A Flexible Sensor Based On Surface Microstructure

The 21st century entered the era of big data in an information network.Information terminals are gradually moving from mainframes to wearable devices,and electronic devices face the challenge of flexibility.Flexible electronic technology develops new electronic materials and devices that simulate the multi-performance of the skin,which is the electronic skin.As one of the important components of electronic skin,flexible tactile sensor can respond to external stimuli and greatly promote the development of intelligent robots,medical health and mobile devices.Through the exploration of different sensing mechanisms,the researchers have developed a variety of tactile sensors represented by capacitive,resistive,piezoelectric,and triboelectric devices to continuously improve the sensing performance of the device.The introduction of microstructures is a strategy for improving the performance of many of the above tactile sensors.For example,using a micropyramid structure as a dielectric layer can effectively improve the sensitivity of the tactile sensor.However,it is extremely difficult for these stable structures to deform in the high pressure region,resulting in a low sensitivity of the device in the high pressure region.Compared with the common stable structure,this paper designs a high aspect ratio micropillars structure which is easy to destabilize to improve the sensitivity of the device and increase the response pressure range.Taking full advantage of the deformation characteristics of the microstructure,combined with the high sensitivity characteristics of the ion capacitor,the sensitivity of the sensor is improved and the performance of the sensor is optimized.In this paper,an array of easily unstable micropillars was prepared by template method.A high aspect ratio microholes structure was fabricated on a silicon wafer by optical exposure and metal catalyzed etching.and then hot embossing and elastomer casting was used to prepare a polydimethylsiloxane having?PDMS?micropillars structure with 5:1 aspect ratio.After the gold plating,the micropillars structure is used as a micro-column electrode,plus the ion-gel film dielectric layer and the polyimide?PI?gold-plated electrode to constitute a flexible capacitive type tactile sensor with a"sandwich"structure.The device's sensitivity is up to 33.16 kPa^-1 in the pressure range of 15-180 kPa,which has extremely high linearity.The device has a response time of 11 ms and a detection limit of 3.1 Pa.Using the device to monitor the movement and health of the human body,the radial artery and carotid artery waveforms of the human body can be clearly detected,and effective health indicators can be obtained from the test data,the device exhibits potential applications in human health and medical fields.In order to sense the shape of the space object,we have prepared a flexible tactile sensor array,and realizing the recognition of the contour of the test object.Finally,the instability principle of the micropillars structure is combined with the actual compression deformation process to illustrate the design basis of the microstructure,and the sensing characteristics of the device are explained based on the electric double layer theory of the ion sensor.This paper innovatively designed an unstable high aspect ratio micropillars structure and provides a new design idea for the structural design of flexible sensors.The device achieves high sensitivity and high linearity in the wide pressure range,which facilitates the mutual conversion between the sensing capacitance signal and the external force.It has made a preliminary exploration for the external force sensing from qualitative analysis to quantitative detection.