Iontronic circuit-based logic gating of molecules Zhenyu Zhang 1,2 , Barak Sabbagh 3 , and Gilad Yossifon 1 1 School of Mechanical Engineering, Tel-Aviv University, Israel, 2 School of Mechanical Engineering, Southeast University, China, 3 Faculty of Mechanical Engineering, Technion–Israel Institute of Technology, Israel Iontronic devices commonly consist of nanometer-size fluidic structures (e.g., nanochannels, ion exchange nanoporous membranes) that exhibit ion permselectivity due to the overlap of their electric double layers 1 . Previous studies on iontronic circuits have primarily focused on single diode-based logic gates 2 . The integration of multiple iontronic components and logic gates into an iontronic circuit enables precise and controlled delivery of ions or charged molecules and promises significant advancements in analog computing, biomimetics, and complex molecule delivery systems 2,3,4 . Here we present the construction of logic gate circuits based on microfluidic bipolar ionic diodes as ion-controlled devices for charged molecule manipulation 5 . Cation and anion exchange polyelectrolyte membranes are chosen for the bipolar diodes. We demonstrate rectification of ion current and fluorescent molecule transport in a single bipolar diode, followed by the integration of three ionic diodes on a microfluidic chip to implement an OR logic gate. Both electrical and optical output signals display high consistency, correlating with discrete low and high logic levels. Using Poisson-Nernst-Planck equations, we systematically conduct numerical simulations to elucidate the non-ideal selectivity mechanism through the bipolar diode junction for both ions and charged molecules. Further results uncover the design principles for constructing logic circuits based on bipolar diodes. Additionally, we investigate the gating of molecules through an iontronic circuit comprising of nanofluidic field-effect-transistors (FETs), which provide enhanced integration levels and improved molecule transport control. We conclude by comparing the ion/molecule gating mechanisms and fabrication challenges of microfluidic bipolar diode and nanofluidic FET-based iontronic circuits. References 1. Stein, D.; Kruithof, M.; Dekker, C. Surface-charge-governed ion transport in nanofluidic channels. Phys. Rev. Lett. 2004 , 93 (3), 035901. 2. Chun, H.; Chung, T. D. Iontronics. Annu. Rev. Anal. Chem . 2015 , 8, 441-462. 3. Han, J. H.; Kim, K. B.; Kim, H. C.; Chung, T. D. Ionic circuits based on polyelectrolyte diodes on a microchip. Angew. Chem. Int. Ed. 2009 , 48 (21), 3830-3833. 4. Karnik, R.; Castelino, K.; Majumdar, A. Field-effect control of protein transport in a nanofluidic transistor circuit. Appl. Phys. Lett. 2006 , 88 (12), 123114. 5. Sabbagh, B.; Zhang, Z.; Yossifon, G. Logic gating of low abundance molecules using polyelectrolyte-based diodes. Faraday Discuss. 2023 (Accepted).
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