Showing papers by "Stefan Zauscher published in 2004"

Fabrication of Stimulus-Responsive Nanopatterned Polymer Brushes by Scanning-Probe Lithography

Abstract: Stimulus-responsive, surface confined poly(N-isopropylacrylamide) (pNIPAAM) brush nanopatterns were prepared on gold-coated silicon substrates in a “grafting-from” approach that combines “nanoshaving”, a scanning probe lithography method, with surface-initiated polymerization using atom transfer radical polymerization (ATRP). The reversible, stimulus-responsive conformational height change of these nanopatterned polymer brushes was demonstrated by inverse transition cycling in water, and water−methanol mixtures (1:1, v:v). Our findings are consistent with the behavior of laterally confined and covalently attached polymer chains, where chain mobility is restricted largely to the out-of-plane direction. Our nanofabrication approach is generic and can likely be extended to a wide range of vinyl monomers.

Capture and release of proteins on the nanoscale by stimuli-responsive elastin-like polypeptide "switches".

Abstract: This article describes the fabrication and characterization of stimulus-responsive elastin-like polypeptide (ELP) nanostructures grafted onto ω-substituted thiolates that were patterned onto gold surfaces by dip-pen nanolithography (DPN). In response to external stimuli such as changes in temperature or ionic strength, ELPs undergo a switchable and reversible, hydrophilic−hydrophobic phase transition at a lower critical solution temperature (LCST). We exploited this phase transition behavior to reversibly immobilize a thioredoxin-ELP (Trx-ELP) fusion protein onto the ELP nanopattern above the LCST. Subsequent binding of an anti-thioredoxin monoclonal antibody (anti-Trx) to the surface-captured thioredoxin showed the presentation of the immobilized protein in a sterically accessible orientation in the nanoarray. We also showed that the resulting Trx-ELP/anti-Trx complex formed above the LCST could be reversibly dissociated below the LCST. These results demonstrate the intriguing potential of ELP nanostruct...

Stimulus-Responsive Poly(N-isopropylacrylamide) Brushes and Nanopatterns Prepared by Surface-Initiated Polymerization

Abstract: In this paper we report the surface-initiated polymerization of poly(N-isopropylacrylamide) (pNIPAAM), a stimulus-responsive polymer, from monolayers of ω-mercaptoundecyl bromoisobutyrate on gold-coated surfaces. pNIPAAM was polymerized in aqueous solution at a low methanol concentration at room temperature to maintain the growing pNIPAAM chains in a hydrophilic and an extended conformational state. Under these conditions thick polymer brush layers (up to 500 nm in the swollen state) are produced after 1 h of polymerization. We present a new and simple strategy to fabricate stimulus-responsive, surface-confined pNIPAAM brush nanopatterns prepared in a “grafting-from” approach that combines “nanoshaving”, a scanning probe lithography method, with surface-initiated polymerization. The reversible, stimulus-responsive conformational height change of bulk and nanopatterned polymer brushes was demonstrated by repeated cycling in water and water/methanol mixtures (1:1, v/v). Our findings are consistent with the ...

Polymer Brushes: Fabrication, Nanopatterning, Actuation and Sensing

Abstract: : We present new strategies to fabricate patterned polymer brush arrays on the micrometer and nanometer length scale by combining common lithography methods. such as scanning probe lithography (SPL) and electron beam lithography (EBL). with surface-initiated polymerization. We studied the mechanics of microcantilevers decorated with stimulus-responsive polymers (SRP) and demonstrated their possible use as sensors. amplifiers. and actuators. The use of SRP brush arrays and coated micro-cantilevers promises great potential for sensing and actuation applications in micro- fluidic and Bio-MEMS devices because of the unique way by which SRPs amplify molecular binding events and changes in the solvent environment. This is significant for the Army. where fast and simple detection of biological agents is critical for soldiers in the field. To date, little research has been done on using the conformational change of polymer thin films to amplify and transduce biological binding events. All of these concepts could be incorporated with "smart", self-sensing, piezoelectric cantilevers. Ultimately, this can lead to field-deployable. reliable. cost-effective, nanobiosensors for the detection of, for example, protein-ligand interactions.