Pressure Sensor With Wide Linear Range Based On Leaf Veins As Spacer

Flexible pressure sensors have received widespread attention due to their application prospects in future robots and wearable devices.The pressure sensor with wide linear range and high sensitivity does not require complicated processing for linear current signal output,which greatly improves the miniaturization of the device and reduces power consumption.Microstructures,the composite material of conductive fillers and insulating matrix are commonly used structure design for the preparation of sensors.The microstructures are usually prepared by template with a relatively small and uniform size,and it is easy to reach a saturation state under load pressure.However,electrical and mechanical properties are often interdependent in composite materials.For example,when trying to increase the electrical conductivity of a composite material by increasing the volume ratio of conductive fillers such as metal nanoparticles,carbon black and carbon nanotubes,the mechanical stiffness of the composite also increases significantly.Due to this coupled tuning effect of electrical and mechanical properties,flexible pressure sensors based on composite materials typically exhibit a performance compromise between sensitivity and linearity.Currently,many studies are currently dedicated to improvement in two directions,one is the conductive active material necessary for manufacturing pressure sensors;the other is the structure of the sensor,which can adjust the contact resistance between the electrode on the substrate and the active material.In this paper,the two-dimensional material molybdenum disulfide is stripped into a highly conductive and hydrophilic 1T-Mo S₂by a simple lithium ion intercalation method.The Raman spectrum,X-ray diffraction(XRD),high-power transmission electron microscope(HR-TEM),extended area electron diffraction(SAED)and other characterization methods were used to characterize the 1T-Mo S₂.At the same time,a flexible PDMS porous skeleton was prepared by a simple method of dissolving salt.Hydrophilic 1T-Mo S₂ was used as a conductive material,and the porous PDMS skeleton was wrapped by a simple soaking method.Finally,the leaf vein of the osmanthus tree are used as a spacer to assemble with a flexible substrate with electrodes to form a flexible pressure sensor.We explored various applications of sensor.The main conclusions are gained as follows.(1)In this paper,the conductive material for the preparation flexible pressure sensors is shifted to transition metal disulfide.Experiments have proved that the application of two-dimensional material 1T phase molybdenum disulfide in pressure sensors is feasible and can be used in the next generation of electronic skin and artificial intelligence.Compared with the one-dimensional material,the interface combined with the flexible substrate and the porous structure is sufficiently strong,and does not require complicated processing to improve the stability of the sensor.Compared with the currently widely studied two-dimensional material graphene,1T-Mo S₂ has hydrophilicity and high electrical conductivity,and no complicated reduction and oxidation treatment process is required in preparing the pressure sensor,which provides a huge potential for the actual development and utilization of the sensor.(2)we propose a simple and cost-efficient approach using 1T Mo S₂ nanosheets coated on porous PDMS matrix networks as flexible active layer,as well as hierarchical microstructure leaf vein as spacer between active conductive layer and electrodes.First,leaf veins have a hierarchical micro-network structure.When external pressure is applied,the transient contact area between the conductive layer and the electrode changes,resulting in a wide detection range.Second,natural veins provide an interesting microstructure strategy that does not rely on the complex and expensive techniques of making patterned structures.(3)Based on the structural design of leaf veins as spacers and 3D highly conductive 1T-Mo S₂ network as the active layer,the pressure sensor shows high sensitivity in a wide pressure range(150 k Pa^-1 less than 1 k Pa,1036 k Pa^-1 is suitable for 1-23 k Pa).Ultra-low pressure detection limit(6.2 Pa),high stability of 10,000cycles and fast response time(<50 ms),corresponding to a human fingertip response time of 30 to 50 ms.The prepared high-performance pressure sensor can successfully monitor the physiological signals of the human body,the movement of tiny muscles and the movement of the human body.More importantly,sensors are used to detect different vibrations,including water pressure tests and fish swimming.The results demonstrate potential applications in diving safety and deep-sea environment research.