Generation of Local Diffusioosmotic Flow by Light Responsive Microgels

Here we show that microgels trapped at a solid wall can issue liquid flow and transport over distances several times larger than the particle size. The microgel consists of cross-linked poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-AA) polymer chains loaded with cationic azobenzene-containing...

Ausführliche Beschreibung

Bibliographische Detailangaben
Veröffentlicht in:Langmuir : the ACS journal of surfaces and colloids. - 1992. - 38(2022), 20 vom: 24. Mai, Seite 6343-6351
1. Verfasser: Sharma, Anjali (VerfasserIn)
Weitere Verfasser: Bekir, Marek, Lomadze, Nino, Jung, Se-Hyeong, Pich, Andrij, Santer, Svetlana
Format: Online-Aufsatz
Sprache:English
Veröffentlicht: 2022
Zugriff auf das übergeordnete Werk:Langmuir : the ACS journal of surfaces and colloids
Schlagworte:Journal Article
Beschreibung
Zusammenfassung:Here we show that microgels trapped at a solid wall can issue liquid flow and transport over distances several times larger than the particle size. The microgel consists of cross-linked poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-AA) polymer chains loaded with cationic azobenzene-containing surfactant, which can assume either a trans- or a cis-state depending on the wavelength of the applied irradiation. The microgel, being a selective absorber of trans-isomers, responds by changing its volume under irradiation with light of appropriate wavelength at which the cis-isomers of the surfactant molecules diffuse out of the particle interior. Together with the change in particle size, the expelled cis-isomers form an excess of the concentration and subsequent gradient in osmotic pressure generating a halo of local light-driven diffusioosmotic (l-LDDO) flow. The direction and the strength of the l-LDDO depends on the intensity and irradiation wavelength, as well as on the amount of surfactant absorbed by the microgel. The flow pattern around a microgel is directed radially outward and can be maintained quasi-indefinitely under exposure to blue light when the trans-/cis-ratio is 2/1, establishing a photostationary state. Irradiation with UV light, on the other hand, generates a radially transient flow pattern, which inverts from inward to outward over time at low intensities. By measuring the displacement of tracer particles around neutral microgels during a temperature-induced collapse, we can exclude that a change in particle shape itself causes the flow, i.e., just by expulsion or uptake of water. Ultimately, it is its ability to selectively absorb two isomers of photosensitive surfactant under different irradiation conditions that leads to an effective pumping caused by a self-induced diffusioosmotic flow
Beschreibung:Date Revised 24.05.2022
published: Print-Electronic
Citation Status PubMed-not-MEDLINE
ISSN:1520-5827
DOI:10.1021/acs.langmuir.2c00259