Abstract findings agreed with Fromm whereby ejected volumeThe dimensionless Ohnesorge number (Oh) describes the increases with decreasing Oh value.
relative importance of viscous to surface tension effects, Several studies [3-5] had been conducted on the effects ofwhich is commonly used to characterize jet breakup. In this Oh on the mechanics of droplet formation, e.g. capillarystudy, the experimental results have proven that single break-off length and time, droplet volume and satellitedroplets can be jetted for 0.02 < Oh < 1.5, for viscosity > 50 formation. Xu and Basaran [5] stated that these parametersmPas, using different mixture compositions of glycerol in depend weakly on Oh when Weber number (We) iswater (0 - 80 wt%) as the ink. This is contrary to previous sufficiently large. Schulkes [6] and Dong et al. [7] had alsopublished literature [1, 2]. However, the findings are in good investigated the effects of Oh on the creation of satelliteagreement with Reis and Derby [2] that the velocity of the droplets due to end-pinching. Experiments and simulations ofejected droplet exhibits a maximum (i.e. inverted 'U' curve) Chen and Basaran [8] studied the effect of Ohnesorge numberand is a function of pulse width. This velocity curve is on the size of droplets produced. They stated that a uni-polarapparently governed by the Ohnesorge numbers. From a waveform could lead to satellite formation rather than a singlepractical standpoint, with the large variety of inkjet printing droplet. With their tailored waveform, droplets smaller thaninks having different properties, these results can be useful for the diameter of the nozzle orifice can be produced atwaveform 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 andIntroduction 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 toooutside itS conventional office/home use in printed graphics lw ..O .8and text. These include fabrication of polymer electronics lo,ie O .8
aompondtext.eseo nincLuDfabricationof polymponernelctrani Bogy and Talke [10] defined the optimum pulse width ofmicrompons, forganical screrics cmpnemnt anrd the applied rectangular pulse at which the ejected droplet hasmppicrtioar s for biolo a screnting. Forthedmose manufact ur the maximum velocity, due to the pressure wave in the cavitys te i t p g m o ms c y being optimally enhanced. They concluded that this optimumis the piezoelectric drop-on-demand method (DOD). The basic
I w iprinciple of operation is via the use of pressure waves induced Puin an ink-filled conduit by piezoelectric sleeve actuation, to the speed of acoustic waves in the fluid. Reis and Derby [2]
overcme*thsuracetnoad p e a f entof i re-enforced this finding that droplet velocity has a maximumovercome th sufc teso an prtrd a fiaeto *n and is a function of pulse width. They added that this pulseout of the orifice. To dispense a droplet successfully, it isstrongly govered by the induced pressure wave, physical width remains unchanged as the amplitude of the drivingdimensions of the nozzle device and the rheological properties waveform is increased, provided ink properties are unchanged.of the ink, such as the viscosity, elasticity, and surface tension However, none have attempted to investigate the effect of Ohtopinch off the ink filament for droplet ejection. The complex on velocity profiles with respect to varying pulse width.
