Piercing of the Human Parainfluenza Virus by Nanostructured Surfaces.

This paper presents a comprehensive experimental and theoretical investigation into the antiviral properties of nanostructured surfaces and explains the underlying virucidal mechanism. We used reactive ion etching to fabricate silicon (Si) surfaces featuring an array of sharp nanospikes with an approximate tip diameter of 2 nm and a height of 290 nm. The nanospike surfaces exhibited a 1.5 log reduction in infectivity of human parainfluenza virus type 3 (hPIV-3) after 6 h, a substantially enhanced efficiency, compared to that of smooth Si. Theoretical modeling of the virus-nanospike interactions determined the virucidal action of the nanostructured substrata to be associated with the ability of the sharp nanofeatures to effectively penetrate the viral envelope, resulting in the loss of viral infectivity. Our research highlights the significance of the potential application of nanostructured surfaces in combating the spread of viruses and bacteria. Notably, our study provides valuable insights into the design and optimization of antiviral surfaces with a particular emphasis on the crucial role played by sharp nanofeatures in maximizing their effectiveness.

Multi-Frequency Resonance Behaviour of a Si FractalNEMS Resonator.

Novel Si-based nanosize mechanical resonator has been top-down fabricated. The shapeof the resonating body has been numerically derived and consists of seven star-polygons that forma fractal structure. The actual resonator is defined by focused ion-beam implantation on a SOIwafer where its 18 vertices are clamped to nanopillars. The structure is suspended over a 10 mtrench and has width of 12 m. Its thickness of 0.040 m is defined by the fabrication process andprescribes Young's modulus of 76 GPa which is significantly lower than the value of the bulk material.The resonator is excited by the bottom Si-layer and the interferometric characterisation confirmsbroadband frequency response with quality factors of over 800 for several peaks between 2 MHzand 16 MHz. COMSOL FEM software has been used to vary material properties and residual stressin order to fit the eigenfrequencies of the model with the resonance peaks detected experimentally.Further use of the model shows how the symmetry of the device affects the frequency spectrum.Also, by using the FEM model, the possibility for an electrical read out of the device was tested. Theexperimental measurements and simulations proved that the device can resonate at many differentexcitation frequencies allowing multiple operational bands. The size, and the power needed foractuation are comparable with the ones of single beam resonator while the fractal structure allowsmuch larger area for functionalisation.