Preparation And Performance Of MXene/ionic Liquid Flexible Force-sensitive Conductive Composites

The flexible strain sensors based on solid conductive media have high sensitivity,but the discontinuity and irreversibility of solid conductive media under strain make the sensors generally have the disadvantage of low linearity.In this work,liquid conductive medium（ionic liquid）is introduced into the solid conductive medium（MXene）to regulate the contradiction between sensitivity and linearity of flexible strain sensors by taking advantages of the fluidity and reversibility of liquid conductive medium.Firstly,highly dispersed MXene nanosheets were prepared by wet-etching technique.The raw material Ti₃AIC₂（MAX）was etched by in-situ generated hydrofluoric acid（HF）to achieve the multilayered precursors with accordion-like structures.The multilayered precursors were further exfoliated by hand shaking or physical ultrasound to prepare two-dimensional flakes with single layer,Ti₃C₂T_X（MXene）.The results showed that the sizes of the wet-etched MXene nanosheets were small and had almost complete edges when the ratio of Li F to MAX is 2:1.The infrared spectra indicated that the surface of MXene had hydrophilic functional groups such as-OH and-O.And the results of electricity conductivity showed that the prepared MXene had a electrical conductivity of about 0.01 S/m.Secondly,MXene@IL/NR composites was prepared by swelling MXene/NR composites with ionic liquid（IL）.Compared with MXene/NR composites,the AC conductivity of MXene@IL/NR was less dependent on frequency.And sensing properties of the composites that swollen at room temperature are superior to those swollen at high temperature（60℃）.MXene@IL/NR composites had a wide detection limit（0-400%）,high sensitivity of 75.18 at high detection limit and high linearity of R² being greater than 0.9.Moreover,human testing of the sensors exhibited regular signals for both human muscle movements and sound changes.Finally,ionic liquid was added to the mixture of MXene and NR latex to make the natural latex flocculated,and then MXene@IL/NR composites were achieved by removing water phase through a freeze-drying technology.When the volume fraction of MXene was 1.6%,the coagulum were easy to be obtained,and the conductivity reached 0.33 S/m.When IL:NR=10%,the sensitivity of the strain sensor was highest,reaching 128.67 at low detection limit（0-70%）and 1311.85 at high detection limit（170%-210%）.A regular force-electric response was observed when the sensor was applied to human skin and pulse.