interplay between all these influential parameters has an Tailoring of the driving waveform based on variation inimmense implication to the inkjetability stabilityof inkjetting Ohnesorge number is a research area which has not beenand droplet formation control. explored in detail by previous literatures. Most literature basedThddropletOhorgetionnumber on the investigation of Oh has been focused on the mechanicsThe Ohnesorge number Of is t sfeension forces of droplet formation without relating to the driving input.usedhtoeprovidtstheradimens vionle saysiofa te nonforces, Hence, the focus of this paper is to investigate the effect of Ohusedrtopletrformdeatdioensionl printing.yUsinf nmerhanicalof on droplet formation (i.e. velocity and volume) of Newtoniandropletions,tFom [1 cuD that fornOvuesighe mixtures, using driving waveforms with varying dwell timestmulatnons,drop m is no tpsl h alscocued (pulse width). Here we investigate the behaviour of dropletthat as theO value isdereae forosam.e input pule, formation over a common range of the Ohnesorge number
n e d d a v n (0.02 <Oh< 1.5). Inourexperiments the fluids are aqueouscomputational fli dyamc (CFD moeln,Ri n mixtures of varying glycerol compositions (0 - 80 wt%) andDeb [2] predicte tha DO prntn ispossible inte.ag are Newtonian in nature. A commercial inkJet printing system
0.1<O 1,*for ceai patclt supnsos Fo Oh (Microfab Technologies Inc), with piezo-actuated glass0.1, multiple satellite droplet formation was observed instead oze fdaeeu0rm a sdfrtergruof a sigl drolt WhenOh> 1, vicu* fetresltn in examinations. The real time formation of droplet was capturedthe dissipation Of pressure pulse in the nozzle capillary by stoocpciaig(ir-eodrslto).uprvn th drpe fro brakn off Their expermenta results show that it iS possible to ink-jet fluids which are more
viscous (Oh > 1, pt > 50 mPas) which is contradicted to the placed at the side of the printer. This is synchronised with therule of thumb guideline in common practices to keep viscosity LED to produce stroboscopic displays of the dropletbelow 40 mPas. This finding provides a wider range of formation. Using the software and camera, the velocity andjettable inks for selection and would be a significant volume of the jetted droplets can be measured. It should beimprovement to ink formulation. From another practical noted that visual (camera) calibration must be done prior tostandpoint, with the aid of Oh study, dilution of the ink can be experiments and the details of calibration would not beminimized for desired inkjet printing. This is thus more covered in this paper.efficient because using relatively more dilute fluids, only littleamount of functional material could be deposited. Software: Driving Waveform
This study attempts to provide an interesting insight onhow the printing process can be enhanced from an external Voltage (V)perspective i.e. waveform tailoring, without delving into thedetailed mechanics of droplet formation. In the experiments,the range of Ohnesorge values whereby a single droplet could | vNbe jetted was investigated, using Newtonian glycerol mixturesas inks. Velocity of the jetted droplet was also quantifiedwhile the pulse width was varied. A brief investigation on thecontrol of satellite formation is included in the results section. X Tim(
*T'ime (s)Experimental SetupHardware: Inkjet Printing System tR tD tF
Rise Dwell Falltime time time
. I Reseoirvc| | W |~~~~~~~~~dPressure
* computer Cotole
Fig. 2. Uni-polar waveform showing rise, dwell and fall time
Fig. 2 shows a simple uni-polar waveform that is used in theexperiments to drive the piezo-actuated nozzle. The variables
Camera~~ ~ ~ ~ ~ ~ E Sroe tR, tD and tF are the rise time, dwell time and fall timeNozzel0.- LErs: trespectively and VD is the voltage applied at dwell. When the
i._._. N @ _ voltage rises, the piezoelectric element contracts and thisaction creates a negative pressure in the nozzle cavity. Thiscontraction is maintained for a period of tD, after which thepiezo-element will expand as voltage applied drops, creating apositive pressure that forces the ink out of the nozzle orifice.In the experiments, the pulse was applied at a constantfrequency of 500 Hz. Variables tR and tF are fixed at 5 pts each
Fig. 1. Schematic setup of MicroFab JETLAB® II while tD is varied. The dwell time (tD) for each glycerolink-jet printer mixture is varied from a minimum limit to a maximum limit in
one second intervals, whereby within these limits, a dropletFig. 1 shows a schematic setup of the MicroFab can be ejected from the nozzle orifice. It can be seen later in
JETLAB® II ink-jet printer. Firstly, the ink sample is placed our results that these limits may vary slightly for each glycerolinto a Teflon cylindrical cartridge (-.5 ml) which is then mixture. As the dwell time is being varied, stroboscopicattached to the reservoir. Prior to this, filtering is usually done images of the ejected droplet were captured. Using thefor particulate based inks through a 4.5 microns filter so that JETLAB® II software, the velocity and volume of this dropletlarger particles do not clog the nozzle in the inkjetting process. can thus be quantified from the captured images. AnThe reservoir is then connected via Teflon tubings to the illustration of these stroboscopic images is shown in Fig. 3.nozzle which is held firmly in place by the nozzle support. It Material preparationis also connected to a pressure controller unit, which adjuststhe pressure of the ink in the cartridge. In the experiments, this The inks used in our experiments were aqueous glycerolpressure was held constant at -0.6 bars. In order to start jetting, mixtures with different concentrations. The mixtures werethe computer sends an electrical signal to the piezo-controlled prepared from a range of 0 - 80 wt% glycerol (Sigma-Aldrich,nozzle, which then responds by contraction or expansion of Reagent Plus 99.90/O) in de-ionized (DI) water. The propertiesthe piezoelectric element. This piezoelectric movement of the various aqueous glycerol mixtures have been extractedgenerates acoustic waves within the ink inside the nozzle from a published source [11] and are shown in Table 1. Thecavity, which when sufficiently strong in overcoming the inter-facial tension (IFT) of the inks was measured using theviscous and surface tension forces, enables a droplet to be OCA4O, a contact angle measurement system fromjetted out of the nozzle orifice (ID =50 pim). In order to Dataphysics. Between each set of experiments, acetone and DIobserve the droplet formation from the nozzle, a camera is
Fig. 4. Plot of Ohnesorge number against glycerolconcentration (wt )
This might be due to viscous effects resulting in dissipation ofpressure waves within the nozzle cavity, as Oh was increased.
