Acoustic metamaterial comprising an array of resonators being attached to the side wall of a rigid duct is investigated in this study. We propose a resonator design by employing a pre-stretched dielectric elastomer (DE) membrane to tune the acoustic property of each resonator. Both numerical and experimental techniques are developed to characterize the acoustic behavior of the proposed device in terms of transmission loss (TL). By connecting multiple resonators, we show that a broadband TL can be achieved which combines the multiple attenuation bands provided by each resonator unit. The resulted attenuation band can be tuned by varying the applied voltage to the DE membranes, showing promising potentials such as adaptive sound control devices for ventilation systems and other engineering applications

The propeller-type flap design is increasingly used in reconstructive surgery for various regions of the body. To date, determinants of perforator patency when subjected to twisting have not been elucidated. We propose a simulation model to study parameters affecting perforator patency under such conditions. Nonlinear finite element procedure was used to simulate a perforator consisting of an artery and a vein with both ends fixed. A rigid body was attached to the top of the perforator for applying prescribed angular displacement. The effect of the following parameters on the pedicle patency was determined: (1) increasing angle of twist, (2) vessel stiffness, (3) vessel length, (4) diameter, (5) intraluminal pressure, and (6) the presence or absence of blood flow during twisting. Simulation results were reported in effective stress and strain on the twisted pedicle. In the context of perforator patency, effective strain, which is a measure of vessel deformation or collapse, is the more relevant outcome. The vein was more prone to occlusion because of its weaker wall and lower intraluminal pressure. Four factors that affected perforator patency were identified: angle of twist, intraluminal blood pressure, and perforator diameter and length. There was no significant difference whether twisting was performed prior to or after restoration of blood flow (P > 0.05). Therefore, to optimize condition for maintaining perforator patency, the angle of twist should be kept 30 mm in length. We found that the propeller flap is a feasible design. This study defined the determinants of perforator patency and will serve as a useful guide when performing such flaps.

Functional and mechanical properties of novel biomaterials must be carefully evaluated to guarantee long-term biocompatibility and structural integrity of implantable medical devices. Owing to the combination of metallic bonding and amorphous structure, metallic glasses (MGs) exhibit extraordinary properties superior to conventional crystalline metallic alloys, placing them at the frontier of biomaterials research. MGs have potential to improve corrosion resistance, biocompatibility, strength, and longevity of biomedical implants, and hence are promising materials for cardiovascular stent applications. Nevertheless, while functional properties and biocompatibility of MGs have been widely investigated and validated, a solid understanding of their mechanical performance during different stages in stent applications is still scarce. In this review, we provide a brief, yet comprehensive account on the general aspects of MGs regarding their formation, processing, structure, mechanical, and chemical properties. More specifically, we focus on the additive manufacturing (AM) of MGs, their outstanding high strength and resilience, and their fatigue properties. The interconnection between processing, structure and mechanical behaviour of MGs is highlighted. We further review the main categories of cardiovascular stents, the required mechanical properties of each category, and the conventional materials have been using to address these requirements. Then, we bridge between the mechanical requirements of stents, structural properties of MGs, and the corresponding stent design caveats. In particular, we discuss our recent findings on the feasibility of using MGs in self-expandable stents where our results show that a metallic glass based aortic stent can be crimped without mechanical failure. We further justify the safe deployment of this stent in human descending aorta. It is our intent with this review to inspire biodevice developers toward the realization of MG-based stents.