DGIST 전자도서관

Hierarchical self-assembly of thickness-modulated block copolymer thin films for controlling nanodomain orientations inside bare silicon trenches

2021-02Polymers, v.13, no.4, pp.1 - 10

We study the orientation and ordering of nanodomains of a thickness-modulated lamellar block copolymer (BCP) thin film at each thickness region inside a topological nano/micropattern of bare silicon wafers without chemical pretreatments. With precise control of the thickness gradient of a BCP thin film and the width of a bare silicon trench, we successfully demonstrate (i) perfectly oriented lamellar nanodomains, (ii) pseudocylindrical nanopatterns as periodically aligned defects from the lamellar BCP thin film, and (iii) half-cylindrical nanostructure arrays leveraged by a trench sidewall with the strong preferential wetting of the PMMA block of the BCP. Our strategy is simple, efficient, and has an advantage in fabricating diverse nanopatterns simultaneously compared to conventional BCP lithography utilizing chemical pretreatments, such as a polymer brush or a selfassembled monolayer (SAM). The proposed self-assembly nanopatterning process can be used in energy devices and biodevices requiring various nanopatterns on the same device and as next-generation nanofabrication processes with minimized fabrication steps for low-cost manufacturing techniques. © 2021 by the authors.

Mussel-Inspired Block Copolymer Lithography for Low Surface Energy Materials of Teflon, Graphene, and Gold

2011-12Advanced Materials, v.23, no.47, pp.5618 - 5622

Mussel-inspired interfacial engineering is synergistically integrated with block copolymer (BCP) lithography for the surface nanopatterning of low surface energy substrate materials, including, Teflon, graphene, and gold. The image shows the Teflon nanowires and their excellent superhydrophobicity. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Soft, thin skin-mounted power management systems and their use in wireless thermography

2016-05Proceedings of the National Academy of Sciences of the United States of America, v.113, no.22, pp.6131 - 6136

Power supply represents a critical challenge in the development of body-integrated electronic technologies. Although recent research establishes an impressive variety of options in energy storage (batteries and supercapacitors) and generation (triboelectric, piezoelectric, thermoelectric, and photovoltaic devices), the modest electrical performance and/or the absence of soft, biocompatible mechanical properties limit their practical use. The results presented here form the basis of soft, skin-compatible means for efficient photovoltaic generation and high-capacity storage of electrical power using dual-junction, compound semiconductor solar cells and chip-scale, rechargeable lithium-ion batteries, respectively. Miniaturized components, deformable interconnects, optimized array layouts, and dual-composition elastomer substrates, superstrates, and encapsulation layers represent key features. Systematic studies of the materials and mechanics identify optimized designs, including unusual configurations that exploit a folded, multilayer construct to improve the functional density without adversely affecting the soft, stretchable characteristics. System-level examples exploit such technologies in fully wireless sensors for precision skin thermography, with capabilities in continuous data logging and local processing, validated through demonstrations on volunteer subjects in various realistic scenarios.

Allosteric control of Ubp6 and the proteasome via a bidirectional switch

2022-02Nature Communications, v.13, no.1

The proteasome recognizes ubiquitinated proteins and can also edit ubiquitin marks, allowing substrates to be rejected based on ubiquitin chain topology. In yeast, editing is mediated by deubiquitinating enzyme Ubp6. The proteasome activates Ubp6, whereas Ubp6 inhibits the proteasome through deubiquitination and a noncatalytic effect. Here, we report cryo-EM structures of the proteasome bound to Ubp6, based on which we identify mutants in Ubp6 and proteasome subunit Rpt1 that abrogate Ubp6 activation. The Ubp6 mutations define a conserved region that we term the ILR element. The ILR is found within the BL1 loop, which obstructs the catalytic groove in free Ubp6. Rpt1-ILR interaction opens the groove by rearranging not only BL1 but also a previously undescribed network of three interconnected active-site-blocking loops. Ubp6 activation and noncatalytic proteasome inhibition are linked in that they are eliminated by the same mutations. Ubp6 and ubiquitin together drive proteasomes into a unique conformation associated with proteasome inhibition. Thus, a multicomponent allosteric switch exerts simultaneous control over both Ubp6 and the proteasome. © 2022. The Author(s).

