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					                                          C99-G08                  1


Title:                   Textile Ink Jet Performance and Print Quality Fundamentals

Project Number:          C99-G08

Investigators:           W.W. Carr (leader), J.F. Morris, F. J. Schork, and W.C. Tincher
                         Georgia Institute of Technology
                         J. Zhu, Institute of Paper Science and Technology

Project Goal:            The goals of this project are: 1) To obtain fundamental understanding of the role
                         of particles in setting the flow behavior and droplet formation characteristics in
                         textile ink jet printing nozzles and 2) To understand at a fundamental level the
                         interactions of a single ink-jet droplet with textile printing media on image
                         formation.
Abstract
         This study is expanding the scientific knowledge base for a technology, which will enhance the
productivity of the American textile industry. Digital ink jet printing, coupling existing rapid design
generation capabilities with a low-waste method of delivering colorant, is a critical technology for mass-
customization manufacturing of textile products; however, hardware reliability and speed limitations are
technical barriers, limiting use of ink jet printing primarily to generation of samples. This project is
directed at obtaining understanding needed to allow rational design of digital ink jet printing systems for
the textile industry. Also, the fundamentals affecting print quality are not well understood. Limited
research has been conducted on printing quality associated with the interactions of droplet impingement
onto a porous, non-elastic surface. The role of substrate surface properties on printing quality was only
recently recognized as an important factor in color ink jet printing. Therefore, research in this project on
the interaction of single ink droplet with substrates will yield better understanding of the fundamentals
affecting printing quality.

Introduction
         Ink jet printing is as a critical technology for mass-customization manufacturing of textile
products; however, hardware reliability and speed limitations are technical barriers, limiting use of ink jet
printing primarily to generation of samples. Post processing is required by most ink jet systems currently
being used. In a previous NTC project (C95-G01), polymerizable ink systems and two-phase ink systems
were shown to have potential of eliminating post processing. However, understanding of dispersion
stability and two-phase flow under the extreme conditions encountered in an ink jet printer is insufficient
for design purposes. Research is critical for realization of the potential of these approaches because the
issues of fine capillary flow and the droplet breakup from a jet, despite being well understood for pure
fluids, are known to be the source of serious clogging and erratic behavior and remain virtually unstudied
for suspensions of solid particles.
         Research on printing quality associated with the interactions of droplet impingement onto a
porous and non-elastic surface has been limited and qualitative in nature (Oliver, 1988; Rultand, 1995;
Hensema et al, 1997). The role of substrate surface properties on printing quality was only recently
recognized as an important factor in color ink jet printing (Larish, 1997). Our research on the interaction
of single ink droplet with substrates, with attention to the role of surface properties on image formation, is
directed at providing a better understanding of the fundamentals affecting printing quality.
         The goal of this project is to develop a fundamental knowledge base on the flow, droplet
formation, and droplet/substrate interaction in two-phase ink jet printing. These issues are being studied
over a range of the controlling parameters, and the parameters required for optimization of the process for
rapid and reliable operation are being defined. We are performing experimental and numerical simulation
studies of the nozzle flow and droplet formation, and experimental studies of the droplet impingement
process. Thus, we are addressing both the “upstream” problem of a pigment-laden ink flow in the



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capillary nozzle and the droplet breakup process, and the “downstream” problem of droplet impingement
on and interaction with the printed medium. These aspects of the problem are complementary and
interconnected. Rapid improvement of the knowledge base, and hence the technology, of ink jet printing
of textiles requires cognizance of all of these factors, and thus the upstream and downstream problems are
attacked simultaneously in this study.
         To accomplish the goals of the project, research is being conducted in three areas: 1) model ink
development, 2) fluid flow studies of particle-laden capillary flow and droplet breakup, and 3)
interactions of a single ink-jet droplet with substrates.

