Development Of Flexible Sensor Based On Conductive Cotton Fabric And Its Application Research

In recent years,various textile-based composite conductive materials have been extensively studied for wearable and flexible electronics due to their high flexibility and bio-friendliness.Among these textile-based electronic products,flexible sensors are of particular interest due to their broad application fields and great application value.Flexible sensors can realize health management by monitoring blood pressure and heartbeat in real time,correct posture by detecting human motion,and monitor human health status by monitoring various physiological indicators in human sweat,tears and blood.Compared with the traditional flexible sensors made of non-renewable elastic materials with poor air permeability,the sensors based on natural fabrics have the advantages of softness and comfort,easy wearing,washing resistance,and renewable materials.Fabrics woven from natural cotton fibers have high porosity,good wetting properties and biocompatibility.Based on this,in this paper,cotton fabric（CF）is used as a flexible substrate,and polyaniline（PANI）,reduced graphene oxide（RGO）and copper nanowires（Cu NWs）are used as conductive active materials.By optimizing the preparation process and experimental conditions,a composite fabric with both flexibility and excellent electrical conductivity was prepared for use in sensors.The main findings of this paper are as follows:1.Fabrication and application of flexible pressure sensor based on reduced graphene oxide conductive cotton fabricUsing CF as a flexible substrate,RGO was deposited on the fabric by vacuum filtration to obtain RGO/CF,and then copper（Cu）and nickel（Ni）were deposited on RGO/CF by magnetic filtration cathodic vacuum arc deposition（FCVAD）technology,respectively,to obtain Cu/RGO/CF and Ni/RGO/CF.The test results show that the as-prepared Cu/RGO/CF and Ni/RGO/CF have good electrical conductivity with a minimum resistance of 2Ω/sq.RGO is tightly bound to the metal layer and maintains high conductivity after repeated washing.Furthermore,the highly conductive fabrics are assembled into different piezoresistive pressure sensors and their properties are explored.The results show that the sensitivity of the Cu-coated sensor is higher than that of the Ni-coated sensor,and the sensitivity of the double-layer fabric-based sensor is higher than that of the single-layer fabric-based sensor.The assembled Ni-and Cu-coated bilayer fabric-based sensor（Ni@Cu/RGO/CF）exhibits better linearity and a wider detection range（0-0.35 MPa）.And under 0.15 MPa pressure,the sensor can maintain its sensitivity for 2000 loading/unloading cycles,showing high repeatability and stability.At the same time,the sensor can monitor various movements of the human body（such as knee,wrist bending,etc.）in real time.2.Preparation and application of flexible pressure sensor based on polyaniline conductive cotton fabricCu and Ni were deposited on CF of in situ polymerized PANI using FCVAD to obtain Cu/PANI/CF and Ni/PANI/CF,respectively.Then Ni/PANI/CF and Cu/PANI/CF were assembled into a double-layer fabric-based piezoresistive pressure sensor,and encapsulated with plastic film to obtain Ni@Cu/PANI/CF.The electrical resistance test results showed that the electrical conductivity of the fabric increased after in-situ polymerization of PANI on CF,and its electrical resistance decreased to about15 kΩ/sq.After depositing Cu and Ni on PANI/CF by the FCVAD technique,the electrical conductivity of the fabric is further improved,and the resistance of Ni/PANI/CF is about 5 kΩ/sq and that of Cu/PANI/CF is about 4 kΩ/sq.The Ni@Cu/PANI/CF piezoresistive pressure sensor exhibits excellent sensing performance,including a sensitivity of 0.011 k Pa^-1 and a fast response time of 30 ms in the pressure range of 0-50 k Pa.What’s more,the sensor can maintain good stability up to 5000loading/unloading cycles.The Ni@Cu/PANI/CF piezoresistive pressure sensor can not only detect the movements of various joints of the human body（such as knees,fingers,elbows,etc.）,but also sense different facial micro-expressions（such as smiles and blinks）.3.Preparation of copper nanowires/reduced graphene oxide cotton fabric and its glucose sensing propertiesRGO was synthesized on CF by hydrothermal reduction method to improve electron transfer ability,and then Cu NWs were deposited on RGO/CF by vacuum filtration method to obtain Cu NWs/RGO/CF electrode,which was applied to non-enzymatic glucose biological sensing.It was explored that the conductivity of RGO/CF and the loading of Cu NWs have important effects on the appearance and morphology of Cu NWs/RGO/CF electrode and its catalytic oxidation performance of glucose.Among them,the optimal resistance of the reduced graphene oxide cotton fabric is 250Ω/SQ/sq,and the optimal loading amount of copper nanowires is 30μL.Under optimized conditions,due to the high specific surface area of Cu NWs and the good electrical conductivity of RGO/CF,the Cu NWs/RGO/CF electrode exhibits excellent glucose catalytic oxidation performance and a series of excellent properties,such as fast response time within 5 s and high sensitivity of 1020μA m M^-1 cm^-2.The Cu NWs/RGO/CF electrode also exhibits excellent long-term stability and anti-interference ability,maintaining 93%of its original sensitivity for 25 days.In addition,the electrode was used to analyze the glucose concentration in human sweat,serum and fruit juice,and the recovery rate was between 97%and 110%（RSD≤5%）,which proved that the electrode has a wide range of application value.In summary,this work prepared a high-performance flexible pressure sensor and a non-enzymatic glucose sensor based on conductive cotton fabrics,which finally realized the application of physiological signal monitoring and human-computer interaction,and provided a new idea for the development of flexible sensor devices.