Chronic wounds pose a substantial global health challenge, further complicated by the presence of biofilms, which are pathogenic bacterial colonies protected by a biopolymer matrix. These biofilms are notably resistant to both traditional antibiotics and host immune responses, underscoring the critical demand for innovative therapeutic strategies. Among such advancements, transdermal drug delivery mechanisms, particularly microneedle patches, have shown promise in addressing biofilm-related infections effectively. This research introduces a drug delivery system incorporating a piezoelectric transducer (PZT) with a strategically arranged array of drug-infused microneedles. The activation of this system through voltage application to the transducer generates ultrasound waves, facilitating the targeted dispersion of drugs through the creation of localized acoustic fields and fluid streaming. This study delves into the optimization of ultrasound parameters and the mechanics of acoustically assisted drug distribution, identifying the conditions under which ultrasound waves can enhance the transfer of therapeutic agents via microneedles. It distinguishes between resonant and non-resonant frequencies, which influence the pattern and efficiency of drug diffusion into biofilms. The analysis extends to the simulation of drug penetration into biofilms, offering insights into concentration profiles at various depths. This investigation not only highlights the potential of ultrasound-enhanced drug delivery for precision medicine but also suggests its applicability in treating a wide array of medical conditions. The ability to precisely control drug delivery, coupled with real-time monitoring, signifies a transformative approach to medical treatment, with the potential to significantly improve patient outcomes and quality of life.
In this paper, an elastic metamaterial is presented to achieve complete conversion from Lamb modes into the fundamental shear horizontal mode. Modal analysis with Bloch-Floquet boundary condition is performed to obtain the dispersion features of the metamaterial system. By analyzing the resonant modes of the unit cell, a complete SH0 mode generation band within the A0 and S0 modes bandgap can be formed in a wide frequency range. Thereafter, finite element model (FEM) harmonic analyses for an elastic metamaterial plate are carried out to explore the mode conversion efficiency. Finally, a coupled field transient dynamic FEM is constructed to acquire the response of the structure. A 30- count tone burst incident wave containing both A0 and S0 modes is excited to propagate into the elastic metamaterial system. The frequency-wavenumber analysis results demonstrate the achievement of the mode conversion behavior, manifested by the strong coupling between guided waves and resonant modes of the composite stubs. The proposed mode conversion behavior may possess great potential in future Structural Health Monitoring (SHM) and Nondestructive Evaluation (NDE) applications. The paper finishes with summary, concluding remarks, and suggestions for future work.
In this study, an omnidirectional shear horizontal (SH) wave acoustic transducer (OSH-WAT) is proposed, composed of a circular aluminum structure driven by twelve thickness-mode (d33) piezoelectric wafer active sensors (PWAS). The OSH-WAT contains six units to form an axisymmetric structure, and each unit consists of a cylinder with a cantilever beam and two cubic stubs. Two d33 PWASs acting like a couple, as the actuation sources, are bonded on the opposite sides of the cantilever beam to drive the excitation. The thickness-mode PWASs can produce a forcing pair, which can be converted to a circumferential shear deformation by two adjacent cubic stubs, contributing to the omnidirectional SH0 wave generation. Multiphysics finite element model (FEM) is constructed based on such a design. Harmonic analysis is conducted to obtain the spectral response of a circular aluminum plate to investigate the omni-directivity of the SH0 wave excited by the OSH-WAT, so as to identify the “sweet” frequency bands. Thereafter, the coupled field transient dynamic FEM simulations are carried out to acquire the dynamic response of a pitch-catch active sensing procedure. A voltage signal in the form of a 5-count tone burst is applied on each d33-type PWAS to generate SH0 mode waves into the aluminum host plate. The received signals demonstrate the outstanding performance of the successful generation and reception of SH0 waves. The proposed OSH-WAT may possess great potential in future Structural Health Monitoring (SHM) and Nondestructive Evaluation (NDE) applications. The paper finishes with summary, concluding remarks, and suggestions for future work.
In this paper, a bandgap meta-surface is carefully designed for enhancing the identifiability of nonlinear ultrasonic superharmonics for fatigue crack detection. In the unit cell design stage, modal analysis with Bloch-Floquet boundary condition is performed to obtain the dispersion features of guided waves in the meta-surface. Then, a finite element model (FEM) for a chain of unit cells is simulated to verify the bandgap effect. In practice, due to the inherent nonlinearity from the electronic instrument and bonding adhesive, the corresponding weak superharmonic components will adversely affect the identifiability of the nonlinear characteristics raised by wave crack interactions. In the current approach, the guided waves generated by the transmitter propagate into the structure, carrying the inherent nonlinearity with them. Immediately afterwards, they pass through the meta-surface with optimized transmission of the fundamental excitation frequency and complete mechanical filtration of the second harmonic component. In this way, the appearance and amplitude of the second harmonic in the sensing signal become evidently indicative of the presence and severity of the fatigue crack along the wave path between the meta-surface and the receiver. The proposed method possesses great potential in future SHM and NDE applications. Nonlinear ultrasonic experiments with the designed meta-surface are conducted to verify the theoretical and numerical investigations as well as to demonstrate the practical application of metamaterial in SHM and NDE. The paper finishes with summary, concluding remarks, and suggestions for future work.
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