The aerodynamic effects of wing corrugation on insect flight have received widespread attention. However, there has hardly been any specific focus on dynamic changes to corrugation angle in the models. The flexible vein joints containing resilin in the wings of dragonflies and damselflies enable the longitudinal veins to rotate and thereby change the corrugation angles throughout flapping cycles. Therefore, a two-dimensional corrugated airfoil with time-varying corrugation angles is proposed and the aerodynamic performance is evaluated in terms of aerodynamic force, power and efficiency. The results indicate that the airfoil with time-varying corrugations outperforms the rigid one in terms of enhancing thrust and reducing power consumption. The aerodynamic performance of time-varying corrugated airfoils is optimal when the angle varies in a specific range, and an excessively large angle variation may have negative effects. In addition, excessive height or a negative leading edge of the corrugation can lead to a reduction in the thrust. A design concept for the 2D airfoil with time-varying corrugations is provided and the findings are of significance for enhancing the aerodynamic performance of biomimetic flexible flapping-wing vehicles.

Dry-powder inhalers (DPIs) are valued for their stability but formulating them is challenging due to powder aggregation and limited flowability, which affects drug delivery and uniformity. In this study, the incorporation of L-leucine (LEU) into hot-melt extrusion (HME) was proposed to enhance dispersibility while simultaneously maintaining the high aerodynamic performance of inhalable microparticles. This study explored using LEU in HME to improve dispersibility and maintain the high aerodynamic performance of inhalable microparticles. Formulations with crystalline itraconazole (ITZ) and LEU were made via co-jet milling and HME followed by jet milling. The LEU ratio varied, comparing solubility, homogenization, and aerodynamic performance enhancements. In HME, ITZ solubility increased, and crystallinity decreased. Higher LEU ratios in HME formulations reduced the contact angle, enhancing mass median aerodynamic diameter (MMAD) size and aerodynamic performance synergistically. Achieving a maximum extra fine particle fraction of 33.68 ± 1.31% enabled stable deep lung delivery. This study shows that HME combined with LEU effectively produces inhalable particles, which is promising for improved drug dispersion and delivery.

This study presents a model experiment method that can accurately reproduce the flapping motion of insect wings and measure related unsteady aerodynamic data in real time. This method is applied to investigate the aerodynamic characteristics of inclined hovering, which distinguishes it from normal hovering by having asymmetric wing rotation during the two half strokes. In the study of the aerodynamic influence of the downstroke rotational angle, it is found that the rotational angle affects lift generation by changing the angle between the wing surface and the horizontal plane in the mid-downstroke. When the wing is almost parallel to the horizontal plane in the mid-downstroke, the vortex structure can maintain structural integrity and a large magnitude, which is conducive to the generation of high lift. In the study of the aerodynamic effect of the upstroke rotational angle, the windward conversion mechanism is proposed to explain the influence of the upstroke rotational angle on the direction and magnitude of thrust. Obtaining the rotational angle that is most conducive to maintaining the flight state of hovering in the present study can provide guidance for the structural design and kinematic control of micro aerial vehicles.

Beetle hindwings have the unique advantages of lightweight and high strength, which play a key role in flight. In this study, the beetle hindwings were cut along the chordal direction, then the first groove microstructure of different vein cross sections was investigated using the 3D microscope system and the laser scanning confocal microscope. It was found that the position of the first groove relative to the entire chordal cross section of the wing gradually moves backward, which has an effect on the flying aerodynamic behaviors of the beetle. Next, three corrugated airfoils learned from the microscopy imaging of the ladybird beetle hindwing were designed. Then, aerodynamic behaviors were calculated by the ANSYS Fluent software, and it was confirmed that the position of the first groove microstructure affects the aerodynamic performance of the airfoil. For further study, the influence of corrugated structural and motion parameters on the aerodynamic, 2D \'simplified\' airfoil models with triangular wave airfoil models (TWA models) was developed and studied. RESEARCH HIGHLIGHTS: The position of the first groove microstructure affects the aerodynamic performance of the airfoil. The pressure difference of different corrugation patterns shows significantly asymmetric during the upstroke and downstroke. The aerodynamic is optimal of 2D-TWA models, when the number of corrugations is five, the corrugation is right angle, and the flapping frequency is 75 Hz.

