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In this paper, we presented a theoretical method for studying the behavior of magnetic field intensity and eddy current inside a magnetostriction based bilayered composite. Firstly, the mathematical model for the electromagnetic field in the composite was established. Then, the governing equation for determining the magnetic field intensity and eddy current was solved. Furthermore, the effect of the composite's conductivity on the magnetic field intensity and eddy current were discussed. Lastly, by comparing with the well known R.L. Stoll's equation, the magnetic field intensity calculated based on our equation showed a less than 0.5% error. [ABSTRACT FROM AUTHOR]

In this work, we propose a novel wireless actuator which is composed of magnetostrictive material/copper bi-layer film. The actuator can be controlled to move like a snake bi-directionally along a pipe by tuning the frequency of external magnetic field near its first order resonant frequency. The governing equation for the actuator is established and the vibration mode shape function is derived. Theoretical analysis shows that motion of the actuator is achieved by asymmetric vibration mode shape, specific vibration bending deformation, and effective net total impacting force. The simulation and experimental results well confirm the theoretical analysis. This work provides contribution to the development of wireless micro robots and autonomous magnetostrictive sensors. [ABSTRACT FROM AUTHOR]

Resonant-mode based cantilevers are an important type of acoustic wave based masssensing devices. In this work, the governing vibration equation of a bi-layer resonantmode based cantilever attached with concentrated mass is established by using a modal analysis method. The effects of resonance modes and mass loading conditions on nodes and mass sensitivity of the cantilever were theoretically studied. The results suggested that the node did not shift when concentrated mass was loaded on a specific position. Mass sensitivity of the cantilever was linearly proportional to the square of the point displacement at the mass loading position for all the resonance modes. For the first resonance mode, when mass loading position xc satisfied 0 < xc < ~0.3l (l is the cantilever beam length and 0 represents the rigid end), mass sensitivity decreased as the mass increasing while the opposite trend was obtained when mass loading satisfied ~0.3l ≤ xc ≤ l. Mass sensitivity did not change when concentrated mass was loaded at the rigid end. This work can provide scientific guidance to optimize the mass sensitivity of a resonant-mode based cantilever. [ABSTRACT FROM AUTHOR]

The existence of "blind point" lowers the mass sensitivity and reliability of magnetostrictive particle (MSP) based biosensors. In addition, asymmetric distribution of mass loading (e.g. bacteria) will cause the shift of "blind point" and change of mass sensitivity of an MSP based biosensor. In this work, a modal analysis method was introduced and conducted to derive the governing vibration equation for an MSP biosensor with asymmetric mass loading. The effects of asymmetric mass loading on the "blind point" shift and mass sensitivity were unveiled by solving the governing vibration equation. It was found that the plot of "blind point" shift showed an "M" shape with the valley located at a/l ~ 0.5 and two peaks located at a/l ~ 0.25 and a/l ~ 0.75. In addition, the theoretical results showed that the resonance frequency shift (Δf) depends on the value of a/l (i.e. both the attached mass and mass distribution) and their relationship is nonlinear. Based on the definition of mass sensitivity (Sm), the values of Sm were derived for the selected values of a/l. The results showed that Sm decreased initially with increasing a/l, reaching the minimum, and then increased until a/l = 1. That is, the maximum mass sensitivity is obtained when a/l equals to a critical value Xc (0 < Xc < l). Based on the result, an optimal mass loading distribution design criterion for developing a more sensitive MSP based biosensor was proposed. [ABSTRACT FROM AUTHOR]