Evaluation of absorption of micro-droplets on paper for creation of paper-based microstructures (original) (raw)
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The size of a single drop determines the smallest detail that can be produced in an ink jet system. Drops of as small as three picoliters can be controllably created at the present level of ink jet technology. The final dot quality of a drop can be easily measured by an image analysis system, but the significance of high speed dynamic interactions between paper and ink cannot be determined from the final print quality. Therefore, VTT Information technology has developed several high-speed camera based systems for ink jet paper research. This paper details a new laboratory-scale test environment developed for the measurement of dynamic interactions between paper and ink with drops of a magnitude of under 20 microns. The equipment is based on a commercial piezo-electric desktop printer, a high-speed CCD camera, an optical fibre light source and a PC with control and analysis software. In this environment, the impact, spreading, penetration and drying of very small 3 pl ink drops on th...
Langmuir, 2002
The wetting and absorption dynamics of water droplets deposited on hydrophobized paper were studied. The objective was to quantify the effect of chemical and physical heterogeneity of a porous surface on its wetting and absorption behavior. Wetting and absorption rates were calculated from the contact angle, volume, and contact line of the droplets on paper. Absorption started only after the drop had wetted the surface to a certain extent. There was a time delay before absorption occurred. By the end of this delay, a pseudoequilibrium contact angle was reached, a metastable contact angle function of chemical composition of the surface. Wetting on a partially hydrophobized porous surface follows a power law model with wetting rates slower than in hydrodynamic wetting by a factor H, a function of surface roughness. Surface roughness also affects the pseudoequilibrium contact angle, as by entrapping air, it renders the surface more hydrophobic. The wetting dynamics was found to be independent of the chemical heterogeneity of the surface.
The impact of ink-jet droplets on a paper-like structure
Inkjet technology has been recognized as one of the most successful and promising micro-system technologies. The wide application areas of printer heads and the increasing demand of high quality prints are making ink consumption and print see-through important topics in the inkjet technology. In the present study we investigate numerically the impact of ink droplets onto a porous material that mimics the paper structure. The mathematical framework is based on a free energy formulation, coupling the Cahn-Hilliard and Navier Stokes equations, for the modelling of the two-phase flow. The case studied here consists of a multiphase flow of air-liquid along with the interaction between a solid structure and an interface. In order to characterize the multiphase flow characteristics, we investigate the effects of surface tension and surface wettability on the penetration depth and spreading into the paper-like structure.
Lab Chip, 2009
Superhydrophobic paper substrates were patterned with high surface energy black ink using commercially available desktop printing technology. The shape and size of the ink islands were designed to control the adhesion forces on water drops in two directions, parallel ('drag-adhesion') and perpendicular ('extensional-adhesion') to the substrate. Experimental data on the adhesion forces shows good agreement with classical models for 'drag' (Furmidge equation) and 'extensional' adhesion (modified Dupr e equation). The tunability of the two adhesion forces was used to implement four basic unit operations for the manipulation of liquid drops on the paper substrates: storage, transfer, mixing and sampling. By combining these basic functionalities it is possible to design simple two-dimensional lab-on-paper (LOP) devices. In our 2D LOP prototype, liquid droplets adhere to the porous substrate, rather than absorbing into the paper; as a result, liquid droplets remain accessible for further quantitative testing and analysis, after performing simple qualitative on-chip testing. In addition, the use of commercially available desktop printers and word processing software to generate ink patterns enable end users to design LOP devices for specific applications.
Fabrication of paper based microfluidic devices
This paper describes an inexpensive method of fabricating paper based microfluidic devices, a new point of care technology. The method uses a solid ink printer, chromatography paper and a heating source. The printer deposits wax onto the surface of the paper which is then melted to allow the wax to penetrate the depth of the paper. This results in hydrophobic barriers capable of guiding fluid movement through the paper. The paper provides a detailed study of process parameters critical to this fabrication process. It discusses the selection of the optimum line width, melting temperature and melting time required to generate impermeable hydrophobic barriers. It was found that line widths play a predominant role in the development of effective wax barriers, more so than other fabrication parameters. A comparison between the melting effectiveness of a hot plate and an oven is also given. To test barrier effectiveness, square chambers were printed and flooded with coloured dye. It was found that barriers narrower then 300µm do not form impermeable hydrophobic barriers.
