Biomimetic artificial sphincter muscles: status and challenges

Abstract

Fecal incontinence is the involuntary loss of bowel content and affects more than 12 % of the adult population, including 45 % of retirement home residents. Severe fecal incontinence is often treated by implanting an artificial sphincter. Currently available implants, however, have long-term reoperation rates of 95 % and definitive explantation rates of 40 %. These statistics show that the implants fail to reproduce the capabilities of the natural sphincter and that the development of an adaptive, biologically inspired implant is required. Dielectric elastomer actuators (DEA) are being developed as artificial muscles for a biomimetic sphincter, due to their suitable response time, reaction forces, and energy consumption. However, at present the operation voltage of DEAs is too high for artificial muscles implanted in the human body. To reduce the operating voltage to tens of volts, we are using microfabrication to reduce the thickness of the elastomer layer to the nanometer level. Two microfabrication methods are being investigated: molecular beam deposition and electrospray deposition. This communication covers the current status and a perspective on the way forward, including the long-term prospects of constructing a smart sphincter from low-voltage sensors and actuators based on nanometer-thin dielectric elastomer films. As DEA can also provide sensory feedback, a biomimetic sphincter can be designed in accordance with the geometrical and mechanical parameters of its natural counterpart. The availability of such technology will enable fast pressure adaption comparable to the natural feedback mechanism, so that tissue atrophy and erosion can be avoided while maintaining continence during daily activities.

In vitro testing of an artificial muscle for the treatment of incontinence

“…23 There are several attempts with limited progress to realise artificial sphincters on the basis of electroactive polymer actuators and devices, see e.g. [27][28][29][30][31][32][33][34][35][36] So far, HASEL technology has not been considered for the implementation into artificial sphincters for severe incontinence treatment. Therefore, the present study focuses on the HASEL principle for artificial muscles with the aim to demonstrate feasibility.…”