A Mechanical Magnetic Connection between Muscles and Prosthesis for Enhanced Proprioception

Abstract

In the context of prosthetic devices, the absence of natural sensory feedback poses a significant challenge, leading to limited proprioceptive sensation and reduced control over artificial limbs. This study explores the potential of establishing a magnetic connection between prosthetic devices and muscles to enhance proprioceptive feedback and facilitate more intuitive control of prosthetic limbs. The primary objective is to ascertain the safe range of forces that can be transmitted magnetically from a prosthesis to a muscle, with ethical considerations guiding the allocation of muscle resources.
Preliminary experiments conducted using Silicone Ecoflex 0030, chosen for its stress behaviour similarity to natural muscle tissue, serve as the cornerstone for this research. A novel methodology is introduced to predict the forces generated when magnets snap, particularly when one magnet is embedded within an elastic medium like silicone, replicating the force distribution characteristics of muscle tissue. The theoretical model guiding these predictions is based on empirical data collected from experiments that investigate the magnetic force interactions between magnets and the distinct properties of silicone materials. Validation of the theoretical model for predicting the snapping point is achieved through a comprehensive series of final experiments.
This study demonstrates that the monopole model, tailored for magnets with parallel-aligned poles, yields highly accurate predictions when compared to empirically measured data concerning magnet force modelling. Additionally, within silicone, the force-displacement relationship exhibits linearity, with stiffness primarily contingent on the length of the implanted object. Force transmission experiments involving a magnet embedded in silicone reveal that magnets snap at forces of less than 3 Newtons.
A significant outcome of this research is the development of a validated methodology for predicting the force when a pair of magnet become unstable and snap. This methodology is applicable to scenarios involving magnets embedded in elastic media like silicone and holds the potential for extending predictions to snap forces in muscle tissue. The implications of this study are promising, suggesting the feasibility of employing magnets as sensors to detect muscle intent and as activators to provide feedback by mobilizing implanted magnets, thereby stimulating muscle spindles. These findings open new avenues for enhancing proprioception and control in prosthetic devices.