Micro-structured Flexible Pressure Sensor Based On Three-dimensional Vertical Graphene

Flexible pressure sensors are core components of wearable smart electronic devices,used to perceive the surrounding environment and convert it into processable electrical signals.They can obtain environmental data such as temperature and humidity,as well as real-time monitoring of biological health parameters such as blood pressure,pulse,health signals,and muscle stress.They have great potential in fields such as smart skin,human-computer interaction,and medical monitoring.In recent years,the rapid development of wearable smart electronic devices has led to a rapid increase in the demand for flexible pressure sensors,resulting in numerous sensors with different structures and excellent properties.Research on flexible pressure sensors has also made significant progress.Sensitivity and sensing range are two important performance indicators of flexible pressure sensors,and there is a certain trade-off between them.Generally speaking,the higher the sensitivity of the sensor,the smaller the pressure change it can detect,but the corresponding sensing range will be reduced.Conversely,sensors with a wider sensing range can detect larger pressure changes,but sensitivity will be reduced.Therefore,the existing flexible pressure sensors have difficulty maintaining a high sensitivity response within a wide sensing range,which will limit their use in different application scenarios.Currently,how to achieve compatibility between the sensitivity and measurement range of flexible pressure sensors while maintaining a wide sensing range has become an urgent challenge in this field.To address the above issues,this study selected three-dimensional vertical graphene（VG）grown by plasma-enhanced chemical vapor deposition（PECVD）as the conductive active material of the sensitive layer,and introduced a micro-pyramid structure design in the sensor.This successfully produced a resistive and capacitive flexible sensor that simultaneously has a wide sensing range and high sensitivity.The theoretical analysis of the pressure sensing model designed was carried out by finite element analysis method,and the sensing mechanism was systematically explored from the microscopic and macroscopic scales.Finally,the produced sensor was applied to object recognition,motion monitoring,and human-computer interaction,demonstrating the excellent performance of the sensor.These research results can provide new ideas and methods for improving the performance and further development of flexible pressure sensors.The specific research is as follows:1.Study on piezoresistive flexible pressure sensor based on micro-pyramidal vertical graphene（VG）film:By using PECVD-grown VG film as the conductive active material,introducing micro-pyramidal structures in the sensitive layer of the VG film,and adding lumpy structures to the top and bottom layers of the sensor,a piezoresistive flexible pressure sensor with high sensitivity and wide sensing range was obtained.The vertical structure of VG,micro-pyramidal structure in the sensitive layer,and the external lumpy holders,enhance the stress concentration effect of the sensor at the nanoscale,microscale,and macroscale respectively when subjected to pressure deformation.By combining the three stress concentration effects through the selection of the sizes and parameters of the micro-pyramidal and lumpy structures,the cooperative stress concentration effect of the sensor was achieved at the nanoscale,microscale,and macroscale.A piezoresistive sensor with a high sensitivity of 131.36 k Pa^-1 and a wide detection range of 0.1–100 k Pa was obtained,achieving high sensitivity and wide sensing range compatibility simultaneously.2.Study on capacitive flexible pressure sensor based on micro-pyramidal dielectric layer and VG film:By using PECVD-grown VG film as the conductive active material for the upper and lower electrodes of the capacitive pressure sensor,and introducing micro-pyramidal structures into the polydimethylsiloxane（PDMS）dielectric layer using the molding method,a capacitive flexible pressure sensor with high sensitivity in a wide sensing range was obtained.Compared with traditional two-dimensional planar carbon-based electrodes,the three-dimensional vertical graphene（VG）film enhances the sensitivity of the sensor due to its excellent conductivity and high-density layer structure.At the same time,the micro-pyramidal structure design of the dielectric layer improves the deformation effect of the dielectric layer under pressure,further increasing the sensitivity of the sensor.The sensitivity of the sensor is 6.04 k Pa^-1 at 0–1 k Pa and 0.69 k Pa^-1 at 1–10 k Pa,which is significantly higher than that of the same type of sensors,achieving high sensitivity in a wide range.