In nano, volume 12, issue 5 – acs nano (acs publications) static electricity images

Seeking a way to produce 3D electronic systems from 2D components, Kim et al. (DOI: 10.1021/acsnano.8b00180) developed a technique that uses a compressive buckling process. The researchers spin-cast a layer of poly(methyl methacrylate) and a layer of polyimide on a silicon wafer. They then fabricated a 2D precursor circuit onto these polymers and released the circuit onto a polydimethylsiloxane stamp, which they applied to an elastomer substrate. When the prestrain of this substrate was released, the 2D system was geometrically transformed into a 3D system by a process of guided delamination and buckling of the nonbonded regions. The researchers used this technique to create architectures ranging from interconnected bridges and coils to extended chiral structures, each embedded with n-channel Si nanomembrane metal-oxide-semiconductor field-effect transistors (MOSFETs), Si nanomembrane diodes, or p-channel Si MOSFETs. The authors suggest that this strategy could prove useful for applications in energy storage, photovoltaics, optoelectronics, and more.

Toward this end, Liese and Netz (DOI: 10.1021/acsnano.7b08479) developed a molecular model for the binding affinity of synthetic multivalent ligands onto multivalent receptors. They examined ligands against three moieties, with varying numbers of attached monovalent ligands ( n): influenza viral hemagglutinin ( n = 3), cholera toxin ( n = 5), and anthrax receptor ( n = 7). Their model, which closely matches experimental data, shows that the angular steric restriction between ligand unit and linker polymer is a key ingredient of multivalent enhancement. In addition, their model suggests that the highest gain in binding affinity is achieved with a ligand core size that matches the receptor size, and that the ideal linker length is slightly longer than the distance between receptor and core. Finally, the model indicates that multivalent ligands can only outperform monovalent ones when monovalent ligand affinity exceeds a core-size dependent threshold value. These findings, the authors suggest, could help steer multivalent drug design.

Chakkarapani et al. (DOI: 10.1021/acsnano.8b00025) report a way to superlocalize gold nanorods within aggregates, even inside the “noisy” environment of cells, by coupling two microscopy techniques. The researchers paired a dove-type prism-based light sheet microscope with a polarization-based differential interference contrast microscope. Bringing these two together into an integrated light sheet super-resolution microscopy system, they used asymmetric light scattering of a nanorod to trigger signals based on the polarizer angle. By turning the polarizer, the researchers were able to achieve controlled photoswitching. They achieved three-dimensional subdiffraction-limited super-resolution images by superlocalization of the scattering signals, made possible by the gold nanorods’ anisotropic optical properties. Varying the polarizer enabled resolution of individual nanorods, even in aggregated locations and in the inhomogeneous interior of cells. The authors suggest that this microscopy technique could be widely applicable in optics, biomedicine, and materials science.