A Novel Technique for the Characterization of Freestanding Ultrathin Film Mechanics*

The contribution of nanoconfinement to ultrathin film mechanics has challenged the field for many years. Our previous work utilized a pseudo-free-standing tensile test which relies on water as a support and has successfully been employed throughout many systems. However, the effect of water on the mechanics of nanoconfined films is unclear. Here, we developed a novel truly free-standing (in air) tensile platform to study sub-100 nm thick films. Tensile characterization of stiff glassy polymer such as polystyrene and soft semicrystalline poly(3-hexylthiophene-2,5-diyl) films has been achieved at sub-80 nm thicknesses. We report negligible differences between the moduli obtained from on water and in air measurements, leading us to conclude that water plays an insignificant role despite other factors such as confinement, which is evident in the reduced modulus of PS with decreasing thickness. Our current work is to utilize this newly developed free-standing tensile platform to provide in-situ characterization of ultrathin film deformation mechanics across multiple size scales.