hemostatic and tissue adhesion applications by conjugating catechol to levan. Prepared hydrogels exhibit significantly improved water solubilities, and adhesion strengths to hydrated porcine skin of up to 42.17 ± 0.24 kPa which is more than three-times that of fibrin glue adhesive. The hydrogels also promote rapid blood clotting and significantly faster healing of rat-skin incisions compared to nontreated samples. In addition, levan-catechol exhibited an immune response close to that of the negative control, which is ascribable to its significantly lower endotoxin level compared to native levan. Overall, levan-catechol hydrogels are promising materials for hemostatic and tissue-adhesion applications.11Nsciescopu


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