Fig. 3. Stroboscopic images of 76 wt% glycerol as dwell Thus, an increased potential difference was chosen to actuatetime (t) is varied in one second intervals the nozzle for mixtures with 60, 76 and 80 wt% glycerol. The
results are tabulated in Table 2.
water was flushed through the cartridge, reservoir and nozzlerespectively for cleaning purposes. Table 2. Applied voltages and corresponding maximum
The dimensionless Ohnesorge number, Oh is defined as velocity for different glycerol concentrationsGlycerol Applied Maximum velocity
Oh IU - 1-() Wt%0 Voltage (V) (m/s)|pR 0 (water) 15 1.98
where ~t, p, a and R are the viscosity, density, surface tension 24 15 1.9of the ink and radius of the nozzle respectively.
3 1
The Ohnesorge number for the glycerol mixtures have 36 15 1.52been computed using equation 1 and tabulated in Table 1. 52 15 1.37
Glycerol IFT density viscosity Oh 80 3 1.94Wt% (mN/m) (kg/mr) (mPas) (gim)0 75.490 0.998 1.000 25 0.023 From Table 2, it can be observed that as the percentage of24 66.623 1.056 1.988 25 0.047 glycerol increases from 0 - 52 wt%, the maximum velocity of36 62.707 1.088 3.088 25 0.075 the ejected droplet decreased while the applied voltage was52 58.860 1.131 6.666 25 0.163 kept constant. This behaviour was expected because more60 57.507 1.153 10.681 25 0.262 energy was consumed to overcome viscous forces within the76 55.677 1.198 40.571 25 0.994 nozzle, resulting in a reduced kinetic energy of the ejected80 54.120 1.209 59.900 25 1.481 droplet with increasing Oh.
For each glycerol mixture, the velocity of the ejectedFrom the results in Table 1, it can be seen clearly that as droplets was recorded as the dwell time was varied in one
the percentage of glycerol in the mixture increases, the density second intervals. In agreement with previous literatures [2],and viscosity increases while the inter-facial tension of the inverted 'U' curves have been obtained. Due to the applicationmixture decreases. These results in an Ohnesorge value which of different voltages, the results have been linearized for easeescalates, as the percentage of glycerol in the mixture is of comparison i.e. the effect of varying Ohnesorge numberincreased. This is depicted very clearly in Fig. 4. and dwell time on droplet velocity. Fig. 5 shows a plot of the
Results ~~~~~~~~~~~~~linearized velocity against the dwell time for all the 7 glycerolResults ~~~~~~~~~~mixtures.Each curve has been obtained by dividing theDropletvelocity velocity of all points with the maximum velocity for each
For water (0 wt% glycerol) and glycerol mixtures of 24, 36 glycerol mixture, e.g. 1.98 m/s for 0 wt% and 1.94 m/s for 80and 52 wt%, a potential difference of i5V was sufficient to wt% (see Table 2). This results each curve having a maximumeject a droplet from the nozzle. However, as the percentage of velocity of unity. The curves also illustrate how the velocityglycerol was further increased, the potential difference of isv profile changes as the dwell time was varied within thewas insufficient to drive a droplet out of the nozzle orifice, minimum and maximum limits for each mixture.
