Granular crystal sensor and actuator for orthopaedic implant stability assessment

We propose a new granular crystal sensor and actuator suite based on highly nonlinear solitary waves to offer a compact, inexpensive, and reliable diagnostic instrument for biomedical applications. A granular crystal sensor/actuator composed of tightly packed elastic particles is assembled to generate and retain self-reinforcing, nondispersive diagnostic solitary waves. Via direct contact, this device can nondestructively evaluate the mechanical integrity of biomedical structures, prosthesis in this study, based on the responsiveness of the solitary waves reflected from the interface between the granular crystal and inspection medium. Using a prototype of granular crystal sensor/actuator, we perform a pilot study to investigate the orthopaedic implant stability of artificial composite femurs in a noninvasive manner. For experimental tests we impose harsh mechanical loading to the artificial femoral implant samples using a femoral load simulator. Preliminary studies show promising results, demonstrating the proposed granular crystal sensor/actuator successfully detects fracture at the stem-bone interface of the composite femoral stem model. This study suggests the granular crystal sensor/actuator might be used as a novel diagnostic instrument for a nondestructive evaluation of mechanical integrity in biomedical implants through enhanced accessibility and reliability.