Baker’s yeast is a common microorganism that is well-known for its fermentation activities. The fermentation process naturally produces CO 2 , leading to a gradual increase in internal pressure within sealed environments. Meanwhile, passive pumps are rising in the microfluidics field for their simplicity, low energy requirements, and suitability for portable and disposable devices. Here, we harnessed yeast fermentation as a biological power source for a passive pump, enabling fluid flow in microfluidic systems. This approach introduces a cost-effective, self-sustaining solution and extends the concept of passive pumping into the realm of biological systems. The custom mechanical pump operates by converting the gas pressure generated by fermentation into continuous fluid movement. The dynamics of gas production within the pump were analyzed experimentally to characterize performance over time. A mathematical four-parameter pump model was developed to predict pressure buildup and guide system configuration based on desired flow rates and operating durations. This model was further extended to a simplified two-parameter form—using only yeast mass and sucrose concentration—making pump setup more intuitive. This biologically driven pump concept holds potential for expansion into self-sustaining microfluidic devices, especially for space orbital experiment modules, educational tools, or low-resource settings where external power sources are limited.

Traditional two-dimensional (2D) cell cultures often fail to replicate the complex three-dimensional (3D) microenvironments foundin vivo, where cells interact with biochemical and mechanical cues. Emerging 3D co-culture platforms better mimic intercellular interactions, cellular differentiation, and drug responses; however, existing methods-such as hydrogel encapsulation and hanging droplets-face challenges in accessibility, scalability, and ease of use. This paper presents the Swivel Microwell, a novel platform that enables efficient spheroid pairing through a simple rotational mechanism. The device, fabricated using computerized numerical control-machined poly(methyl methacrylate) (PMMA) molds and by casting polydimethylsiloxane (PDMS), utilizes gravity, surface tension, and hydrostatic pressure to facilitate spheroid assembly without the need for specialized equipment. Controlled air bubble nucleation guides precise microwell formation, allowing custom well structures on multiple surfaces. Experimental and numerical analyses confirm the platform's ability to generate multiple spheroid pairs and demonstrate its potential for high-throughput applications. The design is expected to support complex co-culture systems, including 2D-3D hybrids and multispheroid assemblies when modified. The Swivel Microwell offers an accessible, scalable, and versatile tool for dynamic spheroid manipulation, opening new possibilities for tissue engineering, drug screening, and cellular biology research.

Baker’s yeast is a common microorganism that is well-known for its fermentation activities. The fermentation process naturally produces CO2, leading to a gradual increase in internal pressure within sealed environments. Meanwhile, passive pumps are rising in the microfluidics field for their simplicity, low energy requirements, and suitability for portable and disposable devices. Here, we harnessed yeast fermentation as a biological power source for a passive pump, enabling fluid flow in microfluidic systems. This approach introduces a cost-effective solution and extends the concept of passive pumping into the realm of biological systems. The custom mechanical pump operates by converting the gas pressure generated by fermentation into continuous fluid movement. The dynamics of gas production within the pump were analyzed experimentally to characterize performance over time. The resulting six-parameter and four-parameter equations accurately capture the experimental trends within the validated operating range. This model was further extended to a simplified two-parameter form—using only yeast mass and sucrose concentration—making the pump setup more intuitive. This biologically driven pump concept holds potential for expansion into autonomous microfluidic devices, especially for space orbital experiment modules, educational tools, or low-resource settings where external power sources are limited.

Nanobubbles (NBs) (<1 & micro;m) exhibit unique physicochemical properties and high stability, which have potential applications in biological systems, including microbial metabolism enhancement, fibroblast proliferation, and tumor inhibition. However, the influence of different gaseous components on cell viability remains unclear. This study examined the effects of nitrogen, oxygen, and hydrogen NBs on human lung fibroblast cell (MRC-5) viability. NBs were generated in a Dulbecco's modified Eagle's medium using a gas-liquid mixing method and characterized by a nanoparticle tracking analysis. After 48 h of culture, cell viability increased 1.34-, 1.30-, and 1.29-fold for nitrogen, oxygen, and hydrogen NBs, respectively, with only nitrogen NBs showing a significant increase (p < 0.05). Flow cytometry with carboxyfluorescein succinimidyl ester analysis showed no difference in proliferation among groups, indicating that enhanced viability might result from gas-specific effects rather than direct stimulation of cell division. These findings highlight the potential biomedical applications of nanobubbles and their constituent gases.

