How to Make a Surface Act as a Micropump. Issue 12 (17th February 2022)

• Record Type: Journal Article
• Authors: Bekir, Marek; Sharma, Anjali; Umlandt, Maren; Lomadze, Nino; Santer, Svetlana
• Is Part Of: Advanced materials interfaces. Volume 9:Issue 12(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-17
• Subjects: azobenzene containing surfactant -- light‐driven diffusioosmosis -- rate of photo‐isomerization; Materials science -- Periodicals; 620.11
• DOI: 10.1002/admi.202102395
• Languages: English
• ISSNs: 2196-7350

Abstract

Abstract: In this paper, the phenomenon of light‐driven diffusioosmotic (DO) long‐range attractive and repulsive interactions between micro‐sized objects trapped near a solid wall is investigated. The range of the DO flow extends several times the size of microparticles and can be adjusted to point towards or away from the particle by varying irradiation parameters such as intensity or wavelength of light. The "fuel" of the light‐driven DO flow is a photosensitive surfactant which can be photo‐isomerized between trans and cis ‐states. The trans ‐isomer tends to accumulate at the interface, while the cis ‐isomer prefers to stay in solution. In combination with a dissimilar photo‐isomerization rate at the interface and in bulk, this yields a concentration gradient of the isomers around single particles resulting in local light‐driven diffusioosmotic ( l ‐LDDO) flow. Here, the extended analysis of the l ‐LDDO flow as a function of irradiation parameters by introducing time‐dependent development of the concentration excess of isomers near the particle surface is presented. It is also demonstrated that the l ‐LDDO can be generated at any solid/liquid interface being more pronounced in the case of strongly absorbing material. This phenomenon has plenty of potential applications since it makes any type of surface act as a micropump. Abstract : It is shown that any surface capable to absorb a large amount of photosensitive surfactant can act as a micropump. The mechanism is based on the generation of a continuous local light‐driven diffusioosmotic flow near the surface, where the strength and direction can be triggered by changing the intensity or wavelength of incoming light.