(619) Differential Stretchable Strain Sensor System for Monitoring Penile Axial Rigidity in Erectile Dysfunction Assessment

Abstract Introduction Erectile dysfunction (ED) is a highly prevalent condition, projected to affect over 320 million men worldwide by 2025, as reported in the Massachusetts Male Aging Study (MMAS). Among the biomechanical indicators of erectile function, axial penile rigidity, defined as the penis’s ability to resist buckling during penetration, is considered the most functionally relevant for successful intercourse. However, existing diagnostic tools such as RigiScan assess only radial rigidity and rely on rigid loop-based hardware that may compromise comfort and fail to capture axial stiffness. These limitations highlight the need for a noninvasive, physiologically accurate, and continuous method to monitor axial rigidity. Objective This study aims to develop and evaluate a stretchable, dual-strain sensor system for assessing axial penile rigidity by capturing differential mechanical response during erection. The goal is to provide a comfortable and clinically meaningful alternative to existing diagnostic tools. Methods A soft, stretchable strain sensor system was fabricated using screen-printed silver-based conductive ink deposited on a medical-grade thermoplastic elastomer substrate (styrene-ethylene-butylene-styrene, SEBS). Two sensors, engineered with different stiffnesses, were designed for longitudinal placement along opposite sides of the penile shaft. During erection, the penis provides natural elongation, passively stretching the sensors. The softer sensor deforms more and shows a greater relative change in resistance, while the stiffer sensor deforms less. As the sensors require far less force to stretch than penile tissue, they do not interfere with the natural erection process. Results Bench-top testing involved elongating both sensors to 100 percent strain under axial forces up to 2.5 N. The results demonstrated clear and repeatable mechanical differentiation between the two sensors. Although these bench conditions do not represent the full physiological range, they establish the principle of using resistance ratios to infer stiffness. In clinical use, the penis itself provides the deforming force, and the resistance ratio can be calibrated against known clinical thresholds. Earlier studies defined axial rigidity as insufficient below 3.9 N, borderline between 3.9 and 4.9 N, sufficient between 4.9 and 9.8 N, and optimal above 9.8 N. More recent cavernosometric data suggest that the ability to resist at least 14.7 N, equivalent to 1.5 kg, corresponds to optimal rigidity and is associated with intracavernosal pressures above 50 mmHg. The system will be calibrated against both sets of standards to ensure clinically meaningful classification of rigidity levels. Conclusions Validation will be carried out in a controlled clinical setting in collaboration with a sexual health research laboratory. The sensor system relies entirely on passive physiological elongation, avoiding any mechanical interference with the erection process. It also enables wireless, remote monitoring of erectile function. The platform is designed to support future integration of a printed temperature sensor, currently under development, allowing multimodal assessment that combines both mechanical and thermal metrics. This differential-stiffness strain sensor system offers a novel, non-invasive, and user-friendly solution for assessing axial penile rigidity. Disclosure Yes, this is sponsored by industry/sponsor: Dycotec, Henkel, Edentech, Vreeberg, Avery Dennison Clarification: No industry support in study design or execution