Graphene oxide enhanced, 3D printable, self-healing, highly tough and elastic dual-network hydrogels for multifunctional wearable biosensors
Date
2019-03-28
Authors
Wang, Yitian
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Abstract
Hydrogels have been widely used in the biomedical sector in recent years. However, conventional hydrogels’ disadvantages of poor mechanical performance and lack of efficient self-healing ability limit their practical application. A novel versatile hydrogel with excellent mechanical properties and extraordinary self-healing efficiency was developed by integrating graphene oxide (GO) nanoparticles into a polyacrylic acid (PAA) hydrogel network crosslinked by an organic crosslinker N,N’ methylenebisacrylamide (MBA) and an inorganic crosslinker Ca2+. The resulting PAA-GO-Ca2+ hydrogel, with both covalent and physical dual-crosslinked networks demonstrated remarkable mechanical properties including an ultrahigh strain of 2500% and high toughness (~9.73MJm-3) along with high stiffness (Young’s modulus:~753.667KPa). In addition, the hydrogel also shows super effective self-healing ability (~87.47%, 88.02% and 86.93% healing efficiency in tensile strength, tensile strain, and toughness respectively) which is attributed to the reversible hydrogen bondings existing in abundant hydrogen-containing functional groups and ionic interactions between COO- groups existing in both PAA and GO. To achieve facile fabrication of the developed multifunctional hydrogels for such advanced applications as biosensors, we adjusted the viscosity of the hydrogels by controlling their degree of crosslinking to allow 3D printing. The 3D printed PAA-GO-Ca2+ hydrogels were further treated with HI vapor to reduce GO on the surface of the hydrogels and produce conductive PAA-rGO-Ca2+ hydrogels for different types of wearable biosensors, including sensors to detect different humans activities such as pulse rate, breathing, finger movement, sensors to monitor sweating levels, and ammonia detectors which detect toxic ammonia gas at low concentrations.
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PAA, GO, tough hydrogel, self-healing, 3D printing, biosensor