Microfluidic devices soft lithography

An alternative microfabrication technique is based on replication moulding. An elastomer is patterned by curing on a micromechanical mold. This technique is termed soft lithography , and is used to make blazed grating optics, stamps for chemical patterning and microfluidics devices. Soft lithography is essentially a subtractive method. 

A final mention should be made of the use of polysiloxanes in the area of microfluidics.377 381 Devices of this type have to have channels or capillaries with dimensions 10-10,000 pm, and their preparation is relatively straightforward with PDMS, using the soft-lithography techniques just described to make the required molds. 

The soft lithography method was developed for rapidly and inexpensively fabricating microfluidic devices with channels >20 pm width using... 

Although conventional soft lithography techniques can be used to fabricate nonspherical particles, the production rate is limited by the mold size, limiting mass production due to the increased complexity in parallel configuration setup, and a possible solution involves the combined use of a microfluidic device and microscope projection lithography, so that the fabrication process for nonspherical objects could be transformed into a continuous. ... 

Microflow is realized as either electroos-motic flow (EOF) or pressure-driven flow. EOF is in many cases not suitable for transport of cell media due to its high ionic strength additionally, the electrical fields may cause adverse effects on a cell population. Thus, pressure-driven flow generated by off-chip or on-chip pumps is preferable for cell assays. On-chip pumps are particularly convenient - of note, pumps formed by multilayer soft lithography have been applied to analyzing T-cell behavior in microfluidic devices [6]. 

The concept behind optical devices which incorporate liquids as a fundamental part of the optical structure can be traced at least as far back as the eighteenth century where rotating pools of mercury were proposed as a simple technique to create smooth spherical mirrors for use in reflecting telescopes. Modem microfluidics has enabled the development of a present-day equivalent of such devices, the development of which we now refer to as optofluidics. As will be described below, the capabilities in terms of fluidic control, mixing, miniaturization, and optical property tuning afforded by micro-, nano-, and electro-fluidics combined with soft lithography-based fabrication provide an ideal platform upon which to build such devices. 

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