Results
Model Ink Development: We are developing model inks for the visualization and ink/media interaction
studies. Attempts are being made to synthesize novel latex particles with very narrow particle size
distributions with controlled average particles sizes in the range of 100-200 nm. Two samples are needed:
one with average particle size in the lower end of the range and the other in the higher end. These will be
blended to provide model systems to study, theoretically and experimentally, the effect of particle size
distribution and particle loading on rheology.
         One latex has been prepared with acceptable properties. The average particles size by three
methods (light-scattering, area and volume average diameters) were 98.62, 99.08, 99.58 nm, respectively.
The coefficient of variance (CV) and the polydispersity index were 9.726 and 1.005, respectively. The
sample latex can be considered monodispersed since by definition monodispersed latex is one with a CV
less than 10. Attempts to produce model latex with a diameter of around 160 nm have been made, but, at
this size, the miniemulsion polymerization becomes very unstable. Colloidal stability was achieved by
adding additional surfactant after sonication; however, the resultant latex had a broad particle size
distribution. This is caused by homogeneous nucleation of methyl methacrylate. To avoid homogeneous
nucleation, oil-soluble initiator and water phase radical scavengers were added to the formula. The
polymerization was stable, but the particle size distribution was still quite broad. Work is continuing to
make a large diameter, monodisperse latex; however, previous experience has shown that as the particle
diameter increases in any latex, the polydispersity increases as well.
         In order to improve color retention in ink jet printing, and eliminate the washing steps necessary
to remove unset dyes, we are attempting to incorporate pigments and dyes into polymeric binders. A
miniemulsion polymerization process is being developed for encapsulation of pigments within polymeric
latex particles. The latexes will then be formulated into ink jet inks, and evaluated. In our efforts to
develop the miniemulsion polymerization, we are studying the encapsulation of titanium dioxide in
submicron polymer particles. We have selected colloidal TiO2, referred to as T-805 (manufactured by the
Degussa Corporation), as our model pigment. It is a type of hydrophobic TiO2 with particle size of 21
nm. Finding a dispersant for T-805 has been difficult, but we have found that Solsperse 32000 from
Avecia is a good dispersant for T-805 into methylmethacrylate (MMA). However, it is very difficult to
disperse T-805 well in its original size due to agglomeration of the TiO2 particles. The particle size
distribution of the dispersion shows multiple peaks with the lowest peak at 55 nm. As an alternative we
dispersed the TiO2 into water, using Triton X 405 as the dispersant. The agglomerates (160 nm) were
even larger.
         Two processes were tried to encapsulate T-805 into MMA colloidal particles. In the first process,
T-805 was first dispersed in water by applying sonication. Separately, the monomer was sonicated into
water to form a miniemulsion. Then the two dispersions were mixed, and additional sonication was
applied. The resulting miniemulsion was initiated to polymerization into polymer latex. In the second
process, T-805 was first dispersed in monomer under sonication. And then the dispersion was mixed with
water. The mixture was sonicated to form a miniemulsion. The miniemulsion was then polymerized into
polymer latex. Latex size was adjusted to around 250 nm because the TiO2 aggregations are too large to
be accommodated in smaller particles. The TiO2/MMA ratio was set at 1/10. AIBN was used as initiator
and NaNO2 was used to suppress homogeneous polymerization. Both processes lead to stable



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polymerizations, but with some coagulum on the stirrer. A thin layer of aggregates also appeared on the
reactor wall.
         Scanning electron microscopy (SEM) was used to determine that that encapsulation occurs for
both processes, but a small amount of almost bare (unencapsulated) TiO2 aggregates, over 500 nm in size,
are present. Ultracentrifuge showed the differences in the latex prepared by the two processes. Although
both processes produce a small portion of particles without TiO2, the first process produces latex particles
with broad density distribution (indicating varying degrees of encapsulation) while the second process
produced only latex particles with density higher than 1.319 g/cm3 (corresponding 15% TiO2) and
particles lacking in TiO2.
         Efforts at perfecting the encapsulation are continuing. After perfecting the encapsulation
technique we will shift from TiO2 to textile pigments, and evaluate the effect of encapsulation on pigment
fastness.

