Daegu Gyeongbuk Institute of Science and Technology

All‐solid‐state batteries (ASSBs) are emerging as a promising alternative to conventional lithium‐ion batteries, offering improved safety and potential for energy density. However, the substantial volume fluctuations of high‐capacity anodes such as lithium and silicon induce interfacial degradation, impeding practical applications. Herein, an aluminum–silicon (Al–Si) alloy anode is introduced that effectively mitigates these challenges by stabilizing volume variation after initial volume expansion and maintaining stable interfacial integrity with the solid electrolyte (SE). By employing a SE‐free wet anode and leveraging advanced characterization techniques, including three‐dimensional X‐ray nanoimaging and digital twin‐based particle‐to‐electrode volume expansion simulations, the structural evolution and electrochemical behavior of Al–Si are elucidated. Furthermore, the integration of an elastic‐recoverable anolyte enables the formation of a robust Al–Si composite anode, effectively suppressing contact loss and enhancing reversibility. ASSBs integrating this Al–Si composite anode and a high‐areal‐capacity LiNi0.8Co0.1Mn0.1O2 cathode (6 mAh·cm⁻²) achieve a capacity retention of 81.6% after 300 cycles, offering a viable pathway toward high‐energy‐density and durable ASSBs.

Stretchable displays are essential components as signal outputs in next‐generation stretchable electronics, particularly for robotic skin and wearable device technologies. Intrinsically‐stretchable and patternable color conversion layers (CCLs) offer practical solutions for developing full‐color stretchable micro‐light‐emitting diode (LED) displays. However, significant challenges remain in creating stretchable and patternable CCLs without backlight leakage under mechanical deformation. Here, a novel material strategy for stretchable and patternable heavy‐metal‐free quantum dot (QD) CCLs, potentially useful for robotic skin and wearable electronics is presented. Through a versatile crosslinking technique, uniform and high‐concentration QD loading in the elastomeric polydimethylsiloxane matrix without loss of optical properties is achieved. These CCLs demonstrate excellent color conversion capabilities with minimal backlight leakage, even under 50% tensile strain. Additionally, fine‐pixel patterning process with resolutions up to 300 pixels per inch is compatible with the QD CCLs, suitable for high‐resolution stretchable display applications. The integration of these CCLs with micro‐LED displays is also demonstrated, showcasing their use in haptic‐responsive robotic skin and wearable healthcare monitoring sensors. This study offers a promising material preparation methodology for stretchable QDs/polymer composites and highlights their potential for advancing flexible and wearable light‐emitting devices.

Tanycytes are a pivotal component of the hypothalamic network that controls energy homeostasis. Despite their importance, the regulatory mechanisms governing tanycyte–neuron interactions in response to metabolic signals remain unexplored. Here we report that adenosine signaling between tanycytes and AGRP/NPY neurons is crucial for tanycytic metabolic regulation mediated by translocator protein 18 kDa (TSPO). Tanycyte-specific Tspo -knockout mice displayed reduced food consumption and weight loss associated with the downregulation of Agrp and Npy expression under high-fat diet feeding. Tspo -deficient tanycytes had elevated levels of intracellular ATP, which was released via connexin 43 hemichannels and extracellularly converted into adenosine by tanycytic ectonucleotidases. The adenosine signal was perceived by adenosine A1 receptors on adjacent AGRP/NPY neurons, reducing ERK phosphorylation, which in turn downregulated Agrp and Npy expression. Our findings underscore the anorexic role of adenosine as a gliotransmitter in the intricate communication between tanycytes and neurons for regulating appetite and body weight.

The 𝑘-th secant variety of a projective variety X ⊂ P N X\subset\mathbb{P}^{N} , denoted by σ k ⁢ ( X ) \sigma_{k}(X) , is defined to be the closure of the union of ( k − 1 ) (k-1) -planes spanned by 𝑘 points on 𝑋. In this paper, we examine the 𝑘-th secant variety σ k ⁢ ( v d ⁢ ( P n ) ) ⊂ P N \sigma_{k}(v_{d}(\mathbb{P}^{n}))\subset\mathbb{P}^{N} of the image of the 𝑑-uple Veronese embedding v d v_{d} of P n \mathbb{P}^{n} to P N \mathbb{P}^{N} with N = ( n + d d ) − 1 N=\binom{n+d}{d}-1 , and focus on the singular locus of σ k ⁢ ( v d ⁢ ( P n ) ) \sigma_{k}(v_{d}(\mathbb{P}^{n})) , which is only known for k ≤ 3 k\leq 3 . To study the singularity for arbitrary k , d , n k,d,n , we define the 𝑚-subsecant locus of σ k ⁢ ( v d ⁢ ( P n ) ) \sigma_{k}(v_{d}(\mathbb{P}^{n})) to be the union of σ k ⁢ ( v d ⁢ ( P m ) ) \sigma_{k}(v_{d}(\mathbb{P}^{m})) with any 𝑚-plane P m ⊂ P n \mathbb{P}^{m}\subset\mathbb{P}^{n} . By investigating the projective geometry of moving embedded tangent spaces along subvarieties and using known results on the secant defectivity and the identifiability of symmetric tensors, we determine whether the 𝑚-subsecant locus is contained in the singular locus of σ k ⁢ ( v d ⁢ ( P n ) ) \sigma_{k}(v_{d}(\mathbb{P}^{n})) or not. Depending on the value of 𝑘, these subsecant loci show an interesting trichotomy between generic smoothness, non-trivial singularity, and trivial singularity. In many cases, they can be used as a new source for the singularity of the 𝑘-th secant variety of v d ⁢ ( P n ) v_{d}(\mathbb{P}^{n}) other than the trivial one, the ( k − 1 ) (k-1) -th secant variety of v d ⁢ ( P n ) v_{d}(\mathbb{P}^{n}) . We also consider the case of the fourth secant variety of v d ⁢ ( P n ) v_{d}(\mathbb{P}^{n}) by applying main results and computing conormal space via a certain type of Young flattening. Finally, we present some generalizations and discussions for further developments.

