Soft-lithography process

In principle, all meltable preceramic (Si/B/N/C) polymers are suitable for the fabrication of lightweight microstructures using the soft lithography process. However, the evolution of gas during pyrolysis must not exceed a limit value to avoid the formation of macroscopic defects. 

Customized sensors to detect proteins, chemicals, and even circulating tumor cells are also highly demanded. It is difficult to develop sensors at the micro scale with high accuracy, high biocompatibility, and high compatibility with a soft lithography process. Biosensors are potential solutions for this problem [20]. However, both sensitivity and throughput rate of bio-sensors need to be improved. 

In 2000, Unger et al. first used an elastic material (PDMS) and standard soft lithography processes to demonstrate a pneumatic pump with a three-membrane-actuator layout controlled by three external electromagnetic valves (EMV)> respectively [1]. Multilayer soft lithography to fabricate the pump and typical microchannel size was... 

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.

Figure 4.1 Schematic representation of the soft lithography process.

Fiorenzo et al. reported a simple modified soft-lithography process to construct a nano- and micro-patterned silk fibroin film [9]. They claimed the creation of the smallest nanopattems in silk fibroin films. Using this technique, high quality films containing intricate 2D and 3D nano- and micropattems were fabricated. 

Various methods have been presented in the literature to fabricate microfluidic devices. One of the most widely used are those made from poly(dimethylsiloxane) (PDMS) gels [8,10]. The materials for these devices are relatively inexpensive and they can be made with established soft lithography processes. This approach also has the potential to form complicated and intricate flow patterns. The soft lithography process is robust and reproducible, which allows replicating flows in different devices that have the same design. 

FIGURE 19.1 Scanning electron micrographs of cross-sections of (a) uncoated and (b) coated PDMS channels. Rectangular PDMS channel dimensions are 50 x 35 pm. This fabrication method combines the ease of soft lithography processing with the benefits of a glass surface. (Reprinted from Abate, A. R. et al. 2008. Lab Chip 8 516-518. With permission.)... 

A number of fabrication techniques meet the general requirements for constructing an efficient and compact microreactor. Popular methods include LIGA, wet and dry etching processes, micromachining, lamination, and soft lithography. 

Fig. 8 (a) Schematic representation of the fabrication process for MIP nanopatteming using a hydrophilic PDMS stamp, (b) Dark field microscopy image of an MIP nanopattemed by soft lithography. Inset AFM topography scan of the MIP nanopattem [85]... 

The formation and replication of patterns into polymer films using instabilities is a new contribution in the field of soft lithography, which typically requires the mechanical contact between a patterned master and the resist. Two classes of instabilities were discussed. The demixing of two incompatible polymers leads to a well known spinodal pattern. In thin films, this structure formation process can be guided by a pattern in surface energy. 

Soft Lithography Lithography is essentially a process for printing features on a planar surface. Nanolithography tools, commonly referred to as soft lithography, allow precisely defined nanoscale features to be produced on a substrate, which can be removed from the substrate as free-standing 3D nano-objects. A number of techniques fall within the field of soft lithography, primarily for construction of micrometer-sized objects ... 

Fabrication of patterned magnetite films by soft lithography and thermal decomposition using Fe(acac)3 is also possible as described by Yang and coworkers . The modality to obtain such structures on gold substrates is illustrated in Scheme 8. The array size could be tuned by changing the dimension of patterns on poly(drmethylsiloxane) stamps, the concentration of Fe(acac)3 solution and the size of water droplets during the condensation process. 

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