Fluid Flow Studies of Particle-Laden Capillary Flow and Droplet Breakup: Our research in the
formation of drops (used interchangeably with droplets) addresses the fundamental mechanisms of droplet
formation from two-phase mixtures that model inks that are used in textile printing. In the past year, we
have established a state-of-the-art facility for generation and imaging of the drop formation in ink jet
systems and at scales large relative to the practical scale. The imaging capabilities are also applied to the
drop impaction process. Simulation of the bulk motions of particle-laden mixtures in a simplified orifice
flow under the very high shear rate conditions has been performed, and it has been determined that the
conditions of the practical ink jet are outside the realm of present direct numerical approaches. We
discuss the simulation issue and the approach motivated by our research, before discussion of the
experimental effort.
         The simulation results, using a discrete particle tracking technique known as Stokesian Dynamics,
are consistent with expectation that the role of Brownian motion is probably negligible, but the detailed
influence of the form of the particle-particle surface interactions are found to be strong. Simplified
examinations of the oscillatory motions of the mixture flow have shown odd behavior (Morris 2001), but
the relevance to the application of interest is likely very small. Our results are consistent with literature
results on the rheology, which is readily incorporated without consideration of the discrete particles,
while agglomeration effects which may result from attractive interactions of the colloidal particles in the
inks is not readily simulated by the method simply because the number of particles simulated is too small.
Furthermore, the role of inertia and the presence of a free-surface flow are outside the present scope of
simulation that recognizes discrete particles. Thus, the research we have performed in the simulation of
solids-laden flow motivates 1) bulk flow modeling of the pulsed drop-on-demand flow, with 2) a detailed
numerical analysis of the particulate effects in the presence of the free surface, especially near the
bifurcation (pinch off) event occurring at the nozzle exit.
         The drop generation capabilities are based at the practical scale upon two single-head devices: an
Imaje continuous ink jet system with drop size of approximately 100 micron diameter, and an Optica
Visionjet drop-on-demand system with drop size down to about 40 micron diameter. We have
demonstrated the capability to image these very small drops clearly at velocities of 15 m/s through the use
of very short-duration high-intensity lighting provided by a pulsed Cu vapor laser (Oxford Lasers). This
laser light source generates approximately 105 W in a 10-20-nanosecond pulse; despite the high speed and
small distances associated with the droplet motion, this extremely short pulse provides us with the ability
to take an instantaneous snapshot of the motion. Because of the laser's firing rate of 10,000 Hz, we are, in
principle, able to image sequentially through the drop pinch-off, and a protocol for imaging of the events
taking place in this critical process is under development now.
         The formation of a drop invariably requires the narrowing of a column (or "neck") of liquid to a
very small dimension. This has been a focus of much past study, and remains an intensely examined area
of research, but only for pure liquids. We have focused upon the role of the particles in this process, and
have performed experiments on millimeter-scale drops in a range of drop formation conditions, in terms



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of flow rate, particle size relative to orifice diameter, and particle fraction. The basic experimental setup is
schematically illustrated below.




Figure 1. Schematic of Setup for Visualizing Droplet Formation

         The results from slow flows have shown a qualitative change in the drop formation process as
particle fraction increases. This is illustrated below in a set of images that shows that, for 2-mm and 5-
mm orifices and particles of 212-250 microns, the neck structure formed in a drop-by-drop mode at
flowrate of 0.38 ml/min changes from a needle and sphere structure to a pear-like structure. This is not
explained by the change of viscosity (see Shi et al 1994). The number of satellite droplets increases, but
also becomes irregular as the particle fraction increases. This is understood to be the effect of the
fluctuation in number density of the mixture.




Figure 2. Examination of particle effects on neck formation: drop generation at 0.38 ml/min from 5 mm
(left) and 2 mm (right) at 0, 0.02, 0.1, and 0.25 volume fraction solid spherical particles of diameter 212-
250 micron diameter.

