Efficient coupling between electronic and biological systems requires an interface for converting electronic signals into ionic (or chemical) signals, and vice versa, ideally with high sensitivity and speed. Unfortunately, the performances and functionalities of present electro-ionic devices poorly compare with those of their electronic and biological counterparts (e.g. transistors and synapses). Emerging fields such as iontronics, bioelectronics, or bioprotonics aim at developing a sophisticated control and sensing of the motion of ions and molecules to record and modulate biological processes, or to perform logic operations mimicking the functioning of the brain. Our project aims at exploring the potential of single-walled carbon nanotubes (SWCNTs) for 1) actively controlling and sensing the motion of ions by an unprecedently large coupling between ions (in the channel) and electrons (in the channel wall) and 2) investigating the new transport phenomena specific to the subcontinuum regime such as ionic capillary evaporation (ICE) and ionic Coulomb blockades (ICBs). Our project gathers experts with strong and complementary skills covering all project needs: SWCNT growth and characterization, fabrication and study of SWCNT-based nanofluidic and FET devices, theoretical modelling and numerical simulations of ion transport in nanochannels. All the partners have successfully collaborated in the past, notably in the frame of the ANR TRANSION project (2012-2016). METHODOLOGY. To address the objectives of the project, our methodology combines: 1) Two types of electro-nanofluidic devices allowing ion and electron transport through a single SWCNT or several SWCNTs in parallel (planar devices for their robustness, thin membranes devices for studying short SWCNTs); 2) Molecular dynamics simulations of ionic transport as a function of the surface charge and edge functions optimized using quantum calculations ; 3) Theoretical modeling (both numerical and analytical) using a variational field-theoretic approach to compute the ionic concentration and the ionic transport. PROGRAM. First, we will control the chemical moieties at tube ends to optimize their selectivity for specific types of ions (objective 1). To do so, we will i) measure ion transport through SWCNT with controlled edge functions, ii) simulate ion transport through SWCNTs with specific edge functionalization, and iii) develop theoretical models of energy-barrier regulation for reproducing the experimental features. Second, we will actively control the electronic charge of a metallic SWCNT and study the effect on the transport of ions through its inner channel (objective 2). With an application focus, we will study the performances (gating response and speed) of this ultimate ionic transistor whose ionic channel is optimally coupled to an all-around electronic gate. In experiments and simulations, we will look for i) stochastic fluctuations of conductance to evidence ICE, and for ii) periodic oscillations of conductance, the expected signature of ICBs. Third, we will investigate the ion species and surface charges in the inner channel of a semiconducting SWCNT by using it as a sensitive electronic FET sensor (objective 3). To strongly enhance the detection range and sensitivity, we will test gating methods known for their higher efficiency (solid top-gate and liquid electrolyte gate) and model the coupling between the ions inside the SWCNT and an outer electrolyte.