Hyoryung Nam

Laser-induced graphene (LIG) is a promising porous carbon electrode for flexible microsupercapacitors (MSCs), and defocusing is an established means of tuning its morphology. Here, a defocusing series was evaluated as a complete process-to-device chain with the CO₂ laser power and scan speed fixed at 5.0 W and 46 mm s⁻¹. A polyimide substrate was positioned 0–3 mm below the focal plane to produce laser-induced graphene fibers (LIGFs), LIG-1, LIG-2, and LIG-3. Increasing the defocusing distance lowered the peak fluence per pulse from 16.7 to 2.1 J cm⁻², transforming a fibrous network into porous LIG, an open-cell-like network, and a film whose smooth, oxygen-rich surface skin covered a porous interior. LIG-2 showed the lowest sheet resistance (15.3 Ω sq⁻¹), I_D/I_G ratio (0.29), and equivalent series resistance (78 Ω), delivering 2.88 mF cm⁻² at 0.05 mA cm⁻² and 97.4% retention after 2000 cycles. LIGF showed the lowest contact angle (12.1°), retained 57.3% of its capacitance at 0.25 mA cm⁻², and surpassed LIG-2 at ≥0.10 mA cm⁻². Both electrodes retained their cyclic voltammetry (CV) response under a single 180° bend. Thus, substrate-height adjustment tunes LIG morphology and rate-dependent MSC performance without changing laser power or scan speed.

Battery-free, at-a-glance thermal readouts are attractive for point-of-care triage and low-resource settings. However, three-dimensional thermochromic hydrogel printing remains challenging because delayed gelation can compromise linewidth control and multilayer structural fidelity. In this study, a syringe-pump-driven extrusion-based direct ink writing platform was integrated with a temperature-controlled coagulation bath to induce immediate in situ gelation during thermochromic chitosan hydrogel printing. Systematic tuning of the nozzle gauge, printing speed, and flow rate, combined with rapid thermal gelation in the heated coagulation bath, mitigated die swelling, with the die-swelling ratio, which ranged from 2.1 to 3.7 at low printing speed, decreasing to approximately 1.0 at intermediate speeds. This enabled parameter-dependent control of strand diameter and reproducible multilayer fabrication. The mechanical properties of the printed hydrogels were further tuned by varying the coagulation bath temperature and chitosan concentration; gelation at 60 °C yielded the highest ultimate tensile strength (0.172 MPa), and a 4.0 wt% chitosan formulation provided the most balanced combination of strength and extensibility. Adjusting the thermochromic pigment composition modulated chromatic separation across temperature states in CIE L*a*b* color space over 26–54 °C. Formulation tuning broadened the separation of color states within an intermediate range of 31–38 °C, which spans normal skin temperature and the febrile range relevant to fever detection. The colorimetric response remained stable over 50 heating–cooling cycles, with color differences below the threshold of visual perceptibility. A multilayer construct further demonstrated layer-resolved colorimetric readout within a single 3D structure, indicating the potential of this passive hydrogel indicator for battery-free, spatially resolved thermal indication in this temperature range.

Blood is a widely used sample for diagnosing diseases such as malaria and diabetes. While diagnostic techniques have advanced, sample preparation remains labor-intensive, requiring steps like mixing and centrifugation. Microfluidic technologies have automated parts of this process, including cell lysis, yet challenges persist. Electrical lysis offers a chemical-free, continuous approach, but lysing small cells like red blood cells requires high electric fields, which can damage electrodes and cause system failures. Here, we present a microfluidic device utilizing ion concentration polarization (ICP) for rapid blood cell lysis at 75 V. Fluorescence imaging confirmed the formation of an ion depletion region near the Nafion^® nanochannel membrane, where the electric field was concentrated across the entire microchannel width. This phenomenon enabled the efficient trapping and lysis of blood cells under these conditions. Continuous blood injection achieved a lysis time of 0.3 s with an efficiency exceeding 99.4%. Moreover, lysed cell contents accumulated near the Nafion membrane, forming a concentrated lysate. This approach eliminates the need for high-voltage circuits or chemical reagents, offering a simple yet effective method for blood cell lysis. The proposed device is expected to advance lab-on-a-chip and point-of-care diagnostics by enabling rapid and continuous sample processing.

Planar heaters are designed to deliver uniform heat across broad surfaces and serve as critical components in applications requiring energy efficiency, safety, and mechanical flexibility, such as wearable electronics and smart textiles. However, conventional metal-based heaters are limited by poor adaptability to curved or complex surfaces, low mechanical compliance, and susceptibility to oxidation-induced degradation. To overcome these challenges, we applied a protein-assisted electroless copper (Cu) plating strategy to electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofiber substrates to fabricate flexible, conductive planar heating membranes. For interfacial functionalization, a protein-based engineering approach using bovine serum albumin (BSA) was employed to facilitate palladium ion coordination and seed formation. The resulting membrane exhibited a dense, continuous Cu coating, low sheet resistance, excellent durability under mechanical deformation, and stable heating performance at low voltages. These results demonstrate that the BSA-assisted strategy can be effectively extended to complex three-dimensional fibrous membranes, supporting its scalability and practical potential for next-generation conformal and wearable planar heaters.

