# gst: the strong impact on nanosheets by the weak van der Waals force

<< Van der Waals is a weak force that allows neutral molecules to attract one another through randomly fluctuating dipoles, depending on distance. Though small, its effects can be seen in the macro world, like when geckos walk up walls. >> 

<< Van der Waals forces are everywhere and, essentially, at the nanoscale everything is sticky, (..) When you put a large, flat particle on a large, flat surface, there's a lot of contact, and it's enough to permanently deform a particle that's really thin and flexible. >> 

Matt Jones. 

<< the ubiquitous, "weak" van der Waals force was sufficient to indent a rigid silver nanosheet. The phenomenon suggests possible applications in nanoscale optics or catalytic systems. >>

<< In further experiments, (..) nanospheres could be used to control the shape of the deformation, from single ridges when two spheres are close, to saddle shapes or isolated bumps when the spheres are farther apart. >> 

Mike Williams. Weak force has strong impact on nanosheets. Rice University. Dec 15, 2020. 

https://phys.org/news/2020-12-weak-strong-impact-nanosheets.html

Sarah M. Rehn, Theodor M. Gerrard-Anderson, et al. Mechanical Reshaping of Inorganic Nanostructures with Weak Nanoscale Forces. Nano Lett. doi: 10.1021/ acs.nanolett.0c03383. Dec 10, 2020. 

https://pubs.acs.org/doi/10.1021/acs.nanolett.0c03383  

Also

keyword 'van der Waals' in FonT

https://flashontrack.blogspot.com/search?q=van+der+Waals

# gst: how small particles could reshape an asteroid

<< In January 2019, NASA's OSIRIS-REx spacecraft was orbiting asteroid Bennu when the spacecraft's cameras caught something unexpected: Thousands of tiny bits of material, some just the size of marbles, began to bounce off the surface of the asteroid—like a game of ping-pong in space. Since then, many such particle ejection events have been observed at Bennu's surface. >>

AA have been studying << asteroids for a long time, and no one had ever seen this phenomenon before—these little particles getting shot off of the surface  (..) such seemingly small occurrences may add up over time—perhaps even helping to give the asteroid its telltale shape, which is often compared to a spinning top. >>

<< basic orbital calculations suggest that all of these particles should do one of two things: Jump off the surface and fall right back down or escape from Bennu's gravity and never come back. >>

<< When particles eventually land on Bennu's surface, many appear to disproportionately fall near its equator where the asteroid has a distinct bulge. As a result, these events could be reshaping the asteroid over thousands or millions of years by moving mass from its north and south to its middle. >>

Daniel Strain. How small particles could reshape Bennu and other asteroids. University of Colorado at Boulder. Sep 9, 2020.

https://phys.org/news/2020-09-small-particles-reshape-bennu-asteroids.html 

McMahon Jay W, Scheeres Daniel J, et al. Dynamical Evolution of Simulated Particles Ejected From Asteroid Bennu. J Geophys Res: Planets. 125 (8). doi: 10.1029/ 2019JE006229. May 18, 2020.

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JE006229 

Scheeres Daniel J, McMahon Jay W, et al. Particle Ejection Contributions to the Rotational Acceleration and Orbit Evolution of Asteroid (101955) Bennu. 

J Geophys Res: Planets. 125 (3). doi: 10.1029/ 2019JE006284. March 11, 2020. 

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JE006284