•PZT-ring/TDF-strip is proposed to achieve magnetically tunable resonance.•The frequency dependence of capacitance is corrected based on jump effect.•Improved sensitivity and resolution of resonance frequency shift are achieved.•This study provides the feasibility of tunable resonance for sonar transducer.By considering the jump effect of magnetostrictive materials, a novel structure of PZT-ring/TDF-strip magnetoelectric composite is proposed to achieve magnetically tunable electromechanical resonance with a DC bias magnetic field. With the jump effect induced piezomagnetic coefficient of the Tb0.3Dy0.7Fe1.92 strip, the resonance properties of the Pb(Zr,Ti)O3 ring are theoretically studied and experimentally measured. The highly consistent results prove that the proposed composite has two resonant frequencies with improved sensitivity (133 Hz/Oe) and enhanced resolution (722 ppm/Oe) of resonance shift, which provide the feasibility of magnetically tunable electromechanical resonance with a low magnetic field and suggest the application potential for controllable sonar transducer.

Based on the principle of Lorentz force induced acoustic vibration, radiation theory comparison between acoustic point and dipole sources was conducted for magnetoacoustic tomography with magnetic induction (MAT-MI). It is proved that each acoustic source of MAT-MI is produced by the divergence of the magnetically induced Lorentz force, and the detected acoustic pressure is the integral of all diffraction sources inside the object. Wave clusters are produced by abrupt pressure changes at conductivity boundaries, and only the configurations in terms of shape and size of phantom models can be reconstructed. However, different from point source, positive and negative pressures are generated by the radiation pattern of dipole sources. Reverse vibration phases of wave clusters in collected waveforms and opposite polarities of borderline stripes in reconstructed images are produced at conductivity boundaries, representing the direction of conductivity changes. The experimentally collected waveforms and reconstructed images of the aluminum foil cylinder and cylindrical saline gel phantom model agree well with simulated results. The favorable results prove the validity of the radiation theory of acoustic dipole source and provide basis for further investigation of conductivity reconstruction for MAT-MI.

In the present study, power ultrasound is applied to improve the permeability of the solid-state fabricated PLA foams with different cell sizes. It is experimentally proved that cell interconnection and the permeability is improved with the increasing of power ultrasound radiation intensity. Furthermore, an insert-substitution testing approach is put forward to perform acoustic measurement and property characterization for the PLA foams before and after ultrasound radiation. The experimental results indicate that the attenuation coefficient of the close-celled PLA foams decreases exponentially with respect to the saturation pressure and it shows linear behavior with respect to the ultrasound radiation intensity. The favorable results suggest the feasibility of the proposed technologies of ultrasound-assisted permeability improvement and acoustic characterization for the application of the solid-state foamed PLA foams in tissue engineering.Highlights► An ultrasound-assisted permeability improvement technology is proposed. ► Pulsed power ultrasound is employed to enhance the interconnectivity for PLA foams. ► An insert-substitution acoustic testing approach for the PLA foams is developed. ► The attenuation coefficient decreases exponentially with the saturation pressure. ► The attenuation coefficient shows linear behavior with the ultrasound radiation intensity.

A thermal gravimetric method is described for evaluating the kinetics of cell size-dependent decomposition and lifetime estimation for microcellular tissue engineering scaffolds made of biodegradable polylactic acid (PLA) foams. PLA foam cell sizes from 550 to 20 μm were fabricated experimentally using a solvent-free solid-state foaming technique under saturation pressures from 1 to 5 MPa. The thermal properties of the PLA foams with respect to the cell sizes were measured using thermal gravimetric analysis in a nitrogen atmosphere and the activation energy and pre-exponential factor were derived to evaluate the decomposition kinetics and estimate lifetime. It was found that small cell sizes can be achieved under high saturation pressures and that the thermal stability of PLA decreases after the fabrication process. The cell size-dependent thermal stability and degradation rate indicate that a PLA foam of larger cell sizes has a shorter degradation time, a few tenths that of the PLA raw material, at a temperature of 37°C. The results suggest that it is feasible to optimize fabrication parameters to obtain appropriate cell sizes and lifetimes that satisfy the application requirements for various organs. This study provides the basis for precise scaffold design and quantitative analysis of PLA foams in tissue engineering applications.