Simple One-Step and Rapid Patterning of PDMS Microfluidic Device Wettability for PDMS Shell Production

Abstract

Double emulsion (DE) droplets with controlled size and internal structure are a promising platform for biological analysis, chemical synthesis, and drug delivery systems. However, to further “democratize” their application, new methods that enable simple and precise spatial patterning of the surface wettability of droplet-generating microfluidic devices are still needed. Here, by leveraging the increase in hydrophilicity of polydimethylsiloxane (PDMS) due to the plasma-treatment used to permanently bond to glass, we developed a one-step method to selectively pattern the wettability of PDMS microfluidic devices for DE generation. Our results show that both Aquapel-treated and 1H,1H,2H,2H-Perfluorodecyltriethoxysilan (PFDTES)-treated devices are functionally showing the generality of our method. With the resulting microfluidic devices, both water-in-oil-in-water (w/o/w) and oil-in-water-in-oil (o/w/o) DE droplets can be produced. Using a PDMS mixture containing cross-linking agents, we formed PDMS microcapsules by solidifying the shell layer of water-in-PDMS-in-water DE droplets. We also characterize the morphological properties of the generated droplets/microcapsules. We anticipate the method developed in this work could be used in a broad range of applications of DE droplets.

Chameleon-Inspired Mechanochromic Photonic Elastomer with Brilliant Structural Color and Stable Optical Response for Human Motion Visualization

“…After curing, the PE with a sandwich structure (PDMS/PS@SiO 2 /PDMS composite film) was successfully prepared (see Section 2 , Materials and Methods for details). Due to the excellent mechanical properties of PDMS [ 44 , 45 ], the resultant PE exhibited excellent flexibility and mechanical compliance when subjected to typical deformations, including twisting, bending and stretching (discussed below), making this an ideal candidate for wearable electronics ( Figure 2 b). Obviously, the highly ordered assemblies and uniform sizes of the PS@SiO 2 PC and corresponding PS PCs, which are close-packed face-centered-cubic (FCC) structures, can be clearly seen in Figure 2 c and Figure S1 .…”

Optimizing the Production of Hydrogel Microspheres Using Microfluidic Chips: The Influence of Surface Treatment on Droplet Formation Mechanism

“…Surface treatment is commonly used to alter the hydrophobicity of microfluidic chip channels. Previous studies have reported several methods for modifying polydimethylsiloxane (PDMS) chips to obtain different properties, including depositing poly­(vinyl alcohol) (PVA) to form superhydrophilic channel surfaces and Aquapel treatment to obtain hydrophobic channels. , However, studies on the surface treatment of channels often overlook the comprehensive impact of other influencing factors (e.g., solution viscosity and flow rate ratio) on droplet behavior. Additionally, the experiment of modifying PDMS channels with PVA is intricate due to temperature control and plasma treatment.…”

Alignment-free construction of double emulsion droplet generation devices incorporating surface wettability contrast

“…11 The hydrophilic state of plasma treated PDMS can also be readily recovered by infusing PFDTES (1 H ,1 H ,2 H ,2 H -perfluorodecyltriethoxysilane) while using compressed air to prevent liquid flow to undesired paths. 12 Both methods are complex to implement, given the requirement for temporary gas sealing. In a similar process, but using sol–gel materials, 16 fluid confinement for regional treatment can be achieved by flushing two liquids simultaneously into a channel generating a sharp affinity interface.…”

“…Previously, several solutions to engineer the wettability of PDMS for double emulsion generation have been shown in either pre-or post-chip sealing layers, including those created with plasma oxidation, [10][11][12][13] sol-gel deposition, [14][15][16] layer-bylayer deposition, 17 polymer coating, 18,19 and surfactant use. 20 For example, the selective plasma oxidation creates silanol groups altering surface properties from hydrophobic to hydrophilic.…”