Analytic theory of nonlinearly coupled electrokinetics in nanochannels

Abstract

The nonlinear electrokinetic response of ionic solutions is important in nanofluidics. However, quantitatively understanding the mechanisms is still a challenging problem because of a lack of analytic approaches. Here, a general framework for calculating the nonlinear electrokinetic coefficients of strongly confined electrolytes is constructed using a perturbation scheme of the pressure and voltage differences across a nanochannel. The theory is applied to an electrically neutral nanochannel filled with electrolytes, and analytic expressions for the first- and third-order electrokinetic coefficients are obtained. We demonstrate that the combination of high hydrodynamic permeability and ion-wall friction plays an essential role in nonlinear electrokinetics. Furthermore, we analytically demonstrate that the external flow induces uniform excess charge inside the nanochannel.

Iontronic Neuromorphic Signaling with Conical Microfluidic Memristors

“…In particular, conical channels have garnered significant interest for such applications [14,15,[19][20][21][22][23], as they exhibit current rectification thereby acting as ionic diodes [9,19,[24][25][26]. This has been extensively studied experimentally [19,22,[27][28][29][30][31] as well as numerically [23,[32][33][34][35] and several analytic descriptions are available [25,[36][37][38]. Because of this interest cones are now comparatively easy to fabricate [39][40][41][42].…”

Iontronic neuromorphic signalling with conical microfluidic memristors

“…In particular conical channels have garnered significant interest for such applications [14][15][16][17][18], as they exhibit current rectification thereby acting as ionic diodes [9,14,[19][20][21]. This has been extensively studied experimentally [14,17,[22][23][24][25][26] as well as numerically [18,[27][28][29][30] and several analytic descriptions are available [20,[31][32][33] . Due to this interest cones are now comparatively easy to fabricate [34][35][36][37].…”

Unveiling the capabilities of bipolar conical channels in neuromorphic iontronics

“…8 The underlying functionality that underpins the memristive behaviour of conical channels is that they exhibit current rectication in the steady state. [54][55][56][57][58] Although conical channels with a homogeneous surface charge distribution are desirable as relatively simple model systems for investigating iontronic systems, 55,57,[59][60][61][62][63][64][65][66][67][68][69][70][71][72] they are not necessarily the best-performing channels for current rectication. 73 In fact, conical channels with a surface charge distribution that changes sign as a function of the distance to the tip are known to exhibit a much stronger current rectication than homogeneously charged ones.…”