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Air-Permeable electrode for highly sensitive and noninvasive glucose monitoring enabled by graphene fiber fabrics

Developing wearable and noninvasive electrochemical devices without intrusive inconvenience or risk of infection is desirable for diabetes diagnostics and management. Their adoptions are restricted by the poor reliability due to diluted glucose densities in commonly-used body fluids while lack of highly sensitive electrodes (usually < 300 μA mM-1 cm-2 for enzymatic electrode). On the other hand, most reported electrode materials including hydrogel patches lack efficient gas permeability thus causing skin irritation and reducing the comfort of wearing.
 we developed a textile material with high-speed transfer paths for electrons, electrolytes and glucose, as well as a 3-dimensional structure to directly load enzymes and body fluids. This material is macroscopically paper-like and assembled by wet-fused graphene fibers composited with Prussian blue as the transducer. It showed good air-permeability which has rarely been addressed in other works. As a result, the glucose oxidase-modified textile film protected by a chitosan layer exhibits both high selectivity and electrochemical sensitivity to hydrogen peroxide (7298.7 μA mM-1 cm-2) and glucose (1539.53 μA mM-1 cm-2 in the concentration range of 2-220 μM). The outstanding performances are ascribed to a synergetic effect of following factors:
1. Fused junctions of high-quality graphene fibers connect conductive paths for fast electron transport, effectively eliminating the contact resistance.
2. Unique penetration paths of the graphene fiber fabric and intrinsic hydrophily of the Prussian blue enable fast mass transfer for electrolytes and glucose.
3. Spontaneous absorption of body liquids enables improved utilization of active area inside the electrode. 
In vivo noninvasive glucose measurements with reverse iontophoresis (RI) technology performed on the graphene fiber fabric as a dry sensing patch showed good correlation to glucose levels measured by a commercial finger-prick glucometer. Such flexible, air-permeable and water-absorbent material provides a promising protocol for highly sensitive and wearable devices for metabolites analysis.
The work was published in Nano Energy entitled as “Air-Permeable electrode for highly sensitive and noninvasive glucose monitoring enabled by graphene fiber fabrics. It was financially supported by National Key R&D Program of China (2017YFC0111300), Zhejiang Province Natural Science Fund for Distinguished Young Scholars (LR19H180001), National Natural Science Foundation of China (52073051), Science and Technology Development Project of Wenzhou Longwan’s (2016YG15), Leading Talent Innovation and Entrepreneurship Project of Wenzhou (RX2016005), and Public Projects of Wenzhou (2020005).
Link: https://www.sciencedirect.com/science/article/pii/S2211285521011538