Design And Fabrication Of Flexible Pressure Sensor Based On DLP 3D Printing

Flexible pressure sensors have great application prospects in the development of today’s digital information society,whether in microelectronics,flexible robotics,health care,or the Internet of Things and other research fields.Flexible pressure sensors have been widely studied by scholars for their flexible characteristics.Compared with traditional sensors,most of the flexible pressure sensors are designed and manufactured based on flexible materials.However,the processing of flexible materials using common manufacturing methods introduces many limitations in the design and manufacturing of flexible sensors,such as: the difficulty of processing flexible materials for additive and subtractive materials,and the difficulty of simple and economical manufacturing of highperformance flexible pressure sensors with surface microstructures.Therefore,it is important to investigate the novel manufacturing technology for making flexible pressure sensors.Digital Light Processing(DLP)3D printing technology has been applied to manufacture flexible materials with high molding accuracy in recent years,which can easily print sensitive components with surface microstructures for making flexible pressure sensors.In this study,DLP printed conductive hydrogel was used as the sensitive element of the flexible pressure sensor,and it was encapsulated and fabricated to obtain a high-performance flexible pressure sensor.Firstly,the DLP printing process of conductive hydrogel was investigated to improve the printing accuracy of conductive hydrogel.To improve the performance of the sensor,conductive hydrogels with fingerprint-like surface microstructures were designed and printed to be used as sensitive elements to make flexible pressure sensors.The role of the surface microstructure of conductive hydrogel in enhancing the sensor performance is comparatively analyzed by simulation,and the advantages of the fingerprint-like microstructure design are verified.Finally,the performance of the fabricated pressure sensors was experimentally tested to demonstrate the application of the pressure sensors fabricated based on DLP printing technology in human motion detection or multifunctional sensing integration.The details of the research in this paper are as follows.(1)Conductive hydrogel was selected as the sensitive element of the fabricated flexible pressure sensor,and the DLP printing process of forming conductive hydrogel was further investigated.By adjusting the single exposure energy of UV light during DLP printing and reducing the penetration depth of UV light in the conductive hydrogel,the printing accuracy of conductive hydrogel can be improved,and the final printing accuracy of DLP printed conductive hydrogel can reach 150 μm.Based on the optimal printing process parameters,the factors affecting the mechanical and electrical properties of the printed conductive hydrogels were analyzed.The Young’s modulus,fracture strain,deformation recoverability,and ionic conductivity of the printed conductive hydrogels can meet the requirements for making pressure sensors by changing the components of the conductive hydrogels to adjust the degree of cross-linking of the internal network of the hydrogels.(2)Design and printing of conductive hydrogels with fingerprint-like surface microstructures as sensitive elements for flexible pressure sensors Based on the conductive hydrogel that can be printed with high precision,we propose to design conductive hydrogel with fingerprint-like surface microstructure as a sensitive element for a flexible sensor in order to improve the performance of the pressure sensor.The force compression deformation of different size design microstructure is analyzed by simulation,and the suitable design parameters of microstructure size are obtained by comparison.In addition,the mechanism of the designed flexible pressure sensor to achieve sensing is analyzed in detail based on the principle of electric double layer,combined with the simulation of the microstructure under pressure deformation process.Finally,the printed conductive hydrogel with surface imitation fingerprints was encapsulated to fabricate the flexible pressure sensor.By detecting the characteristic signal of the pressure sensor,it is initially verified that the fabricated sensor can realize the pressure sensing function.(3)The performance parameters of the sensors are tested and the potential applications of the fabricated flexible pressure sensors are verified using demonstration experiments.By comparing with sensors made of conductive hydrogel without surface microstructure,the fingerprint-like surface microstructure design can improve the sensitivity of the sensor by a factor of 2.In addition,the fabricated sensor has a maximum pressure detection limit of up to 70 k Pa,a minimum detection limit of 26 Pa,a response time of 320 ms,and a cyclic loading stability of the response signal.The designed and fabricated sensor can be successfully applied for touch sensing of slight pressure and for attaching to human joints to detect changes in joint motion.To further explore the potential of the fabricated pressure sensor for multifunctional sensing integration,a DLP printed temperature-responsive shape memory polymer was used to fabricate a temperature-responsive switch,and the fabricated pressure sensor and temperature-responsive switch were integrated to achieve both pressure and temperature sensing.Through performance tests and demonstration experiments,it finally proved that it is feasible to fabricate flexible pressure sensors based on DLP printing technology,which provides a new approach to design and manufacture flexible sensors.