Implantable and Non-Surgical System Solutions for Assisting Dysfunctional Bladder

Abstract

Dysfunctional bladder encompasses a range of lower urinary tract disorders, among which urinary retention (often chronic) is a clinically important presentation. In many patients it is driven by impaired detrusor contractility, resulting in incomplete emptying and reduced quality of life. Conventional treatments such as catheterisation and sacral neuromodulation each present significant limitations. Catheterisation carries high risks of urinary tract
infections and long-term dependence. Sacral neuromodulation does not restore detrusor contractility and often fails in severe myogenic cases. This thesis presents a dual-track engineering approach to address these limitations via the development of both implantable and non-surgical bladder assistive systems.

The first track introduces a wireless, implantable bladder assistive system featuring a bistable actuation mechanism and an integrated Ag-Ecoflex piezoresistive strain sensor. The bistable shape memory alloy (SMA) actuator achieves repeatable voiding efficiencies of 95–100%, followed by passive restoration, eliminating sustained mechanical stress on the bladder wall. Wireless power and real-time data transfer are achieved through inductive
coupling and Bluetooth, allowing users to control voiding via a mobile interface. The system maintains thermal safety guidelines and demonstrates structural integrity through prolonged cyclic operation. These results highlight its potential for long-term bladder management.

The second track develops an intraurethral magnetic valve-pump system for non-surgical urinary management, targeting patients unsuited for surgical intervention. The 5-mm diameter device comprises a magnetically coupled micro-axial pump and a shaft-actuated valve, positioned within the prostatic urethra to assist in emptying the bladder. Radial magnetic coupling through the anterior abdominal wall enables transcutaneous actuation, achieving physiological flow rates of 13 mL/s and head pressures of 37 cmH2O at coupling distances up to 6.5 cm. Comprehensive characterisation encompasses hydraulic performance, magnetic torque transmission capacity, and positioning tolerance across radial and circumferential orientations, with in-vitro validation demonstrating 95% voiding efficiency under anatomically constrained conditions.

Together, the two systems address critical gaps in current management of urinary retention associated with impaired detrusor contractility: implantable autonomy for surgical candidates and minimally invasive alternatives for broader patient populations. The findings demonstrate significant advances in soft robotics, bioelectronic integration, and translational bladder device design, providing a platform for future closed-loop, patient-specific urinary management systems.

Date of Award	17 Mar 2026
Original language	English
Awarding Institution	University of Bristol
Supervisor	Faezeh Arab Hassani (Supervisor) & Robert J Piechocki (Supervisor)