Contentspeople.ucalgary.ca/~sspiewak/enmf_529/ENMF_529/20...- Electrical connection to print head cut hStimulated break-off ¾cIJ: disintegration induced by regular wave patterns applied

Jens Ducrée and Roland Zengerle

Praxis beispie l: Ausa rbeitu ngsphaA usarbe itung d er Stan dard-Z

8. Ink-Jet Technology

Contents

1. Introduction

2. Fluids

3. Physics of Microfluidic Systems

4. Microfabrication Technologies

5. Flow Control

6. Micropumps

7. Sensors


9. Liquid Handling

10.Microarrays

11.Microreactors

12.Analytical Chips

13.Particle-Laden Fluids

a. Measurement Techniques

b. Fundamentals of Biotechnology

c. High-Throughput Screening




Ink-Jet: Definition

The ink-jet technology is a contact freedot matrix printing procedure. Ink is issued from a small aperture directly

onto a specific position on a medium.

Quelle: Hue P. Le, Journal of Imaging Science and Technology · Volume 42, Number 1, January/February 1998




MST-Market Study

NEXUS

Market analysis for microsystems 1996 - 2002




Commercial Engagement





1. Continuous Inkjet Technology (cIJ)

2. On-Demand Technology

3. Inkjet Ink Technology




8.1. Continuous Inkjet Technology (cIJ)

1. Background

2. Droplet Delivery

3. Hertz-Type Inkjet

4. Applications




8.1.1. Ink-Jet Technology: History (1)

h 1878: Lord RayleighBreaking of liquid jets into individual droplets[On the instability of jets, in Proc. London Math. Soc. 10 (4), 4–13 (1878)]Surface-tension related stable minimum of energy




8.1.1. Minimum of Surface Energy

h Liquid surfaceSphere (droplet)Radius rSurface area A

h Surface energy of N droplet of same overall volume





h 1951: Elmqvist from Siemens files first patent for device based on Rayleigh principle

„Measuring instrument of the recording type“, U.S. Patent 2566443 (1951)Mingograph: first ink-jet based writer for recording analogue voltage signals

h Early 1960s: Sweet (Stanford University)Distinct pressure wave patternsApplied to orifice of liquid columnJet breaks up into equally spaced droplets of same volume





h Continuous Ink-Jet Technology (cIJ): Dedicated charging of dropletsRecirculation by deflection in transversal electrical fieldProducts: A. B. Dick VideoJet und Mead DIJIT

h 1970s: IBM licenses continuous ink-jet technologyMassive development efforts at IBM to establish ink-jet technology for their printers1976: IBM 4640 (Word-Processing Hardcopy-Output application)





1. Background

2. Droplet Delivery


4. Applications




8.1.2. cIJ: Setup




8.1.2. cIJ: Binary Deflection

hUncharged droplets dispensed on substratehCharged droplets recirculate




8.1.2. cIJ: Multiple Deflection

hUncharged droplets recirculated by gutterhCharged droplets deflected according to q / m-ratioh2-dimensional writing of small areas with single nozzle




8.1.2. Droplet Deliveryh Droplet formation

Emission of cylindrical plug from orificeVaricosity

- Sectioning into thinner and thicker zonesLigaments break

- Electrical connection to print head cut

h Stimulated break-offcIJ: disintegration induced by regular wave patterns applied to orificeGrowth of perturbationsPredetermined breaking pointsCritical parameters

0.20 ms

0.25 ms

0.30 ms

0.35 ms

0.40 ms

0.50 ms

0.60 ms

0.70 ms

nozzle

Ekin

surfacetension

Ekin

viscosity

Weber number Reynolds number




8.1.2. Droplet Delivery

h Droplet sizes and ratesOrifice diameter typically 50 µm to 80 µmDroplet roughly exceeding orifice diameter by factor of twoDroplet sizes below 150 µm common

