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Hydrogel-based plasmonic sensor substrate for the detection of ethanol

: Kroh, Christoph; Wuchrer, Roland; Steinke, Nadja; Günther, Margarita; Gerlach, Gerald; Härtling, Thomas

Fulltext ()

Sensors. Online journal 19 (2019), No.6, Art. 1264, 10 pp.
ISSN: 1424-8220
ISSN: 1424-8239
ISSN: 1424-3210
Bundesministerium für Bildung und Forschung BMBF (Deutschland)
03VP01970; VIP+
Journal Article, Electronic Publication
Fraunhofer IKTS ()
plasmonic; ethanol sensor; hydrogel; nanostructure; hydrogel swelling; refractive index sensor; in-line sensor

The in-line monitoring of ethanol concentration in liquids is a crucial part of process monitoring in breweries and distilleries. Current methods are based on infrared spectroscopy, which is time-consuming and costly, making these methods unaffordable for small and middle-sized companies. To overcome these problems, we presented a small, compact, and cost-effective sensing method for the ethanol content, based on a nanostructured, plasmonically active sensor substrate. The sensor substrate is coated with an ethanol-sensitive hydrogel, based on polyacrylamide and bisacrylamide, which induces a change in the refractive index of the substrate surface. The swelling and shrinking of such hydrogels offer a means to measure the ethanol content in liquids, which can be determined in a simple transmittance setup. In our study, we demonstrated the capability of the sensor principle for the detection of ethanol content ranging from 0 to 30 vol% ethanol. Furthermore, we determined the response time of the sensor substrate to be 5.2 min, which shows an improvement by a factor of four compared to other hydrogel-based sensing methods. Finally, initial results for the sensor’s lifetime are presented.