Dhal, BiswabhusanBiswabhusanDhalNoh, YechanYechanNohPaltasingh, Sanat NaliniSanat NaliniPaltasinghNaman, ChandrakarChandrakarNamanNemala, Siva SankarSiva SankarNemalaRathi, AparnaAparnaRathiKaushik, SuvigyaSuvigyaKaushikCapasso, AndreaAndreaCapassoNayak, Saroj KumarSaroj KumarNayakYeh, Li-HsienLi-HsienYehKalon, GopinadhanGopinadhanKalon2025-08-222025-08-222025-07-012331-8422https://doi.org/10.48550/arXiv.2507.00536https://d8.irins.org/handle/IITG2025/18577Manipulating the electrostatic double layer and tuning the conductance in nanofluidic systems at salt concentrations of 100 mM or higher has been a persistent challenge. The primary reasons are (i) the short electrostatic proximity length, ~3-10 Å, and (ii) difficulties in fabricating atomically small capillaries. Here, we successfully fabricate in-plane vermiculite laminates with transport heights of ~3-5 Å, which exhibit a cation selectivity close to 1 even at a 1000 mM concentration, suggesting an overlapping electrostatic double layer. For gate voltages from -2 V to +1 V, the K+-intercalated vermiculite shows a remarkable conductivity modulation exceeding 1400% at a 1000 mM KCl concentration. The gated ON/OFF ratio is mostly unaffected by the ion concentration (10-1000 mM), which confirms that the electrostatic double layer overlaps with the collective ion movement within the channel with reduced activation energy. In contrast, vermiculite laminates intercalated with Ca2+ and Al3+ ions display reduced conductance with increasing negative gate voltage, highlighting the importance of ion-specific gating effects under Å-scale confinement. Our findings contribute to a deeper understanding of electrostatic phenomena occurring in highly confined fluidic channels, opening the way to the exploration of the vast library of two-dimensional materials.en-USe-Printe-Print123456789/615