Interactions of A Single Ink-Jet Droplet with Substrates: We are conducting research to better
understand ink/textile-media interactions. The objective is to obtain fundamental data and knowledge for
developing reliable and practical ink jet printing technology for textile printing applications. Droplet
impingement on silicon wafers with well-characterized surface chemistry and roughness, and textile
rayon and polyester fabrics are being investigated. The initial droplet impingement data will provide a
foundation for conducting further study on droplet impinge onto textiles, which should lead to a better
understanding of the interaction of an individual droplet with textile printing surfaces.
        Tests are being conducting with two types of setups. The first, which uses ink jet droplet
diameter and velocity typically produced by DOD ink jet printing engines, is shown schematically in



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Figure 3. The apparatus consist of an Optica System, a high-speed camera, and a laser light source. The
Optica System (VisionJet Ltd.) consists of a control unit, a printhead, and a triggering unit. The test
begins with the triggering box sending 5 volt TTL signals to the ink-jet engine control unit and to the
CCD camera control PC, simultaneously. The ink-jet engine control unit fires a single droplet through
the DOD inkjet head to the substrate. The high speed CCD camera captures a picture of the droplet
impacting the substrate. By controlling the delay time of the camera, the picture of the droplet can be
taken at different points in the impacting process.
         The second setup, shown in Figure 4, uses larger droplet diameters and lower droplet speeds to
allow studying the impact phenomena in more detail. Similarity analysis using the important
dimensionless numbers allows us to use larger diameter droplets moving at lower impact velocities if
fluid viscosity is changed appropriately. Since the dimensionless numbers are the same, the phenomena
for the two setups are expected to be the same, but the time in the second setup is scaled to facilitate
making observations.

                             Triggering
                                Box




   Ink-Jet Control Unit                   CCD Camera
                                           Control PC




           Pulsed Copper                    High-speed
            Vapor Laser                    CCD Camera


Figure 3. Experimental setup using a drop-on-demand, ink-jet engine

         Figure 4 shows a schematic of the experimental setup of the single-drop apparatus. A syringe
pump (Mode 230; KD Scientific Corp.) connected to a flat-tipped stainless steel needle (28G) is used to
generate a single droplet. The liquid volume and flow are set so that a single droplet is formed and falls
due to gravity.
         An optical trigger (OPTOLOGICtm QSA157, Fairchild semiconductor) is used to sense when a
single droplet moves between it and a laser light. When this occurs, a 5 volt TTL signal is sent to a pulse
generator which sends 5 volt rising or falling edge signals to a high-speed CCD camera, SensiCam (the
COOKE Corporation, Auburn Hills, MI), after a preset time delay. The camera captures images of the
impingement and loads the digital file in a computer. The series of images are made from single images
of many droplets with different delay times. The high-speed CCD camera was also used to determine
drop diameter and droplet speed using superimposed images in a frame.
         The ink jet inks used in our tests are mixtures of distilled water and glycerin (Fisher Scientific). A
Brookfield viscometer (model DV-1) is used to measure the viscosity of the fluid. Viscosities of 1, 8, and
100 cP are being used for inks for the scale up tests, while ink viscosity of 1 cP is being used for the DOD
printer. A Bubble Pressure Tensiometer BP2 (Krűss GmbH) is being used for measuring dynamic surface
tension. The surface tension is being held fixed for the tests at approximately 72 dyne/cm.




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        Two types of surfaces are being used for the droplet impaction studies. One type is coated and
uncoated silicon wafers with well-characterized surface energy, roughness, and capillarity, and the other
type is fabrics (rayon and polyester). To facilitate optical observation, filament fabrics were selected
because they have smooth surfaces with almost no protruding fibers. Rayon fabric is hydrophilic while
polyester fabric is fairly hydrophobic. The roughness of the fabrics is being determined via Kawabata
system for fabric hand evaluation (KES-FB-4, KES Kato Tech Co., Ltd.) and Scanning Electro
Microscopy (SEM; Leica Stereoscan 430).


