Tunable Mechanical Response of Self-Assembled Nanoparticle Superlattices

Self-assemblednanoparticle superlattices (NPSLs) arean emergentclass of self-architected nanocomposite materials that possess promisingproperties arising from precise nanoparticle ordering. Their multiplecoupled properties make them desirable as functional components indevices where mechanical robustness is critical. However, questionsremain about NPSL mechanical properties and how shaping them affectstheir mechanical response. Here, we perform in situ nanomechanical experiments that evidence up to an 11-fold increasein stiffness (similar to 1.49 to 16.9 GPa) and a 5-fold increase in strength(similar to 88 to 426 MPa) because of surface stiffening/strengtheningfrom shaping these nanomaterials via focused-ion-beam milling. Topredict the mechanical properties of shaped NPSLs, we present discreteelement method (DEM) simulations and an analytical core-shellmodel that capture the FIB-induced stiffening response. This workpresents a route for tunable mechanical responses of self-architectedNPSLs and provides two frameworks to predict their mechanical responseand guide the design of future NPSL-containing devices.