Fig. 3
Flexible, transparent fingerprint sensor. a Schematic illustration of the fingerprint sensor structure. b Photograph of the transparent fingerprint sensor. Scale bar, 1 mm. c Optical transmittance spectrum of the transparent fingerprint sensor (w/ and w/o cellulose nanofiber (CNF)–AgNF layer, thickness: 100 μm). d Optimized transmittance at the wavelength of 550 nm and a dielectric constant at a frequency of 1 MHz with various cover layer films. e Real-time single-cell capacitance change according to the ridge–valley position change. f Capacitance change depends on the fingerprint ridge and valley with various cover layers. g Captured 2 mm × 2 mm fingerprint pattern
