In-Situ Studies of Stress Environment in Amorphous Solids Using Negatively Charged Nitrogen Vacancy Centers in Nanodiamond

TL;DR

This study introduces a novel in-situ method using negatively charged nitrogen vacancy centers in nanodiamonds to measure local stress within amorphous polymers during chemical processes, providing microscopic insights into their mechanical properties.

Contribution

The paper presents a new protocol for in-situ stress measurement inside amorphous solids using nanodiamond NV centers, applicable to transparent materials at nanoscale.

Findings

Measured local pressure and strain during polymer curing and polymerization.

Probed internal shear stress in polymers in situ.

Provided microscopic explanation for tensile strength of bulk solids.

Abstract

Amorphous solids, which show characteristic differences from crystals, are common in daily usage. Glasses, gels, and polymers are familiar examples, and polymers are particularly important in terms of their role in construction and crafting. Previous studies have mainly focused on the bulk properties of polymeric products, and the local properties are less discussed. Here, we designed a distinctive protocol using the negatively charged nitrogen vacancy center in nanodiamond to study properties inside polymeric products in situ. Choosing the curing of poly dimethylsiloxane and the polymerization of cyanoacrylate as subjects of investigation, we measured the time dependence of local pressure and strain in the materials during the chemical processes. From the measurements, we were able to probe the local shear stress inside the two polymeric substances in situ. By regarding the surprisingly large shear stress as the internal tension, we attempted to provide a microscopic explanation for the ultimate tensile strength of a bulk solid. Our current methodology is applicable to any kind of transparent amorphous solids with the stress in the order of MPa and to the study of in situ properties in nanoscale. With better apparatus, we expect the limit can be pushed to sub-MPa scale.