Flexible Sweat Monitoring based on All-Solid-State Metal-Organic Frameworks/graphene Composite Sensors

For the first time, an improved wearable electrochemical sensor is proposed for monitoring ammonium content in sweat using a specific ionophore as the ion selective membrane (ISM) on a 3D porous structure comprising of Metal- organic framework/graphene (MOF/graphene) network. The sensor exhibits an almost ideal Nernstian slope of 59.23±1.52 mV/log [NH4+] (4.72 % RSD, N=4). The sensor also presents an extremely low charge transfer resistance (Rct). Furthermore, the hydrophobic property of the porous MOF/graphene layer promotes an excellent reversible sensing response to a wide range of NH4+ concentrations by inhibiting aqueous layer generation between the ISM and the screen-printed carbon electrodes (SPC) interface. Screen-printing technology allows the sensor to be fabricated at a low cost with enhanced flexibility in component design and integration.