Bright and uniform light emission from stretchable, dual-channel energy conversion systems: Simultaneous harnessing of electrical and mechanical excitations

2022-03Applied Physics Reviews, v.9, no.1

Recently, significant progress has been made in the development of new techniques for the fabrication of mechanically durable, bright, and deformable electroluminescent devices, leading to the emergence of various technologies, such as soft robots, actuators, flexible/stretchable/wearable electronics, and self-healable devices. However, these devices mostly possess coplanar structures, wherein the internally generated light must be transmitted through at least one of the electrodes, and require a thin emissive layer (EML), causing low brightness and less applicability in soft devices. This is particularly challenging in the case of stretchable electroluminescent devices, which require electrodes exhibiting both high transmittance and low resistance even in the stretchable state because thin EMLs have low tolerance to external mechanical deformations. Herein, we report in-plane electric-field-driven, stretchable alternating-current electroluminescent devices with high brightness by utilizing a thick EML comprising multiple parallelly patterned silver nanowires embedded in a zinc-sulfide-embedded polydimethylsiloxane layer. Since the device is driven by an internal in-plane electric field, it can utilize a thick EML without using planar electrodes. At an electric field of 8 V/ μm, the device showed 3.8 times higher electroluminescence luminance than a thin coplanar-structured device and achieved a maximum brightness of 1324 cd/m<jats:sup>2</jats:sup> (at 9.12 V/ μm), suggesting that the electric field expands throughout the thick EML. Furthermore, the device exhibited strong mechanoluminescence and good durability of dual-channel luminescence under simultaneous electromechanical stimulation. We believe that our results represent a breakthrough in electroluminescence and mechanoluminescence research and provide important insights into the development of sustainable and stretchable devices with high brightness.

Identification of organophosphate modifications by high-resolution mass spectrometry

2022-03Bulletin of the Korean Chemical Society, v.43, no.3, pp.444 - 449

Organophosphate (OP) compounds exhibit neurotoxicity by binding to serine residues of acetylcholinesterase (AChE) in the cholinergic nervous system and subsequently lead to the accumulation of acetylcholine in neuromuscular junctions of synapses. AChE capable of hydrolyzing choline esters is known to be inhibited in patients with nerve agents poisoning. Since OP is known to be transported by covalent bonding to human serum albumin (HSA), OP-HSA adducts are considered potential diagnostic markers for OP exposures. In this study, HSA modification sites by OP or OP-like compounds such as V-type (VX) and Novichok-type (A234), insecticide (DFP), and serine protease inhibitor (PMSF) were studied using liquid chromatography-high-resolution tandem mass spectrometry. As a result, we have discovered a novel OP-HSA modification site, Y341. © 2022 Korean Chemical Society, Seoul & Wiley-VCH GmbH

Highly Active and Durable NiCoSeP Nanostructured Electrocatalyst for Large-Current-Density Hydrogen Production

2022-03ACS Applied Energy Materials, v.5, no.3, pp.2937 - 2948

Large-scale hydrogen production via electrochemical water splitting requires low-cost and efficient electrocatalysts that work well at high current densities with a low overpotential for the hydrogen evolution reaction (HER). Herein, we report the production of a NiCoSeP nanostructured electrocatalyst by a low-cost, one-step electrodeposition technique. The catalyst exhibits very high current densities at small overpotentials (100 mA cm-2 at 151 mV, 500 mA cm-2 at 286 mV, and 1000 mA cm-2 at 381 mV) in 1.0 M KOH electrolyte. Moreover, NiCoSeP shows excellent HER performance in an acidic medium with small overpotentials of 93 and 131 mV to deliver large current densities of 100 and 500 mA cm-2, respectively. The unique morphology of NiCoSeP, superhydrophilic, and superaerophobic properties could facilitate electrolyte diffusion and rapid delivery of the generated bubble, respectively. Our experimental data confirm that the advantages of the excellent HER activity and stability of NiCoSeP nanostructure originate from the high active surface area, bimetal double-anion effect, and enhanced mass transfer of reactants and hydrogen bubbles. This work may provide a promising way for rational design and simplify the synthesis process of practical electrocatalysts. © 2021 American Chemical Society. All rights reserved.

