Scanning Ion Conductance Microscopy

Scanning ion conductance microscopy (SICM) has emerged as a versatile tool for studies of interfaces in biology and materials science with notable utility in biophysical and electrochemical measurements. The heart of the SICM is a nanometer-scale electrolyte filled glass pipette that serves as a scanning probe. In the initial conception, manipulations of ion currents through the tip of the pipette and appropriate positioning hardware provided a route to recording micro- and nanoscopic mapping of the topography of surfaces. Subsequent advances in instrumentation, probe design, and methods significantly increased opportunities for SICM beyond recording topography. Hybridization of SICM with coincident characterization techniques such as optical microscopy and faradaic electrodes have brought SICM to the forefront as a tool for nanoscale chemical measurement for a wide range of applications. Modern approaches to SICM realize an important tool in analytical, bioanalytical, biophysical, and materials measurements, where significant opportunities remain for further exploration. In this review, we chronicle the development of SICM from the perspective of both the development of instrumentation and methods and the breadth of measurements performed.

Direct writing of 3D conjugated polymer micro/nanostructures for organic electronics and bioelectronics

3D direct writing and meniscus-guided pen writing methods, which are capable of fabricating 3D micro/nanostructures from soluble π-conjugated polymers (CPs) and CP precursors, and recent advances in these techniques are addressed in this review.

Patterning Cu nanostructures tailored for CO2 reduction to electrooxidizable fuels and oxygen reduction in alkaline media

Due to the limited availability of noble metal catalysts, such as platinum, palladium, or gold, their substitution by more abundant elements is highly advisable. Considerably challenging is the controlled and reproducible synthesis of stable non-noble metallic nanostructures with accessible active sites. Here, we report a method of preparation of bare (ligand-free) Cu nanostructures from polycrystalline metal in a controlled manner. This procedure relies on heterogeneous localized electrorefining of polycrystalline Cu on indium tin oxide (ITO) and glassy carbon as model supports using scanning electrochemical microscopy (SECM). The morphology of nanostructures and thus their catalytic properties are tunable by adjusting the electrorefining parameters, i.e., the electrodeposition voltage, the translation rate of the metal source and the composition of the supporting electrolyte. The activity of the obtained materials towards the carbon dioxide reduction reaction (CO₂RR), oxygen reduction reaction (ORR) in alkaline media and hydrogen evolution reaction (HER), is studied by feedback mode SECM. Spiky Cu nanostructures obtained at a high concentration of chloride ions exhibit enhanced electrocatalytic activity. Nanostructures deposited under high cathodic overpotentials possess a high surface-to-volume ratio with a large number of catalytic sites active towards the reversible CO₂RR and ORR. The CO₂RR yields easily electrooxidizable compounds - formic acid and carbon monoxide. The HER seems to occur efficiently at the crystallographic facets of Cu nanostructures electrodeposited under mild polarization.

Progression in the Fountain Pen Approach: From 2D Writing to 3D Free-Form Micro/Nanofabrication

The fountain pen approach, as a means for transferring materials to substrates, has shown numerous incarnations in recent years for creating 2D micro/nanopatterns and even generating 3D free-form nanostructures using a variety of material "inks". While the idea of filled reservoirs used to deliver material to a substrate via a capillary remains unchanged since antiquity, the advent of precise micromanipulation systems and functional material "inks" allows the extension of this mechanism to more high-tech applications. Herein, the recent growth in meniscus guided fountain pen approaches for benchtop micro/nanofabrication, which has occurred in the last decade, is discussed. Particular attention is given to the theory, equipment, and experimentation encompassing this unique direct writing approach. A detailed exploration of the diverse ink systems and functional device applications borne from this strategy is put forth to reveal its rapid expansion to a broad range of scientific and engineering disciplines. As such, this informative review is provided for researchers considering adoption of this recent advancement of a familiar technology.

Write-Read 3D Patterning with a Dual-Channel Nanopipette

Nanopipettes are becoming extremely versatile and powerful tools in nanoscience for a wide variety of applications from imaging to nanoscale sensing. Herein, the capabilities of nanopipettes to build complex free-standing three-dimensional (3D) nanostructures are demonstrated using a simple double-barrel nanopipette device. Electrochemical control of ionic fluxes enables highly localized delivery of precursor species from one channel and simultaneous (dynamic and responsive) ion conductance probe-to-substrate distance feedback with the other for reliable high-quality patterning. Nanopipettes with 30-50 nm tip opening dimensions of each channel allowed confinement of ionic fluxes for the fabrication of high aspect ratio copper pillar, zigzag, and Γ-like structures, as well as permitted the subsequent topographical mapping of the patterned features with the same nanopipette probe as used for nanostructure engineering. This approach offers versatility and robustness for high-resolution 3D "printing" (writing) and read-out at the nanoscale.

Local surface modification via confined electrochemical deposition with FluidFM

Hollow AFM cantilevers enable local electroplating and grafting followed by the in situ imaging of the created surface patterns.