PDMS, bonding oxidation

She et al. [128] used rolling contact to estimate the adhesion hysteresis at polymer/oxide interfaces. By plasma oxidation of the cylinders of crosslinked PDMS, silica-like surfaces were generated which could hydrogen bond to PDMS r olecules. In contrast to unmodified surfaces, the adhesion hysteresis was shown to be larger and proportional to the molecular weight of grafted polymer on the substrate. The observed hysteresis was interpreted in terms of the orientation and relaxation of polymer chains known as Lake-Thomas effect. 

The PDMS channel slab should be bonded to a cover substrate in order to create a sealed chip. This can be achieved by irreversible bonding after oxidation of the PDMS layer to create the silanol groups [170,960,1033,1043]. The PDMS surfaces can be oxidized in an 02 plasma [1033],Telsa coil [171,172], RIE system... 

On the other hand, reversible bonding of PDMS was also used. In this case, no oxidation of the PDMS layers was needed [748,858]. Although the surface... 

Figure 14.13 Peptide synthesis by p,CP.85 An oxidized PDMS stamp is inked with an IV-Boc-L-amino acid and pressed into a contact against an amino-functionalized gold substrate to yield a covalent peptide bond.

The channels in the PDMS replica are sealed by bonding a flat piece of PDMS following surface oxidization in air plasma. The oxidized PDMS surfaces bond when brought into conformal contact forming an irreversible... 

When making the bond between the top and the bottom PDMS parts of the device by plasma oxidation, the edge surface of the membrane between the top and bottom parts was aligned along the profile formed by the photoresist pattern (Figure 4.6A) using a thin layer of methanol between the two parts.25... 

Removing the PDMS stamp (to which gold has poor adhesion) from the plastic substrate transfers the gold/titania metal from the raised regions of the stamp to the substrate. The entire procedure occurs at ambient conditions with contact times less than 15 sec. Scotch tape adhesion tests further confirm that the transferred patterns are strongly bonded to the substrate. Since aluminum also readily forms surface oxides, the same interfacial chemistry can be used to generate aluminum patterns... 

Forced peptide synthesis, formation of an amide bond by physically pushing the reactants together. A plasma-oxidized flat PDMS stamp inked with an N-Boc-L-amino acid was pressed into contact with an amine monolayer on gold to form an amide bond. Following this approach, an RGD peptide ( Arg-Gly-Asp ) was synthesized and shown to support cell adhesion, and a 20-mer peptide nucleic acid ( PNA) strand was synthesized step-by-step on the surface and proven to hybridize with a 16-mer dsDNA [T. P. Sullivan et al., Angew. Chem. Int. Ed. 2004, 43, 4190]. 

These radical species then induce chain scission, radical transfer, oxidation, and disproportionation to generate functional surface groups such as hydroxyl and carboxyl moieties (Fig. 1). For some materials, such as PDMS, these activated surfaces can be bonded to fabricate channels, as shown in Fig. 2. Plasma treatment of microchannels can also be used to control surface properties by incorporating reactive molecules or... 

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