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.

Microwells are used in studies to mimic the in vivo environment through an in vitro environment by generating three-dimensional cell spheroids. These microwells have been fabricated in various shapes using different methods according to the research purpose. However, because all microwells up to now have an open top, it has been difficult to culture spheroids of floating cells due to their low density, such as human adipose-derived stem cells (hASCs) that differentiate into adipocytes. Therefore, the labor-intensive hanging droplet method has been mainly used for the study of adipocytes. Here, we introduce a sigma-well, which is a microwell in the shape of the Greek letter sigma (σ) with a roof. Because of its unique shape, the sigma-well is advantageous for the culture of floating cells by reducing cell loss and external interference. The sigma-well was fabricated using the principle of surface tension of polydimethylsiloxane as well as air trapping and thermal expansion. Unlike conventional microwells, because the center of the bottom surface and the inlet of the sigma-well are not located on the same line and have a difference of approximately 218 μm, the spheroids are cultured more stably and may not escape the cavity. In this study, hASC and adipocyte spheroids differentiated using these sigma-wells were successfully cultured. In addition, through cytokine diffusion simulation, it was confirmed that the diffusion and mass transfer in the sigma-well was lower than that in the conventional microwell. It is expected that the morphological features of the sigma-well, which cannot be easily obtained by other methods, can be beneficial for the study of buoyant cell types such as adipocytes.

A cell spheroid culture has the benefit of simulating in vivo three-dimensional cell environments. Microwell systems have been developed to mass-produce large quantities of uniform spheroids, and are frequently used in research areas, such as cell biology, anticancer drug development, and regenerative therapy. Recently reported concave-bottomed microwell systems have delivered more benefits in producing spheroids of higher quality and facilitating more effective research. However, microwell fabrication methods are often complicated or expensive, and there are inherent limitations in the functions and characteristics of existing microwells. Therefore, further studies on concave microwell systems are required. In this study, we fabricate spherical microwells with funnel-shaped entrance structures for spheroid culture; the shape is an upside-down omega (), and is thus named 'Omega-well'. The Omega-well array is fabricated using the capillary action of liquid polymer on the pins of a computer central processing unit, which is accomplished without requiring expensive materials or difficult procedures. Various characteristic analyses are performed by experiments and computer simulation. It is demonstrated that cell loss is minimized during cell seeding, a produced spheroid does not easily escape, and that crosstalk between microwells is significantly reduced. The novel fabrication method and Omega-well platform proposed in this study are highly practical, and thus will be useful tools in biology and pharmaceutical labs.

External pumps (e.g. syringe pump) that operate microfluidic fuel cell (MFFC) devices are inefficient because the amount of electricity required to run such pumps easily exceeds that generated by the MFFC. Herein, we propose a suitable small, lightweight, and external power-free osmosis-driven pump embedded with an MFFC system, capable of steady-flow generation. Methanol and vanadium are used as fuel, and the electrodes are made of carbon paper. We do not utilize sputtering equipment, commonly used for electrode fabrication. To incorporate the carbon paper-based electrode into the MFFC, the cross section of the microchannel is uniquely designed into a bridge-shaped channel, and its electrochemical and fluid dynamic influences are analyzed through experiments and simulations. The total weight of our MFFC system is less than 20g, the size is approximately 5cm, and the power density generated is approximately 0.3 mW cm(-2). The presented methods will contribute to the development of standalone MFFCs operable for prolonged durations (similar to 1 d), thereby enhancing the possibility of MFFC commercialization.