(367b) Composite Dielectric Material for Multimodal Sensing of Breath

Soft material-based capacitive (and resistive) sensors are a powerful tool for understanding the state, health, and motion of the human body in complex environments performing every day, work day, and athletic tasks. Creating sensors that can accurately couple mechanical deformation and electrical behavior to deliver a precise picture of the activity of interest with the necessary sensitivity is a challenge that requires substantial device development and material optimization. The literature is full of examples of simple test cases where tensile tensors are mounted onto gloves at finger joints and pressure sensors are placed into shoe soles. Our work seeks to push farther into the biomedical space and investigate how to measure one of the most important biophysical markers, breathing behavior. While there are many external medical devices that measure breathing from spirometers to more complicated respiratory measurements and biochemical indicators, soft material sensors have largely been left out of this space despite that soft materials may enable wearable devices that could be used in clinical, rehabilitation, and home care spaces. In this work, we develop capacitive sensors with high sensitivity and load capacity to measure breath as (a) part of a wearable sensor system and (b) as a component of an instrument. For (a), work is undertaken to determine how to best match sensor mechanical and adhesive properties while maintaining electrical integrity and dielectric sensitivity. The first steps towards location optimization will also be discussed in order to best capture the physiology of breathing. For (b), the sensors are further optimized to not only reliably deform with respect to pressure (particularly for percussion), but also optimized to detect vibration, which is a mode of sensing that has largely been previously neglected by soft material sensors. All sensors will be based on composites of the room temperature liquid metal galinstan (gallium-indium-tin) in an elastomer (based on biocompatibility and adhesion). Electrodes and form of the sensor are optimized for sensitivity in the required deformation mode. Vibration in particular requires significant electrode pattern optimization and the correct balance of low modulus and high permittivity. Work presented will describe our efforts in engineering the material, device, and electronics to deliver on the multifunctionality required for a complete understanding of breathing behavior.