Capillary filling is the key phenomenon in plar chromatography techniques such as paper chromatography and thin layer chromatography. Recent advances in micro/notechnologies allow the fabrication of noscale structures that can replace the traditiol statiory phases such as paper, silica gel, alumi, or cellulose. Thus, understanding capillary filling in a nochannel helps to advance the development of plar chromatography based on fabricated nochannels. This paper reports an alysis of the capillary filling process in a nochannel with consideration of electroviscous effect. In larger scale channels, where the thickness of electrical double layer (EDL) is much smaller than the characteristic length, the formation of the EDL plays an insignificant role in fluid flow. However, in nochannels, where the EDL thickness is comparable to the characteristic length, its formation contributes to the increase in apparent viscosity of the flow. The results show that the filling process follows the Washburn's equation, where the filled column is proportiol to the square root of time, but with a higher apparent viscosity. It is shown that the electroviscous effect is most significant if the ratio between the channel height (h) and the Debye length (? -1) reaches an optimum value (i.e. ?h 蠴). The apparent viscosity is higher with higher zeta potential and lower ion mobility.
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