| In recent years,with the development and utilization of various functional materials,micro-nano manufacturing has become particularly important in many fields,such as flexible electronics,optical devices,and microfluidic devices.Among the current mainstream micronano manufacturing methods,there are still problems such as expensive equipment,low processing efficiency,limited molding range,and low manufacturing accuracy,which are difficult to meet the existing application requirements.Electrohydrodynamics(EHD)direct printing is a new type of micro-nano-scale printing method.As a maskless,non-contact,direct writing and additive manufacturing process,it has the advantages of fast forming speed,material with good compatibility and high printing resolution.In this paper,we select the polymer polystyrene as the research object,systematically study the fabrication process of the structure-controllable polystyrene(PS)with EHD direct printing.The controllable PS microstructure printing process was optimized on the basis of the EHD direct printing platform;the fabricated PS microstructure was used as a sacrificial template,and the polydimethylsiloxane(PDMS)micro-channel was molded by soft lithography.Meanwhile,a process program for preparing cross-scale micro-channels based on EHD direct printing was proposed,and the specific applications of different-scale channels were demonstrated.The main research contents of this thesis are as follows:1.Exploring the printing law of PS solution in continuous cone-jet mode.By changing the mass fraction of the printing solution,applied voltage,extrusion pressure and the movement speed of the collector,the optimization of the direct printing process parameters is realized.The results show that:(1)The concentration of the solution determines the morphology of the PS line.By increasing the mass fraction of the PS solution(10% to 18%),a PS line with higher surface quality can be obtained;(2)A single jet which is suitable for printing can be obtained in the range of 0.5-1.0kV,and the higher the voltage applied,the smaller the diameter of the PS line will be obtained;(3)The stable printing can be obtained by controlling the extrusion pressure in the range of 5-30kPa,and the diameter of printing lines increase with the increase of air pressure within this range;(4)A continuous PS line can be obtained by controlling the speed of the collector between 15-30 mm/s,and the diameter of the line decreases with the increase of the speed of the collector.2.Comparing the droplet forming results with DC voltage and pulse voltage applied on the nozzle,it is found that pulse voltage has better effect in terms of droplet deposition controllability and uniformity.The optimization results of pulse voltage process parameters show that:(1)PS solution with a mass fraction of 5% is suitable for direct write printing of droplets under the action of pulse voltage;(2)The pulse voltage duty cycle has an important influence on the printing stability,a stable printing process can be realized at 20% duty cycle;(3)The diameter of the droplet decreases with the increase of DC voltage,while increases with the increase of pulse amplitude.3.Based on the optimization of the PS solution printing process,PS lines of different scales were prepared as sacrificial templates and applied to cross-scale micro-channel molding.While characterizing the size of the prepared PS template,the micro-channel structure on the PDMS surface was observed;elemental analysis was performed on the surface of the channel to ensure that there were no residual PS lines inside the channel;the morphology and surface quality of the channel were measured and analyzed,the roughness of the inner wall of the detection channel is less than 300nm.Finally,the encapsulated channels were filled with common ink and liquid alloy respectively,and Y-type micro-mixers and flexible resistive sensors were successfully fabricated,demonstrating the potential of EHD direct printing in the field of microdevice preparation. |
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