Development of Capacitive Wearable Sensors for Limb Volume Measurement Towards Swelling Management

Abstract

Lymphedema represents a chronic medical condition characterized by progressive limb swelling due to compromised lymphatic drainage, affecting millions of people globally and necessitating continuous monitoring for effective clinical management. Current assessment methodologies rely predominantly on infrequent clinical measurements and subjective evaluations, creating substantial gaps in patient care protocols and treatment optimization strategies. This research addresses these critical limitations through the development of an advanced wearable sensing system utilizing highly stretchable capacitive strain gauge (HSCSG) technology for continuous limb volume monitoring applications in people living with lymphedema. The investigation employed a systematic methodological approach encompassing comprehensive literature review, advanced fabrication technique optimization, multiphysics simulation modeling, and extensive experimental validation protocols. Following thorough comparative analysis of available sensing modalities, capacitive sensing utilizing interdigitated electrode (IDE) array configurations was selected based on superior linearity characteristics, minimal drift properties, and enhanced compatibility with wearable electronics applications. Direct ink writing (DIW) fabrication processes were systematically optimized for IDE sensor production, incorporating thermoplastic polyurethane (TPU) substrate materials selected for their advantageous mechanical properties in wearable electronics implementations (Chapter 3). A novel sensor generation software platform was developed to enhance fabrication precision and manufacturing repeatability, while comprehensive COMSOL Multiphysics simulation studies provided detailed design space optimization guidance (Chapter 4). The research successfully developed optimized HSCSG sensors demonstrating linear sensing response capabilities extending to 25% mechanical strain while approaching theoretical gauge factor sensitivity limitations. Extensive characterization protocols confirmed exceptional durability performance under high elongation conditions and cyclical loading environments (Chapter 5). A novel limb volume phantom model (LVPM) incorporating pneumatic artificial muscle technology was developed for comprehensive sensor calibration and validation procedures, enabling precise assessment of circumferential monitoring capabilities with minimal calibration requirements (Chapter 6). This comprehensive study established significant contributions to the field of soft robotic sensing both scientifically and technologically. These contributions include: i) enhanced understanding of IDE capacitive sensor behavior under large mechanical deformations, ii) innovative DIW fabrication protocols optimized for stretchable electronics applications, and iii) practical validation methodologies for wearable sensing system implementation, which collectively provide a robust foundation for future clinical deployment in lymphedema monitoring applications.