A solar updraft tower (SUT) is a renewable energy system whose performance depends strongly on its structural configuration. Structural modifications intended to enhance performance inevitably alter the internal volume of the system. However, the role of internal volume in governing thermal storage and airflow behavior remains unclear, making it difficult to distinguish whether performance changes arise from volumetric effects or geometric design parameters. This study investigates the effect of inlet height and collector volume by introducing volume-coupled inlet (VCI) and volume-decoupled inlet (VDI) configuration, enabling isolation of volume-related effects. A numerical thermofluid analysis was conducted to evaluate flow behavior and energy conversion characteristics. Both VCI and VDI models improved the SUT performance by 15.91% and 15.49%, respectively, compared with the control case. Although the VDI model, which maintains a constant internal volume, increased internal temperature and thermal capacity, it did not enhance overall performance due to increased flow resistance that suppressed air flow acceleration. In contrast, the VCI model, which allows volume variation, achieved higher efficiency by more effectively converting thermal energy into kinetic energy and sustaining a higher mass flow rate through the chimney. These findings highlight that preserving favorable flow structures is more critical than increasing thermal storage for improving SUT performance. The findings provide design insights applicable to solar thermal collector systems with similar operating principles.

Plant roots are essential organs that anchor plants in the soil and absorb water and other nutrients. Studying root growth contributes to the enhancement of plant growth. In this study, we designed a microfluidic platform to investigate the effects of microhydrodynamic stimulation on plant root growth. A wide range of microfluidic flow rates was applied to Medicago sativa seedling roots using a syringe pump. Higher inlet flow rates promoted main root elongation by 60.7% and suppressed root hair growth by 65.7%. A threshold response of root growth was observed between the inlet flow rates of 0.1 and 1 μL min-1. The normalized distribution pattern of root hair lengths shifted from a sigmoid pattern at low flow rates to an exponential pattern at high flow rates. Computational fluid dynamics was used to investigate the direct and indirect hydrodynamic stimulation of the roots. Higher maximum wall shear and bending stresses were observed at higher flow rates and longer root hairs. The Péclet number of the secreted ethylene was larger at higher flow rates and had minor differences depending on root hair length. These results suggest that M. sativa tends to promote main root elongation rather than root hair elongation in mechanically stressful and advection-dominant environments. The microfluidic system and analytical method used in this study provides a mechanistic understanding of the effects of fluid dynamics on plant root growth and has the potential to be valuable tools for future research, ultimately contributing to improve crop productivity and addressing future food security concerns.

Blowers, essential for aerator operation, are pivotal mechanical devices that induce airflow through an impeller. Extensive research has explored impeller geometrical parameters, such as size, angle, and blade count. However, limited attention has been paid to the synergic effect of optimizing the bell mouth of the blower inlet and the nose cone of the impeller eye. This study utilized computational fluid dynamics (CFDs) to analyze the impact of the bell mouth and nose cone on the blower through a geometric case study and evaluate the synergy between these components. A bell mouth decreases the wake by 91.76%, and a nose cone decreases the stagnation at the impeller eye and expands the effective impeller area by 76.29%. Moreover, this study demonstrated a significant synergistic effect between the bell mouth and nose cone, which reduced the head loss by 81.4% compared with the base model. This study presents a simple and effective method to improve blower efficiency and reduce power consumption by applying aerodynamically designed bell mouths and nose cones to blowers.

Various mechanisms, including inflammation, oxidative stress, and apoptosis, are involved in the transition from acute kidney injury to chronic kidney disease (AKI-to-CKD). In this study, we aimed to determine the pathway linking acute injury and fibrosis under static magnetic fields (SMFs). Human tubular epithelial cells (hTECs) were cultured on SMF platforms (119 mT; outward vs. inward direction) for 3 days, followed by treatment with adenine and p38 mitogen-activated protein kinase (MAPK) inhibitor to verify the role of MAPK pathway. In-vivo, mice were orally administered adenine (2mg/mouse/day) for 14 days to induce tubular injury, and p38 MAPK inhibitor (iP38, 10mg/kg) was injected intraperitoneally to evaluate its therapeutic effect. Inward SMF exposure significantly increased phospho-p38 (pp38) expression compared to outward SMFs. p38 MAPK inhibition reduced G1/S arrest and oxidative stress, apoptosis, and expression of fibrosis markers under inward SMFs. Additionally, iP38 treatment alleviated inflammation and fibrosis in adenine-induced tubular nephropathy (AITN). This study revealed that SMF-related AKI-to-CKD transition progresses with the direction of SMFs affecting the severity of injury, whereas p38 MAPK inhibition attenuates SMF-induced kidney injury and prevents fibrosis.

