Individuals with an underactive bladder, for example following a spinal cord injury, often cannot sense bladder fullness or are unable to empty the bladder completely. This distressing symptom can seriously affect one’s quality of life. A dysfunctional bladder may also lead to medical complications such as urinary tract infection, as well as physical discomfort and potential for personal embarrassment. 

A team led by Professor Nitish Thakor and a senior research fellow, Dr Arab Hassani, worked closely with researchers from NUS Electrical and Computer Engineering and NUS Biomedical Engineering, the SINAPSE Laboratory in the N.1 Institute for Health, as well as lead collaborator Professor Takao Someya and his research team at the University of Tokyo, a collaboration facilitated by a NU-Tokyo University collaborative program. This technology that can monitor bladder volume in real time and effectively empty the bladder, along with its proof of concept, took more than a year to develop. 

Their breakthrough was first reported in the journal Science Advances on 1 May 2020. This innovation may open up a new treatment option for patients with underactive bladders in the near future.

Soft solution for a weak bladder 

Among patients who have some form of spinal cord injury, about 80 per cent of them suffer from some form of bladder dysfunction. There is currently no cure for the underactive bladder condition, and while some implantable treatment options are available, they can only sense the fullness of the bladder and only empty it up to 43 per cent. 

“To help these patients, what clinicians need is an integrated bladder system that achieves both volume sensing capability and high voiding efficiency. Given that the urinary bladder is unique among human organs as it undergoes large volume changes during the storage and urination phases, the device requires careful compatibility considerations to avoid interference with the extreme volume changes of the bladder,” said Prof Thakor, who supervised the research. 

Dr Arab Hassani’s novel system comprises a sensor integrated with an actuator. The soft and thin sensor monitors the bladder volume continuously while the actuator is equipped with strong emptying force to clear the bladder. The actuator contains a shape memory alloy (SMA) spring, which keeps the sensor in contact with the surface of the bladder at all times for precise volume detection.

Experiments by the team showed that in addition to the real-time volume sensing capability, the device can also effectively empty between 70 to 100 per cent of the bladder. “This is a significant achievement as its performance is comparable to the efficiency of intermittent catheterisation treatment currently being used, which has many shortcomings,” shared Dr Arab Hassani, the first author of this study. “We need a soft but efficient device to support a weak bladder.”

Improvements and potential applications 

Moving forward, the NUS research team is working to improve the functionality of the device, and looking into making the system wireless for ease of use and movement. 

“The bladder system can be adjusted to the user’s bladder size to ensure optimal operation,” suggested Dr Arab Hassani. “The ideal scenario would be to integrate the device with a mobile application, which can retrieve and process the sensor data to allow the user to trigger voiding at will.”

The team’s advances in soft materials and their fabrication techniques also hold other potential applications to treat not only the bladder dysfunction, but also to treat other organ failures in the medical field. 

“Our soft system demonstrated on a bladder can serve as a model for augmenting other organs as well,” elaborated Prof Thakor. “I believe this novel design can pave the way for the development of sensors and actuators that are compatible with other soft and distensible organs like blood vessels, the heart, and the gastrointestinal system, as these organs require both sensing and actuation to achieve functions like pumping and peristalsis under soft actuation and control.”