- Volumes between 4 fl and 1 plDroplet frequencies in order of 100 kHzSpecial devices up to 1 MHz

h Satellite dropletsFrequently formedHigh q / m ratio

- Large deflectionErroneous droplets

h Droplet deflectionCharging by passing electric fieldRing or tunnel electrode





1. Background

2. Droplet Delivery


4. Applications




8.1.3. Hertz-Type Inkjet

h HistorySeparate branch of cIJ technologyDevelopments at Lund Institute (S) in late 1960s~1976: device by Hertz et al. cIJ-procedure with gray-scale capabilityLicense for Iris Graphics and Stork which develop color ink-jetLater licensed by Iris Graphics and Stork

h Working principle of gray-scalingMultiple droplets dispensed on same spotControl of number of droplets forming single dropDifferential charging of continuous droplet streamMutual repulsion of dropletsFurther downstream, plate catches deflected dropletsDrawback: slightly gray background surrounding dotsHigh droplet ratesContinuous half-tone scheme





1. Background

2. Droplet Delivery


4. Applications




8.1.4. Applications

h DrawbacksComplex recirculation

- Prone to errors- Expensive

Deflection according to charge-to-mass ratio- Limited accuracy

Necessity of charging- Restriction to conducting ink formulas

h SummaryHigh-speed printingLow qualityRather expensive systems

h ApplicationsIndustrial small-character printing (SCP)

- High throughput- Low resolution











8.2. On-Demand Technology

1. Impulse Printing

2. Droplet Dynamics

3. Piezo-Actuation

4. Thermal Inkjets

5. Valve-Jet

6. Ultrasonic Droplet Generation

7. Orifice Plates

8. Inkjet Nozzleplate by Microparts





h 1970s: On-Demand (DoD) TechnologyAdvantage: error-prone charging and recirculation obsoletePressure generated by voltage pulse applied to piezo elementPioneering work

- By Zoltan, Kyser und SearsProducts

- Siemens (PT-80 serial character printer,1977)- Silonics (1978)

h Up to early 1980s: problems of IJ-technology Clogging of nozzlesInconsistencies in printing quality





h 1979: Canon invents bubble-jet (BJ) technologyPressure built up by expanding vapor bubble above small heat elementHigh precision due to microtechnological fabrication

h ~1979: Hewlett-Packard(Independently) develops on-demand impulse methodTermed „thermal Ink-Jet“

h 1984: ThinkJet by Hewlett PackardFirst commercially successful low-lost printer based on BJ-principleDisposable cartridges elegantly eliminate reliability problem

h Late 1980s: IJ-technology replaces dot-matrix pin printers to conquer low-cost market of rapidly expanding PC industry

h 1990s: low-cost color ink-jet printer become standard equipment in home and office solutions




8.2.1. Impulse Methods

h Mechanism of droplet formationThermalPiezo-electricElectrostaticAcoustic

h Thermal and piezo-electrical principles primarily used

h Electro-static and acoustic principles under developmentMany patentsFew commercial products




8.2.1. Impulse Method: Setup





1. Impulse Printing

2. Droplet Dynamics

3. Piezo-Actuation

4. Thermal Inkjets

5. Valve-Jet


7. Orifice Plates





8.2.2. pIJ: Droplet Formation

h Acoustic pressure wavePressure drop due to viscosityPressure drop due to surface tension

h Dynamic pressure (kinetic energy)





1. Impulse Printing

2. Droplet Dynamics

3. Piezo-Actuation

4. Thermal Inkjets

5. Valve-Jet


7. Orifice Plates





8.2.3. Piezo-Electric IJ: Principle

h On-demand impulse method

h Deformation of piezo-ceramics

h Change in volume

h Pressure wave propagatesto nozzle

hProblem of pIJ-TechnologyDeflection of piezo-ceramics in sub-µm rangePiezo-element has to be much larger than orificeMain problem: miniaturization




8.2.3. pIJ: Modes of Deformation for Piezo-Ceramic Plate




8.2.3. pIJ: Types




8.2.3. pIJ: Squeeze-Mode

h Thin piezo-ceramic tube surrounds glass nozzleGould´s Impulse-Ink-Jet

h Piezo-ceramic tube cast in plastics surrounds ink channelSiemens PT-80 (1977)- Matrix composed of 12 nozzles- Innovative service station- First truly successful office ink-jet printer

