Omniphobic “R^F Paper” Produced by Silanization of Paper with Fluoroalkyltrichlorosilanes

Abstract

This paper describes the fabrication and properties of "fluoroalkylated paper" ("R F paper") by vapor-phase silanization of paper with fluoroalkyl trichlorosilanes. R F paper is both hydrophobic and oleophobic: it repels water (θ app H 2 O >140°), organic liquids with surface tensions as low as 28 mN/m, aqueous solutions containing ionic and non-ionic surfactants, and complex liquids such as blood (which contains salts, surfactants, and biological material such as cells, proteins, and lipids). The propensity of the paper to resist wetting by liquids with a wide range of surface tensions correlates (with a few exceptions) with the length and degree of fluorination of the organosilane, and with the roughness of the paper. R F paper 2 maintains the high permeability to gases, and the mechanical flexibility of the untreated paper, and can be folded into functional shapes (e.g. microtiter plates and liquid-filled gas sensors).When impregnated with a perfluorinated oil, R F paper forms a "slippery" surface (paper slippery liquid-infused porous surface, or "paper SLIPS") capable of repelling liquids with surface tensions as low as 15 mN/m. The foldability of the paper SLIPS allows the fabrication of channels and flow switches to guide the transport of liquid droplets.

Folding Analytical Devices for Electrochemical ELISA in Hydrophobic RH Paper

“…The ease of modifying its surface chemistry allowed us to render the paper hydrophobic using a 5 min vapor-phase treatment with decyl trichlorosilane (C 10 H ). 5 The modified paper can be easily printed with conductive inks, 45 and it facilitates the physical adsorption of biomolecules on its surface through hydrophobic interactions. The roughness of the paper affords a large surface area for the adsorption of proteins on the surface of the functionalized paper.…”

“…5 The silanizing reagent, decyl trichlorosilane, was transferred into a glass vial and placed inside the chamber together with the samples. Each experiment typically required approximately 100 mg of silane in 5 mL of anhydrous toluene.…”

“…C 10 H paper 5 (cellulose paper that has been rendered hydrophobic by vapor-phase silanization with decyl trichlorosilane) has several other properties that make it an attractive substrate for the fabrication of devices for electrochemical ELISA: (i) Its low surface free energy allows the printing of electrodes with high reproducibility. 45 (ii) Its hydrophobicity and high surface area facilitates the immobilization of the capture biomolecules (antibodies and antigens) on its surface.…”

“…The devices are made entirely from a sheet of C 10 H paper 5 (cellulose paper that has been rendered hydrophobic by vapor-phase silanization with decyl trichlorosilane) and ink, using only embossing, printing, and folding as techniques for fabrication. Despite the remarkable simplicity of these devices (simplicity in the materials used, the fabrication method, and the operation) they are highly sensitive and exhibit the electrochemical behavior typical of conventional electrochemical cells.…”

Paper-based microfluidic devices by asymmetric calendaring

“…When such pressure is targeted/localized, and with the appropriate lubrication to mitigate fiber damage, a channel can be created (Figure 2(a)). We 28,29 and others 5,[30][31][32][33][34][35][36] have shown that paper can be rendered hydrophobic by treatment with alkyl trichlorosilanes (Figures 1(b) and 1(c); see details in the supplementary material Figure S1). 29 We, therefore, hypothesized that co-deposition of an appropriately functionalized silane during the asymmetric calendaring could lead to a channel with desired wetting properties.…”