title: Pick up, move and release of nanoparticles utilizing co-non-solvency of PNIPAM brushes.
abstract: A critical complication in handling nanoparticles is the formation of large aggregates when particles are dried e.g. when they need to be transferred from one liquid to another. The particles in these aggregates need to disperse into the destined liquid medium, which has been proven difficult due to the relatively large interfacial interaction forces between nanoparticles. We present a simple method to capture, move and release nanoparticles without the formation of large aggregates. To do so, we employ the co-non-solvency effect of poly(N-isopropylacrylamide) (PNIPAM) brushes in water-ethanol mixtures. In pure water or ethanol, the densely end-anchored macromolecules in the PNIPAM brush stretch and absorb the solvent. We show that under these conditions, the adherence between the PNIPAM brush and a silicon oxide, gold, polystyrene or poly(methyl methacrylate) colloid attached to an atomic force microscopy cantilever is low. In contrast, when the PNIPAM brushes are in a collapsed state in a 30-70 vol% ethanol-water mixture, the adhesion between the brush and the different counter surfaces is high. For potential application, we demonstrate that this difference in adhesion can be utilized to pick up, move and release 900 silicon oxide nanoparticles of diameter 80 nm using only 10 × 10 μm2PNIPAM brush.
authors.affiliation: Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands. s.j.a.debeer@utwente.nl.
authors.forename: Yunlong
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Physics of Fluids, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands.
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Lopez de la Cruz
authors.affiliation: Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands. s.j.a.debeer@utwente.nl.
authors.forename: Bernard D
authors.initials: BD
authors.lastname: Kieviet
authors.affiliation: Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands. s.j.a.debeer@utwente.nl.
authors.forename: Hubert
authors.initials: H
authors.lastname: Gojzewski
authors.affiliation: Physics of Fluids, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands.
authors.forename: Adeline
authors.identifier: http://orcid.org/0000-0002-9628-8699
authors.initials: A
authors.lastname: Pons
authors.affiliation: Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands. s.j.a.debeer@utwente.nl.
authors.forename: G
authors.initials: G
authors.lastname: Julius Vancso
authors.affiliation: Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands. s.j.a.debeer@utwente.nl.
authors.forename: Sissi
authors.identifier: http://orcid.org/0000-0002-7208-6814
authors.initials: S
authors.lastname: de Beer