Nonlinear Magneto-Electro-Mechanical Response of Physical Cross-Linked Magneto-Electric Polymer Gel

This work reports on a novel magnetorheological polymer gel with carbon nanotubes and carbonyl iron particles mixed into the physical cross-linked polymer gel matrix. The resulting composites show unusual nonlinear magneto-electro-mechanical responses. Because of the low matrix viscosity, effective conductive paths formed by the CNTs were mobile and high-performance sensing characteristics were observed. In particular, due to the transient and mutable physical cross-linked bonds in the polymer gel, the electromechanical behavior acted in a rate-dependent manner. External stimulus at a high rate significantly enhanced the electrical resistance response during mechanical deformation. Meanwhile, the rheological properties were regulated by the external magnetic field when magnetic particles were added. This dual enhancement mechanism further contributes to the active control of electromechanical performance. These polymer composites could be adopted as electromechanical sensitive sensors to measure impact and vibration under different frequencies. There is great potential for this magnetorheological polymer gel in the application of intelligent vibration controls

Study on the damping properties of magnetorheological elastomers based on cis-polybutadiene rubber

Magnetorheological elastomers (MREs) are composed of magnetizable particles (iron particles) and a soft rubber-like matrix. Their mechanical properties, including modulus and damping capability, can be controlled by an external magnetic field. The damping properties of MREs, which play an important role in applications, depend mainly on particle content. This paper aims to investigate MRE’s damping capabilities by studying two categories of cis-polybutadiene rubber-based MREs: isotropic and structured MREs. Both isotropic and structured MRE samples with various iron particle contents (60, 70, 80 and 85 wt%) were fabricated and their damping properties were measured by using a modified dynamic mechanical analyzer (DMA) and a universal testing machine. The results show that the loss factor in the glass transition region decreases with the increment of iron particle content. The loss factors of structured MREs are lower than those of isotropic MREs when the iron particle contents are the same. Furthermore, dynamic testing was conducted to study the effect of strain amplitude, frequency and magnetic field on the loss factor of MREs. In addition, the stress-softening experiments indicate that the ratio of remaining strain energy versus initial strain energy shows a decreasing trend with iron particle content and loading time

Interactive Micromanipulation of Picking and Placement of Nonconductive Microsphere in Scanning Electron Microscope

In this paper, classified theoretical models, consisting of contact with and placement of microsphere and picking operations, are simplified and established to depict the interactive behaviors of external and internal forces in pushing manipulations, respectively. Sliding and/or rolling cases, resulting in the acceleration of micromanipulations, are discussed in detail. Effective contact detection is achieved by combining alterations of light-shadow and relative movement displacement between the tip-sphere. Picking operations are investigated by typical interactive positions and different end tilt angles. Placements are realized by adjusting the proper end tilt angles. These were separately conducted to explore the interactive operations of nonconductive glass microspheres in a scanning electron microscope. The experimental results demonstrate that the proposed contact detection method can efficiently protect the end-tip from damage, regardless of operator skills in initial positioning operations. E-beam irradiation onto different interactive positions with end tilt angles can be utilized to pick up microspheres without bending the end-tip. In addition, the results of releasing deviations away from the pre-setting point were utilized to verify the effectiveness of the placement tilt angles