                                                                        S y rin g e P u m p



                                    F la t-tip p e d N e e d le
                                                                             P u ls e
              Laser
                                                       O p tic a l        G e n e ra to r
              L ig h t
                                                      D e te c to r



                                           L ig h t
          H ig h S p e e d
                                         D iffu s e r                 L ig h t S o u rc e
          C C D C a m e ra




                             C C D C a m e ra
                             C o n tro l P C




Figure 4. Experimental setup of a single-drop apparatus

                  Silicon wafers are being used with three different surface chemistries: poly vinylidene
fluoride (PVF, Aldrich) coating, 1,1,1,3,3,3, Hexamethyl disilazane (HMDS, Aldrich) coating, and
uncoated silicon wafers. The coatings applied to the silicon wafers were selected to mimic the properties
of selected fabrics. This was done to provide well-characterized surfaces with properties similar to those
of the fabrics. The coatings were applied using a CEE Model 100CB Spinner. The surfaces are being
characterized in terms of these three parameters: surface chemistry, roughness and capillarity. First the
critical surface tension is being estimated using Zisman’s technique with liquids having known surface
tensions. This task has not been completed; however, the surface chemistry of the substrate has been
characterized by contact angles with two different liquids, as shown in Table 1. Contact angles were
measured using a VCA2500KE Contact Angle Surface Analysis System.
Table 1. Contact angles of water and tetradecane with silicon wafers.

Substrates                                                                       Liquids      Contact angles

                                                                                   Water           33°
Uncoated silicon wafer
                                                                           Tetradecane             0°
Hexamethyl disilazane (HMDS)
                                                                                   Water           75°
coated silicon wafer
Poly vinylidene fluoride (PVF)
                                                                                   Water          100°
coated silicon wafer
        Table 1 shows the contact angles of two different liquids on the three surfaces. The contact
angles for n-tetradecane (Aldrich) and distilled water on an uncoated silicon wafer are 0° and 33°,
respectively. Tetradecane totally wets the uncoated silicon wafer, but water does not totally wet it. The


                                National Textile Center Annual Report: November 2001
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contact angles of water with HMDS and PVF coated silicon wafers are of 75° and 100°, respectively.
Thus the PVF polymer coated silicon wafer has the highest hydrophobicity.
         The droplet/substrate interaction can be separated into two stages. The first stage is referred to as
impact. Over a very short time period, the droplet impacts the substrate, spreads, retracts, in some cases
rebounds, and then spreads and comes to rest. We are observing retraction and rebound, and measuring
maximum spread and resting diameter ratio. After the impact period is over and the droplet has come to
rest on the substrate, the wicking period begins. Depending on the porosity and surface chemistry of the
substrate, the droplet can wick either partially or totally into the substrate. The wicking period is much
longer the impact period. Our study has addressed the impact, but not wicking phenomenon. Wicking
will be a subject of future study. The impaction tests have been limited primarily to the coated and
uncoated silicon wafer surfaces; however, more tests using the fabric surfaces are planned.
         Impact can consider in four stages. Stage (a) is before impact. The droplet impact energy consists
of kinetic energy, surface energy, and potential energy; Stage (b) is at maximum spread. This is the point
at which the liquid flow changes direction from spreading outwards to recoiling inwards. The surface
energy of the droplet is at a maximum while the kinetic energy is zero. Stage (c) is at maximum
recoil/rebound. At this moment, the droplet changes its direction of motion from up to down under the
influence of gravity. Stage (d) is quasi-equilibrium (constant diameter). The droplet kinetic energy has
been either changed into surface energy or viscously dissipated.
         Maximum spread during the impact process is an important factor influencing print quality.
Factors affecting spreading after impact are droplet inertia, viscous forces within the spreading fluid and
droplet surface tension. Reynolds number and the Weber number, which contain these factors, are the
dimensionless numbers used to characterize the impact process.

