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A thermal catalytic device that reduces the energy required for the catalytic oxidation of volatile organic compounds (VOCs) was developed. The catalytic oxidation of VOCs is typically performed under indirect heating conditions resulting in high energy consumption. The proposed device drastically decreases the energy consumed and increases the amount of toluene decomposed during catalytic oxidation because the catalysts are heated directly via a carbon nanotube (CNT) element. The proposed device consists of a glass-fiber textile coated in CNTs, α-MnO2 nanostructures, and Pt nanostructures. The effect of different α-MnO2 nanostructures (granular and urchin-like) on device performance was investigated. Moreover, the effect of each device component on the toluene decomposition efficiency and energy consumption of the device was explored by determining the toluene concentration of gaseous toluene after the catalytic oxidation process and the associated energy consumption. The device featuring urchin-like α-MnO2 nanostructures coated in a thin layer of Pt achieves higher toluene decomposition efficiency than the device featuring granular α-MnO2 nanostructures coated in Pt nanoparticles. Moreover, the device featuring urchin-like α-MnO2 nanostructures coated in a thin Pt layer achieves higher toluene decomposition efficiency and lower energy consumption under direct heating conditions than under conventional indirect heating conditions.

As water scarcity has become a major global problem, fog-harvesting technologies are considered an effective sustainable solution for water resources. Here, we report a novel approach to the fog-harvesting technology using zinc oxide-silver hierarchical nanostructures to mimic the Stenocara beetle’s back. Vertically aligned zinc oxide nanowires are first fabricated by a cost-effective and scalable hydrothermal method to produce a superhydrophilic surface. Silver nanoparticles are then selectively synthesized by an additional photo-induced synthetic process on the zinc oxide nanowire surfaces to form a hydrophobic surface using the hierarchical nanostructures. The fog-harvesting performance was investigated using an artificial fog flow and by measuring the amount of harvested water for efficient fog harvesting. On the superhydrophilic surface, although the water droplets immediately were captured, they formed a puddle at the bottom of the surface due to the high adhesion between water and the surface. In contrast, on the hydrophobic surface, the capturing rate was very low even though the water droplets easily rolled off the surface. Compared to the non-patterned surface, the captured water film on the patterned hydrophilic region grew rapidly into a spherical shape and separated from the surface due to the surrounding hydrophobic regions. As a result, the patterned surface with 0.5 mm pattern size afforded a higher fog collection rate of 1233 mg/h than those of the superhydrophilic and hydrophobic surfaces of 1105 mg/h and 879 mg/h respectively.

Fluorescence-linked immunosorbent assay (FLISA) is a commonly used, quantitative technique for detecting biochemical based on antigen–antibody binding reactions using a well-plate platform. With the developments in the manufacturing technology of microfluidic systems, FLISA can be implemented onto microfluidic disk platforms, which allows the detection of trace biochemical with high resolutions. Apart from requiring a lower proportion of reagent (1/10), this method also reduces the time required for the entire process to less than an hour. The incubation process involves antigen–antibody binding reactions as well as the binding of fluorogenic substrates to target proteins. The protocol for FLISA on a microfluidic platform necessitates the appropriate execution of liquid reagent movements during each step in order to ensure sufficient binding reactions. Herein, we propose a novel microfluidic disk comprising a 3D incubation chamber. Vascular endothelial growth factor as concentration with ng mL-1 is detected sequentially using a benchtop process employing this 3D microfluidic disk. The 3D microfluidic disk is implemented without requiring manual intervention or additional procedures for liquid control. During the incubation process, microbead movement is controlled through centrifugal force, generated due to disk rotation, and gravitational force via bead sedimentation on the sloped floor of the chamber.

A microfluidic circuit on a disk platform, also known as lab-on-a-disk, is an integrated system for automated high-throughput screening for biochemical analysis. The microfluidic circuit on a disk performs biochemical analysis through sequential processes such as filtration, separation, detection, and synthesis of reagents. Sequential processes in microfluidic circuits operate through the systematically linked components, which include channels, valves, and chambers. The microchannels should have micrometer-scale for precise micro-volume liquid control in the microfluidic circuit on a disk. However, it is difficult to also consider productivity in the traditional technology. In addition, as the channel length increases, much effort is required to construct the components of the microfluidic circuit in the limited space of the disk. 3D printing is drawing attention as a microfluidic channel fabrication technique in order to overcome the physical limitations of the traditional methods. A new concept of a 3D slope valve has been developed, which performs precise and sequential micro-volume liquid control through centrifugal and gravitational forces. Micro-volumes of liquids in a slope valve-equipped circuit are controlled over a wide range of angular velocities through the control of the valve geometry, types of liquid and volume. For sequential micro-volume of liquid control, three lines of assembled modules are connected to a microfluidic circuit. In the microfluidic circuit with slope valves, the detection of fluorescent dye tagged-VEGF is possible through sequential mixing and reaction processes. As a result, micro-volume liquid is successfully controlled with high accuracy using the 3D microfluidic circuit with a slope valve.

