Rapid prototyping method for 3D PDMS microfluidic devices using a red femtosecond laser

A rapid prototyping technique is demonstrated which uses a red femtosecond laser to produce a metallic mould which is then directly used for the replica moulding of PDMS. The manufacturing process can be completed in less than 6 h making it a viable technique for testing new designs quickly. The technique is validated by creating a microfluidic device with channels of height and depth of 300 µm, with a ramp test structure where the height and width of the channels reduces to 100 µm to demonstrate the techniques 3D capabilities. The resulting PDMS device was easily removed from the metallic mould and closely replicated the shape aside the expected shrinkage during thermal curing. As the technique uses a single replica process, the surface roughness at the base of the channels corresponds to the un-ablated polished metal mould, resulting in a very low surface roughness of 0.361 nm. The ablated metallic mould surface corresponds to the top of the PDMS device, which is bonded to glass and does not affect the flow within the channels, reducing the need for optimisation of laser parameters. Finally, the device is validated by demonstrating laminar flow with the no-slip condition.

Nanoadhesive layer to prevent protein absorption in a poly(dimethylsiloxane) microfluidic device

Poly(dimethylsiloxane) (PDMS) is widely used as a microfluidics platform material; however, it absorbs various molecules, perturbing specific chemical concentrations in microfluidic channels. We present a simple solution to prevent adsorption into a PDMS microfluidic device. We used a vapor-phase-deposited nanoadhesive layer to seal PDMS microfluidic channels. Absorption of fluorescent molecules into PDMS was efficiently prevented in the nanolayer-treated PDMS device. Importantly, when cultured in a nanolayer-treated PDMS device, yeast cells exhibited the expected concentration-dependent response to a mating pheromone, including mating-specific morphological and gene expression changes, while yeast cultured in an untreated PDMS device did not properly respond to the pheromone. Our method greatly expands microfluidic applications that require precise control of molecule concentrations.

Enhanced microchip electrophoresis separations combined with electrochemical detection utilizing a capillary embedded in polystyrene

A polystyrene–PDMS device utilizing an embedded fused silica capillary and electrochemical detection was used for improved efficiency separations of catecholamines.

Fast selective trapping and release of picoliter droplets in a 3D microfluidic PDMS multi-trap system with bubbles

A surface acoustic wave (SAW) induces a bubble in a 3D designed multi-trap polydimethylsiloxane (PDMS) device for the selection, incubation and on-demand release of aqueous droplets from a continuous oil flow.

Continuous monitoring of adenosine and its metabolites using microdialysis coupled to microchip electrophoresis with amperometric detection

Reversibly sealed all-PDMS device with CF working electrode for continuous on-line analysis of microdialysis samples.

Droplet trapping and fast acoustic release in a multi-height device with steady-state flow

Novel multilayer PDMS device for selective storage and release of single emulsion droplets via surface acoustic waves at constant flow with a high drop rate.