| Piezoelectric devices can be used for precise sensing and actuating control of basic physical quantities such as dynamic force,acceleration,and precise micro-displacement.These quantities are the essential sensing and actuating elements which are indispensable and essential in precision engineering fields such as aerospace,medical equipment,optical imaging.Piezoelectric ceramic thick films with a thickness ranging from micrometers to hundreds of micrometers have combined the advantages of both bulk piezoelectric ceramic and piezoelectric thin films,and thus to obtain the merits of a high-performance and a strong compatibility in the MEMS process.However,the piezoelectric thick film also has difficulties in matching the forming process and complex regulation of piezoelectric properties,which limits the application of high-performance piezoelectric thick film devices.In this paper,firstly a new manufacturing method of curved piezoelectric thick-film using E-jet printing was proposed,and an E-jet printing equipment of piezoelectric thick-film with five-axis was established.Secondly,the key printing process of the microstructures of the piezoelectric thick film and the structures of the curved piezoelectric thick film was studied,and a high-performance piezoelectric thick film printing strategy was developed.Finally,a micro motor stator of the piezoelectric thick film and a new type of omnidirectional shock sensor of the curved thick film were built.（1）Firstly,the printing mechanism of curved piezoelectric thick film using E-jet printing was studied,and the E-jet printing equipment of piezoelectric thick film with five-axis was developed.The mechanical characteristics of the cone-jet of the E-jet was analyzed,and the mechanism of the curved substrate and its motion trajectory in the stable electric jet was studied.The electrostatic field simulation model of E-jet printing was established,and the influences of printing distance,angle and the path of the peak distribution of printing field intensity and the shape of the cone-jet were verified.Accordingly,a printing strategy of curved piezoelectric thick film as"microelement vertical"was proposed,and a curved substrate cooperative motion device,a piezoelectric thick film E-jet printing device,a microstructure visual positioning device and an in-situ heat treatment device were developed.The control program of the device was written to realize the coordinated control among the functional devices,and an E-jet printing equipment of piezoelectric thick-film with five-axis motion was built for printing of the microstructures of the piezoelectric thick-film and the structures of the curved piezoelectric thick-film on a provided base.（2）Second,the E-jet printing process of the microstructures of the piezoelectric thick film and the structures of the curved piezoelectric thick film was studied.The PP composite slurry made from ball milling of PZT sol and PZT powder was developed.The influences of different substrates on the micro-morphology,the phase composition,the residual stress and the film-substrate bonding force of printed thick films were studied,and the printing parameters were also explored for the manufacturing of the thick film microstructure.The influences of annealing crystallization curve and the parameters in the polarization process on PZT thick film d33 were analyzed.A systematically optimized high-performance E-jet printing strategy of piezoelectric thick film was formed with three parts of substrate material preparation,printing parameters matching and crystal polarization.The microstructures of the line array of the PZT thick film and the cantilever array of the"T-shaped"piezoelectric thick film were manufactured by E-jet printing with a line width of 70μm and a mechanical quality factor of 688,which is higher than that of piezoelectric film.The hemispherical piezoelectric thick film structures with different millimeter diameters were manufactured.The effective piezoelectric constant d33 is131 p C/N,better than that of screen printed PZT thick film,which could provide process technology for miniature piezoelectric thick film devices.（3）Based on the microstructure E-jet printing process of the piezoelectric thick film,a micro motor stator of the piezoelectric thick film was built.The necessary conditions of stator for traveling wave formation of bending vibration of PZT thick film were proved,and the driving mechanism of mass point ellipse was analyzed.Accordingly,the stator structure of the micro piezoelectric thick film motor was designed.The relationship between the structural parameters of the stator and modal frequency was simulated and analyzed,the characteristics of the piezoelectric thick-film stator about the amplitude-frequency and transient status and those of the piezoelectric motor about the contact stress and mechanical output were analyzed.A PZT thick film component was directly printed on elastomers by E-jet printing to form a micro motor stator of the piezoelectric thick film.A high-precision multi-zone synchronous polarization device was developed to realize the one-time synchronous polarization of the micro motor stator.The radius of the micro stator is 2.15 mm.The excitation voltage of the motor was20 V and it realized a locked rotor torque of 120 m N·mm,which is about 3 orders of magnitude higher than that of PZT thin film piezoelectric stator with comparable size.While the PZT thick film motor stator can meet the application requirements of narrow space,low driving voltage and large output torque.（4）Based on the E-jet printing process of the curved piezoelectric thick film,an omnidirectional shock sensor of the curved piezoelectric thick film was built.The mechanical model of the piezoelectric shock sensor was established,and the key parameters affecting the signal output of the sensor were found out.An omnidirectional shock sensor of the hemispherical piezoelectric thick film was designed.The natural frequency and vibration frequency of the impact sensor system was simulated and analyzed,and the deformation mechanism of the lateral impact for the sensor and the influence of electrode partition on the omnidirectional sensitivity of the impact acceleration were studied.An omnidirectional impact sensor of the hemispherical piezoelectric thick film was built based on the E-jet printing process of the curved thick film,and a test device for this sensor was built.The sensitivity is 1.25 p C/g in an acceleration range of 10000 g.The linearity of impact output signal in the angle range from 0 to 90°is 9.3%,which is comparable to that of single-axis commercial piezoelectric accelerometers.The piezoelectric shock sensor has the advantages of an omnidirectional sensitivity and a large response range in meeting the application requirements. |
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