Artificial urethral valve driven by SMA actuators with transcutaneous energy transmission system

Abstract

Abstract. This paper presents the development of a mechanical SMA urethral valve driven by a portable transcutaneous energytransmission system, which is powered by batteries. Structure of the valve was improved by introducing a bite mechanism inorder to prevent the pinch of urethra by the valve. The cycling characteristics and energy transmission efficiency were examinedby laboratory tests. Experimental results show that the stable operation can be obtained by introducing a voltage regulatingcircuit to the energy transmission system and utilizing the sinusoidal oscillation in the energy transmission system can enhancethe transmission efficiency. Furthermore, the function of the valve system was tested by the vitro and vivo animal experiments. 1. IntroductionUrinary incontinence is the involuntary discharge of urine caused by trauma to the urethral sphincteror the weakness of the sphincter due to aging and the expansion of the prostate gland. The early andappropriate treatment of urinary incontinence is of great importance since the incontinence might causeurinary canal infection and bedsoreif it is not treated. However, the difference in ages, sexof the patientsandthe variouscausesof thedisorder makeit difficult to treat the diseasesimplyby medicinesor surgery.On the other hand, shape memory alloys (SMAs), especially nickel-titanium alloys (nitinol, NiTi),show many unique characteristics, among them the most important two are the ability of shape recoveryand the excellent biocompatibility. For this reason, their applications to the medical field are widelystudied. Using an SMA nitinol plate as the actuator, the authors developed an artificial urethral valve forthe treatment of urinary incontinence [1]. Thevalveis closedto clogthe involuntary dischargeof urineatthe body temperature and is opened to allow the micturition when the SMA plate is heated by runningelectric current through the nichrome wire attached to it. It is verified by the animal experiments usingcanine urethras that the valve functions well as artificial urethral sphincter in controlling the dischargeof urine.