Corrugated surface microparticles comprising levofloxacin (LEV), chitosan and organic acid were prepared using the 3-combo spray drying method. The amount and the boiling point of the organic acid affected the degree of roughness. In this study, we tried to improve the aerodynamic performance and increase aerosolization by corrugated surface microparticle for lung drug delivery efficiency as dry powder inhaler. HMP175 L20 prepared with 175 mmol propionic acid solution was corrugated more than HMF175 L20 prepared with 175 mmol formic acid solution. The ACI and PIV results showed a significant increase in aerodynamic performance of corrugated microparticles. The FPF value of HMP175 L20 was 41.3% ± 3.9% compared with 25.6% ± 7.7% of HMF175 L20. Corrugated microparticles also showed better aerosolization, decreased x-axial velocity, and variable angle. Rapid dissolution of drug formulations was observed in vivo. Low doses administered to the lungs achieved higher LEV concentrations in the lung fluid than high doses administered orally. Surface modification in the polymer-based formulation was achieved by controlling the evaporation rate and improving the inhalation efficiency of DPIs.

Co-suspension drug-loading technology, namely Aerosphere™, can improve fine particle fraction (FPF) and delivered dose content uniformity (DDCU). However, because of its poor drug-loading efficacy, the phospholipid carrier dosage in Aerosphere™ is usually dozens of times greater than that of the drug, resulting in a high material cost and blockage of the actuator. In this study, spray-freeze-drying (SFD) technology was used to prepare inhalable distearoylphosphatidylcholine (DSPC)-based microparticles for pressurized metered-dose inhalers (pMDI). Water-soluble, low-dose formoterol fumarate was used as an indicator to evaluate the aerodynamic performance of the inhalable microparticles. Water-insoluble, high-dose mometasone furoate was used to investigate the effects of drug morphology and drug-loading mode on the drug delivery efficiency of the microparticles. The results demonstrated that DSPC-based microparticles prepared using the co-SFD technology not only achieved higher FPF and more consistent delivered dose than those of drug crystal-only pMDI, but the amount of DSPC was also reduced to approximately 4% of that prepared using the co-suspension technology. This SFD technology may also be used to improve the drug delivery efficiency of other water-insoluble and high-dose drugs.

UNASSIGNED: Discovery of falsified Symbicort 320/9 Turbohaler identified in the UK in 2013 demonstrated that falsified dry powder inhalers were also present in the European market. This work aimed to investigate the current situation of formoterol-containing dry powder inhalers in Europe and North Africa by assessing their aerodynamic performance profile.
UNASSIGNED: A total of eight registered formoterol-based dry powder inhalers over the European and North African markets were involved in this study, including the reference drug Foradil. Samples were prepared using a multistage liquid impinger (MsLI) and further analyzed by a validated HPLC-UV method to determine the delivered and the fine particle doses (FPDs). This study also examined the impact of freezing-thawing cycles on sample stability in terms of analytical purpose handling.
UNASSIGNED: No substandard dry powder inhalers were identified among the medicinal products involved in this work. The delivered dose (DD) of assessed drugs varied from 8.33 to 9.69 µg, while the FPD was between 1.86 and 3.35 µg. As expected, this work confirmed that the capsule composition and the barrier properties of the primary packaging can affect the FPD of dry powder for inhalation use.
UNASSIGNED: The FPD of products C and B was, respectively, 17.4 and 14.2% superior to Foradil, products D and H had the closest values compared to the original drug, and product F was 34.5% inferior. Additionally, this work showed that a high FPD can be achieved using HPMC capsules and moisture-impermeable primary packaging.

