Fig. 4

Actuation of sucking disk-type (SD) strip biosensor embedded with CNPs/APTS/GOx-treated sensing paper. a Schematic and optical images image of the sucking disk-type (SD) strip sensor. The CNPs/APTS/GOx-treated sensing paper was inserted in the reaction chamber. Scale bar = 5 mm. b Schematic image of the optical system to capture the colorimetric images of the CNPs/APTS/GOx-treated sensing paper in the reaction chamber with a tiny window to the SD strip biosensor. c Real image (original) and normalized image (filtered) of the sensing paper in the reaction chamber of SD strip biosensor before and after treatment of glucose solution (1.2 mM). The normalized image was obtained with an image processing algorithm. d Correction test for comparison of sensing paper performance. We monitored color variation by calculating the normalized blue (normalized b) value between sensing paper before and after being loaded into the SD strip biosensor. Data were presented as the mean ± standard deviation (n = 5). NS: No significant difference