Development of 32-nozzle follow-up printhead faileddue to problems with nozzle-to-nozzle uniformity




8.2.3. pIJ: Bend-Mode

h Piezo-ceramic platelet bonded to diaphragmBi-laminar electro-mechanical transducer

h Voltage pulse (E || P) generates dropleth Tektronix Phaser 300 and 350 and

Epson Color Stylus 400, 600, 800




8.2.3. pIJ: Push-Mode

h Piezo-ceramic rod (E || P) pushes against ink nozzle

h Diaphragm protects piezo-ceramics against reaction with ink

h Commercial products: Dataproducts, Trident and Epson




8.2.3. pIJ: Shear-Mode

h Polarization of piezo-ceramics perpendicular to E-field

h Piezoceramics as active wall in direct touch with inkStiction of ink on wall crucial parameter

h Shear-motion generates droplet

h Pioneers: Spectra and Xaar




8.2.3. Thick-Film PZT Actor

h Epson Color Stylus 800 printhead




8.2.3. pIJ: Shear Mode




8.2.3. pIJ: Fabrication by Stacking

h Several photochemically structured layers of stainless steel

h Intermetal bonding by layer of Au or Ni at high temperature

h Uniform thickness of layerUniform performance of channelsHermetic sealing of channels

h Printheads by Tektronix (352 nozzles, below)and Sharp (48 nozzles)

SEM-images of steel-laminated printhead by Tektronix




8.2.3. pIJ: Alternative Bonding

h Spectra

Soldering

Epoxy

Electro-platedNi-orifice





1. Impulse Printing

2. Droplet Dynamics

3. Piezo-Actuation

4. Thermal Inkjets

5. Valve-Jet


7. Orifice Plates





8.2.4. Thermal Ink-Jet Technology

h Commercially most successful

h Variant 1: roof shooterHeater above orificeHewlett-Packard, Lexmark and Olivetti

h Variant 2: side-shooterHeater lateral to orificeCanon and Xerox




8.2.4. tIJ: Phases of Droplet Formation

hHeating (some µs)Overheated inkAt 300°C: nucleation of bubble

•ExpansionEjection of inkParallel to bubble expansionBubble pressure (empirical)

hDroplet formationCollapsing vapor bubbleRetraction of bulk inkRefilling of cavity (80-200 µs)

-Speed-critical step




8.2.4. tIJ: Droplet Formation




8.2.4. tIJ: Nozzle of DJ 850C Color printhead

h Heater (roof shooter, aperture plate removed)h 6000 droplets à 32 pl per second

Cycle time 170 µs

h Width and height of ink channel on µm rangeh Critical production parameters

Dimensional stabilityPrecisionUniformity of nozzles

h Drop performanceFrequencyVolumeSpeed




8.2.4. tIJ: Trends

h Enhancement of frequenciesSpeed of printing

h Reduction of volumeQuality of printing

h Cost reduction

Further miniaturizationProblem: reliability

h Example: HP 890C (roof shooter)192 nozzles (3 colors)12000 droplets at 10 pl / secondHeater surface 1 mm²Series of small openings to avoid clogging by particles




8.2.4. tIJ: Further Trends

h Canon BJC 7000480 nozzles in single printheadLargest density in small-office arena6 colors, hence 80 nozzles per color

h Market need for low-cost printheadsLarger ink containersPermanent or semi-permanent printheads





