Nacre-like Layered Polymer Composites For Intelligent Actuation And Wearable Sensing

Recently,great attention has been focused on flexible sensors.However,the reported sensors have difficulty in combining wide detection range,fast response/recovery and excellent sensing performance and cannot monitor electrocardiography/electromyography(ECG/EMG)signals.Besides,the sensors have the single function and cannot be actuated under external stimuli.Herein,we prepared a nacre-like polymer composite,which not only combined simultaneously sensing and actuation functions,but also improved its mechanical performances.The main studies are as follows.1.Inspired by the nacre with excellent mechanical performance,polymer composite films with nacre-like layered structure were prepared by simple water-evaporationinducedself-assemblyof MXene/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/poly(vinyl alcohol)and polyethylene.Thanks to the nacre-like layered structure and the interaction between the nanosheets and polymer chains,the mechanical properties of the polymer composite film were improved.In addition,the composite film simultaneously integrated flexibility,electrical conductivity,hydrophilicity,hygroscopicity,and photothermal conversion performance of MXene nanosheets and polymers,leading to the preparation of multifunctional and intelligent flexible electronic devices.2.Inspired by the asymmetric structure of sunflower and mimosa in nature,a bilayer multi-responsive actuator based on a nacre-like layered polymer composite film was designed.Taking advantage of the notable different hygroscopic properties and the large difference in thermal expansion coefficients between the two layers,the actuator can achieve excellent humidity/NIR light-driven actuation performance,such as large bending deformation under humidity/NIR light(NIR)stimulation(～1170.14°at RH86%;～613.10°at 75 m W/cm~2NIR irradiation).In addition,the soft actuator could be employed as humidity/light response-controlled smart curtains for reversible opening and closing of windows.3.Flexible sensor was assembled by combining a nacre-like layered polymer composite film with the interdigitated electrode face-to-face.The sensor exhibited excellent sensing performance:wide detection range(125Pa-166.7 k Pa),fast response and recovery(5/13 ms),which can be used for information encryption,detection of human macroscopic motion,wireless motion monitoring,and human-machine interaction.Meanwhile,nacre-like layered polymer composites could be used as epidermal sensors to detect slight electrophysiological signals(such as ECG/EMG)of human body,showing great potential for health detection/medical diagnosis.Through the design of materials and device structures,the nacre-like layered polymer composite film could achieve excellent sensing properties and outstanding actuation performances simultaneously,showing huge promising applications in personal health monitoring/diagnosis,human-machine interaction and intelligent switch.