Soft-lithography

Soft lithography, developed in the 1990s in George Whitesides Laboratories at Harvard University, involves printing, molding, and other mechanical processes 

Tennant, J.E. Bjorkholm, R.M D Souza, L. Eichner, R.R. Freeman, J.Z. Pastalan, L.H. Szeto, O.R. Wood, T.E. Jewell, W.M. Mansfield, W.K. Waskiewic, D.L. White, D.L. Windt, and A.A. MacDowell, Reflective mask technologies and imaging results in soft x ray projection htho graphy, J. Vac. Set Technol. B 9(6), 3176 (1991). 

Process of soft lithography (microcontacting printing method). 

Nakamatsu, R. Kometani, K. Kanda, Y. Haruyama, and S. Matsui, Bakable Lamellar Grating Fabrication by Room-Temperature Nanoimprint Using Hydrogen SUsesquioxane (HSQ), in 5th International Nanoimprint and Nanoprint Technology Conference, San Francisco, 2006, p. 231. 

Hagiwara, K. Ishibashi, M. Kokubo, H. Okuyama, and S. Fukuyama, 

Colburn, S. Johnson, S. Dample, T. Bailey, B. Choi, M. Wedlake, T. Michaelson, S. V. Sreenivasan, J. Ekerdt, and C. G. Willson, Proc. SPIE, 3676 (1999) 379. 

DAROQURE1173, Ciba Special Chemicals, http //www.basf.com. 

The relief parts of the PDMS stamp can also be used to transfer patterns. In this approach, the PDMS stamp is first filled with a polymer precursor and then pressed against the substrate. After curing (solidifying) the polymer, the PDMS stamp is removed and a pattern matching its relief parts remains on the substrate. This process is called microtransfer molding. Many other processes implement similar concepts. 

Typically, the stamp employed is created by casting prepolymers against a master patterned by conventional lithographic techniques. This stamp is then 

Microcontact Printing (mCP). An ink of alkanethiols is spread onto a patterned PDMS stamp. The stamp is then brought into contact with the substrate, which can range from coinage metals to oxide layers. The thiol ink is transferred to the substrate where it forms a self-assembled monolayer that can act as a resist against etching. 

Replica Moulding. A PDMS stamp is cast against a conventionally patterned master. Polyurethane is then moulded against the secondary PDMS master. 

In this way, multiple copies can be made without damaging the original master. 

The first step involving the preparation of master is spin coating of silicon wafer with SU-8 negative resist. Subsequently, UV exposure is carried out with a clear field mask. This is followed by the development of SU-8 master. Glass posts are placed on SU-8 master to define the inlets and reservoirs. PDMS is mixed with prepolymers having weight ratio of the base and 

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To realize micro reactors with sensing and surface-control structures, the underlying fabrication methods have to go beyond MEMS and classical micro machining [75]. Plastic and glass manufacture and also novel innovative methods such as soft lithography have to be developed further and applied. 

Deng T., Wu H.K., Brittain S.T., Whitesides G. M., Prototyping of masks, masters, and stamps/molds for soft lithography using an office printer and photographic reduction, Anal. Chem. 2000 72 3176-3180. 

Xia Y, Whitesides GM (1998) Soft lithography. Angew Chem Int Ed Engl 37 550-575... 

Hsu JWP (2005) Soft lithography contacts to organics. Mater Today 8 42-54... 

Zhou, W. et al. 2005. Mechanism for stamp collapse in soft lithography. Appl. Phys. Lett. 87 251925. 

Huang, Y. Paloczi, G. T. Scheuer, J. Yariv, A., Soft lithography replication of polymeric microring optical resonators, Opt. Exp. 2003, 11, 2452 2458... 

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

Multilayer sheet extrusion, VDC copolymers in, 25 725, 734 Multilayer soft lithography, for lab-on-a-chip valves, 26 975... 

Soft independent modeling of class analogy (SIMCA), 10 330 Soft lithography, 15 192... 

Whitesides, G. M. Soft lithography, in Seigel, R. W., Hu, E. and Roco, M. C. (eds), R D Status and Trends in Nanoparticles, Nanostructured Materials and Nanodevices in the United States, International Technology Research Institute, Baltimore, MD, USA, 1998. 

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. 

A new methodology, which combines traditional (top-down) lithography and self-assembly (bottom-up) approaches, has been developed for fabrication of complex nanoscale colloidal stmctures on a surface over a large domain. The principle of this method is to create a chemically patterned surface by well-established soft lithography, followed by self-assembling nanoparticles selectively deposited... 

Dip-pen nanolithography (Jiang and Stupp 2005) and soft lithography (Hung and Stupp 2007) have been used to control the placement and orientation of PA nanofibers on two-dimensional substrates. The soft lithographic technique is the more... 

Hung AM, Stupp SI. Simultaneous self-assembly, orientation, and patterning of peptide-amphiphile nanofihers by soft lithography. Nano Lett 2007 7 1165-1171. 

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