Mechano-electrospininig Direct-writing Technology And Application In Large-area Microstructures

Flexible electronics offer an attractive alternative to conventional IC in the future. The inkjet printing is a key fabrication technology by enabling the creation of large area, flexible devices at low cost and high efficiency. However, several issues, including low printing resolution and bad compatibility with organic material, are to be researched, In this dissertation, a new continuous direct-written method is developed and some theoretical, practical achievements are obtained in the issues of the depositon process, including the mechanism of manufacture, process parameters control, design and fabrication of device, The main research work and contributions of the dissertation are introduced as follows:Firstly, a tunable direct-written mechano-electrospinning technology is developed, in which pulling force coming from moving substrate and electric static force are used to manipulate the fiber controllable. The numerical model for the flight of the electrified jet in near-field is established to investigate its spatial dynamics behavior resulted from the non-uniform electrical field and stretch of the substrate. The effect of process parameters, including velocity of the substrate, nozzle-to-substrate height and operation voltage, on flight behavior of jet and morphology of the deposited fibers is investigated. Then, the transformation from the ’buckling’ to ’catenary’ and geometry of the fiber are analysed, which is able to explain the relationship between them. The relationship between pulling force exerted on the jet tail and process paramters are proposed by simulation. The stable direct-written region is given on parameter plane. It is used to realize the precision positioning and control fiber morphology. Following this principle, micro/nano straight fiber array and bead-on-string structure could be fabricated efficiently in a large area.Secondly, a multi-quadratic regression equation formula is established to analyse the couplings between process parameters and its sensitivity to fiber width based on response surface methodology, and thereby the width of the fiber under any process parameters can be predicted in good agreement with the actual width of the fiber. The planning principle of process parameters is proposed, which can figure out the combination of process parameters for desired micro/nano structure with large area. According to the established planning principle, the optimized combination of process parameters can be obtained.Thirdly, the PVDF nanofiber array with high precision is directly deposited by mechano-electrospinning, and the polarization is also achieved in this process. The effect of velocity of the substrate on the polarization is revealed. By combining photographed electrode, and flexible package, the piezoelectric device is successfully fabricated and the voltage and current are generated from cyclic bending loop. By this method, the polarization of piezoelectric material and electrical properties of devices could be controlled by selection of process parameters. It supplies a digital manufacturing method to manufacture the flexible devices a in the future.Finally, a processing scheme for fabricating all flexible devices with various structure is illustrated based on the different electrohydrodyanmic jetting modes. Following this thought, a multi-functional electrohydrodyanmic jet printer with roll-to-roll transportation and the local environmental control is implement. In this printer, the mainly operating mode is mechano-electrospinning, but the electrospray and electrohydrodyanmic inkjet printting are also achieved. The self-organization of colloid microarrays, highly stretchable buckling fiber and thin film are fabricated in large area by using this printer.