Screen Printingof MXene Inks For Electromagnetic Shielding,Joule Heater And Piezoresistive Sensor

As a new family of 2D layered transition metal carbides or nitrides,MXenes have become promising candidate for formulation of printable inks because of their remarkable electronic,optical,and hydrophilicity properties.Considerable efforts so far have focused on the formulation of various MXene inks by including the additives like carbon nanotubes,graphene,layered double hydroxides,cellulose and so on.The additives of cellulose and polymers were proposed to improve the dispersion and stabilization of MXene inks.Although these MXene inks exhibited excellent printability,the electrical conductivity of the printed MXene films was moderate（<1×10⁴ S/m）.In addition,the addition of inorganic additives will result in complicated processability and high cost of MXene inks.The high loading of dissimilar inorganic components may hinder highly dense structure formed in the printed MXene films.Ideally,low content of additives or even additive-free in MXene inks would be promising for scalable production of MXene devices.In this work,aqueous MXene inks have been formulated by tuning the weight ratio beween exfoliated MXene and xanthan gum.Such hybrid inks were environment friendly,and offered tunable viscosity,excellent printability and long-term stability.The main contents are as follows:Single-layer Ti₃C₂T_x nanosheets were obtained by etching the mixed solution of HCl+Li F.Subsequently,the structure,transverse size,height and surface chemical state of the nanosheets were analyzed by XRD,SEM,AFM,TEM and XPS.These characterization methods proved the Ti₃C₂T_x nanosheets are few layers and unoxidized.The hybrid inks of MXene-xanthan gum（MX ink）and MXene-PEDOT:PSS（MP ink）with printing performance were designed.For printing electronics,the high-quality ink that meets the requirements of screen printing is the key to ensure the printing quality,so the appropriate ink formula is crucial.Compared with pure MXene ink,MX ink can achieve high-precision printing on different substrates,and the nanosheet arrangement is more dense,and the printed film has higher conductivity.The MP ink printing film has better bending resistance,and the in-plane crack can deflect and absorb a lot of energy under bending.Screen-printed flexible MXene films using such hybrid inks exhibit a high conductivity up to 4.8×10⁴ S/m,which is suitable to construct multifunctional devices mainly including electromagnetic shielding,Joule heater and piezoresistive sensor.The average electromagnetic interference shielding（EMI SE）value can reach to 40.1 d B.In Joule heater application,the heating rate of printed MXene film can reach 20°C/s under a driving voltage of 4 V.MXene-based piezoresistive sensor prepared by the printing interdigital electrode also presents good sensing performance with a short response time of 130 ms and wide pressure region up to 30 k Pa.As a result,screen-printed MXene film exhibits reinforced multifunctional performance,which is promising for application in the next-generation of intelligent and wearable devices.