Adhesion and fingering in the lifting Hele-Shaw cell: Role of the substrate

• Published in: The European physical journal. E, Soft matter and biological physics Vol. 25; no. 3; pp. 267 - 275
• Main Authors: Sinha, S., Dutta, T., Tarafdar, S.
• Format: Journal Article
• Language: English
• Published: Bologna Società Italiana di Fisica 01.03.2008; Springer
• Subjects: Biological and Medical Physics; Biophysics; Chemistry; Complex Fluids and Microfluidics; Complex Systems; Exact sciences and technology; General and physical chemistry; Nanotechnology; Physics; Physics and Astronomy; Polymer Sciences; Regular Article; Soft and Granular Matter; Solid-liquid interface; Surface physical chemistry; Surfaces and Interfaces; Thin Films; 47.20.Gv Viscous and viscoelastic instabilities; 61.30.Hn Surface phenomena: alignment, anchoring, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions, and wetting transitions; 47.54.-r Pattern selection; pattern formation; 68.35.Np Adhesion; Ethylene glycol; Patterning; Liquid solid interface; Wetting; Perspex; Silicone oil; Glass; Glycerol; Olive oil; Paint; Adhesion; Ethylene oxide polymer; Substrate; Castor oil; Hele Shaw cell; Soybean oil; Fingering
• ISSN: 1292-8941; 1292-895X
• DOI: 10.1140/epje/i2007-10289-9

. The lifting Hele-Shaw cell (LHSC) is used to study adhesion as well as viscous fingering. In the present paper we report a series of observations of development of the interface for different viscous fluids, both Newtonian and non-Newtonian, in a LHSC operated at a constant lifting force. Glass and perspex are used as the plates in two different sets of experiments. The objectives are 1) to measure the time required to separate the plates as a function of the lifting force and 2) to note the force above which viscous fingering appears. We find that for the Newtonian fluids, the plate separation time follows a universal power law with the lifting force, irrespective of fluid and substrate. The non-Newtonian fluids too, with proper scaling obey the same power law. The appearance of fingering, however, depends on the properties of the fluid as well as the substrate. We suggest a modified form of the capillary number which controls the onset of fingering; this new quantity, termed the “fingering parameter” involves the dielectric constants of the substrate and fluid in addition to the viscosity and surface tension.