                     PVF coated silicon         HMDS coated silicon         Uncoated silicon
  Time (ms)
                          wafers                     wafer                      wafer

      0.0



      5.0



      9.0



     800

Figure 5. Impact of a 2.3 mm water droplet on the PVF coated, HMDS coated, and uncoated silicon
wafers.

         The single-drop apparatus has been used to observe droplets impacting silicon wafers with the
three different surface chemistries. Figure 5 shows the impact sequence of a distilled-water droplet on a
PVF coated, an HMDS coated, and uncoated silicon wafers. The camera was setup a little above the
horizontal for obtaining clear images of the droplet spread upon impact. The impact velocity of the 2.3
mm-diameter drop was about 1 m/s, and the corresponding Reynolds number (Re = ρuD/µ) and Weber
number (Re = ρu2D/γ) were 2004 and 24, respectively.



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         The photographs taken at t = 0.0 ms show the spherically shaped droplets just before impact (see
Figure 5). At t = 5.0 ms, the droplets on the PVF and HMDS coated surfaces are approximately at the
maximum spreading ratio, which is the ratio of the contact diameter to the original drop diameter just
before impact. However, the droplet on the uncoated silicon wafer does not reach its maximum ratio until
t = 9.0 ms (see Figure 6). The maximum spreading ratio for the uncoated silicon wafer is only about 10-
20 % greater than for the other two surfaces. The surface energy of the pure silicon is high, and thus the
interaction between the distilled water and the pure silicon wafer is greater than for the other two surfaces.
Spreading is driven by kinetic energy and interfacial energy due to the interaction of the liquid with the
solid surface. For the Weber and Reynolds numbers for this test, the interfacial energy relative to kinetic
energy is sufficiently large so that it has an effect on spreading. However at higher Reynolds and Weber
numbers (Re ~ 5000 and We ~ 150, as shown in Figure 7), the maximum spreading ratios are almost
identical for the three surfaces, and it takes almost identical times (about 4.5 ms) to reach this value (see
Figure 7). Apparently at the higher Reynolds and Weber numbers, spreading is dominated by the kinetic
energy of the system. The maximum spreading ratio for the uncoated silicon wafer is only about 2-4%
greater than for the other two surfaces.

       3.5
                   PVF coating wafer
        3          HMDS coating wafer
       2.5         Uncoated silicon wafer

        2
 D/d




       1.5
        1
       0.5
        0
             0.1                   1                10             100                1000
                                            Log (time (ms))
                                             Log (time;ms)
Figure 6. Spreading ratio after impacting on the PVF coated, HMDS coated, and uncoated silicon wafers
(Re = 2000 and We = 24).

        At t = 9 ms, the recoil stage can be observed for the droplets on the PVF and HMDS coated
surfaces; however, the droplet on the uncoated silicon surface recoiled very little. At t = 800 ms, constant
spreading ratio at quasi-equilibrium can be observed. The resting diameter for the droplet on the
uncoated silicon surface is much larger than for the other two surfaces. This is not surprising since the
contact angle of water on the uncoated silicon surface was much smaller than for the other two surfaces.
         Similar results were obtained for the spreading of water on HDMS coated silicon wafer and
tetradecane on uncoated silicon wafers (see Figure 8). The contact angles for these two cases were 75 and
0°, respectively.




                          National Textile Center Annual Report: November 2001
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           5
         4.5
           4
         3.5
           3
 D/d




         2.5
           2
         1.5                   i    l
                                    i     er
                     HM DS coatng sicon waf
           1               ed l i
                     Uncoat sicon waf er
         0.5                 i    i
                                  l
                     PVF coatng sicon wafer
           0
               0.1            1                10                  100             1000
                                       Log (time;ms)
                                      Log (time (ms))
Figure 7. Spreading ratio after impacting on the PVF coated, HMDS coated, and uncoated silicon wafers
(Re ~5000 and We ~150).