In the field of environment and building engineering, the airflow pattern is one of the main factors controlling the indoor environmental quality. The control of airflow patterns has been examined, yet it remains problematic owing to a number of factors related to the location of the air inlets and outlets, and distributions of the indoor pollutants. Herein, we present a novel ventilation control strategy using artificial intelligence to rapidly remove hazardous airborne materials in an isolation room. The isolation room was designed with nine inlets on the ceiling and six outlets at the floor level to control airflow patterns through selective on/off switching of the inlets. To build a database of the indoor environment, numerical simulations were performed on different distributions of airborne particles and airflow patterns. We preprocessed the dispersion data of the airborne particles by discretizing the simulated volume into several cuboids and averaging the concentration data for use as the input variables for artificial intelligence. The artificial intelligence model predicted an efficient ventilation condition based on the distribution of the airborne materials within a prediction accuracy of 91%. The controlled strategy decreased the removal time up to maximum 63.65%, compared to conventional ventilation system. Furthermore, the proposed control strategies for airflow patterns can effectively prevent the spread of infectious viruses and reduce the risk of indoor infection transmission.

During a thin film application, the surface of the coating liquid applied to the substrate becomes uneven because of the geometry of the substrate, viscosity of the coating liquid, surface tension, and its contact angle with the substrate. The surface is particularly uneven at the edge corner portion of the substrate and is thicker than the average coating thickness. This study used the volume-of-fluid (VOF) method to examine the surface unevenness of the coating liquid in terms of the contact angle of the substrate surface and sides. After the coating liquid was evenly applied to the substrate, the maximum height of the uneven region of the coating liquid at the edge of the substrate increased as time passed. The point of maximum height moved away from the edge corner portion of the substrate. The coating liquid applied to the substrate with a contact angle less than 90&deg, exhibited a pinning effect in which the contact point was fixed at the edge. The surface unevenness was more pronounced in the absence of the pinning effect than in its presence, due to the effects of the viscosity of the coating fluid and the surface energy of the substrate.

In the study, a new method to enhance the performance of a thermoelectric generator (TEG) device by utilizing the water-film evaporative cooling is proposed. An experimental device was constructed by incorporating a water-film cooling pond with a commercially available TEG. Experiments were performed to investigate the effects of the main operating conditions (ambient temperature Tamb was 25 °C), TEG hot-side temperature (TH = 50–100 °C), ambient relative humidity (RH = 15–90%), and water-film thickness (twater = 1–9 mm) on the TEG output performance. Additionally, the output performance of TEG under different cooling methods was compared. A TEG prototype device was constructed to generate electricity/steam using seawater evaporation cooling without external electrical energy. The results indicated that TEG hot-side temperature and water-film thickness significantly affected output performance. However, the ambient relative humidity did not considerably affect TEG output performance. Given TEG hot-side temperature TH = 100 °C, ambient relative humidity RH = 15%, the TEG prototype device-generated open-circuit voltage of Uopen = 1.55 V, maximum output power of Pmax = 290.32 mW, and a steam generation rate of 9.82 mg/s. The results showed that evaporative cooling is an innovative method to improve the performance of TEG.

Theoretical model of thermoelectric generator (TEG) cooled by direct evaporative cooling technology is developed. In the theoretical model, thermoelectric material properties depending on temperature change and effects of heat loss by radiation, conduction, and Thomson phenomenon are considered. To investigate the effect of evaporative cooling to the efficiency of TEG, the simulation conditions are set as hot-side temperature of 40–120 °C and 1 mm thickness of thin water film covering for cold-side. The ambient temperature is 25 °C and the relative humidity of the air is set from 25% to 75%. Based on the developed theoretical model, the output power of TEG is increased as increasing hot side temperature under fixed relative humidity or as decreasing relative humidity under fixed hot-side temperature. Consequently, the maximum output power of 130.69 W m−2 and an efficiency of 1.63% are obtained with 25% relative humidity and 120 °C for the hot-side temperature condition. The results show that the output power and efficiency are increased 100.53 and 10.53 times higher than without evaporative cooling (natural convection case, output power of 1.30 W m−2 and efficiency of 0.1548%), respectively.

Zinc oxide(ZnO) is a versatile semiconductor material and its use is expanding into photoelectric applications. Anisotropic growth characteristics of ZnO are advantageous for growing a nanowire structure. ZnO nanowire based sensors exhibit enhanced performance in terms of photodetection due to their large specific surface area. ZnO nanowires on a highly aligned electrospun poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) nanofiber-based film are fabricated high performance ultraviolet (UV) detector. The movement of photo-induced electrons from ZnO nanowires is more effective in aligned electrospun film substrate (Rsq,off/Rsq,on = 551.0) than random electrospun film substrate (Rsq,off/Rsq,on = 47.8) under continuous UV irradiation. The current difference is 3.98 times higher on ZnO nanowires on aligned electrospun film than it is on random electrospun film in UV light on-off cycles. As a result, we improve the performance of photo sensitivity of electrospun nanofiber-based ZnO nanowires through controlling the directionality and fabrication time of the electrospun film without additional processes.