Fig. 5. Plot of linearized droplet velocity (V) against varying 04dwell time (t) for all mixtures 0.3
0.1 rts( S)
As shown in Fig. 5, with the increase in glycerol 20 21 22 23 24 25 26
concentration, the peak whereby the maximum velocityoccurred was slowly shifted to the left. This implies that the Fig. 7. Plot of Oh against optimum dwell time (t)acoustic wave generated by the piezo-element increased inspeed as the Ohnesorge value and viscosity of the mixture was Bogy and Talke [10] stated that optimum pulse width for aincreased! This interesting phenomenon is in agreement with rectangular pulse is given byand has been documented by the experimental results of i/c,-(2)Saggin and Coupland [12] and can be seen in Fig. 6 [12], Twhich clearly shows that the acoustic velocity increased as the where x is the optimum pulse width, I is the cavity length andglycerol concentration was increased. c is the speed of acoustic waves in the fluid.
Rearranging, we obtain
1800 I = -cc-------- (3)
a andO l Table 4 shows the value of c (extrapolated from Fig. 6), T,and the computed 1 value using equation 3, for glycerol1700 mixtures of 0 - 52 wt%. Note that the rise time (tR) and fall
E \ time (tF) have been taken into account and included.
X ( Table 4. Cavity length (1) based on ultrasonic velocity (c) andoptimum pulse width (T) in 0 -52 wt% glycerol
Glycerol wt% | c (m/s) | (ps) I (m)0 1470 36 0.053
Q.6 0.056
0 10 20 30 40 50 36 1660 34 0.056
LGlyccrollI w/v 52 1750 32 0.056
Clearly, the computed cavity length is almost the same forFig. 6. Plot of ultrasonic velocity against glycerol these mixtures. This is expected as only one nozzle was used
concentration [12] in our experiments. However, the nozzle only has a length ofapproximately 20mm, which is much smaller than the
Here, the optimal dwell time is defined as the dwell time at computed value above.which the jetted droplet has the greatest velocity, which asstated in previous literature, is a function of fluid properties Droplet Volumeand does not change with driving voltage amplitude [2]. This In adiint. h rpe eoiy h oueo h
was oundto eingoodagremen wit ou exprimetal ejected droplets can also be quantified using the JETLAB® IIresults, refer to Table 3 and Fig. 7. The curve clearly depicts camera and software. No distinct trend in the volume wasthat as the Ohnesorge number increased, the optimal dwell obevdath dwltie asardwthO fraltime is reduced.
mixtures. Fig. 8 shows a plot of the ejected droplet volume bandwidth for stable inkjetting. It is clearly evident that Ohagainst dwell time for the 80 wt% glycerol mixture. does not play a significant role in this reduced bandwidth by
comparison with the printing range of 52 wt% glycerol (Oh =i'\olumlle pL) 0.163). In addition, it is interesting to note that this change in
13(0 Maximum volume Oh has not altered the optimum dwell time, i.e. 24 Its.120
Fig. 8. Plot of droplet volume for varying dwell time (t) for 20 2 2~ 6 2IS 19 21t 7 3 2 . 6 2
80 wt% glycerol mixture
Fig. 9. Plot of linearized droplet velocity (V) against dwellHowever, it iS interesting to observe that the maximum time (t) for modified 36 wt% glycerol (IFT =20 mN/in)
droplet size ejected for each mixture does not occur at the showing optimum dwell time of 24 pisoptimum dwell time. Instead, this maximum valueconsistently occurred at a dwell time lesser than the optimum EfetoOhnprtalrngadstliefrmin
for all mixtures (Refer to Table 5).It was observed that the lower dwell time limit for all the
Tabl 5. aximmdrpletvolue an itscorrsponing glycerol mixtures ranged from 8 to 12 p.is (see Fig 5 and Tabledwelltimeforarios glyerolmixtres.6). However, the upper dwell time limit decreased steadily as
Ohnesorge number was increased. It was not elucidated that|Glycerol |Oh |Optimum Dwell Max. DwlTaimem at the effects of viscous force s were significant because higher
wt% T1me (ps) Volume (pL) volume (pis) voltages (see Table 2) was required for mixtures with higher0 0.023 26 103.9 18 glycerol wt%. In addition, stroboscopic images revealed that
24 0.047 25 93.3 20 satellite drops were only produced for glycerol mixtures 0 -|36 10.075 24 81.0 22 36 Wt%W;wthin a Certain dwell time range. HOWeVer, thiS range| 52 10.163 22 82.3 18 was small as compared to the whole printable range. FOr 52 -
1 60 1 0262121 89 1 18 80 wt%o glycerol mixtures (IFT < 59 mN/in, Oh > 0.1), n1O6 0.22 1 8.18 satellite drops were observed. As surface tension increased76 0.994 20 105.9 15 beyond 60 mN/in, i.e. Oh < 0.1, satellite droplet formation80 1.481 20 106.7 15 resulted, and the range which this occurs widened as surface
tension was further increased. Nevertheless, the experimentalEffect of surfactant on Oh and droplet formation results showed that with proper tailoring of the waveform e.g.
