Inkjet-printed Ti3C2Tx MXene electrodes for multimodal cutaneous biosensing

Among the existing 2D materials, MXenes, i.e., transition metal carbides, nitrides and/or carbonitrides, stand out for their excellent electrochemical properties. On account of their high charge storage capacity, metal-like conductivity, biocompatibility as well as hydrophilicity, Ti3C2Tx MXene-based inks hold great potential for scalable production of skin conformable electronics via direct printing methods. Herein, we develop an aqueous MXene ink and inkjet-print MXene films on freestanding, flexible conducting polymer-based substrates. These skin-adherent MXene electrodes detect electrocardiography signals with high signal-to-noise ratio while exhibiting preserved electrical performance after 1000 cycles of bending with a 50 day-long shelf life in ambient conditions. We show that printed MXene films can further be functionalized to perform as multifunctional biosensing units. When integrated with a sodium (Na+) ion-selective membrane, MXene electrodes detect Na+ in artificial sweat with a sensitivity of 40 mV per decade. When the films are functionalized with antibodies, they generate an electrical signal in response to a pro-inflammatory cytokine protein (interferon gamma) with a sensitivity of 3.9 mV per decade. Our findings demonstrate how inkjet-printed MXene films simplify the fabrication of next-generation wearable electronic platforms that comprise multimodal sensors.