Droplet Behaviors on Substrates in Thin-Film Formation Using Ink-Jet Printing
JSME International Journal Series B, 2004
Physical phenomena associated with the dynamic spreading and dried shape of droplets on solid surfaces were demonstrated reviewing several models and discussed with regard to designing the most suitable thin-film formation processes using ink-jet printing. After droplets strike a substrate surface and expand for several microseconds, they spread semistatically for tens of seconds and asymptotically approach the final equilibrium shape determined by droplet volume and contact angle. The contact angle and the volume, number, and impact velocity of droplets for various ink-jet-deposition applications can be designed by using semi-empirical formulas. If the contact angle at the edge of droplet on the substrate is small, a large amount of solute might accumulate there during the drying process because the evaporation rate there is high. The evaporation rate distribution on droplet surfaces should therefore be controlled to be uniform in radial direction during drying.
Wicking in Paper Strips under Consideration of Liquid Absorption Capacity
Chemosensors, 2020
Paper-based microfluidic devices have the potential of being a low-cost platform for diagnostic devices. Electrical circuit analogy (ECA) model has been used to model the wicking process in paper-based microfluidic devices. However, material characteristics such as absorption capacity cannot be included in the previous ECA models. This paper proposes a new model to describe the wicking process with liquid absorption in a paper strip. We observed that the fluid continues to flow in a paper strip, even after the fluid reservoir has been removed. This phenomenon is caused by the ability of the paper to store liquid in its matrix. The model presented in this paper is derived from the analogy to the current response of an electric circuit with a capacitance. All coefficients in the model are fitted with data of capillary rise experiments and compared with direct measurement of the absorption capacity. The theoretical data of the model agrees well with experimental data and the convention...
Inkjet patterned superhydrophobic paper for open-air surface microfluidic devices
Lab on a Chip, 2014
We present a facile approach for the fabrication of low-cost surface biomicrofluidic devices on superhydrophobic paper created by drop-casting a fluoroacrylic copolymer onto microtextured paper. Wettability patterning is performed with a common household printer, which produces regions of varying wettability by simply controlling the intensity of ink deposited over prespecified domains. The procedure produces surfaces that are capable of selective droplet sliding and adhesion, when inclined. Using this methodology, we demonstrate the ability to tune the sliding angles of 10 μL water droplets in the range from 13°to 40°by printing lines of constant ink intensity and varied width from 0.1 mm to 2 mm. We also formulate a simple model to predict the onset of droplet sliding on printed lines of known width and wettability. Experiments demonstrate open-air surface microfluidic devices that are capable of pumpless transport, mixing and rapid droplet sampling (~0.6 μL at 50 Hz). Lastly, post treatment of printed areas with pH indicator solutions exemplifies the utility of these substrates in point-of-care diagnostics, which are needed at geographical locations where access to sophisticated testing equipment is limited or non-existent. Tel: +1 (312) 996 3436 † Electronic supplementary information (ESI) available: Mathematical derivation, accompanying images, and videos are available in the supplementary information. See
Nano-ink Drops’ Behavior on the Polymeric Substrates’ Surfaces
Periodica Polytechnica Electrical Engineering and Computer Science, 2016
The aim of this paper is analysis of the nano-ink behavior onto the polymeric substrates' surfaces. For this reason, three types of commonly used polymeric substrates for inkjet printing technology, polyethylene terephthalate (PET), polyethylene naphthalate (PEN) and polyimide (PI) were analyzed. The impact of the surfaces' temperature on the ink spreading was mainly analyzed by using the microscopic methods. The higher temperature of substrate causes the fast evaporation process of the ink onto the substrates surface as well as causes the viscosity decreasing of the nano-ink. For this purpose, 2 silver based nano-inks were deposited by inkjet printer Jetlab 4xl-A with orifice diameter 70 μm. The main benefit of this paper lays in the optimizing of the spreading and coffee ring effect of several silver based nano-inks through the surface temperature changes and investigation of the deposited structures' shapes after the sintering.