Novel manipulation in Environmental SEM for measuring the mechanical properties of single nanoparticles

A novel nanomanipulation technique has been developed to measure the mechanical properties of single nanoparticles. The principle of this technique is to compress single nanoparticles between two flat surfaces comprising a glass slide and the tip of a calibrated glass cantilever inside the chamber of an environmental scanning electron microscope (ESEM), so that the force being imposed on them and their deformation can be determined by a series of images of the particles and the position of the cantilever. The cantilever is held by a nanomanipulator that has a resolution of 0.5 nm. The novel nanomanipulation technique, and a previously developed micromanipulation technique, were first used to measure the force required to compress single microparticles (ranging from 1 to 3 mu m in diameter) of methacrylic acid copolymer Eudragit E100 to different deformations under dry mode conditions, to validate results from the former. Results showed that there is no significant difference in the data obtained using these two techniques, which implies that the new nanomanipulation technique is highly reliable. The new technique was then applied to single polymethylmethacrylate (PMMA) particles ranging from 530 to 950 nm in diameter. They were compressed and held, compressed and released, and compressed to different deformations, and the force imposed on the particles was determined simultaneously. This work demonstrates the feasibility of measuring the mechanical properties of single nanoparticles, and the developed technique can find wide application in mechanical characterisation of different nanoparticles.