PDMS stamps

Kim, Y.-K. Kim, G T. Ha, J. S. 2007. Simple patterning via adhesion between a buffered-oxide etchant-treated PDMS stamp and a Si02 substrate Adv. Fund. Mater. 17 2125-2132. 

Fig. 9.13 a) Preparation of laterally structured SAMs by the microcontact printing (pCP) technique. A structured PDMS stamp is inked with self-assembling molecules (hexa-decanethiols HDT) and placed onto a planar substrate (gold). SAM formation occurs within seconds at the areas of contact (I). The structure can be further processed by etching (II) or deposition of a second SAM (III) onto... 

Microcontact printing (p-CP) is another technique that can be used to place NAs onto different target surfaces. This technique makes use of an elastomeric stamp of polydimethylsiloxane (PDMS) and produces features with lateral resolution in the submicrometer range. The PDMS stamp is topographically structured by casting a PDMS prepolymer against a 3D master. The stamp is then inked with the molecules of interest, rinsed with buffer, blown dry under a stream of nitrogen, and then used to print the material onto the substrate surface (see Fig. 20). 

The transfer of the printing material from the PDMS stamp to the support is a process driven by a careful balance based upon the affinity of the two surfaces (that of the stamp and that of the substrate) for the NA molecules. The surface of the PDMS stamp has to be attractive enough to DNA molecules to... 

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]... 

An amino-functionalized TPEDA SAM was synthesized onto a glass surface as described previously. Then a PDMS stamp previously inked in an acetonitrile solution of the fluorophore (TAMRA or lissamine) was brought into contact with the SAM for a few seconds, resulting in the covalent attachment of the fluorophore to the layer. The slide was subsequently immersed in an acetonitrile solution of a reactive molecule for the attachment of the binding groups onto the surface (i.e., urea or amide) at the sites of the unreacted surface amino groups (Fig. 10). 

Microcontact Printing. An ink of alkanethiols is spread on 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. 

Microtransfer Moulding. A PDMS stamp is filled with a prepolymer or ceramic precursor and placed on a substrate. The material is cured and the stamp is removed. The technique generates features as small as 250 nm and is able to generate multilayer systems. 

Micromoulding in Capillaries. Continuous channels are formed when a PDMS stamp is brought into conformal contact with a solid substrate. Capillary action fills the channels with a polymer precursor. The polymer is cured and the stamp is removed. 

Solvent-assisted Microcontact Moulding. A small amount of solvent is spread on a patterned PDMS stamp and the stamp is placed on a polymer, such as a photoresist. The solvent swells the polymer and causes it to expand to fill the surface relief of the stamp. 

Fig. 1. Schematic procedures for pCP (A) printing on a planar substrate with a planar PDMS stamp (B) printing on a planar substrate with a rolling stamp and (C) printing on a curved substrate with a planar stamp...

After the patterns on these polymer films are transferred into photoresist films coated on silicon substrates using photolithography, the developed photoresist patterns can serve as a master to make the required PDMS stamps. By combining this method of rapid prototyping with soft lithographic techniques, we can fabricate patterned microstructures of polymers and metals within 24 h of the time that the design is completed. Rapid prototyping makes it possible to produce substantial numbers of simple microstructures rapidly and inexpensively. 

Chick embryo heart muscle cells were patterned and grown on a fibronectin (FN) surface patterned by PDMS stamping. The PBS solution (containing Ca2+ and K+) was used to stimulate spontaneous muscle contraction [198]. Laminar flows provide a reaction path (buffer plus 1-octanol) and a control patch (buffer only) for study of communication between excitable cells (cardiomyocytes) through gap junctions (see Figure 8.18) [198]. 

Andres and coworkers demonstrated the iCP of densely packed alkanethiolate-functionalized Au nanoparticle arrays in monolayer and multilayer structures.81,82 Dense and hexagonally packed monolayers of nanoparticles were first assembled on a water surface. By using the Langmuir-Schafer technique, the Au nanoparticle monolayer was transferred to a PDMS stamp, and printed onto a substrate. Multilayers were prepared by repeating the printing process in an LbL scheme, in which subsequent particle layers may be made up of the same or different types of particles. Similarly, the assembly of irregular, densely packed monolayers of polystyrene nanoparticles on iCP substrates via carbodiimide coupling was reported.83 The conformal contact of the carbodiimide-functionalized polystyrene particles resulted in the covalent attachment of the nanoparticles at a carboxylate-functionalized surface. 

Wolf et al. introduced the self-assembly, transfer, and integration (S ATI) of nanoparticles with high placement accuracy.86 87 Silica and polymer nanoparticles were positioned on a PDMS stamp through convective assembly (Fig. 13.14). By controlling the printing temperature or by using a thin polymer layer as an adhesion layer, nanoparticles of different shapes and sizes were printed onto the target substrate. 

---