Urinary Bladder Volume Monitoring System With Antenna Array-Based Flexible Sensor

Urinary incontinence is one of the common problems that come with age and mostly affects older adults with dementia and other neurological disorders. Clinical research suggests that continence issues are better managed with continuous monitoring of bladder volume. The common existing catheter-based methods are invasive, uncomfortable, and may cause infection when used for a long duration. This article presents a noninvasive approach to monitor urinary bladder volume using a sensing system configured with an antenna array for a narrow beam scan. The antenna array is designed and modeled in the computer simulation technology (CST) simulator package, and simulations are conducted with a customized voxel pelvis biomodel. The model resolution is set to $0.98\times 0.98\times 1$ mm3, and the simulated environment is optimized to detect the urinary bladder contraction and expansion with approximate bladder volumes of 102 to 300 mL (changes in radii from 29 to 41 mm). For antenna array fabrication, a careful choice of flexible substrate has been made to make the sensor embeddable in a piece of furniture or chair. Experimental results are validated using the fabricated antenna, integrated with a prototype pelvis model made of polyvinyl chloride (PVC) material (a dielectric constant of 3.8–4.0). This sensing system effectively detects bladder fluid with a maximum range of 100–500 mL. The optimum results were obtained at a linear distance of 20 cm and an angular displacement of 60° in the experimental setup. The specific absorption rate is evaluated for the safe application of the proposed sensor, which is 0.104438 W/kg (SAR <0.4 W/kg) at the wavelength of 119.917 mm. The initial results indicate that the proposed sensing system is efficient and safe and shows good potential to integrate with monitoring setups for urology care.