1. Impulse Printing

2. Droplet Dynamics

3. Piezo-Actuation

4. Thermal Inkjets

5. Valve-Jet


7. Orifice Plates





8.2.5. Valve-Jet

h Non-contact principle

h Drop-on-demandOften confused with impulse jet

h Working principleInk held under pressureDynamic opening of valve

- Micro-electromechanicalSpraying of fine jet





1. Impulse Printing

2. Droplet Dynamics

3. Piezo-Actuation

4. Thermal Inkjets

5. Valve-Jet


7. Orifice Plates





8.2.6. Ultrasonic Droplet Generation

h Acoustic transducer

h Constructive interference of wavesSimilar to Fresnel lens





1. Impulse Printing

2. Droplet Dynamics

3. Piezo-Actuation

4. Thermal Inkjets

5. Valve-Jet


7. Orifice Plates





8.2.7. IJ-Technology: Nozzle Design (1)

h Geometry parameters of nozzleDiameterDepth

h Effect on dropletsVolumeSpeedDeflection angle

h Effect on ink supply (refilling)Capillary forces

h Fabrication tolerances limit picture qualityh Fabrication of orifice plates

Laser-ablation in polyimide, especially for small nozzles (10 pl, 20 µm)Nickel-electroplatingElectro-discharge machining (EDM)Micro-punchingMicro-pressing









Electroplated Ni-nozzle





Nozzle plate formed by laser ablation in polyimide





Stainless-steel nozzle (Electro-Discharge Machining)





1. Impulse Printing

2. Droplet Dynamics

3. Piezo-Actuation

4. Thermal Inkjets

5. Valve-Jet


7. Orifice Plates





8.2.8. Inkjet Nozzleplate by Microparts











8.3. Ink-Jet Technology: Media

h High-quality color prints require special inks and mediaCapillary forces make ink follow pores and fibersInk penetrates paper too slow to allowabsorption of multiple droplets at same spotConsequences: intercolor-bleeding und ink-spreading

h Special coatings of substratesh Designated ink basesh Designated colorantsh Design parameters for ink-substrate combination

Droplet volumeRate of evaporationTime of penetrationThickness of coatingPorosity, etc.




8.3. Inkjet Ink Technology

1. Types of Ink

2. Colorants

3. Inkjet Print Media




8.3.1. Chemistry of Ink-Jet Ink

h Critical component of IJ-technologyQuality of printingDynamics of droplet formationReliability

h Frequently: water-based inkstIJ: vapor bubbleHewlett-Packard DeskJet, Canon BJC and Epson Color Stylus SeriesViscosity range between 2 x 10-2 and 8 x 10-2 Pa sDrying comparatively slow, penetration prevailsWater-absorbing layer enhances printing quality

Water-based ink

Paper




8.3.1. Constituents of Water-Based Ink

<1Chelator, anti-foam, ...Others

0.1-0.5Stabilizes pH-value of inkBuffer

0.05-1Avoids biological growthBiocide

0.1-10Wetting, penetrationTensides

1-10ColoringColor or pigment

5-30Wetting, control of viscosityWater-soluble solvent

60-90Aqueous carrier mediumDI-water

Concentration [%]PurposeComponent




8.3.1. Ink-Jet Technology: Media

h Alternative: solid ink Also hot-melt or phase changeSolidification at contact with mediumWidely independent from properties of substrateFew spreading on substrateBrilliant colors

h Pioneering work at Teletype with electrostatic cIJ

h First DoD devices byExxon and Howtek

h Recent activitiesTektronixDataproducts, Spectra and Brother




8.3.1. Phase-Change Ink

h Often based on wax

h Solid at room temperature

h Typical temperatures: 120-140°C

h Typical viscosities: 8-15 x 10-2 Pa sCompare: water ~ 1 x 10-3 Pa s

h Nozzle of printhead ejects hot melt

h Instantaneous solidification upon contact avoids spreading

h Print results widely independent from substrate

h High speed of printing: 6 pages per min (Tektronix Phaser 350)




8.3.1. Solid-Ink: Phases




8.3.1. Solid-Ink Technology: Mechanisms




8.3.1. Phase-Change Ink: Constituents

0.05-2Heat resistanceAntioxidant

1-10ColorDye / pigment

1-15FlexibilityPlasticizer

1-15Adhesion on substrateAdhesive

5-20Reduction of viscosityViscosity modifier

40-70Ink-vehicleMixture of wax

Concentration [%]PurposeComponent




8.3.1. Phase-Change Ink

hSolidified ink on Xerox 4024 Paper hHemispherical dots, no spreading




8.3.1. Phase-Change Ink: Fusion

hIn practice: solidified ink needs further adhesionhTektronix Phaser 300: pressing of droplets with roller




