Introducing innovative products such as novel optoelectronics based on quantum dots, nanowires and nanorods or wear resistant coating using new nanostructures relies on having confidence in how these materials behave at the nano-scale.
Understanding the strength of materials at the nano-scale as opposed to in bulk is essential. Atomic interactions may dominate nano-scale properties and being only a few atoms thick may make a material very delicate to handle. Before the world’s most innovative manufacturers can start using nano-materials, they need to reliably measure nano-scale material properties.
Miniaturised materials and objects need miniaturised test methods. Atomic Force Microscopy (AFM) is a popular method for measuring nano-properties such as elasticity. It works by applying a load to a probe tip and measuring how much it sinks into the material. The tip is held in place by a tiny piece of material called a cantilever. Unfortunately cantilevers flex and compromise measurements by reducing the applied force. Greater accuracy in measuring cantilever stiffness and determining how much of the applied load is transferred to the test material are needed for calibrations of AFM used for measuring nano-material properties.
The EMRP project, Traceable measurement of mechanical properties of nano-objects, looked at methods for determining cantilever stiffness.
The project developed well defined nano-objects with known response to loads and used these to compare different AFM calibration methods, determining which factors have the greatest effect on measurement accuracy and how improvements can be made. Cantilever vibrations were analysed to simplify their contributions to complex calculations of the forces applied during AFM testing. The acquired measurement data was then compared to precise computer models. This allowed verification of proposed new corrections and the achievement of greater calibration accuracy for AFM measurements of nanoscale material strength.
NanoWorld AG, a leading manufacturer of high quality probe tips for AFM and similar measurement technologies, used the cantilever stiffness calibration method developed by the project to bring traceability to their own CalibLever reference cantilevers.
NanoWorld’s certified cantilever enables SI traceability for their own in house calibration methods, confirming the stiffness uncertainty of their commercially available AFM cantilevers, and allowing them to offer a calibration service to users. As a result, NanoWorld has increased sales of cantilevers with measured force constants to customers around the world.
Improved robustness for AFM measurements of elasticity at the nanoscale is increasing our understanding of nanomaterial behaviour in situ, so providing greater confidence in the use of nano-wires and other nano-structure innovations in new products.
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