Study On Preparation And Multifunctional Application Of Flexible Bioinspired Electronic Skins

In recent years,biological skin,as one of the most sensitive and complicated sensing networks for human and living body,has inspired the design and development of wearable electronic device-electronic skin（E-skin）due to keen perception ability for external mechanical deformation.As the medium of artificial intelligence（AI）,soft robots and health monitoring devices,flexible E-skin has attracted widespread attention.With the rapid development of these key fields,it is more and more important to fabricate the multi-functional interactive E-skin based on conductive polymer composites（CPCs）.However,it is still a huge challenge to integrate multiple functions such as excellent sensing capabilities,adjustable optical characteristics and reliable power supply into an E-skin.In this work,inspired by the light-emitting mechanism of cephalopod skin and the ultra-sensitive response of spider-slit-organ,thermoplastic polyurethane（TPU）fluorescent mat（TFM）with good flexibility,lightweight and biocompatibility is employed as the matrix material,commercial fluorescent agent（FA）with low cost and high stability is used as an efficient luminescent material,highly conductive ink composed of 2D Ti₃C₂T_x（MXene）and 1D carbon nanotube（CNT）is used to construct the synergy conductive network.Finally,we achieve a bioinspired multifunctional flexible E-skin through electrospinning,high-pressure spraying and pre-stretching process.We investigate the relationship between the material-structure-performance of E-skin and explore the strain sensing properties,mechanoluminescence characteristics and triboelectric nanogenerator performance of E-skin,and practical applications in the wearable field.The specific research content is as follows:1.The study of preparation and structure of bioinspired multifunctional E-skin.（1）Through electrospinning,high-pressure spraying technology and the pre-treatment of microstructure,the bioinspired E-skin based on TFM and MXene/CNT is successfully achieved.The influence of the content of the fluorescent agent（FA）and MXene on the optical,mechanical and sensing properties of the E-skin is studied,it is found that the TFM with 4 wt.%FA possesses the best fluorescence intensity and higher elongation at break（792%）,50 vol%MXene not only endows the CPCs better conductivity,but also guarantees the E-skin with high sensitivity and wide response range simultaneously.（2）The surface,cross-section and conductive layer micromorphology of E-skin （with 4 wt.%FA,50 vol%MXene）are investigated in detail.The thickness of the E-skin is very uniform,the MXene/CNT conductive filler is uniformly distributed on the TFM,and the flexible matrix and conductive network have good bonding and structural stability.Besides,the E-skin possesses excellent flexibility,lightweight and so on.2.Study on the performance and application of strain sensing and bending sensing of E-skin.（1）The E-skin possesses excellent strain sensing performances,including wide strain range（65%strain）,ultra-high sensitivity（maximum sensitivity GF is 3.92×10⁷）,fast response time（5 ms）,ultralow detection limit（0.001%strain）and excellent durability and stability（45000 stretching/releasing cycles）.（2）During inward bending and outward bending,the E-skin has a large response range（72%strain of inward bending,86%strain of outward bending）and a highly sensitive response.It demonstrates stable response and long-term durability in various bending strain cycle tests（1000 bending/releasing cycles）.（3）The E-skin has a wide range of applications in the field of human health monitoring,not only can accurately monitor the pulse of different parts of the human body,but also acquire and analyze physiological parameters by the obtained pulse signals to monitor human health.3.Study on mechanoluminescence characteristics and visual sensing of E-skin.（1）Based on the flexibility and fluorescence properties of the TFM,the excellent UV shielding ability of the MXene/CNT conductive layer and the unique strain-dependent microcrack structure,the E-skin displays rapid and reversible mechanoluminescence properties in the process of stretching and recovery.The mechanoluminescence properties of E-skin in different tensile processes are quantitatively evaluated by the fluorescence spectrum,and the quantitative relationship among fluorescence intensity,sensing performance and tensile strain is established.（2）The E-skin can clearly distinguish the bending angle of the finger and different gestures through the obvious fluorescence distribution and accurate bending sensing behavior,which can realize the application in visual sensing.4.E-skin as triboelectric nanogenerator（TENG）for energy harvesting and tactile sensing.（1）Because the insulated TFM has strong triboelectric positivity and good flexibility, and the MXene/CNT synergistic conductive network shows excellent electron transmission ability,the double electrode mode TENG（D-TENG）shows excellent triboelectric output performance,including the open-circuit voltage(V_OC=540 V),short-circuit current(I_SC=42μA),short circuit charge(Q_SC=317 n C),high power density（7.42 W/m²）,and good charging ability.D-TENG can be used as a reliable and stable power source to power electronic devices,such as lighting up 1080 LEDs and driving an electronic watch.（2）The single-electrode mode TENG（S-TENG）has a high sensitivity(3.443 m V pa^-1)in the small pressure range of 0-5 k Pa,which can effectively collect biomechanical energy and sense tactile stimuli.By integrating multiple single S-TENG units to form an 8×8 S-TENG sensing array,the finger touch trajectory is successfully mapped to a two-dimensional region,which has an excellent performance in the application of self-powered tactile sensing.