Position-resolved Surface Characterization and Nanofabrication Using an Optical Microscope Combined with a Nanopipette/Quartz Tuning Fork Atomic Force Microscope

In this work, we introduce position-resolved surface characterization and nanofabrication using an optical microscope(OM) combined with a nanopipette-based quartz tuning fork atomic force microscope(nanopipette/QTF-AFM) system. This system is used to accurately determine substrate position and nanoscale phenomena under ambient conditions. Solutions consisting of 5 nm Au nanoparticles, nanowires, and polydimethylsiloxane(PDMS) are deposited onto the substrate through the nano/microaperture of a pulled pipette. Nano/microscale patterning is performed using a nanopipette/QTF-AFM, while position is resolved by monitoring the substrate with a custom OM. With this tool, one can perform surface characterization(force spectroscopy/microscopy) using the quartz tuning fork(QTF) sensor. Nanofabrication is achieved by accurately positioning target materials on the surface, and on-demand delivery and patterning of various solutions for molecular architecture.

Conductive polymer hydrogel-coated nanopipette sensor with tunable size

Nanopipette-based sensors are one of the most effective tools for detecting nanoparticles,bioparticles,and biomolecules.Quantitative analysis of nanoparticles with different shapes and electrical charges is achieved through measurement of the blockage currents that occur when particles pass through the nanopore.However,typical nanopipette sensors fabricated using a conventional needle-pulling method have a typical pore-diameter limitation of around 100 nm.Herein,we report a novel conductive hydrogel-composited nanopipette sensor with a tunable inner-pore diameter.This is made by electrodepositing poly(3,4-ethylenedioxythiophene)polystyrene sulfonate onto the surface of a nanopipette with a prefabricated sacrificial copper layer.Because of the presence of copper ions,the conductive polymer can stably adhere to the tip of the nanopipette to form a nanopore;when nanoparticles pass through the conductive nanopore,more distinct blocking events are observed.The size of the nanopore can be changed simply by adjusting the electrodeposition time.In this way,suitable nanopores can be obtained for highly sensitive screening of a series of particles with diameters of the order of tens of nanometers.

Voltage-modulated polymer nanopore field-effect transistor for multi-sized nanoparticle detection

Solid-state nanopores offer a range of distinct advantages over biological nanopores,such as structural diversity and greater stability and durability;this makes them highly promising for high-resolution nanoparticle sensing.Biological nanopores can exhibit gating characteristics with stress-responsive switches and can demonstrate specificity toward particular molecules.Drawing inspiration from biological nanopores,this paper introduces a novel polymer nanopore with field-effect characteristics,leveraging a conductive polymer in its construction to showcase intriguing gating behavior.Notably,in this device,the polymer layer serves as the gate,enabling precise control over the source–drain current response inside and outside the pore by simply adjusting the gate voltage.This unique feature allows fine-tuning of the nanopore’s sensitivity to nanoparticles of varying sizes and facilitates its operation in multiple modes.Experimental results reveal that the developed polymer nanopore field-effect transistor demonstrates remarkable selectivity in detecting nanoparticles of various sizes under different applied voltages.The proposed single device demonstrates the exceptional ability to detect multiple types of nanoparticle,showcasing its immense potential for a wide range of applications in biological-particle analysis and medical diagnostics.