Developing functional solid polymer electrolytes (SPEs) is crucial for flexible, lightweight, and portable supercapacitors. This work presents an electrospinning approach to fabricate SPEs using poly(vinyl alcohol)-sodium chloride (PVA-NaCl) nanofibers (PNNF). CuNi 2 O 3 nanoparticles deposited on nitrogen-doped omnichannel carbon nanofibers (CuNi 2 O 3 @N-OCCFs), coated onto a carbon cloth (CC), serve as the positive electrode, enhancing faradaic capacitance. Meanwhile, the rationally designed N-OCCFs, also coated onto CC, function as the negative electrode, providing a high-surface-area, and facilitating rapid electron transport. Comprehensive characterization revealed insights into the morphology and chemical composition of both electrodes and the PNNF electrolyte. An all-solid-state asymmetric flexible supercapacitor (AFSC) device, CuNi 2 O 3 @N-OCCFs-1.5//N-OCCFs-1.5, was assembled using PNNF as both the electrolyte and separator and evaluated against devices employing gel and aqueous electrolytes. The PNNF electrolyte enabled a wider potential window (2.2 V) compared to gel (2.0 V) and liquid (1.8 V) electrolytes. The AFSC achieved an impressive energy density of 63.6 Wh kg ⁻¹ at a power density of 1100 W kg ⁻¹ , with 96.2% capacitance retention after 6000 charge/discharge cycles at 10 A g⁻ ¹ . When two devices were connected in series, they powered a red LED for 5.33 min and a blue LED for 1.43 min, demonstrating practical applicability. This study provides a simple and effective strategy for fabricating high-energy–density AFSCs with excellent cycling stability and broad potential for flexible electronics. Graphical Abstract

The accurate and timely detection of nitrogen dioxide gas (NO2) is of utmost relevance in environmental monitoring and industrial applications. This study examines the process of functionalizing multi-walled carbon nanotubes (FMWCNTs) by treating them with a combination of sulfuric acid and nitric acid. The proposed treatment method improves the chemical reactivity of carbon nanotubes by the addition of hydroxyl and carboxylic functional groups. The FMWCNTs combined with zinc oxide (ZnO) are synthesized via a hydrothermal process, forming FMWCNTs@ZnO composites. The synthesized materials underwent various material characterizations. The composites are then printed over a silicon wafer substrate with lithographically patterned interdigitated electrodes in a square shape. 10 mg FMWCNTs in Zn(NO3)2·6H2O (CNTZ2) showed the best gas-sensing capability. The sensor exhibits good gas response and fast response/recovery times at room temperature (RT) with values of 80% and 131/156 s at 100 ppm, respectively, as well as lifetime testing for 40 days. The spray printing method is simple and economical which can be utilized for coating on various substrates. Moreover, the proposed functionalization process allows good gas-sensing properties even at RT. This work paves the way towards new opportunities and fostering an optimistic outlook for the future of gas-sensing technology.

The gauge factor (GF) is a critical parameter for strain sensors, but it faces limitations in achieving high GF values across a wide strain range. This work proposes a novel approach to enhance resistance changes within strains through synergistically combining controlled‐crack sizing and an ion‐bridging structure. This ion‐conductive bridge forms at the interface between graphene and polyvinyl chloride (PVC) gel. Precise management of the crack initiation and propagation on graphene is achieved by controlling adhesion force between graphene and PVC gel. The resulting PVC gel/graphene‐based strain sensor featuring this synergistic design exhibits exceptional sensitivity. It achieves GFs of 635 (ε < 40%), 1.5 × 10⁶ (40% < ε < 80%), and 7.8 × 10⁵ (80% < ε < 100%) over a 100% stretching range. This innovative ion‐bridging construction enables precise control over bridge connectivity at the interface, mitigating graphene's inherent stretchability limitations and enhancing the GF of PVC gel, thereby enhancing strain sensor performance. The sensor detects bending motions and monitors angles within higher strain ranges, making it suitable for wearable applications in human motion tracking. Furthermore, a PVC‐based posture correction system distinguishes various motions, including shoulder band stretching, armband stretching, and even full squats, showcasing its practicality and versatility.

