2014) 'Control of the particle distribution in inkjet printing through an evaporation-driven sol-gel transition.', ACS applied materials interfaces., 6 (12). pp. 9572-9583.Further information on publisher's website:http://dx.doi.org/10.1021/am501966nPublisher's copyright statement:This document is the Accepted Manuscript version of a Published Work that appeared in nal form in ACS Applied Materials Interfaces, copyright c American Chemical Society after peer review and technical editing by the publisher. To access the nal edited and published work see http://dx.doi.org/10.1021/am501966n. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract A ring stain is often an undesirable consequence of a droplet drying. Particles inside evaporating droplets with a pinned contact line are transported towards the periphery by radial flow. In this paper, we demonstrate how suspensions of laponite can be used to control the radial flow inside picolitre droplets and produce uniform deposits.The improvement in homogeneity arises from a sol-gel transition during evaporation.Droplets gel from the contact line inwards, reducing radial motion of particles and thus inhibiting the formation of a ring stain. The internal flows and propagation of the gelling front were followed by high-speed imaging of tracer particles during the evaporation of picolitre droplets of water. In the inkjet nozzle, the laponite network * To whom correspondence should be addressed † Department of Chemistry, Durham University, Durham, DH1 3LE, United Kingdom ‡ School of Engineering and Computing Sciences, Durham University, Durham, DH1 3LE, United Kingdom 1 is broken down under high shear. Recovery of the low shear viscosity of laponite suspensions was shown to be fast with respect to the lifetime of the droplet, which was instrumental in controlling the deposit morphology. The radial and vertical particle distributions within dried deposits were measured for water droplets loaded with 1%w and 5%w polystyrene spheres and various concentrations of laponite. Aggregation of the polystyrene spheres was suppressed by addition of colloidal silica. The formulation can be tuned to vary the deposit profile from a ring to a pancake or a dome.
A number of colloidal systems, including polymers, proteins, micelles and hard spheres, have been studied in thermal gradients to observe and characterize their driven motion. Here we show experimentally the thermophoretic behaviour of unilamellar lipid vesicles, finding that mobility depends on the mean local temperature of the suspension and on the structure of the exposed polar lipid head groups. By tuning the temperature, vesicles can be directed towards hot or cold, forming a highly concentrated region. Binary mixtures of vesicles composed of different lipids can be segregated using thermophoresis, according to their head group. Our results demonstrate that thermophoresis enables robust and chemically specific directed motion of liposomes, which can be exploited in driven processes.
Publisher's copyright statement:Reprinted with permission from the American Physical Society: Talbot, E.L., Berson, A., Brown, P.S. and Bain, C.D. Physical Review E, 85, 061604, 2012. c 2012 by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modied, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. The evaporation of picoliter water and ethanol droplets generated by drop-on-demand inkjet printing was investigated on substrates with apparent contact angles between 10• and 135• and thermal conductivities between 0.25 and 149 W m −1 K −1 . Drying times were calculated from a diffusion-limited model for droplets with both pinned and moving contact lines as a function of droplet diameter and apparent contact angle. Droplets with a moving contact line take longer to dry on hydrophilic substrates than pinned droplets. The difference in drying times between evaporative modes vanishes at large apparent contact angles. Hence similar drying times are obtained for both modes on hydrophobic substrates. The predicted drying times for glass and silicon substrates were in good quantitative agreement with experimental data, suggesting that thermal effects are negligible for substrates of these base materials. However, on a PTFE substrate which has a lower thermal conductivity more relevant to inkjet printing, evaporative cooling reduces the evaporation rate causing drying times to be underpredicted by isothermal models.
Two-dimensional hexagonally ordered honeycomb surfaces have been created by solvent casting polybutadiene films under controlled humidity. Subsequent CF(4) plasmachemical fluorination introduces cross-linking and surface texturing, leading to hierarchical surfaces with roughness on both the 10 μm (honeycomb) and micrometer (texturing) length scales. For microliter droplets, these display high water contact angle values (>170°) in combination with low contact angle hysteresis (i.e., superhydrophobicity) while displaying bouncing of picoliter water droplets. In the case of picoliter droplets, it is found that surfaces which exhibit similar static contact angles can give rise to different droplet impact dynamics, governed by the underlying surface topography. These studies are of relevance to technological processes such as rapid cooling, delayed freezing, crop spraying, and inkjet printing.
The impact of picoliter-sized water droplets on superhydrophobic CF(4) plasma fluorinated polybutadiene surfaces is investigated with high-speed imaging. Variation of the surface topography by plasmachemical modification enables the dynamics of wetting to be precisely controlled. Final spreading ratios as low as 0.63 can be achieved. A comparison of the maximum spreading ratio and droplet oscillation frequencies to models described in the literature shows that both are found to be much lower than theoretically predicted.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.