Design And Evaluation Of Pizeoresistive Fabric Sensor Matrix

With the increasing demand for the application of pressure distribution monitoring between human skin and surface of objects,domestic and foreign scholars have explored the design of different types of pressure distribution monitoring sensors.In particular,fabric-based flexible pressure distribution monitoring sensors have received special attention in recent years.Among them,the resistive fabric-based sensor often adopts a multi-layer structure formed by an electrode layer and a piezoresistive layer.Researchers usually pay attention to the design of the piezoresistive layer in the sensor structure,while ignoring the constituent elements such as electrodes,leads,and sensing circuits.The impact of the configuration on the performance of the sensing system.For example,rigid materials such as copper wires are used in the prototype verification of these sensing arrays.Some of the sensing arrays have many manufacturing processes and are not compatible with the textile processing technology,and have high cost.Therefore,it is necessary to construct a full-fabric pressure distribution monitoring sensor compatible with the textile processing technology,which overcomes the complicated preparation process of the piezoresistive layer and the connection stability of the signal leads of the sensing circuit existing in the developed sensing system.Based on the above deficiencies,this paper designs a full-fabric,easy-to-manufacture,low-cost piezoresistive fabric sensor matrix with n×m+1 multi-layer structure.The materials of the sensor are textile materials and compatible with textile processing technology.Firstly,this paper discusses the material structure and size of the sensing unit and the influence of the sensor circuit on the sensing performance.Then,the piezoresistive fabric sensor matrix is constructed with the preferred sensing unit,and the single-point and multi-point sensing sensors are discussed.The difference in response between the units and the reason,the final application of the sensor matrix to monitor the finger touch motion,proves that the sensor matrix has the potential to be applied to human-computer interaction scenarios.The specific research contents and conclusions are as follows:?1?Based on the n×m+1 structure,this paper designs a piezoresistive fabric sensor matrix with simple structure and low energy consumption and its data acquisition circuit.In particular,the connection stability between the electrode layer and the silver-plated conductive yarn is investigated.The results confirmed that the designed sensor structure is reasonable,and it is found that the connection resistance obtained by the stitch joint method is more stable and reliable.The piezoresistive fabric sensor matrix has five layers,which are a package protection layer,an upper electrode layer,an isolation layer,a piezoresistive layer,and a lower electrode layer.The upper electrode layer is composed of n×m electrode units,and the lower electrode layer is a complete electrode shared as a sensing unit.The sensing unit is connected in series with a fixed value resistor,and the change in the resistance of the sensing unit can be calculated by collecting the voltage change across the fixed value resistor.Among them,the silver-plated conductive yarn is used as the connection line between the sensor and the data acquisition circuit,and the connection mode with the electrode layer mainly has the adhesion and the stitch.By comparing the stability of the connection resistance in different ways and the contact state of the silver-plated conductive yarn at the joint with the electrode layer,it is known that the stitch-slot contact is stable and the connection resistance fluctuation is small.?2?Studying the impedance characteristics of the sensor,explaining the influence of the difference of the constituent materials of the sensor structure on the sensor performance and the sensing mechanism,and optimizing the electrode and the isolation layer material of the sensor.The results show that the sensor works as pure resistance,the sensing response changes from the resistance of the piezoresistive layer and the contact resistance of the electrode layer and the piezoresistive layer,and the conductive cloth and the hole-like fabric are the electrode layer and the isolation layer of the sensing unit.The best material.In order to investigate whether the sensor has capacitive reactance during operation,an electrochemical workstation was used to test the impedance change when the sensor was compressed.According to the electrochemical workstation test,the phase angle of the electrical impedance of the sensor sensitive material is kept at 0°,that is,the sensor is a pure resistor.Subsequently,comparing the influence of electrode materials on the sensing performance,conductive cloth and copper foil were used as the basic electrode materials.The upper and lower electrodes were tested as conductive cloth/conductive cloth,copper foil/copper foil and conductive cloth/copper foil.Under the sensor response,it is found that the resistance response of the sensor includes the contact resistance between the electrode layer and the piezoresistive layer,and the flatter the contact surface between the electrode layer and the piezoresistive layer,the smaller the contact resistance.Subsequently,further studies are conducted to compare the effects of the geometry of the isolation layer on the sensing performance.Comparing the grid-like fabric and the hole-like fabric as the isolation layer,the difference of the sensor response under the pressure is compared and tested.Since the grid-like fabric is the isolation layer,the grids included in each sensing unit in the pressure-applying zone are included.There are different numbers,and the resistance response has a large difference between the sensing units,and the holes correspond to each sensing unit one by one,and the response is basically the same,so that it is more suitable as an isolation layer.?3?Studying the structure and size of the sensing unit to respond to the sensor under pressure.The results show that in order to improve the response sensitivity of the sensor,the hole size of the sensing unit should be smaller than that of the upper electrode unit,and the sensor response depends on the relative relationship between the effective working area and the size of the sensing unit.In order to select a suitable sensing unit structure,two sensing unit structures were fabricated,one having a larger hole size than the upper electrode unit and the other opposite.By comparing the sensing performance of the sensing units of the two structures,it is known that when the hole size is smaller than the upper electrode unit,the sensitivity of the sensing unit is greater,so the sensing unit structure should be selected.In order to select a suitable size of the sensing unit,five sets of sensing units of different sizes were fabricated.Comparing the sensitivity and effective response range of the sensing unit,when the size of the upper electrode unit is 6mm×6mm and the hole size is 4mm×4mm,the performance of the sensing unit is the best,and the sensitivity is up to 74.64?·kPa^-1.The range is 5³00kPa and the response time is 81ms.In order to explore the effect of the area of the indenter on the response of the sensing unit,it is found that the response of the sensing unit differs depending on the indenter,using different indenters to compress the same sensing unit,depending on the effective area and the size of the sensing unit.The relative relationship.?4?Studying the response of the sensing matrix to the distributed pressure,comparing the response difference between the single-point and multi-point sensing units,and verifying the application potential of the sensor.The results show that the sensing matrix can effectively resolve the pressure magnitude and action position of different action points,and the recognition ability of finger touch motion confirms the potential of the sensor matrix for human-computer interaction.In order to explore the ability of the sensing matrix to identify the magnitude and distribution of the pressure,the response of each sensing unit can be known by the multi-point action.The sensing matrix can accurately know the pressure action position and basically perceive the pressure.The sensing unit response deviation is 8.33%compared to the single point effect.Sensing matrix response bias may be mainly due to the non-uniformity and crosstalk effects of textile materials.When the finger presses the piezoresistive fabric sensor matrix,the sensor response is fast and stable,indicating that the fabric sensor matrix can be applied to scenes such as human-computer interaction.Based on the above discussion,the piezoresistive fabric sensor matrix and its data acquisition circuit have a simple structure,and the silver-plated conductive yarn is used as a connecting line,which is soft and stable.When the sensor is operating,it exhibits a pure resistance characteristic.The change in resistance of the sensor includes not only the change in resistance of the piezoresistive layer,but also the change in contact resistance between the electrode layer and the piezoresistive layer.In order to ensure excellent and stable sensor performance,it is preferable to use a conductive cloth tape and a hole-like fabric as an electrode layer and an isolation layer.In order for the sensing unit to have high sensitivity,the sensing unit should have a smaller hole size than the upper electrode unit.When the effective area of the pressure action is different,the response of the sensing unit will also change.The sensing matrix can effectively sense the role of distributed pressure and is suitable as a bridge for human-computer interaction.