壓電噴墨液滴生成與噴覆於長方型微凹槽之特性研究

Study on the evolution of piezoelectric inkjet droplets and their deposition in rectangular microcavities

詹佳諺(Chia-Yen Chan)

指導教授 ： 劉通敏

國立清華大學/工學院/動力機械工程學系/博士(2009年)

摘要

Micro-flow visualization (μ-FV) and computational fluid dynamics are complementarily performed to study the evolution of a single inkjet droplet ejected from a bend-mode piezoelectric inkjet printhead and the equilibrium film characteristics of the droplet deposition in microfabricated cavities. The numerical simulation is characterized by the coupled piezoelectric-structural- fluid solution procedure and verified by the μ-FV results. The numerical code is applied to investigate the influences of electric voltage, pulse shape, ink property (fluid viscosity μ and surface tension σ), and nozzle diameter Dn on the droplet volume, velocity, and configurations. Besides, by varying the droplet Weber number (We), droplet impact velocity Vd, sidewall contact angle (θs) of the microcavities, and microcavity length-to-width ratio (L / W) various deposition characteristics in microcavities are examined and the critical We (Wec) for filling microcavities with uniform ink films are identified. The computed results are found in good agreement with the experimental ones. For inkjet droplet evolution, new findings are to discover the critical ranges of electric waveform parameters, μ and σ outside which the phenomena of satellite droplets and puddle formation at the nozzle opening are absent. In addition, the imbedded physical rationales for these critical ranges are provided. The results are new in terms of the identifications of the critical σ and Dn for the reference of improving the droplet quality. For droplet deposition in microcavities, Wec have been found relating to the ability of the droplet to wet the side walls and fill a microcavity with a uniform film. The results are also new in terms of the identifications of the critical contact angle (θs)c and critical impact velocity (Vd)c. At (θs)c and at and beyond (Vd)c, the formation of an intact flat film in the cavity is fulfilled. The functional dependences between Wec and normalized θs as well as L / W are deduced for the first time. These correlations are believed to provide useful engineering references for operating inkjet printheads and fabricating uniform thin film coating on the bottom substrate of microcavities.

關鍵字

壓電噴墨 ； 微凹槽 ； 臨界填滿韋伯數 ； 側壁接觸角 ； 微凹槽長寬比

並列摘要

無資料

並列關鍵字

Piezoelectric Inkjet ； Microcavity ； Critical Filling Weber Number ； Sidewall Contact Angle ； Microcavity Length-to-width Ratio

參考文獻

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