Geo-material surface modification of microchips using layer-by-layer (LbL) assembly for subsurface energy and environmental applications

• Published in: Lab on a chip 2018-01, Vol.18 (2), p.285-295
• Main Authors: Zhang, Y. Q, Sanati-Nezhad, A, Hejazi, S. H
• Format: Article
• Language: English
• Subjects: Assembly; Clay minerals; Coatings; Contact angle; Dynamic stability; Flooding; Glass substrates; Kaolinite; Mineral oils; Montmorillonite; Polydimethylsiloxane; Rocks; Sandstone; Semiconductors; Silicone resins; Wettability
• ISSN: 1473-0197; 1473-0189
• DOI: 10.1039/c7lc00675f

A key constraint in the application of microfluidic technology to subsurface flow and transport processes is the surface discrepancy between microchips and the actual rocks/soils. This research employs a novel layer-by-layer (LbL) assembly technology to produce rock-forming mineral coatings on microchip surfaces. The outcome of the work is a series of 'surface-mimetic micro-reservoirs (SMMR)' that represent multi-scales and multi-types of natural rocks/soils. For demonstration, the clay pores of sandstones and mudrocks are reconstructed by representatively coating montmorillonite and kaolinite in polydimethylsiloxane (PDMS) microchips in a wide range of channel sizes (width of 10-250 μm, depth of 40-100 μm) and on glass substrates. The morphological and structural properties of mineral coatings are characterized using a scanning electron microscope (SEM), optical microscope and profilometer. The coating stability is tested by dynamic flooding experiments. The surface wettability is characterized by measuring mineral oil-water contact angles. The results demonstrate the formation of nano- to micro-scale, fully-covered and stable mineral surfaces with varying wetting properties. There is an opportunity to use this work in the development of microfluidic technology-based applications for subsurface energy and environmental research. A key constraint in the application of microfluidic technology to subsurface flow and transport processes is the surface discrepancy between microchips and the actual rocks/soils.