Ion diode logics for pH control

Abstract

Electronic control over the generation, transport, and delivery of ions is useful in order to regulate reactions, functions, and processes in 5 various chemical and biological systems. Different kinds of ion diodes and transistors that exhibit non-linear current versus voltage characteristics have been explored to generate chemical gradients and signals. Bipolar membranes (BMs) exhibit both ion current rectification and water splitting and are thus suitable as ion diodes for the regulation of pH. To date, fast switching ion diodes have been difficult to realize due to accumulation of ions inside the device structure at forward bias -charges that take a long time to deplete at reverse bias. Water splitting occurs at elevated reverse voltage bias and is a feature that renders high ion current rectification impossible. 10This makes integration of ion diodes in circuits difficult. Here, we report three different designs of micro-fabricated ion bipolar membrane diodes (IBMDs). The first two designs consist of single BM configurations, and are capable of either splitting water or providing high current rectification. In the third design, water-splitting BMs and a highly-rectifying BM are connected in series, thus suppressing accumulation of ions. The resulting IBMD shows less hysteresis, faster off-switching, and also a high ion current rectification ratio as compared to the single BM devices. Further, the IBMD was integrated in a diode-based AND gate, which is capable 15 of controlling delivery of a hydroxide ions into a receiving reservoir.

Electrical pumping of potassium ions against an external concentration gradient in a biological ion channel

“…The results are of relevance for the mechanisms regulating the transport through ion channels, [17][18][19] for electric signal transduction in cell cycle and embryogenesis, 14,16 and for building ionic circuits in the emerging field of nanofluidics. 6,[20][21][22][23][24][25] The set-up used in the experiments is shown schematically in Fig. 1.…”

Electrochemical mechanism of ion current rectification of polyelectrolyte gel diodes

“…The ionic groups of polyelectrolyte gels are essentially immobile (and thus are treated as uniform fixed charges), and, in contrast, their counterions freely diffuse in the entire volume of the system; our model thus extends the treatments of these ions that have been developed in soft matter physics [17][18][19][20][21][22][23] to electrochemical systems. Analogous models are used to treat electrolyzers [13][14][15]24,25 and fuel cells [26][27][28] that use polymer electrolyte membranes. We treat the cases in which counterions are not the reactants or products of electrochemical reactions.…”

“…Nanochannels of asymmetric shapes were shown to rectify ion currents that are generated by Ag/AgCl electrodes [3][4][5][6] . Polyelectrolyte gel diodes (PGDs) that are the double layers of two oppositely charged polyelectrolyte gels (that are swollen in aqueous solutions), sandwiched by two symmetric metal electrodes, are another type of ionic diodes that rectify ion currents [7][8][9][10][11][12][13][14][15][16] . These diodes are designed to operate with a physical mechanism that is analogous to conventional semiconductor diodes-the asymmetry in the permeability of ions across the interfaces between the two oppositely charged gels [8][9][10][11][12] .…”

Cylindrical glass nanocapillaries patterned via coarse lithography (>1 μm) for biomicrofluidic applications

“…In particular, the static and dynamic properties of single DNA molecule confined in nanochannels ranging from tens to hundreds of nanometers have been well characterized, 8 and applications including DNA stretching 9,10 and DNA entropic trapping 11 have been reported. Moreover, the nanofluidic ionic current diodes [12][13][14][15][16][17] and ionic field effect transistors 18,19 have been developed as active nano-electronic-fluidic devices that could possibly lead the way to a diverse set of applications ranging from biosensing 20,21 to transport of molecules. 22 To pattern nanochannels, silica-based (e.g., silicon, glass, quartz) substrates are most commonly preferred due to their robustness and compatibility with microelectronics fabrication technologies.…”