Carbon nanofiber-polyelectrolyte triggered piezoelectric polymer-based hydrophilic nanocomposite for high sensing voltage generation

2022-03Journal of Materials Research and Technology, v.17, pp.3246 - 3261

Flexible electronic devices with flexible sensors have drawn enormous attention due to their wide variety of applications, such as wearable health monitoring devices, bendable touch screens, flexible storage devices, artificial skins, etc. However, the mechanical and electrical performance of devices should be enhanced by new materials design or an innovative device structure to fulfill the requirements for such applications. Here, a poly(vinylidenefluoride) (PVDF) piezoelectric polymer-based hydrophilic nanocomposite (PHNC) sensing membrane using carbon nanofibers (CNF) and poly-acrylamido-methyl-propane-sulfonic acid (PAMPS) polyelectrolyte exhibiting enhanced mechanical and electrical performance is demonstrated. The hydrophilic PAMPS intruded in the PVDF/CNF composition, triggering microstructural changes and facilitating a strong polar β-phase PVDF formation. A dc conductivity of 0.43 S/cm and high electric current density (3.64 μA/cm2) were achieved from PVDF/CNF/PAMPS (80/2/18) PHNC. The piezoelectric performance of the PHNC was investigated for several bending cycles, and it generates the maximum peak output voltage up to 3.65 V under the repeated bending-releasing test procedure. A wearable sensor application is demonstrated by exposing it to different human body movements. During finger motion and elbow movements, the developed PHNC generated piezoelectric maximum peak output voltage up to 3.58 V at a bending angle of 180° for finger motion and 2.2 V for elbow movement. The fabricated PHNC are highly flexible and exhibit outstanding reproducibility and reliability, making them ideal for energy harvesting, the self-powered sensor in wearable electronic devices, electronic skin (e-skin), and soft robotics applications. © 2022 The Author(s)

Colloidal Metal-Halide Perovskite Nanoplatelets: Thickness-Controlled Synthesis, Properties, and Application in Light-Emitting Diodes

2022-03Advanced Materials, v.34, no.10

Colloidal metal-halide perovskite nanocrystals (MHP NCs) are gaining significant attention for a wide range of optoelectronics applications owing to their exciting properties, such as defect tolerance, near-unity photoluminescence quantum yield, and tunable emission across the entire visible wavelength range. Although the optical properties of MHP NCs are easily tunable through their halide composition, they suffer from light-induced halide phase segregation that limits their use in devices. However, MHPs can be synthesized in the form of colloidal nanoplatelets (NPls) with monolayer (ML)-level thickness control, exhibiting strong quantum confinement effects, and thus enabling tunable emission across the entire visible wavelength range by controlling the thickness of bromide or iodide-based lead-halide perovskite NPls. In addition, the NPls exhibit narrow emission peaks, have high exciton binding energies, and a higher fraction of radiative recombination compared to their bulk counterparts, making them ideal candidates for applications in light-emitting diodes (LEDs). This review discusses the state-of-the-art in colloidal MHP NPls: synthetic routes, thickness-controlled synthesis of both organic-inorganic hybrid and all-inorganic MHP NPls, their linear and nonlinear optical properties (including charge-carrier dynamics), and their performance in LEDs. Furthermore, the challenges associated with their thickness-controlled synthesis, environmental and thermal stability, and their application in making efficient LEDs are discussed.

