CUED Publications database

Colloidal suspension rheology and inkjet printing

Hoath, SD and Hsiao, WK and Yow, HN and Biggs, SR and Butler, SA and Mackley, MR and Martin, GD and Hutchings, IM (2014) Colloidal suspension rheology and inkjet printing. In: UNSPECIFIED pp. 157-161..

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© 2014 Society for Imaging Science and Technology. This work reports the first systematic survey of colloidal suspension jetting [1], as opposed to dripping liquids containing particles [2] , and it complements a previous survey of the jetting of complex fluids [3]. Colloidal suspensions of stabilised polystyrene particles in water/ethylene glycol were formulated for maximum stable loadings (vol%) and low poly-dispersity index (PDI), for a range of spherical particle sizes (80 nm to 850 nm). Each preparation batch was characterised using squeeze mode rheometry [4] and filament stretching devices [5, 6] while being independently assessed using drop-on-demand (DoD) inkjet printing from MicroFab nozzles with either 30 μm or 80 μm diameter. Nozzle blocking was reduced for the jetting tests by maintaining a 100 Hz printing frequency throughout waiting periods. Additional experiments used a transparent containment chamber around the 30 μm nozzle exit to examine jetting behaviours that might be caused by the humidity level. Jetting for each batch (characterised by colloidal particle size, vol%, nozzle size, etc.) was considered successful if high speed videos used for measurements of drop speed and determination of the jet break-off time from nozzle meniscus were reliably and consistently achieved at several drive voltages. Jetted drop speeds for all the colloid suspensions tested showed a linear dependence on drive voltage above a threshold voltage as previously reported for Newtonian and weakly elastic drop speeds [7] . Mapping of successful DoD jetting as a function of colloidal particle size (nm) and vol% for 80 μm (30 μm) nozzle diameter reached 37 vol% (30 vol%) without any evidence for any spherical 80-850 nm (300-850 nm) particle size effect on jetting. The rheology of these colloidal suspensions, obtained independently from jetting, exhibits rather Newtonian behaviour with a range of viscosities within a factor of 2. Likewise, the filament stretching experiments that are sensitive to non-linear effects such as relaxation time [5, 6] could not discriminate between solvent and suspensions. Beyond issues with blocking (and stability), colloidal suspensions were jetted easily, in line with expectations based on the measured rheology and low nonlinear effects.

Item Type: Conference or Workshop Item (UNSPECIFIED)
Divisions: Div E > Production Processes
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:04
Last Modified: 17 Aug 2017 01:25