A novel approach to finding mechanical properties of nanocrystal layers

Abstract

The onset of bifurcations during bending is used to estimate the shear modulus of silicon nanocrystal layers on PDMS.

Mechanical and Optical Properties of Stretchable Silicon Nanocrystal/Polydimethylsiloxane Nanocomposites

“…SiNCs were produced using a nonthermal plasma technique, as reported previously and described in the Experimental Section. [ 14,16,17,37 ] We characterized the SiNCs using X‐ray diffraction (XRD) and transmission electron microscopy (TEM) ( Figure ).…”

“…The average size of a single SiNC was estimated using TEM image analysis to be ≈4 nm in diameter and confirmed to be ≈3.7 nm using Scherrer broadening analysis of the XRD peaks. [ 17,38 ]…”

“…Previously, we estimated μ for nonfunctionalized SiNC layers deposited on PDMS and found a value of 345 kPa, approximately twice the value for PDMS. [ 17 ] Although the parameters influencing this value are undoubtedly complicated, we can at least use it as an approximation for the modulus of the SiNC inclusions in the composites. Our CLSM imaging confirmed that a large fraction of SiNCs are not individually dispersed within the PDMS matrix but instead are grouped together in clusters up to several hundreds of nanometers in diameter and thus have a high amount of self‐same interaction rather than exclusively interacting with the matrix, and so considering their modulus within the nanocomposite as being similar to the modulus of SiNC layers is a reasonable approximation for the purposes of our analysis.…”

“…We performed a standard uniaxial tensile test as reported previously to evaluate the mechanical properties of the plain as well as the nanocrystal‐infused PDMS. [ 17 ] Rectangular samples were cut from the cast PDMS and SiNC–PDMS composites to final dimensions of 0.8–1 cm width and 3.0–3.5 cm length, making sure to trim the edges to eliminate thickness irregularities due to surface tension between the PDMS and the mold and to measure sample thickness each time. Each rectangular sample was mounted on a custom‐built uniaxial tensile test machine and four black dots were applied on it as fiducial markers.…”

“…SiNCs are made from an abundant and nontoxic material, and exhibit exciting tunable optical properties such as photoluminescence (PL). [ 9–18 ] PDMS is a commonly used silicone‐based cross‐linking elastomer used in biomedical, industrial, microfluidic, and optoelectronic applications. [ 9,19–28 ] As a host for nanocrystals, PDMS offers easy fabrication, tunable mechanical behavior, biocompatibility, high translucency in ultraviolet (UV) through near‐infrared (NIR) spectral range, and unlike many other cross‐linked materials it has stable mechanical properties over time.…”