UNASSIGNED: Dry powder inhalations are an attractive pharmaceutical dosage form. They are environmentally friendly, portable, and physicochemical stable compared to other inhalation forms like pressurized metered-dose inhalers and nebulizers. Sufficient drug deposition of DPIs into the deep lung is required to enhance the therapeutic activity. Nanoscale surface roughness in microparticles could improve aerosolization and aerodynamic performance. This study aimed to prepare microspheres with nanoscale dimples and confirm the effect of roughness on inhalation efficiency.
UNASSIGNED: The dimpled-surface on microspheres (MSs) was achieved by oil in water (O/W) emulsion-solvent evaporation by controlling the stirring rate. The physicochemical properties of MSs were characterized. Also, in vitro aerodynamic performance of MSs was evaluated by particle image velocimetry and computational fluid dynamics.
UNASSIGNED: The particle image velocimetry results showed that dimpled-surface MSs had better aerosolization, about 20% decreased X-axial velocity, and a variable angle, which could improve the aerodynamic performance. Furthermore, it was confirmed that the dimpled surface of MSs could cause movement away from the bronchial surface, which helps the MSs travel into the deep lung using computational fluid dynamics.
UNASSIGNED: The dimpled-surface MSs showed a higher fine particle fraction value compared to smooth-surface MSs in the Andersen Cascade Impactor, and surface roughness like dimples on microspheres could improve aerosolization and lung deposition.

Rotor plays a vital role in the dynamical system of an unmanned aerial vehicle (UAV). Prominent aerodynamic and acoustic performance are a long-term pursuit for the rotor. Inspired by excellent quiet flight characteristics of owls, this work adopted bionic edge design and rational material selection strategy to improve aerodynamic and acoustic performance of the rotor. A reference model of rotor prototype with streamlined edges was firstly generated by reverse engineering method. With inspiration from owl wings and feathers, bionic rotors with rational design on leading and trailing edges were obtained. Original and bionic rotors were fabricated with polyamide PA 12 and Resin 9400 by 3D printing technique. Aerodynamic and acoustic performance of the as-fabricated rotors were experimentally measured and analyzed in detail using a self-established test system. Comparative experimental results indicated that the aerodynamic and acoustic performance of the rotors was closely related to the bionic structures, material properties, and rotational speeds. At the same rotational speed, bionic rotor fabricated with Resin 9400 can produce a higher thrust than the prototype one and its power consumption was also reduced. The resulting noise of different bionic rotors and their directivities were comparatively investigated. The results verified the bionic edge design strategy can effectively control the turbulent flow field and smoothly decompose the airflow near the tailing edge, which resulting in enhancing the thrust and reducing the noise. This work could provide beneficial inspiration and strong clues for mechanical engineers and material scientists to design new abnormal rotors with promising aerodynamic and acoustic performance.

In vitro assessment of dry powders for inhalation (DPIs) aerodynamic performance is an inevitable test in DPI development. However, contemporary trends in drug development also implicate the use of in silico methods, e.g., computational fluid dynamics (CFD) coupled with discrete phase modeling (DPM). The aim of this study was to compare the designed CFD-DPM outcomes with the results of three in vitro methods for aerodynamic assessment of solid lipid microparticle DPIs. The model was able to simulate particle-to-wall sticking and estimate fractions of particles that stick or bounce off the inhaler\'s wall; however, we observed notable differences between the in silico and in vitro results. The predicted emitted fractions (EFs) were comparable to the in vitro determined EFs, whereas the predicted fine particle fractions (FPFs) were generally lower than the corresponding in vitro values. In addition, CFD-DPM predicted higher mass median aerodynamic diameter (MMAD) in comparison to the in vitro values. The outcomes of different in vitro methods also diverged, implying that these methods are not interchangeable. Overall, our results support the utility of CFD-DPM in the DPI development, but highlight the need for additional improvements in these models to capture all the key processes influencing aerodynamic performance of specific DPIs.