Preparation And Micromechanical Analysis Of Flexible Piezoelectric Polylactic Acid Sensor

In recent years,the application of biodegradable electroactive polymer materials in sensor devices has gradually become a popular strategy to achieve the biocompatibility of devices while maintaining the required performance.Among them,the application of biodegradable films based on the piezoelectric effect of polylactic acid in sensors,transducers and actuators has gradually become one of the emerging research hotspots.In this work,the flexible piezoelectric sensor array was prepared and studied by using polylactic acid as pressuresensitive material and ultraviolet curing acrylate film as a packaging layer.Firstly,the flexible piezoelectric polylactic acid sensor in a 3×3 array contacts was designed using the “sandwich” structure.The sensor was composed of a packaging layer,a polylactic acid piezoelectric layer,upper and lower gold electrodes,conductive zebra paper and a flexible circuit board.Through COMSOL Multiphysics simulation,the signal interference between units of the sensor array under different unit spacing or size was analyzed.It was found that the increase of unit size and spacing can reduce the signal interference between units.Finally,the size and spacing of piezoelectric units were determined to be 3mm×3mm and 2 mm,respectively.Then,the preparation technology and optical characterization of flexible piezoelectric polylactic acid sensors were studied.The preparation process of the sensor included solution casting,magnetron sputtering,laser cutting,mask preparation,ultraviolet curing and other processing methods.Six groups of polylactic acid films with different treatment conditions were tested by X-ray diffraction,scanning electron microscope and Raman spectroscopy.The results showed that the crystallinity of polylactic acid increased with the increase of annealing time.Finally,in order to realize the micromechanical analysis of flexible piezoelectric sensor,a micromechanical test system was built,and the basic mechanical test methods such as bending,compression and tension were realized.The micromechanical analysis of flexible piezoelectric sensors was carried out,including the testing of four groups of acrylate ultraviolet curing films,six groups of sensor devices made of polylactic acid piezoelectric films and the flexible sensor array.The results showed that: The tensile ratio of the four groups of ultraviolet curing films can reach more than 4 times,and the adhesive strength of the ultraviolet curing films with the same volume ratio of dodecyl acrylate and hydroxybutyl acrylate was the highest;The piezoelectric properties of polylactic acid were correlated with the crystalline properties,and the piezoelectric properties of polylactic acid films stretched 4 times and annealed for 8 hours were the strongest;The pressure sensitivity of the sensor encapsulated with ultraviolet curing film was more than 3 times higher than that encapsulated with polyimide,which is about 1.29 m V/MPa;Through the impact test of the sensor array,it was found that the signal interference of adjacent array units is weak,and the response signal of the device has good stability;The sensor array can detect finger pressing and sliding and wrist bending,and produce 2～4 m V voltage peak signal during the test.The above research shows that the flexible piezoelectric sensor has good sensing performance,can realize effective response to external contact or bending stimulation,has good flexibility,can adapt to various curved surfaces,and has huge application and development space in the field of electronic skin,intelligent robot and so on.There are 48 figures,6 tables and 49 references in this dissertation.