Bonding and in‐channel microfluidic functionalization using the huisgen cyclization

Abstract

The bonding of layers of silicone elastomers during the manufacturing of microfluidic devices is often accomplished using plasma oxidation. The process can be costly, may require a clean room and materials that ensure the flatness of the bonding layers and, as a consequence of hydrophobic recovery, can lead to high variability in the degree of adhesion. As importantly, the process precludes incorporation of chemical functionalities that work as anchors to immobilize biomolecules within the microfluidic channel. We hypothesized that it would be possible to fabricate microfluidic channels using the Huisgen 1,3-dipolar cycloaddition of azides to alkynes to crosslink silicones and form PDMS elastomers and, in a subsequent step, bond one PDMS layer to another simply by heating, with the added advantage of producing microfluidic channels with embedded chemical functionalities. After thermal bonding, the microfluidic devices underwent cohesive failure (rupture of the elastomer layer) at $145 kPa during pressure tests, but did not exhibit adhesive failure (delamination), showing that the azide-alkyne reaction provides a strong bond between elastomer layers. Furthermore, the internal microfluidic channel surfaces retained alkyne and azide functionality during the process, as shown by the grafting of one or more fluorescent dyes, through Huisgen cyclization.

New Control Over Silicone Synthesis using SiH Chemistry: The Piers–Rubinsztajn Reaction

“…[47] Rambarran et al showed that, following the PR reaction,H uisgen or azide/alkyne click reactions could be used to create silicone/PEG (or cyclodextrin) surfactants (Figure 9B), [48] elastomers ( Figure 9C), [49] copolymers [50] or adhesives. [51] The most important orthogonal reaction in silicone systemsisp latinum-catalyzed hydrosilylation (see below). [52]…”

Purple to Yellow Silicone Elastomers: Design of a Versatile Sensor for Screening Antioxidant Activity

“…They may be prepared in flat sheets, as described here, but also in much more complex forms, including via 3D printing . The DPPH elastomer here constitutes an example of a responsive polymer, which are of increasing value in a wide variety of (bio)analytical assays, including microfluidic technologies that are used to measure antioxidant activity of target molecules . This practical, easy to fabricate sensor may be prepared in a variety of physical formats, and can be optimized to test for antioxidant activity in a variety of liquid media.…”

Layer-by-Layer Assembly of Microgel Colloidal Crystals via Photoinitiated Alkyne–Azide Click Reaction

“…The azide- and alkyne-modified microgel spheres in the samples were selectively labeled with FAM alkyne (5-isomer) and sulfo-cyanine5 azide fluorescence dye, respectively, using copper-catalyzed azide–alkyne click reaction. 61 Initially, stock solutions of the dyes with a concentration of 1 mg/mL were prepared using a mixed solvent (9:1 v/v deionized water–DMSO mixture). Then, a mixed solution containing ∼1 × 10 –3 mg/mL FAM alkyne (5-isomer), 1.3 mg/mL CuSO 4 ·5H 2 O, and 1.7 mg/mL l -ascorbic acid was prepared.…”

“…Prior to imaging, the samples were initially fluorescently stained. The azide- and alkyne-modified microgel spheres in the samples were selectively labeled with FAM alkyne (5-isomer) and sulfo-cyanine5 azide fluorescence dye, respectively, using copper-catalyzed azide–alkyne click reaction . Initially, stock solutions of the dyes with a concentration of 1 mg/mL were prepared using a mixed solvent (9:1 v/v deionized water–DMSO mixture).…”