Yazar "Jun, Martin Byung-Guk" seçeneğine göre listele

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    Cold spray-based rapid and scalable production of printed flexible electronics
    (Elsevier, 2022) Akin, Semih; Lee, Seungjun; Jo, Seunghwan; Ruzgar, Duygu Gazioglu; Subramaniam, Karthick; Tsai, Jung -Ting; Jun, Martin Byung-Guk
    Flexible electronics (FE) is attracting great attention from both scientific and industrial communities, and plays a crucial role in smart device applications. Despite great promise, traditional printing approaches (e.g., screen printing, ink-jet printing, etc.) often need a high-temperature post-sintering process to produce FE with desired electrical conductivity and adhesion strength. The post-sintering processes, however, often lead to fast oxidation of the functional coating while limiting the use of low-thermal budget substrates. Exponential advance of FE in a large-scale and energy-efficient manner relies on rationally eliminating the post-sintering processes. To this end, with the aim of uncovering process-structure-properties relationships, we employ the emerging cold spray (CS) technique for rapid and scalable production of FE without a need for high-temperature post-sintering. In this regard, micron-scale Tin (Sn) particles are directly written on a flexible polymer substrate (PET) by cold spraying under ambient conditions. The effect of CS process parameters on the resultant coatings is comprehensively characterized in terms of microstructure, film thickness, electrical conductivity, linewidth, and adhesion strength. The resulting electrodes show excellent electrical conductivity (6.98 x 105 S m-1), adhesion strength, long-term stability, and flexibility without significant conductivity loss after 1000 bending cycles. By leveraging the CS operational settings, a resistive macro-heater (12 x 15 cm2) and an LED circuit (2.5 cm x 18 cm) are fabricated to demonstrate the applicability of the CS in printed FE. Moreover, to address the low-spatial reso-lution of CS writing, a case study on sequential CS and femtosecond laser machining is performed, which further led to ultra-high resolution (i.e., 30 mu m linewidth) custom-designed flexible electrodes. Thus, the present study reveals the immense potential of the CS technique for rapid and scalable production of FE without the need for post-sintering.
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    Design and fabrication of auxetic stretchable force sensor for hand rehabilitation
    (Iop Publishing Ltd, 2015) Ko, Junghyuk; Bhullar, Sukhwinder Kaur; Cho, Yonghyun; Lee, Patrick C.; Jun, Martin Byung-Guk
    Using a melt electrospinning technique, stretchable force sensors were designed for use in an application of hand rehabilitation. The main purpose of this study was to verify that the use of auxetic sensors improved hand rehabilitation practices when compared to their absence. For this study, novel stretchable poly (epsilon-caprolactone) (PCL) force sensors were fabricated into the following formations: auxetic microfiber sheets (AMSs), auxetic solid sheets (ASSs), microfiber sheets (MSs), and solid sheets (SSs). A femtosecond laser device was used to make an auxetic structure in the MSs and SSs. Subsequently, these sensors were coated with gold particles to make them conductive for the electrical current resistance assays. Through the cycles of applied stress and strain, auxetic structures were able to retain their original shape once these forces have been dissipated. This stretchable sensor could potentially measure applied external loads, resistance, and strain and could also be attachable to a desired substrate. In order to verify the workability and practicality of our designed sensors, we have attempted to use the sensors on a human hand. The AMS sensor had the highest sensitivity on measuring force and resistance among the four types of sensors. To our knowledge, this is the first study to form a stretchable force sensor using a melt electrospinning technique.
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    Development of Bioactive Packaging Structure Using Melt Electrospinning
    (Springer, 2015) Bhullar, Sukhwinder Kaur; Özsel Kaya, Burçak; Jun, Martin Byung-Guk
    Recent research attention is shifting towards the use of bioactive antimicrobial and/or antioxidant packaging materials and their fabrication with non-toxic techniques. The process of melt electrospinning produce fibers from polymer melt without any solution hence environmentally friendly because use of toxic solvents can be avoided. The objectives of this study were fabrication of biodegradable polymeric microfibrous structure using melt electrospinning and characterization of the effect of plant based natural extract on fabricated structure. We found that incorporation of this structure with natural extract provide sufficient support for bioactive compounds without changing thermal stability, physical properties and amorphous phase and also increase the antimicrobial efficacy. Moreover, homogeneously dispersion and good interaction of polymer and natural plant based extract demonstrating the potential of such polymer blend as a bioactive antimicrobial material for packaging industry including especially food and healthcare.
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    Highly Flexible, Conductive, and Antibacterial Surfaces Toward Multifunctional Flexible Electronics
    (Korean Soc Precision Eng, 2024) Ruzgar, Duygu Gazioglu; Akin, Semih; Lee, Seungjun; Walsh, Julia; Lee, Hyowon Hugh; Jeong, Young Hun; Jun, Martin Byung-Guk
    Conductive metallization of polymer surfaces, owing to the integration of unique features of dissimilar materials (i.e., polymer + metal), is becoming the central focus in flexible polymer electronics. However, fabrication of multifunctional surfaces on polymers in a high-throughput and robust manner at ambient conditions remains challenging. In this study, we employ the cold spray (CS) particle deposition technique to produce multifunctional hybrid surfaces on a flexible polymeric substrate (PET) toward flexible electronics. In this regard, soft metal particles (Sn), are deposited on the polymer surface as an interlayer followed by the over-coating of hard metal (Cu) film to create hybrid (Sn + Cu) surfaces. Studies on microstructure, adhesion strength, and water contact angle are conducted to characterize the resulting surface structure. By leveraging the optimum CS settings, multifunctional surfaces with promising electrical conductivity (5.96 x 10(5) S.m(-1)), flexibility, adhesive strength, and hydrophobicity (contact angle approximate to 122 degrees) were achieved. Moreover, the antibacterial performance of the surface is confirmed by the in vitro antibacterial tests in a manner that > 99% of the bacteria were inhibited. This work provides a promising strategy for high-throughput manufacturing of multifunctional surfaces (flexible + conductive + antibacterial surfaces) toward multifunctional flexible electronics.