Shape Memory Alloy Artificial Muscles for Treatments of Fecal Incontinence

Shape memory alloys (SMAs) have the features of large force-to-weight ratio and large deformation, are considered suitable for actuator uses. This paper describes the applications of an SMA material with two-way shape memory as artificial muscles for the treatment of fecal incontinences. Two designs of the proposed artificial sphincters are presented; one for a complete replacement of the anal sphincter and the other as an auxiliary sphincter to assist the puborectal muscles for maintaining fecal continence. Their functional evaluations have been conducted through fundamental experiments on the thermal responses and the mechanical deformation. The functionality of both was confirmed by in vitro experiments. The first design, the artificial anal sphincter was subjected to animal experiments for up to 4 weeks. Satisfactory results in respects of the biofunctionality of the SMA artificial sphincter imply its potential for practical uses.