Abstract

Wearable nanocomposite strain sensors are a promising technological advancement for real-time monitoring of human biomechanics. However, characterization of these sensors for biomechanical use can be complex due to factors such as creep-related resistance drift and environmental influence (humidity and temperature). The purpose of this work is to investigate and quantify these factors as well as seek to mitigate their effects. The first portion of this thesis is a study on creep-related drift of the electrical behavior of the sensors, investigating the impact of material cure levels and application of a compressive prestrain in ameliorating the observed drift. DSC testing of post-cure heat treatment methods (to complete cure) was executed, and mechanical testing was performed to determine the ideal treatment. The effects of cure on the electrical performance of the sensors were then tested. Subsequently, the creep behavior of the sensors was quantified and a compressive prestrain was implemented and chosen through mechanical and electrical testing. Application of both the heat treatment and the prestrain resulted in sensors with greater material linearity and improved electrical stability during cyclic testing, making their strain-resistance behavior much easier to interpret. Additionally, an environmental effects analysis was performed on sensor samples to quantify the impact of typical humidity and temperature conditions encountered on the skin, to which sensors would be exposed when affixed. Resistance fluctuations for sensor samples held at a static 10% strain were collected while varying relative humidity and ambient temperature within a custom humidity chamber and temperature-controlled room, respectively. Testing uncovered a strong negative correlation between humidity and resistance and a strong positive correlation between temperature and resistance. The causes of these trends are hypothesized. Potential tactics for reducing environmental effects on sensor readings, such as insulating layers or coatings, were also recommended based on findings from similar studies. The findings of these studies have led to practical measures and recommendations to improve sensor consistency and facilitate accurate interpretation of biomechanical movements, thus enhancing their capabilities for use in the field.

Degree

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

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