Photolithography soft lithography

Figure 25.1 Schematics of typical nano and micro fabrication techniques Photolithography, soft lithography, hot embossing, and direct writing. See color plates.

Design and fabrication of the objects The design and fabrication of the individual objects are two important and closely related problems in this area. Useful techniques for fabrication include the combination of photolithography and electrodeposition of metals (this technique was employed to make the objects in Figure 15B), the use of a mold (this technique was employed to make the objects in Figure 15C), soft lithography, synthesis of colloids, and reactive ion etching. Improved techniques will be needed in the future to make complex objects on a nanometer and micron scale. 

Within the last decade, comparatively inexpensive and scaleable tchniques known as soft lithography have been the focus of much development. Patterning of a substrate is afforded by using a master elastomeric stamp that contains a nanostructured pattern, known as a relief on its surface. Contrary to photolithography, the resolution of the final pattern is not limited by light diffraction, but only depends on the... 

Figure 6.65. Comparison of (a) conventional photolithography/electroplating with (b) soft lithography. Shown in (b) is replica molding which consists of the formation of a PDMS stamp, and subsequent replication of a master in a photo- or thermally curable prepoiymer. Reproduced with permission from Gates, B. D. Xu, Q. Stewart, M. Ryan, D. Willson, C. G. Whitesides, G. M. Chem. Rev. 2005, 105, 1171. Copyright 2005 American Chemical Society.

Microcontact printing ( J,CP) [17,29,30] is part of a set of nonphotolithographic fabrication techniques known as soft lithography. In iCP, features are patterned with inexpensive, elastomeric PDMS stamps (see Section 5.5.2 for details on stamp fabrication). Consequently, [iCP can be less expensive in terms of capital and operation costs compared to photolithography for patterning large-area micron- or submicron-sized, features [31,32]. 

Structures on Patterned Surfaces SAMs can be printed by soft lithography (64). A stamp is made by curing of a PDMS prepolymer on a photoresist having a pattern created by photolithography. The surface of the stamp is inked with an... 

Multianalyte detection in a single sample has been reported extensively using electrochemical, piezoelectric, electrical resistance, - and oph-capo 11,33 39 methods. The sensor arrays were fabricated by photolithography and soft lithography, - inkjet-, screen-, and pin-prinhng, - and photodeposition.i 34,i4,45 jhese techniques involve labor-intensive multistep fabrication and image analysis and pattern-recognihon codes. The monochromatic or multicolor OLED excitation platform in (micro)arrays would drastically simplify fabrication and reduce cost. 

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