A 3D Printed Implantable Device for Voiding the Bladder Using Shape Memory Alloy (SMA) Actuators

Abstract

Underactive bladder or detrusor underactivity (DU) is defined as a reduction of contraction strength or duration of the bladder wall. Despite the serious healthcare implications of DU, there are limited solutions for affected individuals. A flexible 3D printed implantable device driven by shape memory alloys (SMA) actuators is presented here for the first time to physically contract the bladder to restore voluntary control of the bladder for individuals suffering from DU. This approach is used initially in benchtop experiments with a rubber balloon acting as a model for the rat bladder to verify its potential for voiding, and that the operating temperatures are safe for the eventual implantation of the device in a rat. The device is then implanted and tested on an anesthetized rat, and a voiding volume of more than 8% is successfully achieved for the SMA‐based device without any surgical intervention or drug injection to relax the external sphincter.

Design and Anchorage Dependence of Shape Memory Alloy Actuators on Enhanced Voiding of a Bladder

“…A similar reduction at the voiding percentage was also observed previously for the parallel device. [14] Reduction of the applied voltage and the time duration of voltage application are suggested to reduce this effect.…”

“…The device proposed in the previous work was used for voluntary voiding of the bladder upon sensation of fullness in myogenic UAB patients (Case 1). [14] By contrast, the proposed actuating device in this paper can be an alternative approach to the treatment for neurogenic UAB patients (Case 2). Figure 1b shows the schematic contraction of the actuating device integrated with a force sensor, and the consequent activation of the device and voiding of the bladder after receiving a signal from the force sensor.…”

“…[14] Our study broadens the application of the actuating device also to neurogenic UAB patients suffering from both damaged detrusor muscle and nervous system; these patients are not able to rely on the natural nerve pathways to realize The use of shape memory alloy (SMA) actuators to restore voiding of bladder for myogenic under active bladder (UAB) patients is proposed recently. Even though previous work show the unique capability of this technology for bladder voiding, the low voiding volume and high energy consumption of the device limit the advancement of this technique.…”

“…[14] Since a fixed length was considered for SMA wires in this design, the device could be used for only one bladder size that was matched with the total inner diameter of actuator. The proposed design in our study has a more conformable vest that can be fitted for a wider range of bladder sizes in rats with similar body weight, and can substantially improve the voiding volume and energy consumption of the device.…”

“…[3] Voluntary repeatable shape transformation, material biocompatibility, and small weight of NiTi shape memory alloy (SMA) actuators make them suitable for medical applications. [4][5][6][7][8][9][10][11][12] Usage of NiTi SMA actuators for muscular contraction, [8] artificial anal sphincter, [7] urethral valve, [13] myocardium, [8] drug delivery system, [3] and most recently, voiding of a bladder, [14] has been reported.The previous SMA-based actuator for voiding of a bladder consisted of a flexible vest that covered the bladder surface and physically contracted it upon the actuation of assembled SMA wires. [14] Since a fixed length was considered for SMA wires in this design, the device could be used for only one bladder size that was matched with the total inner diameter of actuator.…”