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Microchannel deformations due to solvent-induced PDMS swelling.
Rémi Dangla1, François Gallaire, Charles N Baroud
1LadHyX and Department of Mechanics, Ecole Polytechnique, CNRS, 91128 Palaiseau Cedex, France.
Lab on a Chip
|September 18, 2010
Summary
Swelling solvents like Hexadecane deform polydimethylsiloxane (PDMS) microchannels, causing inward roof bending. This geometry change, unlike with non-swelling oils, significantly alters droplet trajectories in soft lithography applications.
Area of Science:
- Soft lithography
- Materials science
- Fluid dynamics
Background:
- Polydimethylsiloxane (PDMS) is widely used in microfluidics but can swell when exposed to certain solvents.
- The impact of this swelling on microchannel geometry and fluid behavior is not well understood.
- Understanding solvent-PDMS interactions is crucial for reliable microfluidic device design.
Purpose of the Study:
- To experimentally quantify the geometric deformations of PDMS microchannels caused by swelling solvents.
- To investigate the relationship between solvent diffusion, PDMS swelling, and microchannel roof deformation.
- To analyze the effect of these deformations on droplet trajectories in microchannels.
Main Methods:
- Model experiments were conducted to measure solvent diffusion dynamics and PDMS volume dilation.
- PDMS microchannels of varying widths were subjected to swelling (Hexadecane) and non-swelling (perfluorodecalin) solvents.
- Optical microscopy was used to measure the inward bending (subsidence) of the microchannel roof.
- Droplet movement within the deformed microchannels was tracked and analyzed.
Main Results:
- Hexadecane caused the microchannel roof to bend inwards with a parabolic shape, up to 7 μm deformation in a 1 mm wide channel.
- The inward bending increased with channel width, reaching 28 μm in a 2 mm wide channel.
- Non-swelling perfluorinated oils did not affect the microchannel geometry.
- Droplets in swelling solvent channels were pushed to the edges, while those in non-swelling solvent channels remained centered.
Conclusions:
- Solvent-induced swelling significantly deforms PDMS microchannel geometry, particularly the roof.
- The degree of deformation is dependent on solvent type and microchannel width.
- These geometric changes critically influence droplet behavior and trajectories within microfluidic devices.
- Careful solvent selection is necessary to maintain microchannel integrity and predictable fluid flow in soft lithography.
