| Sensors are playing an extrememly important role in modern science and technology.It can convert many physical indicators into electrical signals,providing the key technical support for achieving automation,intelligence,and digitization.Interestingly,Flexible sensor technology has become one of the major trends in intellectual device development.The application fields have extended from national defense,aviation to public security,smart machinery,and medical health,etc.As one of the most frontier research fields,the flexible strain sensor will maintain high-speed progress.Sensitivity,ductility,durability and linearity are important indicators for evaluating the performance of the flexible strain sensors,and their interrelationship cannot be ignored.During the design process of the sensors,the above indicators need to be balanced and considered comprehensively to achieve optimal performance.However,most of the current researches of the flexible strain sensors are focused on how to improve the sensitivity,while ignoring the coupling effect of ductility,durability and linearity with sensitivity,leading to obvious limitations in the engineering applications.The reasons why the high sensitivity is difficult to cooperater with other indicators are multiaspect.First,the high sensitivity is derived from the break of the conductive path under the vibration of micro-strain while the outstanding ductility requires the sensor to maintain the path open under the large strain,so researchers must balance the ductility and high sensitivity.Secondly,sensory performance will degrade due to fatigue,and plastic deformation of the polymer substrate under high frequent strain,fracture,and curving of sensory nano-material,so it is difficult to maintain stability,durability,and high sensitivity simultaneously.Thirdly,the inhomogeneous change of the conductive network or micro-structure can lead to the nonlinear response output during the stretching process,so it is difficult to balance the stretchability and high sensitivity.Therefore,there are many challenges and difficulties of fabricating multi-functional coupling sensor devices to improve the adaptability in application situations.Under the natural rule of survival of the fittest,creatures gradually evolved a set of skills that are suitable for their living situation.Scorpions,as a nocturnal species,the visual system degraded seriously,the evolved slit sensillum on its body surface can perceive micro-vibration signals and the super perceptive skill can make the scorpions cope with any complex natural situation easily.The perception mechanism of the scorpion patella slit sensillum can provide the theoretical guidance for the design of the ultra-perceptive sensors.Its unique parallel distribution style is different form many other slit sensillums,which is similar to microscopic parallel structures in many natural fold structure patterns,and provides a reference for the fabrication of the flexible strain sensors with high ductility and linearity.Obviously,In the common structure design of the sensors,a single type structure cannot realize multifunction concurrently,but in nature,the combination of different structures can realize the coupling effect to give the surprise change for the bio-inspired sensors,so the idea of coupling bionics is applied in this work.Everything in nature has its meaning of existence.For example,the spider webs,as the special tools for hunting,mating,and populating for the spiders,is always seen as intact structure due to outside disturbance.However,the imperfect webs can be still used by the spider due to their structure with strong stability and outstanding mechanical performance.The examples can provide reference value for improving the stability and durability of the sensors.In this work,the scorpion named Heterometrus Petersii is selected as the research object.The internal and external structure of the slit sensillum on the patella of the scorpion is characterized by the stereo microscope,the ultra-depth microscope,the field emission scanning electron microscopy,and the tissue fixation section technology.The existence of the patella slit sensillum was discovered,and its morphology and cross-section were characterized.The parallel staggered distribution of the straight slit unit of the patella slit sensillum was discovered.Above the findings can provide theoretical guidance to design and fabricate flexible strain sensors with hypersensitive,high tensile strength,and high linearity.Then,the material composition of the patella slit sensillum is characterized by the Fourier transform infrared spectroscopy,the Toloniumchloride stain method,and nanoindentation.The α-chitin and arthropodin were discovered in the patella slit sensillum.The difference of the elastic moduls,hardness and some other parameters between the upper epidermal membrane and the epidermal membrane were demonstrated.During the dynamic responsing analysis of the slit sensillum,the mechanical activation response test device of the patella slit sensillum is fabricated.The differential characteristics of the stress loading on slit sensillum on the femur and the patella during relative locomotion were analyzed.During the bioelectricity responsing detection of the slit sensillum,the frequency response characteristics of the slit sensillum unit were analyzed under outside vibration,and the hypersensitive perceptive features of the patella slit sensillum under weak biration signal were demonstrated.During the directional recognition characteristics of the slit sensillum,the modeling and the finite element analysis of the biological prototype were carried out,and the selective reponse to different direction stimulation signals of the slit sensillum were discovered.In the research part of collaborative effect of ductility,durability,linearity with sensitivity of the flexible strain sensors respectively,based on the hypersensitive perception mechanism and the collaborative effect of parallel crack structure and its staggered distribution patterns,the flexible strain sensing devices(GF=21450.1,strain range 0%-200%)were fabricated.Based on the steadiness of the reticular V-shaped groove structure,the flexible strain sensing devices(GF=2742.3,8000 cycles under 0.5% strain)were fabricated through the twice-transferring template method which transformed the bionic structure to the PDMS substrate.Besides,based on the crack control characteristics of the bio-inspired wrinkle structure,the crack region can be controlled by the strain of the composite film redistributed,and the flexible strain sensing devices(GF=22.98,linearity is 0.9985)were fabricated. |
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