8.3.1. Phase-Change Ink: Offset Printing

hPrinthead writes on thin Si film attached to warm Al drumhPattern transferred by transfix roller onto preheated paper

Tektronix Phaser 350 color ink-jet printer




8.3.1. Phase-Change Offset Printer: Print Result

Al-substrate

Paper




8.3.1. Further Types of Ink

h Oil-based InkFor large-format printers(Raster Graphics PiezoPrint 5000, Xerox ColorgrafX)Both printers based on Nu-Kotepiezo shear-mode printheadsUnpolar oil minimizes negative effectsof E-fields on ink and printheadZeneca: faster evaporation, high-quality printing

h UV-curable inksNon-absorbing substrates like glasses, metals and plasticsUV photo-initiators, monomers and oligomers availableMarket entry expected





1. Types of Ink

2. Colorants





8.3.1. Mechanisms of Drying

Oxidation, Polymerization

cIJ with piezoReactive

PolymerizationcIJ with piezoUV curable

Phase change

liquid ⇒ solid

PiezoHot-melt

EvaporationcIJ with piezoSolvent-based

Absorption, penetrationcIJ with piezoOil

Continuous absorption, penetration, evaporation

tIJ and pIJAqueous

Mechanism of DryingPrintheadType of Ink




8.3.2. Drying of Water-Based Ink




8.3.2. Pigment-Based Ink

h Particle dispersionDye: solution

h Advantages in terms ofPicture qualityStability of color

- Time and weatheringReliability of jettingCosts

h DisadvantagesFaster clogging of nozzles

h Companies: 3M, Dupont and Kodak




8.3.2. Comparison between Inks based on Dye and Pigments

Pigment-based Dye-based





1. Types of Ink

2. Colorants





8.3.3. Inkjet Print Media

h Fibers in paper act as poresCapillary forcesSpreading of ink dotsInsufficient on-site mixingIntercolor bleedingDrying process depends on paper quality

h Early 1980s: Jujo Paper and Mitsubishi Paper MillsDevelopment of glossy paper types for ink jet printouts

h Nowadays: Canon, Xerox, Asahi Glass,Arkwright, Folex, 3M and Imation




8.3.3. Effects from User‘s Point of Viewh Ink clumping

Areas of heavy ink coverageSurface tension „clumps“ ink in globsOrange peel („crackle“) effectImprovement

- Improved wetting of paper by ink

h Muddy colors„Intercolor bleeding“Wicking of ink along fibersPhoto from same printer,but on different media

h Poor surface textureAbsorption of inkGrainy „sandpaper“ surfaceFeels not good for sharingphotos with your friends

h WaterfastnessInkjet prints will run at least hint of moistureSolution: e.g. chemical bondbetween ink and paper




8.3.3. Pictorio Paper

Housebrand

Pictorio




8.3.3. Plain Paper Optimized Printing (P-POP)

h Canon BJC-7000 series

h Black printheadPreparation of substrate with jet some milliseconds prior to inkCoupling to dye which is instantaneously fixed on paper

h Water-resistant

h Similar results as on coated glossy paper

h In case reliability can be demonstrated:Technological breakthrough of IJ-Ink technology (!?)




8. Summaryh Ink-jet technology

Continuous Ink-JetThermal ink-jet (bubble jet)Piezo-electrical ink-jet

h IJ-technology most mature discipline of microfluidicsh Strong commercial involvement, few pure academic researchh Technological solutions for

MiniaturizationReliability

- Clogging- Variations in droplet volume

SpeedFabrication technology, often without SiChemistry of ink-jet inkCosts

h Typical problems of microfluidicsExtremely application-specific solutionsInterdisciplinary R&DBroad range of applications, e.g. office printers, biotechnology

Documents

Contentspeople.ucalgary.ca/~sspiewak/enmf_529/ENMF_529/20...- Electrical connection to print head cut hStimulated break-off ¾cIJ: disintegration induced by regular wave patterns applied