| With the continuous improvement of micro/nano devices and system integration,the devices have developed from a single plane structure to a three-dimensional(3D)micro/nano structure.The micro/nano scale 3D structure has a certain application prospect in the fields of electronic information and bio-medical treatment.And its manufacturing technology is of great significance to the development of 3D micro/nano devices.Electrohydrodynamic jet(E-Jet)printing has the advantages of high resolution,wide material adaptability and simple process.At present,the 3D micro/nano structure printed by E-Jet generally adopts the method of accumulative construction layer by layer.Most of the obtained structures have resolution-limited and surface morphology defects.Based on the theory of electrohydrodynamics and fluid heat transfer characteristics,a new method named electrohydrodynamic jet printing regulated by thermal field was put forward.The PCL/PVP composite scaffolds and high aspect ratio sub-micro PZT needle structure were printed with high efficiency and high quality.The research content mainly includes the following five parts:(1)The mechanism of electrohydrodynamic jet printing regulated by thermal field was studied,which based on the theory of electrohydrodynamics and fluid heat transfer characteristics.The stress of the electrohydrodynamic jet printing regulated by thermal field was analyzed.A numerical simulation model of thermal-flow jet was established.The charge motion behavior and jet velocity evolution of multi-field composite fluid was analyzed.The mechanism of thermal field viscosification refining jet was studied.The change of concentration-viscosity due to solvent volatilization was obtained.The influence of temperature and voltage flow on the formation of jetting was studied by simulation,the mechanism of action of key process parameters on the shape and size ofjet was revealed,and the optimal parameter range of stable thermal field to regulate the formation of electrohydrodynamic jet was obtained.(2)An on-line measurement and feedback control method for e electrohydrodynamic jet current and jetting parameters was established.The equipment of electrohydrodynamic jet printing regulated by thermal field and its key device were developed.The thermal field space position was determined and the thermal field control device was developed.A current measuring device was developed.The current characteristics under different printing modes were analyzed and the influence of pulse frequency,flow rate on jet current and printed structure size was studied.The experimental results showed that the current range of stable controllable jet and highly consistent printing structure was easy to be obtained.By selecting the current range reasonably and adjusting the flow rate online,the printing and manufacturing of a variety of complex 2D graphene microstructures have been realized.This paper developed a control system for printing equipment,realizing the cooperative control between the function modules and improving the controllability of the printing equipment.(3)The printing process of PCL/PVP composite scaffold with electrohydrodynamic jet printing regulated by thermal field was studied.The mechanism of thermal field-flow field composite bonding,thinning jet and curing structure was analyzed.The effects of temperature,voltage,flow rate and horizontal tensile velocity on jet behavior and printed structure characteristics were studied.The size of printed structure was inversely proportional to temperature,voltage and horizontal drawing speed,and directly proportional to liquid flow.The complex 2D figure with the minimum feature size of 700 nm and the high aspect ratio structure flat surface morphology with were printed,and the PCL/PVP composite biological scaffold with cell scale fibers was prepared.And the fiber spacing is orderly and controllable.The MC3T3-E1 Subclone 14 chondrocyte culture results showed that the scaffold had good biocompatibility.(4)The continuous integrated printing process of PZT micro scale needle with electrohydrodynamic jet printing regulated by thermal field was studied.The influence of temperature,voltage,vertical tensile velocity on the behavior and size of 3D jet were studied when the PZT sol as the functional material.The mechanism of thermal field-electric field collectively driving the traction deformation of high viscosity PZT columnar structure was studied.The influence law of electric field intensity,spacing and other parameters to drive traction deformation was studied.And the PZT micro scale needle with spatial geometric characteristics was printed and manufactured with the printing speed of 30 mm·s-1.The minimum feature size of 500 nm and the aspect ratio of 200.The potential of electrohydrodynamic jet printing regulated by thermal field in the fabrication of sub-micron scale structures was demonstrated.(5)The mechanical and piezoelectric properties of PZT needle were studied.And the post-treatment process of PZT was explored.XRD,EDS,Raman spectroscopy and TEM tests showed that the sintered PZT needle obtained the standard polycrystalline perovskite crystal structure with the optimal orientation in the direction of(100);and the structure was dense and free of defects.The maximum elongation of the printed PZT microne is up to 6.97%,the young modulus is 32 GPa,and the piezoelectric constant d31 is 236.5×10-12 C N-1.The 3D PZT jet column with few solvents and high viscosity formed by the thermal field regulation of jet reduces the internal cavity and surface roughness caused by solvent volatilization in the post-treatment,inhibits surface defects of the structure.And obtains the PZT needle structure with flat surface morphology and homogeneous internal structure.The PZT needle used for airflow testing were printed,and the PZT needle airflow testing system was developed.The piezoelectric response of PZT needle at different wind speeds was tested and analyzed to realize the perception at low wind speeds,which provided a feasible scheme for the design and manufacture of airflow sensors. |
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