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

Abstract

for such transformation. [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. 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.The previous SMA-based actuator was proposed for assisting the detrusor muscle in myogenic underactive bladder (UAB) patient with detrusor muscle contractility disorder but intact nerves. [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. This study proposes a novel approach using an interlaced configuration to overcome these limitations. In this device, SMA actuators are threaded through rigid anchor points of the flexible vest. The novel anchorage of SMA actuators provides more conformability for the vest and lower energy consumption for the device, while the new interlaced configuration enhances the voiding volume. The device is tested initially on a rubber model for the bladder, then it is implanted in an anesthetized rat, and a voiding volume of more than 20% at 4 V is successfully achieved. A commercial force sensor is integrated with the device to make it suitable for neurogenic UAB patients. The sensor provides a feedback control signal to the patient to initiate the actuation of the device upon fullness of bladder. The overall system is a promising advance over the state-of-the-art providing bladder voiding in UAB patients.

Progress inTENGtechnology—A journey from energy harvesting to nanoenergy and nanosystem

“…To overcome those disadvantages, the triboelectric nanogenerator (TENG) was first invented by Zhong Lin Wang in 2012, and has attracted worldwide research interests and underwent significant developments, becoming a promising technology in energy harvesting and especially in nanoenergy and nanosystem (NENS) 12‐14,22,23,43‐65 . The working mechanism of TENG comes from the coupling of the triboelectrification effect and the electrostatic induction effect.…”

Evolving Flexible Sensors, Wearable and Implantable Technologies Towards BodyNET for Advanced Healthcare and Reinforced Life Quality

“…Since the first implantable cardiac pacemaker for arrhythmia patients in the 1960s, implantable health devices have been continuously investigated and developed for disease prevention, diagnosis, and treatment [58]- [62]. For instance, implantable actuators to help underactive bladder void have been developed to meet particular clinical need [63]- [65]. In the meantime, the thriving energy harvesting technologies such as nanogenerators are pushing forward the progress of fully integrated and self-powered implantable systems, with representative efforts in the self-powered pacemakers in recent years [44], [66]- [68].…”

Soft sensors for a sensing-actuation system with high bladder voiding efficiency

“…These actuators consist of soft electrodes that are directly attached on the bladder surface for electrical stimulation of the muscle (22) or its related nerves (23). To avoid possible electrical stimulation of untargeted neighboring muscles or nerves, soft actuators capable of physical bladder compression have been developed (33). These actuators were compatible with bladder volume changes and capable of voiding 25% of the bladder in one activation cycle (33).…”

“…To avoid possible electrical stimulation of untargeted neighboring muscles or nerves, soft actuators capable of physical bladder compression have been developed (33). These actuators were compatible with bladder volume changes and capable of voiding 25% of the bladder in one activation cycle (33). SMA-based actuators with bistable characteristics were able to efficiently advance, voiding up to about 80% (34).…”