Abstract
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.
Highlights
Manufacturing of microfluidic devices is performed using a variety of lithography methods including photolithography and soft lithography
Similar to the technique performed by the surface roughness at the base of the channels is similar to the surface roughness of the initial polished metal disk.[40]
Due to the top-lid design of the microfluidic device, it is thermally bonded to a glass slide and does not affect the flow within the device
Summary
Manufacturing of microfluidic devices is performed using a variety of lithography methods including photolithography and soft lithography. Photolithography allows for patterning of features with a high resolution (1 mm under standard conditions), it requires expensive equipment, a clean room, training and often hazardous substances. Soft lithography is a technique where elastomeric stamps or moulds are used to generate the desired features on a substrate.[1] This method allows for high resolution (down to 30 nm), the manufacturing of the initial elastomeric stamp/ mould requires microlithographic methods (either photolithography or micromachining). PDMS has gained significant interest in the scientific field for the manufacturing via soft lithography and as the final material in microfluidic devices. PDMS has many desirable properties for use in microfluidics, such as inertness, biocompatibility (non-toxicity), porous to allow oxygen to diffuse through for live cells, optical
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