Pulse Control Of Electrohydrodynamic Jet-printing And Preparation Of Functional Micro-scale Structures

Electrohydrodynamic jet printing(E-jet printing)has many advantages,such as high manufacturing precision,wide ink adaptability and suitable for complex structures.It is widely used in micro/nano electronic devices,sensors and so on.In this work,graphene ink was chosen as the printing liquid.Pulse control of E-jet printing was researched.The influence of printing parameters on printing structures' size and printing stability was discussed.The graphene with nano layer was printed.The drop-on-demand printing of graphene micro-structures was achieved.Pt/graphene composite microelectrodes for the microfluidic chip detection and graphene-based FETs were prepared and their properties were tested.First of all,the platform hardware and software control system for pulsed printing were completed.The influence of pulse parameters on the size of the printed structures and printing stability was studied.The main parameters that affected the printing process were pulse voltage amplitude,duty cycle,flow rate,platform movement speed,pulse frequency,working distance and so on.When the pulse voltage amplitude increased,the printing stability was weakened.When the duty cycle and flow rate decreased,the size of the line structures decreased.Depending on the speed of the platform movement,dot arrays or line structures could be printed,and the size of the line structures decreased with the increase of the speed of the platform movement.After optimizing the printing parameters,graphene line arrays of about 20 ?m was pinted using the nozzle with the internal diameter of about 50 ?m.The drop-on-demand printing technique was formed,and the control method of micro-scale complex graphic printing was obtained.The effect of different kinds of drop-on-demand printing methods on printing results was analyzed.It showed that by changing the standard pulse voltage into stepped pulse voltage,the large droplet which appeared in the printing process could be avoided.A variety of micro-scale graphics were printed with the silicon substrate.Then,the micro-structures of graphene were characterized,and the relationships among the number of printed layers,thickness,resistivity and surface morphology of the structures were studied.It was found that with the increase of the number of printed layers,structures' thickness increased,and both of them were roughly proportional.When the number of printed layers were 1 and 50,the thickness were 5 nm and 730 nm,respectively.The resistivity decreased with the increase of the number of printed layers.When the number of printed layers was 20,the connection between the adjacent graphene sheets was close to saturation and the decrease of resistivity which was 1.4 m?·cm was no longer obvious.The surface morphology was more smooth with the increase of the number of printed layers.Finally,by combining MEMS with pulsed electrohydrodynamic jet printing technique,Pt/graphene composite microelectrode was fabricated and microfludic chip device was formed.Electrochemical detection of potassium ferricyanide was carried out with the device and for the solution of 5 mmol/L,the composite electrode's detection response signal was higher about 150% than platinum electrode.The graphene-based field effect transistor sensor was fabricated.The mercury ion and sulfur ion were detected by the resistance and the current method,respectively,which showed high sensitivity.