letter . 2020 Oct 27;20(21):6116. doi: 10.3390/s20216116
© 2020 by the authors.
Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Figure 1.
Flowchart of the experimental procedure.