MRI Compatibility of Silicone-Made Contractile Dielectric Elastomer Actuators

Actuators based on dielectric elastomers, a specific class of electroactive polymers, appear to be suitable candidates for new MRI-compatible technologies, due to their intrinsic material properties and working principle. This paper presents the first investigation into the MRI compatibility of a recently developed linear contractile actuator made of a silicone elastomer. The apparent absence of any degradation of both the actuator electromechanical performance in the MRI environment and the quality of images acquired from a phantom demonstrates the MRI compatibility of the actuator. These results suggest the suitability of this soft actuation technology as a possible new entry in the class of MRI-compatible mechatronic systems.     

Evaluation of Electrorheological Fluid Dampers for Applications at 3-T MRI Environment

This paper evaluates the use of electrorheological fluids (ERFs) within a magnetic resonance imaging (MRI) environment. ERF is a semiactive variable impedance material, which could be used as an alternative type of resistive force/torque generation or in combination with other actuators as a damper/clutch to modulate the output force/torque of the actuator. In this paper, an ERF damper/brake is introduced and its magnetic resonance (MR) compatibility is examined at a 3-T MR imaging environment by measuring the output performance of the damper and the SNR of the MRI images. The experimental results showed that damper's resistive force generation while positioned within the MRI is almost the same as that in normal operation. The signal-to-noise investigation was performed both with a phantom and human. The results indicated that the ERF damper did not affect the MRI images when it was operated over 30 cm away from the MRI's RF coil. We hope that the synthesis and tables presented in this paper can facilitate the choice of ERF brake actuation principle to various applications in an MR environment.     

MR_CHIROD v.2: magnetic resonance compatible smart hand rehabilitation device for brain imaging.

This paper presents the design, fabrication, and testing of a novel, one degree-of-freedom, magnetic resonance compatible smart hand interfaced rehabilitation device (MR_CHIROD v.2), which may be used in brain magnetic resonance (MR) imaging during handgrip rehabilitation. A key feature of the device is the use of electrorheological fluids (ERFs) to achieve computer controlled, variable, and tunable resistive force generation. The device consists of three major subsystems: 1) an ERF based resistive element, 2) handles, and c) two sensors, one optical encoder and one force sensor, to measure the patient induced motion and force. MR_CHIROD v.2 is designed to resist up to 50% of the maximum level of gripping force of a human hand and be controlled in real time. Our results demonstrate that the MR environment does not interfere with the performance of the MR_CHIROD v.2, and, reciprocally, its use does not cause fMR image artifacts. The results are encouraging in jointly using MR_CHIROD v.2 and brain MR imaging to study motor performance and assess rehabilitation after neurological injuries such as stroke.