Recent advancements in ovarian cancer treatment, particularly with PARP inhibitors, have markedly enhanced the recurrence-free interval, shifting the treatment paradigm and increasing treatment success in patients with BRCA mutations or HRD (homologous recombination deficiency). However, a significant proportion of cases experience relapse, resulting in poorer long-term survival rates when compared to other female cancers, such as breast cancer. This review explores the potential of adeno-associated virus (AAV) vectors for gene therapy in ovarian cancer and examines rational gene therapy strategies by categorizing them based on target cells and target genes to determine the most effective approach for ovarian cancer treatment. Specifically, it examines strategies such as anti-angiogenesis and immune modulation, highlighting the strategy of gene supplementation to hinder ovarian cancer progression. Innovations in AAV capsid design now allow for targeted delivery, focusing on ovarian cancer stem cells (CSCs) identified by specific markers. Additionally, leveraging DNA sequencing technologies enhances the identification and incorporation of therapeutic genes into AAV vectors, promising new avenues for ovarian cancer gene therapy.

Obstructive sleep apnea (OSA) can have many adverse effects on people's health, including cognitive decline and high blood pressure. Typical surgical treatment methods include the commonly performed uvulopalatopharyngoplasty and the highly successful maxillomandibular advancement (MMA). These surgical methods are more effective than non-surgical methods because they widen the airway where a collapse has occurred through direct treatment. However, few studies has shown that moving the upper and lower jaws in a specific manner is the most efficient way to treat OSA during an MMA surgery. In this study, the airway of an OSA patient was reproduced digitally, and computational fluid dynamics analysis was performed on various models with changed airway shapes, including the original model based on an actual CT image and three resizing models of the retropalatal (RP) and retroglossal (RG) regions of the airway. Consequently, it was possible to provide more quantitative predicted flow data, which could be helpful in performing sophisticated OSA surgery. Among the four airway models of the OSA patient, a reduction in the epiglottis regional pressure difference of up to 40.2% was evident in the model with an expanded RG region, and a reduction in the wall shear stress of up to 25.8% was confirmed. The proposed process could be an important aid for surgeons in determining the optimal surgical method suitable for an individual patient's uniquely-shaped airway.

A solar updraft tower (SUT) is a power-generating structure that transforms solar energy into electricity through the kinetic energy of air rising due to solar-radiation-induced buoyancy. In traditional architecture, a vestibule is a small room that leads to the main room, and it separates the indoor and outdoor atmospheres, thereby reducing heat loss and improving the thermal performance of the main room. Herein, we propose a canopy-attached divider structure that can create a vestibule-like space and increase the overall thermo-fluid dynamic efficiency of SUTs. A computer simulation study was conducted for various divider geometries in terms of their locations and shapes to create diverse vestibules. The control parameters were the gap between the divider tip and the ground and the length along the radial direction, which determines the vestibule volume. SUT efficiency was analyzed using the velocity, temperature, and turbulence kinetic energy (TKE) contours obtained herein. The vestibule created by installing a divider with a gap of 60 mm and a length of 4.6 m can increase the outlet velocity by up to 6.97 %. The study demonstrated that integrating the well-established technology of the 'vestibule' with the SUT resulted in enhanced performance, showcasing a synergy between the conventional approach and the innovative SUT.

Solar updraft towers (SUTs) represent a promising avenue for renewable energy generation, leveraging solar energy to drive their operation. Although the collector of SUTs is generally vacant, ongoing research have focused on auxiliary structures inside the collector aimed at enhancing the overall efficiency. This study delved into the computational fluid dynamics (CFD) analysis of a SUT model featuring a 5 m radius collector and a 12 m height chimney. Specifically, we investigated the vestibule functions which created by implementing baffle inside the SUT collector with various radial locations. Through rigorous examination, the thermo-fluid dynamic effects of both roof-mounted and bottom-mounted baffles on SUT performance were explored, aiming to ascertain the optimal vestibule parameters. The vestibule was found to mitigate the backward flow leakage, isolate the inner room from the outside air, and enhance the heat exchange efficiency of the main flow. Notably, when the roof-mounted baffle was positioned at a radial location of 4.5 m, a remarkable 11.4 % and 28.1 % increase in the mass flow rate at the chimney outlet and kinetic power were achieved, respectively. These findings highlight the significant performance improvements achievable through the incorporation of a vestibule within SUTs of a given scale.

