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. Author manuscript; available in PMC: 2018 Nov 7.
Published in final edited form as: Lab Chip. 2017 Nov 7;17(22):3772–3784. doi: 10.1039/c7lc00722a

Figure 2.

Figure 2

Characterization of the ion depletion effect. (a) Configuration of the device. (b) The electroosmotic flow was mechanically blocked, forcing the ion depletion zone to continuously grow. (c) Fluorescence images the of the ion depletion process using 50 μM Alexa Fluor 488 in 1×PBS. (d) Fluorescence profile along the channel at different times shown in (c). (e) Fluorescence intensity and depletion factor in the vicinity of the NFC over time. 400 μM Alexa Fluor 488 in 1×PBS was used for the measurement. (f) Electrical resistance of a 510 nm NFC after different time lengths of depletion at 90 V. (g) COMSOL simulation of the back diffusion process of ions over time, when the depletion zone is 1000 μm long. (h) Simulated concentration in the vicinity of the central zone during the back diffusion of ions, at different initial depletion lengths and flow rates. The fluid flow is mainly caused by the uneven fluid levels in different reservoirs. (i) Electrical current through a 200 nm NFC during the back diffusion of ions. 100 mV was applied between the micropatterned Ag/AgCl electrode pair.