Surface Treatment of Flow Channels in Microfluidic Devices Fabricated by Stereolithography

Abstract

Microfluidic devices, which consist of networks of channels with micrometer dimensions, have attracted considerable attention in a wide range of applications including analytical systems, biomedical devices, and as tools for chemistry and biochemistry based experiments 1 5 . These devices can produce monodisperse droplets with exceptional precision, which are useful as individual compartments for chemical reactions and templates for preparation of monodisperse functional particles 6 11 . To date, several types of microfluidic devices have been developed. For example, capillary microfluidic devices consist of coaxial assemblies of tapered glass capillaries on glass slides 12,13 .Although the device can be fabricated at low cost, it is cumbersome to set the positions and sizes of the capillaries precisely. There are also polydimethylsiloxane PDMS devices, which consist of patterned microchannels in a silicone elastomer of PDMS fabricated by soft lithography techniques 14 16 . Although using soft lithography facilitates accurate control of the positions and sizes of the channels in the device through the design of mask patterns, it is difficult to fabricate flow channels in three dimensions, which would limit the utility of the device for many applications. 21 , could be prepared by polymerization of a gelation reagent dissolved in the monodisperse water droplets. Although stereolithography is a promising method for fabricating three-dimensional microfluidic devices, the default properties of the resin are inappropriate for many applications. For example, the device cannot produce oilin-water O/W emulsions and double emulsions, consisting of drops of oil and water assembled into a core-shell structure, owing to the hydrophobic surface properties of the flow channels 22,23 . To broaden the applicability of the devices, control of the wetting characteristics of the surface of channels is necessary. In this paper, we report on the surface treatment of the NOTE Abstract: A microfluidic device with three-dimensional flow channels was fabricated by stereolithography, and hydrophilic surface treatment of the flow channel was performed by coating the wall of the channel with a silica layer. After the treatment, the device produced monodisperse oil-in-water (O/W) emulsions. The silica layer on the channel surface was then coated with a fluorinated silane coupling agent to make it hydrophobic, thus enabling the treated device to produce monodisperse inverted water-in-oil (W/O) emulsions.

The upcoming 3D-printing revolution in microfluidics

“…Lately, silane chemistry has been exploited to modify the surface of SL resins. One strategy has been to coat the walls of a channel with a silicate coating by injecting a hydrolyzed ethyl silicate solution (N-103X, Colcoat Co.) and heating it to allow the solution to vaporize and coat the inside walls of the channel 133 . Silicates have been used traditionally as the base surface on which silane chemistry has been performed.…”

3D‐Printed Microfluidics

“…Epoxy slides have been used to chemically immobilize protein surface gradients by amine-epoxy linkage for chemotaxis experiments, [109] so in principle epoxybased SL resins could be utilized to print chemotaxis devices. Another option is to derivatize the walls of the channel with as ilicate coating, which produces as urface that is amenable to standard silane chemistry.Ohtani et al [110] injected ahydrolyzed ethyl silicate solution (N-103X, Colcoat Co.) into the channel (part of ad roplet generator, [111] see Figure 14 c-e), then heated the device to 120 8 8Cf or 30 min to vaporize the solvent and cure the coating on the walls.A fter the hydrophilic treatment, the silicate surface was derivatized with af luorosilane compound to render it hydrophobic,w hich enabled the treated device to produce monodisperse inverted water-in-oil emulsions (Figure 14 f). Silane derivatization could enable silicate-like coatings made of allylhydridopolycarbosilane that confer polymer surfaces an electrophoretic mobility and as olvent resistance that (while retaining transparency) is indistinguishable from that of glass over at least 90 days.…”

Mikrofluidik aus dem 3D‐Drucker

“…Teilbilder (c) bis (f) aus Lit. mit Genehmigung der Japan Oil Chemists’ Society. Teilbild (g) aus Lit.…”

“…Eine andere Option ist die Derivatisierung der Kanalwandungen mit einer Silicatschicht, was eine Oberfläche ergibt, die konventioneller Silanchemie unterzogen werden kann. Ohtani et al . injizierten eine hydrolysierte Ethylsilicatlösung (N‐103X, Colcoat Co.) in den Kanal (Teil eines Tröpfchengenerators, siehe Abbildung c–e), heizten das Bauelement für 30 min auf 120 °C, um das Lösungsmittel zu verdampfen, und härteten schließlich die Beschichtung auf den Wandungen aus.…”