Highly Stretchable, Transparent, and Adhesive Double Network Hydrogels for the Development of Wearable Strain Sensors
Creators: Dong, Xin Yi
Publisher: name: University of Alberta Library
Year: 2024

<p>The exploration of high-performance hydrogels in this thesis marks the convergence of biomedical engineering and wearable technology. This study delves into the creation and use of a novel silicotungstic acid (SiW)-based hydrogel, designed specifically for wearable strain sensors. Mimicking human tissue mechanics, the SiW hydrogel emerges as an ideal candidate for wearable medical devices.<br>
Recent strides in wearable medical technology, notably spurred by the healthcare challenges of the COVID-19 pandemic, have highlighted the urgent need for materials capable of constant, real-time physiological monitoring. Hydrogels, noted for their high water content and adaptability, have gained significant traction in a variety of biomedical and everyday uses. Yet, finding a hydrogel that perfectly balances mechanical strength, electrical conductivity, and biocompatibility remains a considerable challenge.<br>
This research introduces a SiW-based hydrogel, crafted through a facile one-pot method. This process involves the radical polymerization of acrylamide (AM) with Methylenebisacrylamide (MBAA) and Carboxymethyl cellulose (CMC), resulting in a double-network hydrogel that excels in ionic conductivity and moisture retention. This makes it an ideal solution for wearable strain sensing. The study further investigates the hydrogel’s impressive stretchability, adhesiveness, and transparency, and its potential application towards a wearable strain sensor.<br>
Historically, research on SiW-based hydrogels has primarily focused on their adhesive properties, often at the expense of mechanical strength (cohesion). In this study, we present a novel approach to fabricate a polysaccharide hydrogel that harmoniously balances both adhesion and cohesion via interfacial hydrogen bonds. This hydrogel, composed of carboxymethyl cellulose, PAM, silicotungstic acid, and LiCl, showcases a unique combination of properties: strain-responsive ionic conductivity, superior transparency, remarkable stretchability, and robust adhesion. Contrary to conventional PAM hydrogels, our PAM-SiW networked hydrogel addresses the common challenge of achieving good adhesion without compromising on cohesion. Specifically, our hydrogel demonstrates a maximum toughness of 20.3 MJ/m3 and a strain of 4079%, a feat rarely observed in similar hydrogels. Furthermore, the hydrogel&#39;s adhesion is both reversible and versatile, adhering effectively to a variety of wet and dry substrates. This makes it a promising candidate for advanced healthcare applications, particularly as a mechanically reinforced underwater adhesive with unparalleled stability. We also provide insights into the role of LiCl in the hydrogel matrix, emphasizing its influence on electrostatic interactions without affecting the hydrogen bonds. This study serves as a testament to the potential of harmonizing adhesive and cohesive properties in hydrogels, paving the way for future innovations in the field.<br>
The thesis comprehensively covers the formulation, analysis, and practical applications of the SiW hydrogel. It underscores the hydrogel’s ability to adapt to skin, endure environmental challenges, and remain functional under various conditions. The exploration of its adhesion properties, especially in different moisture conditions, signifies a substantial step forward in hydrogel technology.</p>