Soft-lithography techniques

The top microfluidic architecture was fabricated using a multilayer soft lithography technique with polydimethylsiloxane (PDMS). In the figure, we illustrate a... 

Polysiloxanes are apparently the materials of choice in the new soft-lithography techniques.376 380 The method is outlined briefly in Figure 4.20. In the first step, linear (liquid) PDMS is poured over the surface of the master to be reproduced. It is then cross linked, and peeled away from the master surface. The PDMS surface containing the pattern is then coated with a hydrophobic alkane thiol, and the pattern transferred to a... 

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. 

Combining this self-assembled monolayer chemistry with AFM tip apparatus yields a new AFM-based soft lithography technique, which is often called dip-pen nanohthography (Fig. 4.42). It can be used to write very line patterns on metal and semiconductor surfaces using a solution of monolayer-forming materials as ink. 

These characteristics are typical of bottom-contact pentacene TFTs with source and drain electrodes dehned by ink-jet printing or other soft lithography techniques... 

While imprint lithography does not involve the use of an elastomeric stamp and hence is not a soft lithography technique, it is a next-generation patterning technique that has gained tremendous attention for generating nanoscale features, which is... 

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. ... 

In micromolding techniques, the aspect ratio and the lateral resolution are controlled by the poly(dimethylsiloxane) (PDMS) stamp, which is typically limited to an open channel structure (Fig. 3.57). Moreover, soft lithography techniques require cross-linking reactions that are initiated by external triggers, which leads to the introduction of potentially toxic substances in the products. 

Mkrofluidk Circuits, Fig. 7 (a) Schematic view of experimental setup for local flow ctmtrol at a T-charmel jimction [9] (Reproduced by permission of the Royal Society of Chemistry). MicroChannel structiffes and a flow EET were formed on PDMS using soft-lithography techniques. The length, width, and height of the main channel are 2 cm, 150 pm, and 10 pm, respectively, and the geometric parameters are dj = 50 pm, d2= 125 pm. 

Khademhosseini et al. [8] have successfully cultured murine embryonic stem cells in a microfiuidic array of reversibly sealed channels. These authors have proposed to position micro wells 100 pm apart using standard soft-lithography techniques, leaving sufficient room to overlay individual microchaimels addressing each pattern. Thus, the total required area per microwell would be 200 x 200 pm, with each well possibly operating under different culture conditions. Thus, 2,500 unique tests could be performed in a 1 cm area, far exceeding the capabilities of existing multiwell plates. 

Chang-Yen DA, Gale BK (2005) A monolithic PDMS waveguide system fabricated using soft-lithography techniques. J Lightwave Technol 23 2088-2093... 

Schematic representation of different variants the soft lithography process is given in the work [3], Soft lithography technique was successfully applied in the fabrication of pol)rmer patterns with dimensions down to the sub-lOOnm scale.

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