Control of Droplet Formation in Inkjet Printing Using Ohnesorge Number Category: Materials and Processes

Abstract

findings agreed with Fromm whereby ejected volume The dimensionless Ohnesorge number (Oh) describes the increases with decreasing Oh value. relative importance of viscous to surface tension effects, Several studies [3][4][5] had been conducted on the effects of which is commonly used to characterize jet breakup. In this Oh on the mechanics of droplet formation, e.g. capillary study, the experimental results have proven that single break-off length and time, droplet volume and satellite droplets can be jetted for 0.02 < Oh < 1.5, for viscosity > 50 formation. Xu and Basaran [5] stated that these parameters mPas, using different mixture compositions of glycerol in depend weakly on Oh when Weber number (We) is water (0 -80 wt%) as the ink. This is contrary to previous sufficiently large. Schulkes [6] and Dong et al. [7] had also published literature [1, 2]. However, the findings are in good investigated the effects of Oh on the creation of satellite agreement with Reis and Derby [2] that the velocity of the droplets due to end-pinching. Experiments and simulations of ejected droplet exhibits a maximum (i.e. inverted 'U' curve) Chen and Basaran [8] studied the effect of Ohnesorge number and is a function of pulse width. This velocity curve is on the size of droplets produced. They stated that a uni-polar apparently governed by the Ohnesorge numbers. From a waveform could lead to satellite formation rather than a single practical standpoint, with the large variety of inkjet printing droplet. With their tailored waveform, droplets smaller than inks having different properties, these results can be useful for the diameter of the nozzle orifice can be produced at waveform tailoring to achieve optimal performance for droplet intermediate Oh (-. 0.1 -0.2), but not when Oh is too low ('. formation control. 0.02) or too high (z 1.0). However, results of Gohari and Introduction Chandra [9] disagreed with this finding by producing smaller Inkjet printing has received enormous attention and drops from a 204 ptm diameter nozzle (Oh = 0.21 -1.73), interetas a mufactugtechnology with the applications using a pneumatic DOD generator. Their results also stated otintertst manvenuionglgyfice/home use in printed graphics that single droplets could not be produced when Oh was too outside itS conventional office/home use in printed graphics lw ..O .8 and text. These include fabrication of polymer electronics lo,ie O .8 aompondtext.ese o nincLuD fabricationof polymponernelctrani Bogy and Talke [10] defined the optimum pulse width of micrompons, forganical screrics cm pnemnt anr d the applied rectangular pulse at which the ejected droplet has mppicrtioar s for biolo a screnting. Forthedmose manufact ur the maximum velocity, due to the pressure wave in the cavity s te i t p g m o ms c y being optimally enhanced. They concluded that this optimum is the piezoelectric drop-on-demand method (DOD). The basic I w i principle of operation is via the use of pressure waves induced Pu in an ink-filled conduit by piezoelectric sleeve actuation, to ...

Systematic Design of Jettable Nanoparticle-Based Inkjet Inks: Rheology, Acoustics, and Jettability

“…Literature data from Tai et al,. 23 Tsai and Hwang, 19 and Bogy and Talke 18 (also plotted in Figure 3a) agree well with our findings. In mapping the jettability window, we observed several characteristic jetting stability breakdown mechanisms in the areas enumerated in Figure 3b,c.…”

“…20 Since then, several authors have attempted to define a jettability range using the Z number, resulting in the following: 1 < Z < 10, 21 4 < Z < 14, 22 and 0.67 < Z < 50. 23 The inconsistencies in reported Z-value ranges suggest that the Z number alone cannot define jettability. Although the other dimensionless parameters relevant to droplet formationRe, We, and capillary (Ca) numbereach balance only two of the force terms pertinent to drop formation (inertial, viscous, and surface tension), the Z value encompasses all three.…”

Paper‐Based Inkjet‐Printed Microfluidic Analytical Devices

“…(1)] have been utilized to evaluate the practical printability of fluids under DOD conditions. [52][53][54] …”

“…[55] This approximation has been modified and could be further modified to suit the printability of inks with more challenging rheological properties. [53,54,56] All of these numerical and experimental investigations are geared towards attaining stable, satellite-free printable inks that form welldefined patterns without clogging the nozzle. To achieve the required ink properties, it is often necessary to adjust the viscosity and surface tension by modifiers.…”

Coupled CFD-Response Surface Method (RSM) Methodology for Optimizing Jettability Operating Conditions

“…This dimensionless value was later known as the Z number and defines a jettability range [11]. From the literature, different Z intervals for jettability purposes, ranging from 1 to 10 [12], 4 to 14 [13], or even 0.67 to 50 [14], can be found. This clearly means that the Z value alone is not able to indicate the jettability conditions.…”