Long valued for their therapeutic qualities, shiitake mushrooms (Lentinula edodes) are a staple of traditional Asian medicine and cuisine. They are high in bio-actives such as polysaccharides, proteins, lipids, vitamins, minerals, sterols, and phenolic compounds, which exhibit immunomodulatory, anticancer, antibacterial, anti-inflammatory, and anti-oxidant properties. Despite these advantages, the limited bioavailability and stability of shiitake's bio-active components often restrict their therapeutic use. Recent advances in nanotechnology have led to the development of nanoemulsions to encapsulate bioactives, which enhanced their bioavailability, stability, and therapeutic efficacy. In this study, we developed a biopolymeric blend of zein and chitosan as a nanoemulsion for the encapsulation of crude shiitake extract. Focusing on the synthesis and refinement of bio-compatible nanoemulsion formulations, this study investigates the medicinal potential of shiitake mushrooms and their nanoemulsions using several in vitro assays: the DPPH assay for anti-oxidant activity; the BSA denaturation assay for anti-inflammatory activity; the MIC test for antimicrobial activity; and the MTT assay for anticancer activity. This study aimed to attain three main goals: synthesis of nanoemulsions, biochemical analysis of shiitake extracts, and in vitro characterization of the therapeutic efficacy of the resulting formulations. This study found that shiitake nanoemulsions showed significantly improved bio-availability and therapeutic efficacy, suggesting promising applications in pharmaceuticals, nutraceuticals, cosmetics, medicine, and the food industry.

Perovskite ink based on a green or non‐toxic solvent meets industrial requirements for efficient perovskite solar cells (PSCs). Perovskite inks must be developed with non‐toxic or involve the limited use of toxic solvents to fabricate efficient inkjet‐printed (IJP) perovskite photovoltaics. Herein, γ‐valerolactone is used as a solvent with a low environmental impact, and the strategy showed category 3 toxicity, even with a small quantity of toxic solvents employed to dissolve the perovskite salts. The structural, optical, and electronic properties of IJP perovskite films are improved by adding 1,3‐dimethyl‐2‐imidazolidinone (DMI) to the green perovskite ink. The IJP perovskite films developed by green solvents with 15% (volume %) of DMI exhibited high thickness uniformity (≈97%), and thicker and smoother surfaces than their counterparts. An additive‐modified IJP‐PSC device achieved a maximum power conversion efficiency (PCE) of 17.78%, higher than that of an unmodified device (14.75%). The performance of the IJP‐PSC device is superior primarily because of its exceptional film‐thickness homogeneity, larger grains, and appropriate structures. These attributes significantly decreased unwanted reactions of the perovskite with solvents, ensuring phase purity and enhancing overall efficiency. The innovative green‐solvent ink‐engineering strategy for producing large‐scale perovskite films shows great promise for advancing perovskite solar module technology (with PCE of 13.14%).

A physically unclonable function (PUF) is a promising hardware-based cryptographic primitive to prevent confidential information leakage. However, conventional techniques, such as weak and strong PUFs, have limitations in overcoming the trade-off between security and storage volume. This study introduces nanoseed-based PUFs that overcome the drawbacks of conventional PUFs using optical and electrical randomness originated from nanoseeds and a unique on-demand cryptographic algorithm. Ideally mixed PbS quantum dots and Ag nanocrystals in the same medium are exploited as nanoseeds to simultaneously promote independent optical and electrical randomness. The number of secured keys that can be generated on-demand by combining the optical and electrical features in parallel using shuffling method is almost infinite (>10 ⁵⁸⁷⁴¹ per square millimeter). The proposed PUF achieves a near-ideal Hamming distance in uniqueness and randomness tests, validating its cryptographic efficacy. Last, storage-free and on-demand PUF with the shuffling method are demonstrated using smartphones, realizing manufacturer-/user-friendly cryptography system.

MXene-based functional 2D materials hold significant potential for addressing global challenges related to energy and water crises. Since their discovery in 2011, Ti3C2Tx MXenes have demonstrated promising applications due to...

The development of stable and multifunctional monitoring or actuating systems for implantable biomedical devices necessitates a high-capacity power supply. By using the oscillation of a magnetic field, energy can be transmitted through various media such as skin, fat, liquids, metals, and fabrics. We demonstrate a magnetically actuated implantable triboelectric generator that can effectively transfer energy independently of the surrounding media. The oscillation of the magnetic field enables contact of elastomeric magnets with the top and bottom electrodes of the generator, generating a path for electrical energy through contact electrification. The performance of the magnetically actuated triboelectric generator exhibits high tolerability for lateral and angular misalignment, transferring energy through different media including tissue, liquid, air, wood, metal, and fabrics. This addresses a critical issue present in ultrasound approaches. These findings suggest that a magnetically actuated triboelectric generator can be an alternative technology capable of overcoming the medium-related challenges of ultrasound, providing power to medical implants.