Peroxiredoxin 3 deficiency induces cardiac hypertrophy and dysfunction by impaired mitochondrial quality control

2022-05Redox Biology, v.51

Mitochondrial quality control (MQC) consists of multiple processes: the prevention of mitochondrial oxidative damage, the elimination of damaged mitochondria via mitophagy and mitochondrial fusion and fission. Several studies proved that MQC impairment causes a plethora of pathological conditions including cardiovascular diseases. However, the precise molecular mechanism by which MQC reverses mitochondrial dysfunction, especially in the heart, is unclear. The mitochondria-specific peroxidase Peroxiredoxin 3 (Prdx3) plays a protective role against mitochondrial dysfunction by removing mitochondrial reactive oxygen species. Therefore, we investigated whether Prdx3-deficiency directly leads to heart failure via mitochondrial dysfunction. Fifty-two-week-old Prdx3-deficient mice exhibited cardiac hypertrophy and dysfunction with giant and damaged mitochondria. Mitophagy was markedly suppressed in the hearts of Prdx3-deficient mice compared to the findings in wild-type and Pink1-deficient mice despite the increased mitochondrial damage induced by Prdx3 deficiency. Under conditions inducing mitophagy, we identified that the damaged mitochondrial accumulation of PINK1 was completely inhibited by the ablation of Prdx3. We propose that Prdx3 interacts with the N-terminus of PINK1, thereby protecting PINK1 from proteolytic cleavage in damaged mitochondria undergoing mitophagy. Our results provide evidence of a direct association between MQC dysfunction and cardiac function. The dual function of Prdx3 in mitophagy regulation and mitochondrial oxidative stress elimination further clarifies the mechanism of MQC in vivo and thereby provides new insights into developing a therapeutic strategy for mitochondria-related cardiovascular diseases such as heart failure. © 2022

Drug-Loaded Mucoadhesive Patch with Active Delivery and Controlled Releasing Ability

ACCEPTAdvanced Intelligent Systems

Herein, a mucoadhesive patch for gastrointestinal tracts with active delivery, hyperthermia, and controlled drug release function using a magnetically actuated capsule is proposed to overcome the drug delivery and efficiency challenges of wireless structures. The proposed patch has excellent adhesion to the gastrointestinal tract and contains anticancer drug doxorubicin and magnetic nanoparticles. This enables hyperthermia and the controlled release of the loaded drug under an alternating magnetic field (AMF). In addition, it can be delivered to multiple intestinal target lesions using a magnetically actuated capsule. Characteristic analyses of the proposed patch are performed, such as morphology, adhesion force measurement with intestine, temperature change under an AMF, and drug release. The feasibility of the patch delivery into the gastrointestinal tract is verified through locomotion performance tests and ex vivo patch delivery experiments using a magnetically actuated capsule. Finally, through an in vitro therapeutic effect test, the death of tumor cells using the proposed patch is confirmed. As a result, the possibility that the multiple mucoadhesive patches can be delivered to target lesions in a digestive tract through a magnetically actuated capsule and can treat the lesions through hyperthermia and active drug release using an AMF stimulation is verified.

Contagious Aggregation: Transmittable Protein Aggregation in Cellular Communities Initiated by Synthetic Cells

2022-03Journal of the American Chemical Society, v.144, no.11, pp.5067 - 5073

Aggregation of amyloidogenic proteins causing neurodegenerative diseases is an uncontrollable and contagious process that is often associated with lipid membranes in a highly complex physiological environment. Although several approaches using natural cells and membrane models have been reported, systematic investigations focusing on the association with the membranes are highly challenging, mostly because of the lack of proper molecular tools. Here, we report a new supramolecular approach using a synthetic cell system capable of controlling the initiation of protein aggregation and mimicking various conditions of lipid membranes, thereby enabling systematic investigations of membrane-dependent effects on protein aggregation by visualization. Extending this strategy through concurrent use of synthetic cells and natural cells, we demonstrate the potential of this approach for systematic and in-depth studies on interrogating inter- and intracellularly transmittable protein aggregation. Thus, this new approach offers opportunities for gaining insights into the pathological implications of contagious protein aggregation associated with membranes for neurotoxicity. © 2021 American Chemical Society. All rights reserved.