Hair loss caused by malfunction of the hair follicle stem cells (HFSCs) and physical damage to the skin is difficult to recover from naturally. To overcome these obstacles to hair follicle (HF) regeneration, it is essential to understand the three-dimensional (3D) microenvironment and interactions of various cells within the HFs. Therefore, 3D cell culture technology has been used in HF regeneration research; specifically, multicellular spheroids have been generally adapted to mimic the 3D volumetric structure of the HF. In this study, we culture HF-derived cells, which are mainly composed of HFSCs, in the form of 3D spheroids using a microwell array and discuss the effects of the 3D cellular environment on HF morphogenesis by expression measurements of Sonic hedgehog signaling and stem cell markers in the HF spheroids. Additionally, the influences of microwell depth on HF spheroid formation and biological conditions were investigated. The biomolecular diffusion and convective flow in the microwell were predicted using computational fluid dynamics, which allows analysis of the physical stimulations occurring on the spheroid at the micro-scale. Although a simple experimental method using the microwell array was adopted in this study, the results provide fundamental insights into the physiological phenomena of HFs in the 3D microenvironment, and the numerical analysis is expected to shed light on the investigation of the geometric parameters of the microwell system.

Over the past few decades, research on life in space has increased. Owing to the expensive nature of and the challenges associated with conducting experiments in real space, clinostats, which continuously randomize the gravity vector by using motors, have been used to generate simulated microgravity (SMG) on Earth. Herein, by using a 3D printing method, we develop a customized small-sized clinostat (CS clinostat) that is easy to manufacture, inexpensive, and robust. Moreover, we develop and fabricate a gas-permeable polydimethylsiloxane culture dish that fits inside the CS clinostat. To validate SMG generation, ovarian cancer cells (OV- 90, TOV-21G, and Caov-3) were applied to demonstrate a significant reduction in caveolin-1 expression, a biomarker of SMG, indicating SMG generation. The proposed CS clinostat system has good accessibility for SMG research, which makes it useful as a tool for biologists, who are unfamiliar with conventional clinostat equipment, to conduct preliminary studies in the space environment.

Abstract Over the past few decades, research on life in space has increased. Owing to the expensive nature of and challenges associated with conducting experiments in real space, clinostats, which create rotational motion by using motors to reduce the effect of gravity, are used to generate simulated microgravity (SMG) on Earth. However, the existing clinostat systems are complex, large, and expensive, which reduces their accessibility to researchers. Here, by using a 3D printing method, we develop a novel customized small-sized clinostat (CS clinostat) that is easy to manufacture, inexpensive, and robust. The dimensions of the CS clinostat are 282 × 140 × 252 mm3, and therefore, it can fit inside a typical 50 L incubator. The two motors of the CS clinostat rotate at 4 rpm (inner axis) and 1.8 rpm (outer axis) such that the accumulated three-axis acceleration is less than 3 × 10-2 G within 1 h. Moreover, we develop and fabricate a novel culture dish that fits inside the CS clinostat. This dish is covered with polydimethylsiloxane to facilitate gas exchange during cell culture. To validate SMG generation in the CS clinostat, we applied it to mammalian cells, OV-90, TOV-21G, and Caov-3, ovarian cancer cells. Western blotting analysis demonstrated significant reduction in Caveolin-1 expression, a biomarker of SMG, indicating SMG generation. The proposed CS clinostat system has good accessibility and reduces the barriers to SMG research, which makes it useful as a tool for biologists, who are unfamiliar with conventional clinostat equipment, to conduct preliminary studies in the space environment.

