Effects of embedded surfactants on the surface properties of PDMS; applicability for autonomous microfluidic systems

Hydrophilic surface modification of polydimetylsiloxane‐co‐2‐hydroxyethylmethacrylate (PDMS‐HEMA) by Silwet L‐77 (heptamethyltrisiloxane) surface treatment

“…To study the effect of Silwet concentration on the hydrophilic surface modification, we treated PDMS‐HEMA films with different Silwet L‐77 concentrations of 0.02%, 0.04%, 0.08%, 0.12%, 0.16%, and 0.2%, while the contact angle of water droplets for each treated specimen was measured (Figure ). It was observed after the treatment with 0.02% Silwet that the WCA decreased dramatically from 104.24° to 24.45°, and this decrease continues with increasing heptamethyltrisiloxane concentration (Figure A), which is consistent with previously reported works . Heptamethyltrisiloxane and related surfactants have been used to modify PDMS, with reported works indicating its effectiveness above critical wetting concentration .…”

“…A surfactant surface modifier which has both the hydrophilic and hydrophobic groups when dispersed in the buffer, its hydrophobic tail is simply adsorbed on the hydrophobic PDMS, thereby modifying the surface characteristics and inhibits the adsorption of analytes . Some researchers have reported the incorporation of surfactant additives onto PDMS during polymerization as a curing agent to improve the wettability of PDMS materials . While the wettability improves, the transparency of the PDMS materials modified by the method deteriorates, hence limiting its application in optical devices.…”

“…Wagner et al reported that the spreading rate of heptamethyltrisiloxane on silicon wafers was high in comparison to other surfactants tested, while Nikolov and coworkers identified heptamethyltrisiloxane solutions as the driving force to spontaneous spreading on the surface tension gradients in the air‐liquid interface, when used on hydrophobic solids. Furthermore, Ivanova et al studied wetting and spreading kinetic aqueous solutions of heptamethyltrisiloxane on a hydrophobic surface and reported that the wetting films only form above critical wetting concentration (CAC), while Radulovic et al linked the T‐shape molecular structure and the large cross‐sectional area of the hydrophobic trisiloxane chain of heptamethyltrisiloxane to its superspreading properties.…”

Polyelectrolytes layer-by-layer surface modification of PDMS microchips for the production of simple O/W and double W/O/W emulsions: From global to localized treatment

“…3) while the aqueous phase (distilled water containing 5% w of Tween 80 and methylene blue) is injected through the side channel (entry A). The pictures of 16 the droplets formed in the microchip are given in the Fig. 8.…”

“…Nevertheless, PDMS remains the most widely used material in microfluidics owing to its flexibility and transparency in UV-Visible spectrum range. This material is hydrophobic by nature and the way to render it hydrophilic in long term is challenging, as the elastomeric property of the PDMS induces its surface recovery, hence, its hydrophobicity [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”