Esophageal cancer (EC) is the eighth leading cause of cancer-related deaths globally, largely due to its late-stage diagnosis and aggressive progression. Esophagectomy remains the primary treatment, typically requiring organ-based reconstruction techniques such as gastric pull-up or colonic interposition. However, these reconstruction methods often lead to severe complications, significantly reducing the quality of life of patients. To address these limitations, tissue engineering has emerged as a promising alternative, offering bioengineered patch-type and tubular-type scaffolds designed to restore both structural integrity and functional regeneration. Recent advancements in three-dimensional (3D) biofabrication—including 3D bioprinting, electrospinning, and other cutting-edge techniques—have facilitated the development of patient-specific constructs with improved biocompatibility. Despite significant advancements, critical challenges persist in achieving mechanical durability, multilayered cellular organization, and physiological resilience post-transplantation. Ongoing research continues to address these limitations and enhance clinical applicability. Therefore, this review aims to examine recent advancements in esophageal tissue engineering, with a focus on key biofabrication techniques, preclinical animal models, and the major translational challenges that must be addressed for successful clinical application.

Drug‐induced cardiotoxicity is regarded as a major hurdle in the early stages of drug development. Although there are various methods for preclinical cardiotoxicity tests, they cannot completely predict the cardiotoxic potential of a compound due to the lack of physiological relevance. Recently, 3D engineered heart tissue (EHT) has been used to investigate cardiac muscle functions as well as pharmacological effects by exhibiting physiological auxotonic contractions. However, there is still no adequate platform for continuous monitoring to test acute and chronic pharmacological effects in vitro. Here, a biohybrid 3D printing method for fabricating a tissue‐sensor platform, composed of a bipillar‐grafted strain gauge sensor and EHT, is first introduced. Two pillars are three‐dimensionally printed as grafts onto a strain gauge‐embedded substrate to promote the EHT contractility and guide the self‐assembly of the EHTs along with the strain gauge. In addition, the integration of a wireless multi‐channel electronic system allows for continuous monitoring of the EHT contractile force by the tissue‐sensor platform and, ultimately, for the observation of the acute and chronic drug effects of cardiotoxicants. In summary, biohybrid 3D printing technology is expected to be a potential fabrication method to provide a next‐generation tissue‐sensor platform for an effective drug development process.

In vitro organ models allow for the creation of precise preclinical models that mimic organ physiology. During a pandemic of a life-threatening acute respiratory disease, an improved trachea model (TM) is required. We fabricated a modular assembly of the blood vessel and TMs using 3D bioprinting technology. First, decellularized extracellular matrix (dECM) were prepared using the porcine trachea and blood vessels. A trachea module was fabricated based on the tracheal mucosa-derived dECM and microporous membrane. Further, a blood vessel module was manufactured using the prepared vascular-tissue-derived dECM. By assembling each manufactured module, a perfusable vascularized TM simulating the interface between the tracheal epithelium and blood vessels was fabricated. This assembled model was manufactured with efficient performance, and it offered respiratory symptoms, such as inflammatory response and allergen-induced asthma exacerbation. These characteristics indicate the possibility of manufacturing a highly functional organ model that mimics a complex organ environment in the future.

Stem cell-laden three-dimensional (3D) bioprinted cardiac patches offer an alternative and promising therapeutic and regenerative approach for ischemic cardiomyopathy by reversing scar formation and promoting myocardial regeneration. Numerous studies have reported using either multipotent or pluripotent stem cells or their combination for 3D bioprinting of a cardiac patch with the sole aim of restoring cardiac function by faithfully rejuvenating the cardiomyocytes and associated vasculatures that are lost to myocardial infarction. While many studies have demonstrated success in mimicking cardiomyocytes' behavior, improving cardiac function and providing new hope for regenerating heart post-myocardial infarction, some others have reported contradicting data in apparent ways. Nonetheless, all investigators in the field are speed racing toward determining a potential strategy to effectively treat losses due to myocardial infarction. This review discusses various types of candidate stem cells that possess cardiac regenerative potential, elucidating their applications and limitations. We also brief the challenges of and an update on the implementation of the state-of-the-art 3D bioprinting approach to fabricate cardiac patches and highlight different strategies to implement vascularization and augment cardiac functional properties with respect to electrophysiological similarities to native tissue.

Controlling the architecture of electrospun fibers is one of the key issues in tissue engineering. This report describes a rapid and reproducible patterning method for the fabrication of an electrospun fibrous scaffold. The electrospun fibers were deposited on a patterned electrode. The patterned scaffold was fabricated using a thin insulating film between layers of this electrode. For a tissue engineering application, poly(lactic-co-glycolic acid) (PLGA), a biocompatible and biodegradable material, was electrospun. Fibroblast cells were cultured on the fibrous PLGA scaffold and the viability, morphology, and distribution of the cells were studied.