Keeping the orifice dimension of the nozzle fixed, the only proper dwell time selection, it was possible to remove satelliteindependent variable that can be changed to alter the drops during the printing process. It is also possible to reduceOhnesorge value is the surface tension of the mixture. This is the production of satellite drops by reducing VD (refer to Fig.because both the viscosity and density of the mixture vary in 2), which shall not be elaborated in this paper.tandem with the percentage of glycerol. With the addition of0.01l wt% of BYK49 (BYK-Chemie GmbH, Germany) into Table 6. Ranges of dwell time for possible drop ejection andthe 36 wt%40 glycerol mixture, the new surface tension of this appearance_of satellite dropletmixture reduced to 20 mN/in. This resulted in a new Glycerol Oh IFT Lower Upper Dwelltime|
Onsrevalue of o.132 (0.075 without surfactant), and the | 40t/ |O (mN/in) |dwell time |dwell time |with satellite|results showed that the surface tension has no significant 0 0.2 75.490s )9ll(s)(seffects on Ohnesorge value. o . 2 5409.3319-251
Fig. 9 shows a plot of the linearized velocity against dwell 24 0.047 66.623 10 . 32 20 -251time for this mixture (Oh =0.132), with the same applied 36 0.075 62.707 12 . 30 22-23|voltage of isV. For dwell time greater than 27 s or lesser than 52 0.163 58.860 11 . 29 |18 s, droplet formation from the nozzle was unstable and thus 60 0.262 57.507 8 . 27 |unsuitable for inkjetting. In comparison with the unalteredmixture (36 wt%o glycerol, Fig. 5), it is apparent that the 76 0.994 55.677 9 . 27 -addition of surfactant has resulted in asignificantly reduced 80 1.14811 54.120 9 27 -
Conclusion dimensionless parameter may be required for such
In this study, the effects of Oh on droplet formation (i.e. characterisation which could be discussed in future works.velocity and volume), using a uni-polar waveform with Acknowledgementsvarying dwell time has been investigated. Aqueous mixtures The authors would like to express their heartfelt gratitudeof varying glycerol compositions (0 - 80 wt%, 0.02 < Oh < to the Singapore Institute of Manufacturing Technology1.5) which are Newtonian in nature, were used. Computations (SIMTech) for their funding and support.show that as the percentage of glycerol in the mixture Referencesincreases, Oh also increases rapidly. 1. Fromm, J.E., "Numerical Calculation of the Fluid
The velocity and volume of the ejected droplets have been Dynamics of Drop-on-demand Jets," IBM Journal ofquantified via stroboscopic images and software. Research and Development, Vol. 28, No. 3 (1984), pp.Experimental results revealed that the velocity profiles follow 322-333.an inverted 'U' curve and were in good agreement with 2. Reis, N., Ainsley, C., Derby, B., "Ink-jet Delivery ofprevious literature [2]. Our results also showed that the Particle Suspensions by Piezoelectric Droplet Ejectors,"maximum droplet velocity decreased as Oh was increased for Journal of Applied Physics, Vol. 97, No. 9 (2005), pp.a particular driving voltage, due to an increase in viscous 0energy dissipation. It was observed that the optimum dwell 094903-094906.
