The surface of water provides an excellent environment for gliding movement, in both nature and modern technology, from surface living animals such as the water strider, to LangmuirBlodgett films. The high surface tension of water keeps the contacting objects afloat, and its low viscosity enables almost frictionless sliding on the surface. Here we utilize the water surface as a nearly ideal underlying support for free-standing ultra-thin films and develop a novel tensile testing method for the precise measurement of mechanical properties of the films. In this method, namely, the pseudo free-standing tensile test, all specimen preparation and testing procedures are performed on the water surface, resulting in easy handling and almost frictionless sliding without specimen damage or substrate effects. We further utilize van der Waals adhesion for the damage-free gripping of an ultra-thin film specimen. Our approach can potentially be used to explore the mechanical properties of emerging twodimensional materials.

We report a novel methodology for thin film tensile testing by floating the specimen on water surface. The tensile testing system consists of a load cell, a linear DC motor and a digital image correlating (DIC) device. E beam evaporated thin gold films have been tested as a model material. The attraction between polydimethylsiloxane (PDMS) coated grips and the specimen was used as a gripping force. By applying a tensile load through the DC motor, the load was measured through the load cell and real time strain monitoring was achieved by DIC device. The obtained mechanical properties for 500nm gold film specimens were young's modulus ~ 65 GPa, yield strength ~ 338 MPa, tensile strength ~ 378 MPa and fracture at strain ~ 0.89%. To verify the validation of introduced method, these results were compared with literature reviewed and it was similar to previously reported values.