Aging of Silicon Nanocrystals on Elastomer Substrates: Photoluminescence Effects

Mechanical behavior of SiNC layers on PDMS: effects of layer thickness, PDMS modulus, and SiNC surface functionality

Thin layers of nanomaterials on stretchable substrates have the potential to enable stretchable, bendable optoelectronic devices, wearable diagnostics, and more. Recently, our group reported on a novel method for finding the neo-Hookean coefficient of thin layers of silicon nanocrystals (SiNCs) on polydimethylsiloxane (PDMS). Here we elaborate on that initial study by examining the effects of the SiNC layer thickness, PDMS neo-Hookean coefficient, and SiNC surface functionality on the neo-Hookean coefficient of the SiNC layers. We found that, while the layer thickness and PDMS neo-Hookean coefficient influence the behavior of the SiNC layers, layers of surface-functionalized SiNCs do not exhibit disparate behavior from layers of bare SiNCs.

Experimental/theoretical estimations of the neo-Hookean coefficients of SiNC layers on PDMS show a dependence on layer thickness as well as on the modulus of the PDMS, but not on the surface functionality of the SiNCs.

A novel approach to finding mechanical properties of nanocrystal layers

Flexible, bendable, stretchable devices represent the future of electronics for a wide range of real-world applications. Due to the fact that these technologies deviate significantly from traditional wafer technologies there is a need to understand and engineer material systems that allow large elastic deformations present in such devices, which requires knowledge about the mechanical properties of these material systems. Here we evaluate the mechanical properties of a bilayer polydimethylsiloxane (PDMS)/silicon nanocrystal system. By observing the formation of instabilities due to finite bending deformation and applying theoretical modeling, we estimated the neo-Hookean coefficient (analogous to shear modulus at low stress/strain) of the silicon nanocrystal film to be 345 ± 23 kPa. The method used here represents a novel approach to evaluating these properties and is widely applicable to many different combinations of systems of nanocrystals and elastomers.

Excluded Volume Approach for Ultrathin Carbon Nanotube Network Stabilization: A Mesoscopic Distinct Element Method Study

Ultrathin carbon nanotube films have gathered attention for flexible electronics applications. Unfortunately, their network structure changes significantly even under small applied strains. We perform mesoscopic distinct element method simulations and develop an atomic-scale picture of the network stress relaxation. On this basis, we put forward the concept of mesoscale design by the addition of excluded-volume interactions. We integrate silicon nanoparticles into our model and show that the nanoparticle-filled networks present superior stability and mechanical response relative to those of pure films. The approach opens new possibilities for tuning the network microstructure in a manner that is compatible with flexible electronics applications.