Nanoparticle-blockage-enabled rapid and reversible nanopore gating with tunable memory.

Gated protein channels act as rapid, reversible, and fully-closeable nanoscale valves to gate chemical transport across the cell membrane. Replicating or outperforming such a high-performance gating and valving function in artificial solid-state nanopores is considered an important yet unsolved challenge. Here we report a bioinspired rapid and reversible nanopore gating strategy based on controlled nanoparticle blockage. By using rigid or soft nanoparticles, we respectively achieve a trapping blockage gating mode with volatile memory where gating is realized by electrokinetically trapped nanoparticles near the pore and contact blockage gating modes with nonvolatile memory where gating is realized by a nanoparticle physically blocking the pore. This gating strategy can respond to an external voltage stimulus (∼200 mV) or pressure stimulus (∼1 atm) with response time down to milliseconds. In particular, when 1,2-diphytanoyl-sn-glycero-3-phosphocholine liposomes are used as the nanoparticles, the gating efficiency, defined as the extent of nanopore closing compared to the opening state, can reach 100%. We investigate the mechanisms for this nanoparticle-blockage-enabled nanopore gating and use it to demonstrate repeatable controlled chemical releasing via single nanopores. Because of the exceptional spatial and temporal control offered by this nanopore gating strategy, we expect it to find applications for drug delivery, biotic-abiotic interfacing, and neuromorphic computing.

Anomalous mechanosensitive ion transport in nanoparticle-blocked nanopores.

Living organisms can sense extracellular forces via mechanosensitive ion channels, which change their channel conformations in response to external pressure and regulate ion transport through the cell membrane. Such pressure-regulated ion transport is critical for various biological processes, such as cellular turgor control and hearing in mammals, but has yet to be achieved in artificial systems using similar mechanisms. In this work, we construct a nanoconfinement by reversibly blocking a single nanopore with a nanoparticle and report anomalous and ultra-mechanosensitive ionic transport across the resulting nanoconfinement upon assorted mechanical and electrical stimuli. Our observation reveals a suppressed ion conduction through the system as the applied pressure increases, which imitates certain behaviors of stretch-inactivated ion channels in biological systems. Moreover, pressure-induced ionic current rectification is also observed despite the high ionic concentration of the solution. Using a combined experimental and simulation study, we correlate both phenomena to pressure-induced nanoparticle rotation and the resulting physical structure change in the blocked nanopore. This work presents a mechanosensitive nano-confinement requiring minimal fabrication techniques and provides new opportunities for bio-inspired nanofluidic applications.

Characterization and manipulation of single nanoparticles using a nanopore-based electrokinetic tweezer.

Manipulation and characterization of nanoscale objects through electrokinetic techniques offer numerous advantages compared to the existing optical methods and hold great potential for both fundamental research and practical applications. Here we present a novel electrokinetic tweezer for single nanoparticle manipulation and characterization based on electrokinetic trapping near a low-aspect-ratio nanopore. We find that this nanopore-based electrokinetic tweezer share lots of similarity with optical tweezers and can be modeled as an overdamped harmonic oscillator, with the spring constant of the system being the trap stiffness. We show that different values of ionic currents through the nanopore and trap stiffnesses are achieved when trapping nanoparticles with different sizes (down to 100 nm) and/or zeta potentials. We also demonstrate that the trap stiffness and nanoparticle position can be easily tuned by changing the applied voltage and buffer concentration. We envision that further development of this electrokinetic tweezer will enable various advanced tools for nanophotonics, drug delivery, and biosensing.