Damage to the sensory hair cells in the cochlea is a major cause of hearing loss since human sensory hair cells do not regenerate naturally after damage. As these sensory hair cells are exposed to a vibrating lymphatic environment, they may be affected by physical flow. It is known that the outer hair cells (OHCs) are physically more damaged by sound than the inner hair cells (IHCs). In this study, the lymphatic flow is compared using computational fluid dynamics (CFD) based on the arrangement of the OHCs, and the effects of such flow on the OHCs is analyzed. In addition, flow visualization is used to validate the Stokes flow. The Stokes flow behavior is attributed to the low Reynolds number, and the same behavior is observed even when the flow direction is reversed. When the distance between the rows of the OHCs is large, each row is independent, but when this distance is short, the flow change in each row influences the other rows. The stimulation caused by flow changes on the OHCs is confirmed through surface pressure and shear stress. The OHCs located at the base with a short distance between the rows receive excess hydrodynamic stimulation, and the tip of the V-shaped pattern receives an excess mechanical force. This study attempts to understand the contributions of lymphatic flow to OHC damage by quantitatively suggesting stimulation of the OHCs and is expected to contribute to the development of OHC regeneration technologies in the future.

Microfluidic devices have emerged as powerful tools for cell-based experiments, offering a controlled microenvironment that mimic the conditions within the body. Numerous cell experiment studies have successfully utilized microfluidic channels to achieve various new scientific discoveries. However, it has been often overlooked that undesired and unnoticed propagation of cellular molecules in such bio-microfluidic channel systems can have a negative impact on the experimental results. Thus, more careful designing is required to minimize such unwanted issues through deeper understanding and careful control of chemically and physically predominant factors at the microscopic scale. In this paper, we introduce a new approach to improve microfluidic channel design, specifically targeting the mitigation of the aforementioned challenges. To minimize the occurrence of undesired cell positioning upstream from the main test section where a concentration gradient field locates, an additional narrow port structure was devised between the microfluidic upstream channel and each inlet reservoir. This port also functioned as a passive lock that hold the flow at rest via fluid-air surface tension, which facilitated manual movement of the device even when cell attachment was not achieved completely. To demonstrate the practicability of the system, we conducted experiments and diffusion simulations on the effect of endocrine disruptors on germ cells. To this end, a bisphenol-A (BPA) concentration gradient was generated in the main channel of the system at BPA concentrations ranging from 120.8 μM to 79.3 μM, and the proliferation of GC-1 cells in the BPA gradient environment was quantitatively evaluated. The features and concepts of the introduced design is to minimize unexpected and ignored error sources, which will be one of the issues to be considered in the development of microfluidic systems to explore extremely delicate cellular phenomena.

Triboelectric nanogenerator (TENG) is one of the emerging energy harvesting technologies with the potential to be an alternative energy source. Owing to the various advantages of TENG, such as low cost, simple design, and high applicability, several researchers reported wearable TENG devices that can power electronics by harvesting human motion. However, as the human body has limited movement, the existing wearable TENG devices can only generate low power to turn on the electronics. In this study, a flow ring-based TENG (FR-TENG) is fabricated, which can be applied to wearable devices to generate high voltage and current output by including an opposite charging intermediate layer. By the simulation and experimental results, FR-TENG is optimized to generate a high output, that is, peak open-circuit voltage and closed-circuit current of up to 1020 V and 260 mA, respectively, owing to the electrostatic discharge. By these results, sleeve-type wearable FR-TENG is fabricated which can effectively harvest energy from arm movement. The sleeve-type FR-TENG can generate a high output owing to the working mechanism of FR-TENG; the high output was used to turn on 200 LEDs.

Researchers are attempting to develop hybrid generators by integrating several mechanical energy harvesting techniques, although most of them employ complicated device structures and fabrication methods. In this paper, we propose a slinky inspired triboelectric-electromagnetic hybrid generator (S-TEHG) that can easily function as a portable power source for devices used in daily life. This S-TEHG generates a high output using a peak voltage and current output of up to 7.4 V and 83.2 mA, respectively. For practical application as a portable power source in everyday life, the S-TEHG is enclosed (packaged) in an acrylic cylinder. In this study, upon hand waving, the proposed packaged S-TEHG successfully illuminated an array of 15 light-emitting diodes and charged a 47 mu F capacitor.

In recent years, the potential of nanobubbles (NBs) for biological activation has been actively investigated. In this study, we investigated the proliferative effects of nitrogen NBs (N-NBs) on fibroblast cells using cell assays with image analysis and flow cytometry. A high concentration of N-NBs (more than 4 × 108 NBs/mL) was generated in Dulbecco’s modified Eagle’s medium (DMEM) using a gas–liquid mixing method. In image analysis, the cells were counted and compared, which showed an 11