Single-step electropolymerization patterning of a polypyrrole nanowire by ultra-short pulses via an AFM cantilever

Direct observation of surface charge and stiffness of human metaphase chromosomes

Metaphase chromosomes in which both polynucleotides and proteins are condensed with hierarchies are closely related to life phenomena such as cell division, cancer development, and cellular senescence. Nevertheless, their nature is rarely revealed, owing to their structural complexity and technical limitations in analytical methods. In this study, we used surface potential and nanomechanics mapping technology based on atomic force microscopy to measure the surface charge and intrinsic stiffness of metaphase chromosomes. We found that extra materials covering the chromosomes after the extraction process were positively charged. With the covering materials, the chromosomes were positively charged (ca. 44.9 ± 16.48 mV) and showed uniform stiffness (ca. 6.23 ± 1.98 MPa). In contrast, after getting rid of the extra materials through treatment with RNase and protease, the chromosomes were strongly negatively charged (ca. -197.4 ± 77.87 mV) and showed relatively non-uniform and augmented stiffness (ca. 36.87 ± 17.56 MPa). The results suggested undulating but compact coordination of condensed chromosomes. Additionally, excessive treatment with RNase and protease could destroy the chromosomal structure, providing an exceptional opportunity for multiscale stiffness mapping of polynucleotides, nucleosomes, chromatin fibers, and chromosomes in a single image. Our approach offers a new horizon in terms of an analytical technique for studying chromosome-related diseases.

Rapidly patterning micro/nano devices by directly assembling ions and nanomaterials

The synthesis and assembly of components are key steps in micro/nano device manufacturing. In this article, we report an optically controlled assembly method that can rapidly pattern micro/nano devices by directly assembling ions and nanomaterials without expensive physical masks and complex etching processes. Utilizing this controllable process, different types of device components (e.g., metallic and semiconductor) can be fabricated and assembled in 10–30 seconds, which is far more rapid and cost-effective than any other micro/nano fabrication method.

Self-assembled amyloid fibrils with controllable conformational heterogeneity

Amyloid fibrils are a hallmark of neurodegenerative diseases and exhibit a conformational diversity that governs their pathological functions. Despite recent findings concerning the pathological role of their conformational diversity, the way in which the heterogeneous conformations of amyloid fibrils can be formed has remained elusive. Here, we show that microwave-assisted chemistry affects the self-assembly process of amyloid fibril formation, which results in their conformational heterogeneity. In particular, microwave-assisted chemistry allows for delicate control of the thermodynamics of the self-assembly process, which enabled us to tune the molecular structure of β-lactoglobulin amyloid fibrils. The heterogeneous conformations of amyloid fibrils, which can be tuned with microwave-assisted chemistry, are attributed to the microwave-driven thermal energy affecting the electrostatic interaction during the self-assembly process. Our study demonstrates how microwave-assisted chemistry can be used to gain insight into the origin of conformational heterogeneity of amyloid fibrils as well as the design principles showing how the molecular structures of amyloid fibrils can be controlled.

FluidFM as a lithography tool in liquid: spatially controlled deposition of fluorescent nanoparticles

The atomic force microscope (AFM) is a powerful instrument for nanolithography, which is well characterized in air where the deposition process is steered by capillary action. In contrast, AFM patterning has been seldom achieved in liquid, mostly via electrochemical deposition. This study investigates the pressure-controlled local deposition of nanoparticles in a liquid environment using a FluidFM. Fluorescent 25 nm polystyrene nanospheres were chosen as nanoobjects to be dispensed because they enable both the in situ monitoring of the process by optical microscopy and the ex situ high-resolution characterization of the pattern by e.g. scanning electron microscopy. The FluidFM microchannel was filled with an aqueous solution of negatively charged nanoparticles to be delivered onto a glass surface coated with a polycation. An overpressure in the internal fluidic circuit leads to the deposition of nanoparticle dots and lines under the tip, while the force control regulates the contact between the probe and the surface. The nanoparticle adsorption process depends both on applied pressure and contact time (respectively tip velocity) and can be described using the Langmuir approximation for the random sequential adsorption model. Moreover, we observed that the force setpoint, which does not influence the capillary-driven mechanism in air, indeed affects the hydrodynamic resistance at the tip aperture and therefore the volumetric flow. The described method demonstrates the potential of FluidFM in depositing nano-sized objects in liquid with nanometre precision.