Design, Development, and Analysis of a Tactile Display Based on Composite Magnetorheological Elastomers

Abstract

In minimally invasive surgery, surgeons carry out the operations by employing small tools and viewing equipment into the patient’s body by means of small incisions. In manual and robotic minimally invasive surgery, surgeons do not have direct touch and natural sense of touch, due to utilization of long and often flexible instruments, and palpation is a necessity to provide perfect diagnoses. As a potential candidate, magnetorheological elastomers were investigated as a stiffness display for surgical application. To this end, three different samples of magnetorheological elastomers with various volume fraction of iron particles and one non-MRE rubber sample were fabricated. Six composite MREs were made by combining two layers of different fabricated samples. The samples were characterized under compression test and perpendicular to the applied magnetic field (MF). The compression test was carried out with the strain range of (5 - 25%) at magnetic field densities of 0, 143, 162, 198, 238, 287, 365 mT. It was observed that the elastic modulus of one-layered MREs and bi-layered MREs increase with increasing the magnetic fields. Moreover, MR-effect was enhanced via bi-layer composition, e.g. mono-layered 45%vol iron particles: 211% , bi-layered 45%vol iron particles: 253%. Afterward, a solution for the medical need of the tactile display during minimally invasive surgeries was proposed. To this end, a tactile display based on the composite magnetorheological elastomers, MiTouch , was designed and prototyped. Also, the electromechanical parameters of MiTouch were identified through a transfer function optimization and a PID controller was fine-tuned to achieve a desired stiffness. Later, validation experiments were carried out to showcase the feasibility of MiTouch for pulse examinations and maintaining a desired stiffness. The results revealed that MiTouch applied a pulsed contact force of 0.6N to the phantom finger. The results were within the range of reported pulse examination forces, i.e. 0.5-2N. In addition, the system was capable of following a desired stiffness of 4N/mm and maintaining it within a range of 4:07 +/- 0.41N/mm. In the end, results confirmed the hypothesis of the feasibility of the suggested solution for surgical applications.