3. Ambravaneswaran, B., Wilkes, E. D., Basaran, 0. A.,timedeceasdaOhinceasd. hisreslt as xpeteddue "Drop Formation from a Capillary Tube: Comparison ofto the fact that acoustic waves travel faster in the mixtures as Oedmenional a Tw-imensional Analyses anthe glycerol concentration (Oh) is increased [12]. However, Occurrenceof atl Drops,mPhsicsao Flus, Vol
theoptmumpule idt asdefnedbyBog an Take 1' Occurrence of Satellite Drops," Physics of Fluids, Vol.the optimum pulse width as defined by Bogy and Talke [10] 14 No. 8 (2002) pp. 2606-2621.was found to be in disagreement for our setup. No distinct ' N - .
trend in the volume was observed as the dwell time was varied 4. Notz, P. K. and Basaran, 0. A., "Dynamics and Breakupwith Oh. However, it was interesting that all peak volumes of a Contracting Liquid Filament," Journal of Fluidalways occur at a dwell time lesser than optimal, which was Mechanics, Vol. 512, No. 1 (2004), pp. 223-256.consistent for all mixtures 5. Xu, Q. and Basaran, 0. A., "Computational Analysis of
The effect of surface tension on Oh was also investigated. Drop-on-demand Drop Formation," Physics of Fluids,Theoretical results showed that surface tension was not a Vol. 19, No. 10 (2007), pp. 102111.significant parameter in practice. Inkjetting of an IFT- 6. Schulkes, R. M. S. M., "The contraction of liquidmodified mixture revealed that the optimal dwell time was filaments," Journal ofFluid Mechanics, Vol. 309 (1996),remained unchanged. However, the bandwidth of stable pp 277inkjetting was significantly reduced. This reduced bandwidth 7. Dong, H., Carr, W.W., Morris, J.F., "An Experimentalwas attributed to the effects of the change in IFT rather than Study of Drop-on-demand Drop Formation," Physics ofOh. Fluids, Vol. 18, No. 7 (2006), pp. 072102-072116.
The ranges of dwell time whereby a droplet could be 8. Chen, A.U. and Basaran, O.A., "A New Method forejected were found to decrease with increasing Oh. In Significantly Reducing Drop Radius without Reducingaddition, it was observed that for Oh < 0.1, IFT > 60 mN/m, Nozzle Radius in Drop-on-demand Drop Production,"an additional satellite droplet was formed for a certain range. Physics ofFluids, Vol. 14, No. 1 (2002), pp. L1-L4.This range increased as Oh decreased. No satellite droplet was 9. Amirzadeh Goghari, A. and Chandra, S., "Producingobserved for 52 - 80 wt% glycerol mixtures. However, no Droplets Smaller than the Nozzle Diameter by Using aconcrete evident showed that the satellite droplets behaviour Pneumatic Drop-on-demand Droplet Generator,"could be governed by the Oh parameter. Experiments in Fluids, Vol. 44, No. 1 (2008), pp. 105-
This study laid the foundation to reveal the insight 114.mechanism on how the piezo-electric DOD printing process 10. Bogy, D.B. and Talke, F. E., "Experimental andcould be enhanced. It was proven that a single droplet could Theoretical Study of Wave Propagation Phenomena inbe jetted for 0.02 <Oh < 1.5, with fluid viscosity> 50 mPas, Drop-on-demand Ink Jet Devices," IBM Journal ofusing a simple uni-polar waveform with proper dwell time Research and Development, Vol. 28, No. 3 (1984), pp.selection. This was contrary to that stated by Chen and 314-321.Basaran [8], Gohari and Chandra [9]. In addition, experiments 11. David R. Lide, Handbook of Chemistry and Physics, CRCalso showed that it was possible to jet single droplets outside Press, 1999the Oh ranges stated by Fromm [1], Reis and Derby [2]. This 12. Saggin, R. and Coupland, J.N., "Concentrationfinding provided a wider range of jettable inks for selection Measurement by Acoustic Reflectance," Journal ofFoodand would be a significant improvement to ink formulation. Science, Vol. 66, No. 5 (2001), pp. 681-685.Furthermore, dilution of the ink could be minimized fordesired inkjet printing, resulting in higher efficiency offunctional material deposition.
In brief, Oh alone is incapable of characterising dropletformation. The complex interplay of many other factors e.g.driving voltage, dwell time and waveform should be taken intoconsideration. An integration of other parameters or a new