       3.5
        3
       2.5
        2
 D/d
 D/d




       1.5
        1                                               HMDS coating silicon wafer with
                                                        water
       0.5                                              Uncoated silicon wafer with
                                                        tetradecane
        0
             0.1             1                10                    100                   1000
                                      Log (time (ms)) )
                                       Log (time;ms
Figure 8. Spreading ratio after impacting on the PVF coated, HMDS coated, and uncoated silicon wafers
(Re = 1978, We = 23.4 for water, and Re = 610, We = 46.0 for tetradecane).

        In Figure 9, two series of figures show single-water-droplet impaction on identical rough
surfaces, but at different impact positions. The photographs taken at t=0 ms shows the spherical
droplet just before impact between monofilaments and impact on the center of the monofilament.
At t=5ms, the drops on two surfaces are almost at maximum spreading in both the directions
(along the axis of the monofilament and the direction perpendicular to the axis). At t=9ms, the
droplet is in the recoil stage. At t ≥ 800ms, the drop has come to rest. The resting diameter for




                      National Textile Center Annual Report: November 2001
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                                       C99-G08                 10


(a) is bigger than diameter (b). Thus, the location of impacted on a rough surface affects
spreading ratio and final resting diameter.

    Time (ms)                0.0                  5.0                  9.0                  800

(a) Impacting
between polyester
mono-filaments

(b) Impacting on
the center of a
polyester mono-
filament
Figure 9. Effect of impact position on spreading - 2.3 mm water on the monofilament polyester surface
(Re = 2000 and We = 24).


Web Site URL Address for C99-G08: http://www.tfe.gatech.edu/faculty/carr/ntcproject.htm
Acknowledgements:
Undergraduate Students: Sean Kerrigan.
Graduate Students: Heungsup Park (PhD, TFE), Jongseung Park (PhD, TFE), Hyunyoung Ok (MS, TFE),
Roy J. Furbank (PhD, ChE), Ryan M. Miller (PhD, ChE)
Research Scientist: Dr. Yingwu Luo

Publications and Presentations
 1. X. D. Shi, M. P. Brenner, and S. R. Nagel, “A cascade of structure in a drop falling from a faucet”,
     Science 265, 219, (1994).
 2. J. F. Morris and R. M. Miller, "Concentrated suspension flow through a contraction", Society of
     Rheology Meeting, Madison, WI, (1999).
 3. J. F. Morris and F. Boulay, "Curvilinear flows of noncolloidal suspensions: the role of normal
     stresses", J. Rheol. 43, 1213-1237, (1999).
 4. W. C. Tincher, "Ink Jet Print Head Technology", AATCC Symposium: Printing 2000: Entering the
     Jet Age, Charlotte, NC, 11-18, (1999).
 5. W. C. Tincher and R. Yang, "Ink Jet Resin-Pigment Printing of Silk Fabrics", IS&T's NIP15:
     International Conference on Digital Printing Technologies, Orlando, FL, (1999).
 6. W. C. Tincher, "The Jet Age Dawns at ITMA", Textile World, 27-32, November 1999.
 7. J .F. Morris, “Anomalous migration in simulated oscillatory pressure-driven flow of a concentrated
     suspension”, Phys Fluids 13, 2457, (2000).
 8. R. Furbank and H. Park, “Droplet Formation from Suspensions of Solid Particles“, CDIT
     Symposium, (2001).
 9. R. J. Furbank, and J. F. Morris, “Droplet Formation from Particulate Suspensions”, NIP 17
     Conference, Ft. Lauderdale, October 2, 2001.
 10. H. Park, W.W. Carr, and J. Zhu, “Interactions of a Single Ink-Jet Droplet with Textile Printing
     Surfaces”, NIP 17 Conference, Ft. Lauderdale, October 2, 2001.




                     National Textile Center Annual Report: November 2001
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