| With the global sub-health problem becoming more and more serious,real-time health monitoring has attracted tremendous attention in recent years,and more and more wearable devices with health monitoring functions have been developed.However,most of these devices are composed of rigid sensors and structural components,which is not conducive to the comfort of wearing.Wearable electronics based on flexible strain sensors have been widely studied due to their advantages of high flexibility,stretchability,skin conformality and high sensitivity.The flexible strain sensors are mainly composed of the flexible substrate and conductive strain-sensitive materials.Therefore,through the modification of flexible substrate and the design of strain-sensitive materials,the tunable properties of high sensitivity and wide strain range can be achieved.In this thesis,highquality three-dimensional porous laser-induced graphene(LIG)materials are rapidly prepared by laser engraving of carbon precursors.Through the design of carbon precursor substrate,high flexibility and even high stretchable strain sensors can be obtained.The specific contents of this thesis are as follows:(1)By using the laser-induced method to directly generate a patterned strainsensitive material LIG on the surface of commercial polyimide(PI)film,a dualfunctional self-alarm electronic skin(e-skin)based on PI substrate can be prepared.Firstly,the influence of laser power parameter and different patterned LIG on the performance of strain sensors and thermoacoustic devices is studied.It is concluded that the shutter patterned e-skin prepared under the 6.6% laser power has the best mechanical and acoustic performance.When the electronic skin works in the strain sensor mode,it achieves a high sensitivity of 316.3 thanks to its excellent piezoresistive characteristics,which is conducive to the application of real-time detecting of physiological health signals,such as breathing,human voice and wrist pulse.When the strain sensor detects some abnormal signal,it can switch to the audible alarm mode,so that it possesses the sound pressure level(SPL)of 59 d B and an ultra-wide spectrum response of 200 Hz-20 k Hz.The electronic skin based on PI substrate and LIG material integrates health monitoring and self-alarm functions into a single device to realize real-time monitoring and early warning of sudden diseases such as sleep apnea.(2)Due to the high modulus of commercial PI film,the tensile property of the prepared strain sensor is poor.Therefore,the tensile strain sensor based on the stretchable polyvinyl alcohol(PVA)film substrate and conductive LIG material is developed.Firstly,the improvement of tensile properties(maximum over 663%)of PVA film by glycerol plasticizer was studied.Then,carbon precursor PI powder was doped into PVA film to further regulate the modulus of PVA/PI film.Through the mechanical optimization of PVA/PI films with different modulus and size welded on low-modulus PVA films,it is concluded that the sensor with high tensile properties can be prepared when the modulus of the upper and lower films is equal,and the sensor configuration with strain-insensitive can be obtained when the modulus of PVA/PI films is much greater than that of PVA films.Therefore,the strain sensor with a wide strain range can be fabricated based on the stretchable PVA/PI film configuration.So,the strain sensor with the strain of 18%,high linearity,and high sensitivity(about 44.7)can be fabricated by combining the serpentine bend Ag NW conductive interconnects.Due to its excellent performance in sensitivity and strain range,it can be used in the field of real-time monitoring of human physiological health signals and detection of moving limb behavior. |
