Research On The Fabrication And Performance Of Bionic Flexible Strain Sensors Inspired By The Epidermal Receptors Of Scorpion

Serving as the media of information acquisition and conversion,sensors play an important role in the social progress and the development of science and technology.Among the sensors,flexible strain sensors have become one of the main research directions of intelligent electronics in the future,which have broad potential applications in electronic skin,human motion or health monitoring,human-computer interaction,and other fields.At present,although many studies have been carried out on the basic sensing properties of flexible strain sensors,such as sensitivity and stability,the flexible strain sensors still face the limitations of low sensitivity and insufficient stability in terms of low strain.Additionally,on one hand,due to the various and strict working conditions background,the flexible strain sensors sometimes face failure under humid or even water-filled environment.On the other hand,since the functional materials or structures used for the flexible strain sensor are anisotropic in the mechanical and electrical properties,the sensors only exhibit sensing function in the uniaxial or biaxial direction so that cannot realize omnidirectional perception.Therefore,flexible strain sensors with waterproof function can expand the sensor to severe underwater applications,and the sensor with omnidirectional sensing function can pick up the mechanical signals presented in any direction,which further cover and extract the multi-source signal information within the surroundings.Accordingly,finding a suitable method to develop a flexible strain sensor with hypersensitivity under low strain,waterproof function,and omnidirectional sensing capacity is a great challenge to achieve weak mechanical signal detection,broaden the application fields of sensor and omnidirectional undifferentiated sensing.Naturally,after 430 million years of evolution,scorpions with nocturnal hunting habits have evolved excellent epidermal vibration sense receptors,which gradually replace the visual organs(eyes)used by most animals to interact with environmental information.The scorpion is such sensitive that it can detect the disturbance caused by burrowing insects a few centimeters underground with 50 cm away from the scorpion,or even the movement of a grain of sand falling motion within 5 cm away from the scorpion's tarsus.In addition,due to the species diversity in the scorpion's living environment,the vibration signals generated by various organisms during their movement are different considering the position and direction that relative to the scorpion.But the scorpion can sense these vibration signals from any direction,and quickly pick up and distinguish these signals,and further accurately locate the vibration source.Therefore,the scorpion's hypersensitive and omnidirectional sensing capacity provides a natural template for the design of corresponding bionic flexible sensor.In this paper,the adult scorpion named Heterometrus Petersii is selected as the study object.The basic morphological structure of the slit sensillum on the scorpion's walking feet is characterized by the 3D ultra-depth microscope,scanning electron microscope and other observation methods.Therefore,the morphological consistency of the slit sensillum on each walking leg is determined.Through the biological behavior observation experiment,it is founded that a single slit sensor has the function of hypersensitivity and omnidirectional perception to vibrations,that is,it has a fast and accurate orientation response to the vibration excitation generated at any direction.Based on the force analysis of the slit sensillum(distributed at the tarsal-metatarsal segment of the walking leg),the micro deformation response of the slit unit under vibration excitation is observed.And the relationship between the morphology of the slit sensillum and the direction of the applied force is analyzed.It is proposed that the curved shape and fan-shaped array distribution of the slit unit of the slit sensillum are the prerequisites for realizing the hypersensitive and omnidirectional sensing function.Based on the boundary conditions of the slit sensillum obtained from the force analysis experiment,the corresponding numerical analysis model is established,and the hypersensitivity and omnidirectional sensing principle of the slit sensillum to the vibration signals is revealed.Then,based on the hypersensitive sensing mechanism of the slit sensillum,the slit unit is used as the structure design template.We compare the strain and displacement response of several common groove structures with different cross-sectional shapes under the same external force by finite element analysis.Given the working principle of the piezoresistive strain sensor and fabricating technology,the V-shaped groove is selected as the basic bionic structure of the scorpion's slit unit.A bionic hypersensitive flexible strain sensor based on linear parallel array grooves is fabricated by using the organic solvent-induced method and structure transferred method.Combined with the well-known superhydrophobic effect of the lotus leaf surface in nature,a bionic flexible and superhydrophobic strain sensor based on linear parallel array groove is developed by the strategy of combined bionics.The sensor can not only serve as a wearable flexible electronic used in the field of human motion monitoring but also can be used as a multifunctional electronic in the water environment.It is expected to be equipped on underwater vehicles and divers to provide real-time motion monitoring function.Furthermore,based on the omnidirectional sensing mechanism of slit sensillum,a bioinspired hypersensitive and omnidirectional flexible strain sensor with ring arrayed curved grooves structure is designed and fabricated.The sensitivity of the sensor reaches as high as 18000 under low strain,and it can pick up the excitation in different directions and distinguish different input signals,which fully shows that the bionic structure has a strong response to external forces in different directions.In conclusion,based on the bionic strategy,this paper reveals the mechanism of scorpion's hypersensitivity and omnidirectional sensing ability by taking the excellent sensing function of the scorpion's slit sensillum as the study object.On this basis,three bioinspired flexible strain sensors are designed and fabricated.And the relationship between the morphology,array distribution pattern of slit sensillum and the performance and function of the bioinspired sensor are explored.At the same time,the superhydrophobic function of the lotus leaf effect is also used to expand the application of bioinspired strain sensors to a more strict underwater environment.On the basis of hypersensitivity,omnidirectional sensing capacity and superhydrophobic function of sensors,it is expected to achieve undifferentiated sensing,recognition and accurate positioning for weak mechanical signals in air or water in the future.